Author(s) ID,Title,Year,DOI,Link,Abstract
"7003307156;57203088154;","Cosmological smoothed particle hydrodynamics simulations: A hybrid multiphase model for star formation",2003,"10.1046/j.1365-8711.2003.06206.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0043200281&doi=10.1046%2fj.1365-8711.2003.06206.x&partnerID=40&md5=4211bac0a4452d63373fb4c0b562323b","We present a model for star formation and supernova feedback that describes the multiphase structure of star-forming gas on scales that are typically not resolved in cosmological simulations. Our approach includes radiative heating and cooling, the growth of cold clouds embedded in an ambient hot medium, star formation in these clouds, feedback from supernovae in the form of thermal heating and cloud evaporation, galactic winds and outflows, and metal enrichment. Implemented using smoothed particle hydrodynamics, our scheme is a significantly modified and extended version of the grid-based method of Yepes et al., and enables us to achieve a high dynamic range in simulations of structure formation. We discuss properties of the feedback model in detail and show that it predicts a selfregulated, quiescent mode of star formation, which, in particular, stabilizes the star-forming gaseous layers of disc galaxies. The parametrization of this mode can be reduced to a single free quantity that determines the overall time-scale for star formation. We fix this parameter numerically to match the observed rates of star formation in local disc galaxies. When normalized in this manner, cosmological simulations employing our model nevertheless overproduce the observed cosmic abundance of stellar material. We are thus motivated to extend our feedback model to include galactic winds associated with star formation. Using small-scale simulations of individual star-forming disc galaxies, we show that these winds produce either galactic fountains or outflows, depending on the depth of the gravitational potential. In low-mass haloes, winds can greatly suppress the overall efficiency of star formation. When incorporated into cosmological simulations, our combined model for star formation and winds predicts a cosmic star formation density that is consistent with observations, provided that the winds are sufficiently energetic. Moreover, outflows from galaxies in these simulations drive chemical enrichment of the intergalactic medium - in principle, accounting for the presence of metals in the Lyman α forest."
"55686667100;55619302054;26667030700;8612652300;9249627300;8979277400;7202079615;16645036600;10243650000;36722732500;14628012000;35231763100;10241462700;10240710000;7003967390;6603370049;7102857642;","Improved climate simulation by MIROC5: Mean states, variability, and climate sensitivity",2010,"10.1175/2010JCLI3679.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650547976&doi=10.1175%2f2010JCLI3679.1&partnerID=40&md5=6e09229388fd769c17e067a409754f06","A new version of the atmosphere-ocean general circulation model cooperatively produced by the Japanese research community, known as the Model for Interdisciplinary Research on Climate (MIROC), has recently been developed. A century-long control experiment was performed using the new version (MIROC5) with the standard resolution of the T85 atmosphere and 18 ocean models. The climatological mean state and variability are then compared with observations and those in a previous version (MIROC3.2) with two different resolutions (medres, hires), coarser and finer than the resolution of MIROC5.A few aspects of the mean fields in MIROC5 are similar to or slightly worse than MIROC3.2, but otherwise the climatological features are considerably better. In particular, improvements are found in precipitation, zonal mean atmospheric fields, equatorial ocean subsurface fields, and the simulation of El Niño-Southern Oscillation. The difference between MIROC5 and the previous model is larger than that between the two MIROC3.2 versions, indicating a greater effect of updating parameterization schemes on the model climate than increasing the model resolution. The mean cloud property obtained from the sophisticated prognostic schemes in MIROC5 shows good agreement with satellite measurements. MIROC5 reveals an equilibrium climate sensitivity of 2.6 K, which is lower than that in MIROC3.2 by 1 K. This is probably due to the negative feedback of low clouds to the increasing concentration of CO2, which is opposite to that in MIROC3.2. © 2010 American Meteorological Society."
"35509639400;7004714030;","Marine boundary layer clouds at the heart of tropical cloud feedback uncertainties in climate models",2005,"10.1029/2005GL023851","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28944450038&doi=10.1029%2f2005GL023851&partnerID=40&md5=f09513bd74190bea6ce77cf8586336c6","The radiative response of tropical clouds to global warming exhibits a large spread among climate models, and this constitutes a major source of uncertainty for climate sensitivity estimates. To better interpret the origin of that uncertainty, we analyze the sensitivity of the tropical cloud radiative forcing to a change in sea surface temperature that is simulated by 15 coupled models simulating climate change and current interannual variability. We show that it is in regimes of large-scale subsidence that the model results (1) differ the most in climate change and (2) disagree the most with observations in the current climate (most models underestimate the interannual sensitivity of clouds albedo to a change in temperature). This suggests that the simulation of the sensitivity of marine boundary layer clouds to changing environmental conditions constitutes, currently, the main source of uncertainty in tropical cloud feedbacks simulated by general circulation models. Copyright 2005 by the American Geophysical Union."
"7201504886;6603247427;6701689939;8696069500;35605362100;56154540200;35611334800;7404732357;7201627869;55581675600;14622350200;12775722600;56270311300;10241177500;57203053317;57205867148;6506238357;7003979342;","Atmospheric component of the MPI-M earth system model: ECHAM6",2013,"10.1002/jame.20015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876732870&doi=10.1002%2fjame.20015&partnerID=40&md5=4edb115fcc07396143dcadedf56c25dc","ECHAM6, the sixth generation of the atmospheric general circulation model ECHAM, is described. Major changes with respect to its predecessor affect the representation of shortwave radiative transfer, the height of the model top. Minor changes have been made to model tuning and convective triggering. Several model configurations, differing in horizontal and vertical resolution, are compared. As horizontal resolution is increased beyond T63, the simulated climate improves but changes are incremental; major biases appear to be limited by the parameterization of small-scale physical processes, such as clouds and convection. Higher vertical resolution in the middle atmosphere leads to a systematic reduction in temperature biases in the upper troposphere, and a better representation of the middle atmosphere and its modes of variability. ECHAM6 represents the present climate as well as, or better than, its predecessor. The most marked improvements are evident in the circulation of the extratropics. ECHAM6 continues to have a good representation of tropical variability. A number of biases, however, remain. These include a poor representation of low-level clouds, systematic shifts in major precipitation features, biases in the partitioning of precipitation between land and sea (particularly in the tropics), and midlatitude jets that appear to be insufficiently poleward. The response of ECHAM6 to increasing concentrations of greenhouse gases is similar to that of ECHAM5. The equilibrium climate sensitivity of the mixed-resolution (T63L95) configuration is between 2.9 and 3.4 K and is somewhat larger for the 47 level model. Cloud feedbacks and adjustments contribute positively to warming from increasing greenhouse gases. ©2013. American Geophysical Union. All Rights Reserved."
"7003543851;7005808242;","An assessment of climate feedbacks in coupled ocean-atmosphere models",2006,"10.1175/JCLI3799.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646848186&doi=10.1175%2fJCLI3799.1&partnerID=40&md5=8f288d7d65067b95eb42729e1932a7cc","The climate feedbacks in coupled ocean-atmosphere models are compared using a coordinated set of twenty-first-century climate change experiments. Water vapor is found to provide the largest positive feedback in all models and its strength is consistent with that expected from constant relative humidity changes in the water vapor mixing ratio. The feedbacks from clouds and surface albedo are also found to be positive in all models, while the only stabilizing (negative) feedback comes from the temperature response. Large intermodel differences in the lapse rate feedback are observed and shown to be associated with differing regional patterns of surface warming. Consistent with previous studies, it is found that the vertical changes in temperature and water vapor are tightly coupled in all models and, importantly, demonstrate that intermodel differences in the sum of lapse rate and water vapor feedbacks are small. In contrast, intermodel differences in cloud feedback are found to provide the largest source of uncertainty in current predictions of climate sensitivity. © 2006 American Meteorological Society."
"7202899330;","Cloud feedbacks in the climate system: A critical review",2005,"10.1175/JCLI-3243.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14644413562&doi=10.1175%2fJCLI-3243.1&partnerID=40&md5=3790274149375e7189dcd50ae4f15bcf","This paper offers a critical review of the topic of cloud-climate feedbacks and exposes some of the underlying reasons for the inherent lack of understanding of these feedbacks and why progress might be expected on this important climate problem in the coming decade. Although many processes and related parameters come under the influence of clouds, it is argued that atmospheric processes fundamentally govern the cloud feedbacks via the relationship between the atmospheric circulations, cloudiness, and the radiative and latent heating of the atmosphere. It is also shown how perturbations to the atmospheric radiation budget that are induced by cloud changes in response to climate forcing dictate the eventual response of the global-mean hydrological cycle of the climate model to climate forcing. This suggests that cloud feedbacks are likely to control the bulk precipitation efficiency and associated responses of the planet's hydrological cycle to climate radiative forcings. The paper provides a brief overview of the effects of clouds on the radiation budget of the earth-atmosphere system and a review of cloud feedbacks as they have been defined in simple systems, one being a system in radiative-convective equilibrium (RCE) and others relating to simple feedback ideas that regulate tropical SSTs. The systems perspective is reviewed as it has served as the basis for most feedback analyses. What emerges is the importance of being clear about the definition of the system. It is shown how different assumptions about the system produce very different conclusions about the magnitude and sign of feedbacks. Much more diligence is called for in terms of defining the system and justifying assumptions. In principle, there is also neither any theoretical basis to justify the system that defines feedbacks in terms of global-time-mean changes in surface temperature nor is there any compelling empirical evidence to do so. The lack of maturity of feedback analysis methods also suggests that progress in understanding climate feedback will require development of alternative methods of analysis. It has been argued that, in view of the complex na ture of the climate system, and the cumbersome problems encountered in diagnosing feedbacks, understanding cloud feedback will be gleaned neither from observations nor proved from simple theoretical argument alone. The blueprint for progress must follow a more arduous path that requires a carefully orchestrated and systematic combination of model and observations. Models provide the tool for diagnosing processes and quantifying feedbacks while observations provide the essential test of the model's credibility in representing these processes. While GCM climate and NWP models represent the most complete description of all the interactions between the processes that presumably establish the main cloud feedbacks, the weak link in the use of these models lies in the cloud parameterization imbedded in them. Aspects of these parameterizations remain worrisome, containing levels of empiricism and assumptions that are hard to evaluate with current global observations. Clearly observationally based methods for evaluating cloud parameterizations are an important element in the road map to progress. Although progress in understanding the cloud feedback problem has been slow and confused by past analysis, there are legitimate reasons outlined in the paper that give hope for real progress in the future. © 2005 American Meteorological Society."
"7005070958;","Intercomparison and interpretation of climate feedback processes in 19 atmospheric general circulation models",1990,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025680011&partnerID=40&md5=d50c5cb95d7ee2ce0540c5f5ffc3a735","This intercomparison uses sea surface temperature change as a surrogate for climate change. The interpretation of cloud-climate interactions is given special attention. A roughly threefold variation in one measure of global climate sensitivity is found among the 19 models. The important conclusion is that most of this variation is attributable to differences in the models' depiction of cloud feedback. It is further emphasized that cloud feedback is the consequence of all interacting physical and dynamical processes in a general circlation model. The results of these processes is to produce changes in temperature, moisture distribution, and clouds which are integrated into the radiative response termed cloud feedback. -from Authors"
"7202899330;7101899854;6602844274;7003468747;","The relevance of the microphysical and radiative properties of cirrus clouds to climate and climatic feedback",1990,"10.1175/1520-0469(1990)047<1742:trotma>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025621744&doi=10.1175%2f1520-0469%281990%29047%3c1742%3atrotma%3e2.0.co%3b2&partnerID=40&md5=f01f662ea51e7ffc31f104565724a915","Observations that relate the ice water content to cloud temperature are incorporated in the parameterization to introduce a temperature dependence to both albedo and emittance. The cloud properties relevant to the cloud feedback are expressed as functions of particles size re, asymmetry parameter g and cloud temperature and analyses of aircraft measurements, lidar and ground based radiometer data are used to select re and g. It was shown that scattering calculations assuming spherical particles with a distribution described by re = 16 μm reasonably matched the lidar and radiometer data. However, comparison of cloud radiation properties measured from aircraft to those parameterized in this study required values of g significantly smaller than those derived for spheres but consistent with our understanding of non-spherical particles scattering. The climate simulations revealed that the influence of cirrus cloud on climate was strongly affected by the choice of re and g: parameters that are both poorly known for cirrus. -from Authors"
"24722339600;","Stratocumulus clouds",2012,"10.1175/MWR-D-11-00121.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867674414&doi=10.1175%2fMWR-D-11-00121.1&partnerID=40&md5=c556917e3c3d6474db57c9330ca53154","This paper reviews the current knowledge of the climatological, structural, and organizational aspects of stratocumulus clouds and the physical processes controlling them. More of Earth's surface is covered by stratocumulus clouds than by any other cloud type making them extremely important for Earth's energy balance, primarily through their reflection of solar radiation. They are generally thin clouds, typically occupying the upper few hundred meters of the planetary boundary layer (PBL), and they preferably occur in shallow PBLs that are readily coupled by turbulent mixing to the surface moisture supply. Thus, stratocumuli favor conditions of strong lower-tropospheric stability, large-scale subsidence, and a ready supply of surface moisture; therefore, they are common over the cooler regions of subtropical and midlatitude oceans where their coverage can exceed 50% in the annual mean. Convective instability in stratocumulus clouds is driven primarily by the emission of thermal infrared radiation from near the cloud tops and the resulting turbulence circulations are enhanced by latent heating in updrafts and cooling in downdrafts. Turbulent eddies and evaporative cooling drives entrainment at the top of the stratocumulus-topped boundary layer (STBL), which is stronger than it would be in the absence of cloud, and this tends to result in a deepening of the STBL over time. Many stratocumulus clouds produce some drizzle through the collision-coalescence process, but thicker clouds drizzle more readily, which can lead to changes in the dynamics of the STBL that favor increased mesoscale variability, stratification of the STBL, and in some cases cloud breakup. Feedbacks between radiative cooling, precipitation formation, turbulence, and entrainment help to regulate stratocumulus. Although stratocumulus is arguably the most well-understood cloud type, it continues to challenge understanding. Indeed, recent field studies demonstrate that marine stratocumulus precipitate more strongly, and entrain less, than was previously thought, and display an organizational complexitymuch larger than previously imagined. Stratocumulus clouds break up as the STBL deepens and it becomes more difficult to maintain buoyant production of turbulence through the entire depth of the STBL. Stratocumulus cloud properties are sensitive to the concentration of aerosol particles and therefore anthropogenic pollution. For a given cloud thickness, polluted clouds tend to producemore numerous and smaller cloud droplets, greater cloud albedo, and drizzle suppression. In addition, cloud droplet size also affects the time scale for evaporation-entrainment interactions and sedimentation rate, which together with precipitation changes can affect turbulence and entrainment. Aerosols are themselves stronglymodified by physical processes in stratocumuli, and these twoway interactionsmay be a key driver of aerosol concentrations over the remote oceans.Aerosol-stratocumulus interactions are therefore one of the most challenging frontiers in cloud-climate research. Low-cloud feedbacks are also a leading cause of uncertainty in future climate prediction because even small changes in cloud coverage and thickness have a major impact on the radiation budget. Stratocumuli remain challenging to represent in climate models since their controlling processes occur on such small scales. A better understanding of stratocumulus dynamics, particularly entrainment processes and mesoscale variability, will be required to constrain these feedbacks. © 2012 American Meteorological Society."
"24329376600;57203049177;7201485519;57210518852;","Forcing, feedbacks and climate sensitivity in CMIP5 coupled atmosphere-ocean climate models",2012,"10.1029/2012GL051607","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861180918&doi=10.1029%2f2012GL051607&partnerID=40&md5=49138d88aafa80b7517b3716f957836f","We quantify forcing and feedbacks across available CMIP5 coupled atmosphere-ocean general circulation models (AOGCMs) by analysing simulations forced by an abrupt quadrupling of atmospheric carbon dioxide concentration. This is the first application of the linear forcing-feedback regression analysis of Gregory et al. (2004) to an ensemble of AOGCMs. The range of equilibrium climate sensitivity is 2.1-4.7K. Differences in cloud feedbacks continue to be important contributors to this range. Some models show small deviations from a linear dependence of top-of-atmosphere radiative fluxes on global surface temperature change. We show that this phenomenon largely arises from shortwave cloud radiative effects over the ocean and is consistent with independent estimates of forcing using fixed sea-surface temperature methods. We suggest that future research should focus more on understanding transient climate change, including any time-scale dependence of the forcing and/or feedback, rather than on the equilibrium response to large instantaneous forcing."
"6701652286;7102875645;","Cloud feedback processes in a general circulation model",1988,"10.1175/1520-0469(1988)045<1397:cfpiag>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024221323&doi=10.1175%2f1520-0469%281988%29045%3c1397%3acfpiag%3e2.0.co%3b2&partnerID=40&md5=82d83c11174a68c69fd81800469e3442","The model used is a general circulation model of the atmosphere coupled with a mixed layer model of the oceans. The sensitivity of each version of the model is inferred from the equilibrium response of the model to a doubling of the atmospheric concentration of carbon dioxide. In response to the increase of atmospheric carbon dioxide, cloudiness increases around the tropopause and is reduced in the upper troposphere, thereby raising the height of the cloud layer in the upper troposphere. This implies a reduction of the temperature of the cloud top and, accordingly, of the upward terrestrial radiation from the top of the model atmosphere. On the other hand, the increase of low cloudiness in high latitudes raises the planetary albedo and thus decreases the CO2 induced warming of climate. However, the contribution of this negative feedback process is much smaller than the effect of the positive feedbakc process involving the change of high cloud. -from Authors"
"7003543851;7005808242;57212781009;6701455548;7005513582;7201520140;","Quantifying climate feedbacks using radiative kernels",2008,"10.1175/2007JCLI2110.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44249092520&doi=10.1175%2f2007JCLI2110.1&partnerID=40&md5=1bb29b3b5c9d7835c3b5d5b9873abcbe","The extent to which the climate will change due to an external forcing depends largely on radiative feedbacks, which act to amplify or damp the surface temperature response. There are a variety of issues that complicate the analysis of radiative feedbacks in global climate models, resulting in some confusion regarding their strengths and distributions. In this paper, the authors present a method for quantifying climate feedbacks based on ""radiative kernels"" that describe the differential response of the top-of-atmosphere radiative fluxes to incremental changes in the feedback variables. The use of radiative kernels enables one to decompose the feedback into one factor that depends on the radiative transfer algorithm and the unperturbed climate state and a second factor that arises from the climate response of the feedback variables. Such decomposition facilitates an understanding of the spatial characteristics of the feedbacks and the causes of intermodel differences. This technique provides a simple and accurate way to compare feedbacks across different models using a consistent methodology. Cloud feedbacks cannot be evaluated directly from a cloud radiative kernel because of strong nonlinearities, but they can be estimated from the change in cloud forcing and the difference between the full-sky and clear-sky kernels. The authors construct maps to illustrate the regional structure of the feedbacks and compare results obtained using three different model kernels to demonstrate the robustness of the methodology. The results confirm that models typically generate globally averaged cloud feedbacks that are substantially positive or near neutral, unlike the change in cloud forcing itself, which is as often negative as positive. © 2008 American Meteorological Society."
"55544443300;7005808242;15026371500;57218978981;","The response of the ITCZ to extratropical thermal forcing: Idealized slab-ocean experiments with a GCM",2008,"10.1175/2007JCLI2146.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53649089903&doi=10.1175%2f2007JCLI2146.1&partnerID=40&md5=afcf15f21ed6eb57c6c9121b4549214d","Using a comprehensive atmospheric GCM coupled to a slab mixed layer ocean, experiments are performed to study the mechanism by which displacements of the intertropical convergence zone (ITCZ) are forced from the extratropics. The northern extratropics are cooled and the southern extratropics are warmed by an imposed cross-equatorial flux beneath the mixed layer, forcing a southward shift in the ITCZ. The ITCZ displacement can be understood in terms of the degree of compensation between the imposed oceanic flux and the resulting response in the atmospheric energy transport in the tropics. The magnitude of the ITCZ displacement is very sensitive to a parameter in the convection scheme that limits the entrainment into convective plumes. The change in the convection scheme affects the extratropical-tropical interactions in the model primarily by modifying the cloud response. The results raise the possibility that the response of tropical precipitation to extratropical thermal forcing, important for a variety of problems in climate dynamics (such as the response of the tropics to the Northern Hemisphere ice sheets during glacial maxima or to variations in the Atlantic meridional overturning circulation), may be strongly dependent on cloud feedback. The model configuration described here is suggested as a useful benchmark helping to quantify extratropical-tropical interactions in atmospheric models. © 2008 American Meteorological Society."
"57193132723;7403318365;6507993848;12241892400;","A prognostic cloud water parameterization for global climate models",1996,"10.1175/1520-0442(1996)009<0270:APCWPF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029751999&doi=10.1175%2f1520-0442%281996%29009%3c0270%3aAPCWPF%3e2.0.CO%3b2&partnerID=40&md5=996ae7eeaa77b5a83495e3fcddf42847","An efficient new prognostic cloud water parameterization designed for use in global climate models is described. The scheme allows for life cycle effects in stratiform clouds and permits cloud optical properties to be determined interactively. The parameterization contains representations of all important microphysical processes, including autoconversion, accretion, Bergeron-Findeisen diffusional growth, and cloud/rain water evaporation. Small-scale dynamical processes, including detrainment of convective condensate, cloud-top entrainment instability, and stability-dependent cloud physical thickness variations, are also taken into account. Cloud optical thickness is calculated from the predicted liquid/ice water path and a variable droplet effective radius estimated by assuming constant droplet number concentration. Microphysical and radiative properties are assumed to be different for liquid and ice clouds, and for liquid clouds over land and ocean. The parameterization is validated in several simulations using the Goddard Institute for Space Studies (GISS) general circulation model (GCM). Comparisons are made with a variety of datasets, including ERBE radiative fluxes and cloud forcing, ISCCP and surface-observed cloud properties, SSM/I liquid water path, and SAGE II thin cirrus cover. Validation is judged on the basis of the model's depiction of both the mean state; diurnal, seasonal, and interannual variability; and the temperature dependence of cloud properties. Relative to the diagnostic cloud scheme used in the previous GISS GCM, the prognostic parameterization strengthens the model's hydrologic cycle and general circulation, both directly and indirectly (via increased cumulus heating). Sea surface temperature (SST) perturbation experiments produce low climate sensitivity and slightly negative cloud feedback for globally uniform SST changes, but high sensitivity and positive cloud feedback when tropical Pacific SST gradients weaken with warming. Changes in the extent and optical thickness of tropical cumulus anvils appear to be the primary factor determining the sensitivity. This suggests that correct simulations of upward transport of convective condensate and of Walker circulation changes are of the highest priority for a realistic estimate of cloud feedback in actual greenhouse gas increase scenarios."
"35509639400;7201504886;15026371500;7006698304;7007181954;57205867148;7103294731;56014511300;6603566335;7102567936;55686667100;7201485519;","Clouds, circulation and climate sensitivity",2015,"10.1038/ngeo2398","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926359595&doi=10.1038%2fngeo2398&partnerID=40&md5=3cc991046f3922dab00d63d9f51143a1","Fundamental puzzles of climate science remain unsolved because of our limited understanding of how clouds, circulation and climate interact. One example is our inability to provide robust assessments of future global and regional climate changes. However, ongoing advances in our capacity to observe, simulate and conceptualize the climate system now make it possible to fill gaps in our knowledge. We argue that progress can be accelerated by focusing research on a handful of important scientific questions that have become tractable as a result of recent advances. We propose four such questions below; they involve understanding the role of cloud feedbacks and convective organization in climate, and the factors that control the position, the strength and the variability of the tropical rain belts and the extratropical storm tracks."
"7202496599;7406514318;","Climate model simulations of the equilibrium climatic response to increased carbon dioxide",1987,"10.1029/RG025i004p00760","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0023466447&doi=10.1029%2fRG025i004p00760&partnerID=40&md5=d27527119a555f5b6a4805a8cb8d119b","The first assessments of the potential climatic effects of increased CO2 were performed using simplified climate models, namely, energy balance models (EBMs) and radiative‐convective models (RCMs). A wide range of surface temperature warming has been obtained by surface EBMs as a result of the inherent difficulty of these models in specifying the behavior of the climate system away from the energy balance level. RCMs have given estimates of ΔTs for a CO2 doubling that range from 0.48° to 4.2°C. This response can be characterized by ΔTs = ΔRTG0/(1 ‐ f), where ΔRT is the radiative forcing at the tropopause due to the CO2 doubling (∼4 W m−2), G0 is the gain of the climate system without feedbacks (∼0.3°C/(W m−2)), and f is the feedback. The feedback processes in RCMs include water vapor feedback (f is 0.3 to 0.4), moist adiabatic lapse rate feedback (f is −0.25 to −0.4), cloud altitude feedback (f is 0.15 to 0.30), cloud cover feedback (f is unknown), cloud optical depth feedback (f is 0 to −1.32), and surface albedo feedback (f is 0.14 to 0.19). However, these feedbacks can be predicted credibly only by physically based models that include the essential dynamics and thermodynamics of the feedback processes. Such physically based models are the general circulation models (GCMs). The earliest GCM simulations of CO2‐induced climate change were performed without the annual insolation cycle. These “annual mean” simulations gave for a CO2 doubling a global mean surface air temperature warming of 1.3° to 3.9°C, an increase in the global mean precipitation rate of 2.7 to 7.8%, and an indication of a soil moisture drying in the middle latitudes. The first GCM simulation of the seasonal variation of CO2‐induced climate change was performed for a CO2 quadrupling and obtained annual global mean surface temperature and precipitation changes of 4.1°C and 6.7%, respectively. Substantial seasonal differences in the CO2‐induced climate changes were found, especially in polar latitudes where the warming was maximum in winter and in the middle latitudes of the northern hemisphere where a soil moisture desiccation was found in summer. Recently, three CO2‐doubling experiments have been performed with GCMs that include the annual insolation cycle. These seasonal simulations give an annual global mean warming of 3.5° to 4.2°C and precipitation increases of 7.1 to 11%. These changes are approximately twice as large as those implied for a CO2 doubling by the earliest seasonal simulation, apparently as a result of a positive cloud feedback. The geographical distributions of the CO2‐induced warming obtained by the recent simulations agree qualitatively but not quantitatively. Furthermore, the precipitation and soil moisture changes do not agree quantitatively and even show qualitative differences. In particular, the summertime soil moisture drying in middle‐latitudes is simulated by only one of the GCMs. In order to improve the state of the art in simulating the equilibrium climatic change induced by increased CO2 concentrations, it is recommended first that the contemporary GCM simulations be analyzed to determine the feedback processes responsible for their differences and second that the parameterization of these processes in the GCMs be validated against highly detailed models and observations. Copyright 1987 by the American Geophysical Union."
"13402835300;7201485519;35509639400;6603925960;7004714030;7402064802;52464731300;7101959253;16679271700;57205867148;7102963655;","COSP: Satellite simulation software for model assessment",2011,"10.1175/2011BAMS2856.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953115248&doi=10.1175%2f2011BAMS2856.1&partnerID=40&md5=b8beadabfa524b6ae8a0f63aab9ae94e","The Cloud Feedback Model Intercomparison Project (CFMIP) community has developed an integrated satellite simulator, the CFMIP Observation Simulator Package (COSP). COSP is a flexible software tool that enables the simulation from model variables of data from several satellite-borne active and passive sensors. COSP facilitates the evaluation of models against observations and comparisons between them in a more consistent manner. Two of the models used in this study are GCMs used in the latest IPCC assessment reports, and the others are two versions of the multiscale modeling framework (MMF) with different horizontal and vertical resolutions of the embedded cloud-resolving model. It is found that the MMF simulations perform better than the other climate models in all the diagnostics, showing a distribution of hydrometeors in the vertical and also in optical depth closer to the observations."
"7403288995;","The role of surface albedo feedback in climate",2004,"10.1175/1520-0442(2004)017<1550:TROSAF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2042426324&doi=10.1175%2f1520-0442%282004%29017%3c1550%3aTROSAF%3e2.0.CO%3b2&partnerID=40&md5=3c70d529e4524b7a8bb6eed4a19c05c7","A coarse resolution coupled ocean-atmosphere simulation in which surface albedo feedback is suppressed by prescribing surface albedo, is compared to one where snow and sea ice anomalies are allowed to affect surface albedo. Canonical CO2-doubling experiments were performed with both models to assess the impact of this feedback on equilibrium response to external forcing. It accounts for about half the high-latitude response to the forcing. Both models were also run for 1000 yr without forcing to assess the impact of surface albedo feedback on internal variability. Surprisingly little internal variability can be attributed to this feedback, except in the Northern Hemisphere continents during spring and in the sea ice zone of the Southern Hemisphere year-round. At these locations and during these seasons, it accounts for, at most, 20% of the variability. The main reason for this relatively weak signal is that horizontal damping processes dilute the impact of surface albedo feedback. When snow albedo feedback in Northern Hemisphere continents is isolated from horizontal damping processes, it has a similar strength in the CO2-doubling and internal variability contexts; a given temperature anomaly in these regions is associated with approximately the same change in snow depth and surface albedo whether it was externally forced or internally generated. This suggests that the presence of internal variability in the observed record is not a barrier to extracting information about snow albedo feedback's contribution to equilibrium climate sensitivity. This is demonstrated in principle in a ""scenario run,"" where estimates of past, present, and future changes in greenhouse gases and sulfate aerosols are imposed on the model with surface albedo feedback. This simulation contains a mix of internal variations and externally forced anomalies similar to the observed record. The snow albedo feedback to the scenario run's climate anomalies agrees very well with the snow albedo feedback in the CO2,-doubling context. Moreover, the portion of the scenario run corresponding to the present-day satellite record is long enough to capture this feedback, suggesting this record could be used to estimate snow albedo feedback's contribution to equilibrium climate sensitivity. © 2004 American Meteorological Society."
"7201485519;7004764167;35509639400;24322005900;","Combining ERBE and ISCCP data to assess clouds in the Hadley Centre, ECMWF and LMD atmospheric climate models",2001,"10.1007/s003820100157","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034791589&doi=10.1007%2fs003820100157&partnerID=40&md5=003c2a1bd7a7ddf5feda5ff8033fed3f","This study compares radiative fluxes and cloudiness fields from three general circulation models (the HadAM4 version of the Hadley Centre Unified model, cycle 16r2 of the ECMWF model and version LMDZ 2.0 of the LMD GCM), using a combination of satellite observations from the Earth Radiation Budget Experiment (ERBE) and the International Satellite Cloud Climatology Project (ISCCP). To facilitate a meaningful comparison with the ISCCP C1 data, values of column cloud optical thickness and cloud top pressure are diagnosed from the models in a manner consistent with the satellite view from space. Decomposing the cloud radiative effect into contributions from low-medium- and high-level clouds reveals a tendency for the models' low-level clouds to compensate for underestimates in the shortwave cloud radiative effect caused by a lack of high-level or mid-level clouds. The low clouds fail to compensate for the associated errors in the longwave. Consequently, disproportionate errors in the longwave and shortwave cloud radiative effect in models may be taken as an indication that compensating errors are likely to be present. Mid-level cloud errors in the mid-latitudes appear to depend as much on the choice of the convection scheme as on the cloud scheme. Convective and boundary layer mixing schemes require as much consideration as cloud and precipitation schemes when it comes to assessing the simulation of clouds by models. Two distinct types of cloud feedback are discussed. While there is reason to doubt that current models are able to simulate potential 'cloud regime' type feedbacks with skill, there is hope that a model capable of simulating potential 'cloud amount' type feedbacks will be achievable once the reason for the remaining differences between the models are understood."
"49664027700;7004714030;35509639400;","On the interpretation of inter-model spread in CMIP5 climate sensitivity estimates",2013,"10.1007/s00382-013-1725-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888055218&doi=10.1007%2fs00382-013-1725-9&partnerID=40&md5=4ceccac16b19a865d199754e9f6dbaf4","This study diagnoses the climate sensitivity, radiative forcing and climate feedback estimates from eleven general circulation models participating in the Fifth Phase of the Coupled Model Intercomparison Project (CMIP5), and analyzes inter-model differences. This is done by taking into account the fact that the climate response to increased carbon dioxide (CO2) is not necessarily only mediated by surface temperature changes, but can also result from fast land warming and tropospheric adjustments to the CO2 radiative forcing. By considering tropospheric adjustments to CO2 as part of the forcing rather than as feedbacks, and by using the radiative kernels approach, we decompose climate sensitivity estimates in terms of feedbacks and adjustments associated with water vapor, temperature lapse rate, surface albedo and clouds. Cloud adjustment to CO2 is, with one exception, generally positive, and is associated with a reduced strength of the cloud feedback; the multi-model mean cloud feedback is about 33 % weaker. Non-cloud adjustments associated with temperature, water vapor and albedo seem, however, to be better understood as responses to land surface warming. Separating out the tropospheric adjustments does not significantly affect the spread in climate sensitivity estimates, which primarily results from differing climate feedbacks. About 70 % of the spread stems from the cloud feedback, which remains the major source of inter-model spread in climate sensitivity, with a large contribution from the tropics. Differences in tropical cloud feedbacks between low-sensitivity and high-sensitivity models occur over a large range of dynamical regimes, but primarily arise from the regimes associated with a predominance of shallow cumulus and stratocumulus clouds. The combined water vapor plus lapse rate feedback also contributes to the spread of climate sensitivity estimates, with inter-model differences arising primarily from the relative humidity responses throughout the troposphere. Finally, this study points to a substantial role of nonlinearities in the calculation of adjustments and feedbacks for the interpretation of inter-model spread in climate sensitivity estimates. We show that in climate model simulations with large forcing (e.g., 4 × CO2), nonlinearities cannot be assumed minor nor neglected. Having said that, most results presented here are consistent with a number of previous feedback studies, despite the very different nature of the methodologies and all the uncertainties associated with them. © 2013 Springer-Verlag Berlin Heidelberg."
"7201485519;7004764167;7103373205;7004169476;7404142321;7003976079;6701715507;57212781009;7003543851;6506103893;7003554208;8979277400;10243650000;7007021059;7004033942;26643217800;8937991200;35509639400;57210518852;","On the contribution of local feedback mechanisms to the range of climate sensitivity in two GCM ensembles",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644666197&partnerID=40&md5=89c13ccd287009c1f39f6ac99786369f","Global and local feedback analysis techniques have been applied to two ensembles of mixed layer equilibrium CO2 doubling climate change experiments, from the CFMIP (Cloud Feedback Model Intercomparison Project) and QUMP (Quantifying Uncertainty in Model Predictions) projects. Neither of these new ensembles shows evidence of a statistically significant change in the ensemble mean or variance in global mean climate sensitivity when compared with the results from the mixed layer models quoted in the Third Assessment Report of the IPCC. Global mean feedback analysis of these two ensembles confirms the large contribution made by inter-model differences in cloud feedbacks to those in climate sensitivity in earlier studies; net cloud feedbacks are responsible for 66% of the inter-model variance in the total feedback in the CFMIP ensemble and 85% in the QUMP ensemble. The ensemble mean global feedback components are all statistically indistinguishable between the two ensembles, except for the clear-sky shortwave feedback which is stronger in the CFMIP ensemble. While ensemble variances of the shortwave cloud feedback and both clear-sky feedback terms are larger in CFMIP, there is considerable overlap in the cloud feedback ranges; QUMP spans 80% or more of the CFMIP ranges in longwave and shortwave cloud feedback. We introduce a local cloud feedback classification system which distinguishes different types of cloud feedbacks on the basis of the relative strengths of their longwave and shortwave components, and interpret these in terms of responses of different cloud types diagnosed by the International Satellite Cloud Climatology Project simulator. In the CFMIP ensemble, areas where low-top cloud changes constitute the largest cloud response are responsible for 59% of the contribution from cloud feedback to the variance in the total feedback. A similar figure is found for the QUMP ensemble. Areas of positive low cloud feedback (associated with reductions in low level cloud amount) contribute most to this figure in the CFMIP ensemble, while areas of negative cloud feedback (associated with increases in low level cloud amount and optical thickness) contribute most in QUMP. Classes associated with high-top cloud feedbacks are responsible for 33 and 20% of the cloud feedback contribution in CFMIP and QUMP, respectively, while classes where no particular cloud type stands out are responsible for 8 and 21%. © Springer-Verlag 2006."
"57206546845;6506819877;7004109472;55768583400;57216005348;7202641466;56985140700;57210518852;","An overview of results from the Coupled Model Intercomparison Project",2003,"10.1016/S0921-8181(02)00193-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037648363&doi=10.1016%2fS0921-8181%2802%2900193-5&partnerID=40&md5=971493431d267006d23bf32dac6868b4","The Coupled Model Intercomparison Project (CMIP) collects output from global coupled ocean-atmosphere general circulation models (coupled GCMs). Among other uses, such models are employed both to detect anthropogenic effects in the climate record of the past century and to project future climatic changes due to human production of greenhouse gases and aerosols. CMIP has archived output from both constant forcing (""control run"") and perturbed (1% per year increasing atmospheric carbon dioxide) simulations. This report summarizes results form 18 CMIP models. A third of the models refrain from employing ad hoc flux adjustments at the ocean-atmosphere interface. The new generation of non-flux-adjusted control runs are nearly as stable as - and agree with observations nearly as well as - the flux-adjusted models. Both flux-adjusted and non-flux-adjusted models simulate an overall level of natural internal climate variability that is within the bounds set by observations. These developments represent significant progress in the state of the art of climate modeling since the Second (1995) Scientific Assessment Report of the Intergovernmental Panel on Climate Change (IPCC; see Gates et al. [Gates, W.L., et at., 1996. Climate models - Evaluation. Climate Climate 1995: The Science of Climate Change, Houghton, J.T., et al. (Eds.), Cambridge Univ. Press, pp. 229-284]). In the increasing-CO2 runs, differences between different models, while substantial, are not as great as one might expect from earlier assessments that relied on equilibrium climate sensitivity. © 2003 Elsevier Science B.V. All rights reserved."
"7004714030;35509639400;","An assessment of the primary sources of spread of global warming estimates from coupled atmosphere-ocean models",2008,"10.1175/2008JCLI2239.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56349157052&doi=10.1175%2f2008JCLI2239.1&partnerID=40&md5=ebe86bfc14aec19c2fab3be7fca91add","Climate feedback analysis constitutes a useful framework for comparing the global mean surface temperature responses to an external forcing predicted by general circulation models (GCMs). Nevertheless, the contributions of the different radiative feedbacks to global warming (in equilibrium or transient conditions) and their comparison with the contribution of other processes (e.g., the ocean heat uptake) have not been quantified explicitly. Here these contributions from the classical feedback analysis framework are defined and quantified for an ensemble of 12 third phase of the Coupled Model Intercomparison Project (CMIP3)/ Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) coupled atmosphere-ocean GCMs. In transient simulations, the multimodel mean contributions to global warming associated with the combined water vapor-lapse-rate feedback, cloud feedback, and ocean heat uptake are comparable. However, intermodel differences in cloud feedbacks constitute by far the most primary source of spread of both equilibrium and transient climate responses simulated by GCMs. The spread associated with intermodel differences in cloud feedbacks appears to be roughly 3 times larger than that associated either with the combined water vapor-lapse-rate feedback, the ocean heat uptake, or the radiative forcing. © 2008 American Meteorological Society."
"25031430500;55717074000;7003666669;7103158465;55717244800;15724543600;7402064802;7401974644;23065650200;9249239700;","Global simulations of ice nucleation and ice supersaturation with an improved cloud scheme in the Community Atmosphere Model",2010,"10.1029/2009JD013797","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957575116&doi=10.1029%2f2009JD013797&partnerID=40&md5=a6e21f9dcb4717934979fd330b8538b1","A process-based treatment of ice supersaturation and ice nucleation is implemented in the National Center for Atmospheric Research Community Atmosphere Model (CAM). The new scheme is designed to allow (1) supersaturation with respect to ice, (2) ice nucleation by aerosol particles, and (3) ice cloud cover consistent with ice microphysics. The scheme is implemented with a two-moment microphysics code and is used to evaluate ice cloud nucleation mechanisms and supersaturation in CAM. The new model is able to reproduce field observations of ice mass and mixed phase cloud occurrence better than previous versions. The model is able to reproduce observed patterns and frequency of ice supersaturation. Simulations indicate homogeneous freezing of sulfate and heterogeneous freezing on dust are both important ice nucleation mechanisms, in different regions. Simulated cloud forcing and climate is sensitive to different formulations of the ice microphysics. Arctic surface radiative fluxes are sensitive to the parameterization of ice clouds. These results indicate that ice clouds are potentially an important part of understanding cloud forcing and potential cloud feedbacks, particularly in the Arctic. Copyright 2010 by the American Geophysical Union."
"7005578774;6602098362;","Simulation of present-day and twenty-first-century energy budgets of the southern oceans",2010,"10.1175/2009JCLI3152.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949340634&doi=10.1175%2f2009JCLI3152.1&partnerID=40&md5=0a1e79b0636938feee755ecded26dbc1","The energy budget of the modern-day Southern Hemisphere is poorly simulated in both state-of-the-art reanalyses and coupled global climate models. The ocean-dominated Southern Hemisphere has low surface reflectivity and therefore its albedo is particularly sensitive to cloud cover. In modern-day climates, mainly because of systematic deficiencies in cloud and albedo at mid- and high latitudes, too much solar radiation enters the ocean. Along with too little radiation absorbed at lower latitudes because of clouds that are too bright, unrealistically weak poleward transports of energy by both the ocean and atmosphere are generally simulated in the Southern Hemisphere. This implies too little baroclinic eddy development and deficient activity in storm tracks. However, projections into the future by coupled climate models indicate that the Southern Ocean features a robust and unique increase in albedo, related to clouds, in association with an intensification and poleward shift in storm tracks that is not observed at any other latitude. Such an increase in cloud may be untenable in nature, as it is likely precluded by the present-day ubiquitous cloud cover that models fail to capture. There is also a remarkably strong relationship between the projected changes in clouds and the simulated current-day cloud errors. The model equilibrium climate sensitivity is also significantly negatively correlated with the Southern Hemisphere energy errors, and only the more sensitive models are in the range of observations. As a result, questions loom large about how the Southern Hemisphere will actually change as global warming progresses, and a better simulation of the modern-day climate is an essential first step. © 2010 American Meteorological Society."
"7005070958;","Cloud feedback in atmospheric general circulation models: An update",1996,"10.1029/96JD00822","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030449120&doi=10.1029%2f96JD00822&partnerID=40&md5=5a320b6b6a5d4a7638fb31ba090d6ab4","Six years ago, we compared the climate sensitivity of 19 atmospheric general circulation models and found a roughly threefold variation among the models; most of this variation was attributed to differences in the models' depictions of cloud feedback. In an update of this comparison, current models showed considerably smaller differences in net cloud feedback, with most producing modest values. There are, however, substantial differences in the feedback components, indicating that the models still have physical disagreements. Copyright 1996 by the American Geophysical Union."
"7006417494;7004390586;","A quasi-equilibrium tropical circulation model-formulation",2000,"10.1175/1520-0469(2000)057<1741:AQETCM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034210719&doi=10.1175%2f1520-0469%282000%29057%3c1741%3aAQETCM%3e2.0.CO%3b2&partnerID=40&md5=1ac8588fdecc5f2a763d9e714c2a6341","A class of model for simulation and theory of the tropical atmospheric component of climate variations is introduced. These models are referred to as quasi-equilibrium tropical circulation models, or QTCMs, because they make use of approximations associated with quasi-equilibrium (QE) convective parameterizations. Quasi-equilibrium convective closures tend to constrain the vertical temperature profile in convecting regions. This can be used to generate analytical solutions for the large-scale flow under certain approximations. A tropical atmospheric model of intermediate complexity is constructed by using the analytical solutions as the first basis function in a Galerkin representation of vertical structure. This retains much of the simplicity of the analytical solutions, while retaining full nonlinearity, vertical momentum transport, departures from QE, and a transition between convective and nonconvective zones based on convective available potential energy. The atmospheric model is coupled to a one-layer land surface model with interactive soil moisture and simulates its own tropical climatology. In the QTCM version presented here, the vertical structure of temperature variations is truncated to a single profile associated with deep convection. Though designed to be accurate in and near regions dominated by deep convection, the model simulates the tropical and subtropical climatology reasonably well, and even has a qualitative representation of midlatitude storm tracks. The model is computationally economical, since part of the solution has been carried out analytically, but the main advantage is relative simplicity of analysis under certain conditions. The formulation suggests a slightly different way of looking at the tropical atmosphere than has been traditional in tropical meteorology. While convective scales are unstable, the large-scale motions evolve with a positive effective stratification that takes into account the partial cancellation of adiabatic cooling by diabatic heating. A consistent treatment of the moist static energy budget aids the analysis of radiative and surface heat flux effects. This is particularly important highlights the role of top-of-the-atmosphere fluxes including cloud feedbacks, and it illustrates the usefulness of this approach for analysis of convective regions. Reductions of the model for theoretical work or diagnostics are outlined.A class of model for simulation and theory of the tropical atmospheric component of climate variations is introduced. These models are referred to as quasi-equilibrium tropical circulation models, or QTCMs, because they make use of approximations associated with quasi-equilibrium (QE) convective parameterizations. Quasi-equilibrium convective closures tend to constrain the vertical temperature profile in convecting regions. This can be used to generate analytical solutions for the large-scale flow under certain approximations. A tropical atmospheric model of intermediate complexity is constructed by using the analytical solutions as the first basis function in a Galerkin representation of vertical structure. This retains much of the simplicity of the analytical solutions, while retaining full nonlinearity, vertical momentum transport, departures from QE, and a transition between convective and nonconvective zones based on convective available potential energy. The atmospheric model is coupled to a one-layer land surface model with interactive soil moisture and simulates its own tropical climatology. In the QTCM version presented here, the vertical structure of temperature variations is truncated to a single profile associated with deep convection. Though designed to be accurate in and near regions dominated by deep convection, the model simulates the tropical and subtropical climatology reasonably well, and even has a qualitative representation of midlatitude storm tracks. The model is computationally economical, since part of the solution has been carried out analytically, but the main advantage is relative simplicity of analysis under certain conditions. The formulation suggests a slightly different way of looking at the tropical atmosphere than has been traditional in tropical meteorology. While convective scales are unstable, the large-scale motions evolve with a positive effective stratification that takes into account the partial cancellation of adiabatic cooling by diabatic heating. A consistent treatment of the moist static energy budget aids the analysis of radiative and surface heat flux effects. This is particularly important over land regions where the zero net surface flux links land surface anomalies. The resulting simplification highlights the role of top-of-the-atmosphere fluxes including cloud feedbacks, and it illustrates the usefulness of this approach for analysis of convective regions. Reductions of the model for theoretical work or diagnostics are outlined."
"35547807400;24329376600;36010237000;57203049177;24528108000;26645289600;","Evaluating adjusted forcing and model spread for historical and future scenarios in the CMIP5 generation of climate models",2013,"10.1002/jgrd.50174","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880273895&doi=10.1002%2fjgrd.50174&partnerID=40&md5=b58739d9cdfcbe6f26d9b7495b352b06","We utilize energy budget diagnostics from the Coupled Model Intercomparison Project phase 5 (CMIP5) to evaluate the models' climate forcing since preindustrial times employing an established regression technique. The climate forcing evaluated this way, termed the adjusted forcing (AF), includes a rapid adjustment term associated with cloud changes and other tropospheric and land-surface changes. We estimate a 2010 total anthropogenic and natural AF from CMIP5 models of 1.9 ± 0.9 W m-2 (5-95% range). The projected AF of the Representative Concentration Pathway simulations are lower than their expected radiative forcing (RF) in 2095 but agree well with efficacy weighted forcings from integrated assessment models. The smaller AF, compared to RF, is likely due to cloud adjustment. Multimodel time series of temperature change and AF from 1850 to 2100 have large intermodel spreads throughout the period. The intermodel spread of temperature change is principally driven by forcing differences in the present day and climate feedback differences in 2095, although forcing differences are still important for model spread at 2095. We find no significant relationship between the equilibrium climate sensitivity (ECS) of a model and its 2003 AF, in contrast to that found in older models where higher ECS models generally had less forcing. Given the large present-day model spread, there is no indication of any tendency by modelling groups to adjust their aerosol forcing in order to produce observed trends. Instead, some CMIP5 models have a relatively large positive forcing and overestimate the observed temperature change. Key PointsRadiative forcing of RCP scenarios in 2095 is underestimatedCMIP5 models have a large spread in temperature changes and radiative forcingClimate sensitivity was not adjusted to reproduce observed temperature trends ©2013. American Geophysical Union. All Rights Reserved."
"57212781009;","A comparison of climate feedbacks in general circulation models",2003,"10.1007/s00382-003-0310-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038170025&doi=10.1007%2fs00382-003-0310-z&partnerID=40&md5=2565fdb9efcd7a994721c5a932479a33","A comparison is performed for water vapour, cloud, albedo and lapse rate feedbacks taken from published results of 'offline' feedback calculations for general circulation models (GCMs) with mixed layer oceans performing 2 × CO2 and solar perturbation experiments. All feedbacks show substantial inter-model spread. The impact of uncertainties in feedbacks on climate sensitivity is discussed. A negative correlation is found between water vapour and lapse rate feedbacks, and also between longwave and shortwave components of the cloud feedback. The mean values of the feedbacks are compared with results derived from model intercomparisons which evaluated cloud forcing derived feedbacks under idealized climate forcing. Results are found to be comparable between the two approaches, after allowing for differences in experimental technique and diagnostic method. Recommendations are made for the future reporting of climate feedbacks."
"7004325649;7004286811;7201826462;6701859365;34770543000;6603685334;54680987900;7006783796;56114842800;7403531523;7404150761;7005070958;7102290666;6701712843;7103271625;7005516084;35468686100;7406228987;13406672500;7202208382;7003899619;7201914101;","Clouds and the earth's radiant energy system (CERES): Algorithm overview",1998,"10.1109/36.701020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032120049&doi=10.1109%2f36.701020&partnerID=40&md5=0831cfefdcc809d7dffd1f55d6309aec","The Clouds and the Earth's Radiant Energy System (CERES) is part of NASA's Earth Observing System (EOS). CERES objectives include the following. 1) For climate change analysis, provide a continuation of the Earth Radiation Budget Experiment (ERBE) record of radiative fluxes at the top-of-the-atmosphere (TOA), analyzed using the same techniques as the existing ERBE data. 2) Double the accuracy of estimates of radiative fluxes at TOA and the earth's surface; 3) Provide the first long-term global estimates of the radiative fluxes within the earth's atmosphere. 4) Provide cloud property estimates collocated in space and time that are consistent with the radiative fluxes from surface to TOA. In order to accomplish these goals, CERES uses data from a combination of spaceborne instruments: CERES scanners, which are an improved version of the ERBE broadband radiometers, and collocated cloud spectral irnager data on the same spacecraft. The CERES cloud and radiative flux data products should prove extremely useful in advancing the understanding of cloud-radiation interactions, particularly cloud feedback effects on the earth's radiation balance. For this reason, the CERES data should be fundamental to our ability to understand, detect, and predict global climate change. CERES results should also be very useful for studying regional climate changes associated with deforestation, desertification, anthropogenic aerosols, and El Nino/Southern Oscillation events. This overview summarizes the Release 2 version of the planned CERES data products and data analysis algorithms. These algorithms are a prototype for the system that will produce the scientific data required for studying the role of clouds and radiation in the earth's climate system. This release will produce a data processing system designed to analyze the first CERES data, planned for launch on Tropical Rainfall Measuring Mission (TRMM) in November 1997, followed by the EOS morning (EOSAMI) platform in 1998. © 1998 IEEE."
"57203049177;7201485519;","Tropospheric adjustment induces a cloud component in CO2 forcing",2008,"10.1175/2007JCLI1834.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40849113474&doi=10.1175%2f2007JCLI1834.1&partnerID=40&md5=ae752ef3dd0e6f4e046ddf9428cf6ede","The radiative forcing of CO2 and the climate feedback parameter are evaluated in several climate models with slab oceans by regressing the annual-mean global-mean top-of-atmosphere radiative flux against the annual-mean global-mean surface air temperature change ΔT following a doubling of atmospheric CO2 concentration. The method indicates that in many models there is a significant rapid tropospheric adjustment to CO2 leading to changes in cloud. and reducing the effective radiative forcing, in a way analogous to the indirect and semidirect effects of aerosol. By contrast, in most models the cloud feedback is small, defined as the part of the change that evolves with ΔT. Comparison with forcing evaluated by fixing sea surface conditions gives qualitatively similar results for the cloud components of forcing, both globally and locally. Tropospheric adjustment to CO2 may be responsible for some of the model spread in equilibrium climate sensitivity and could affect time-dependent climate projections."
"7005513582;7004890337;","The Community Climate System Model, version 2",2004,"10.1175/1520-0442(2004)017<3666:TCCSMV>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4544377258&doi=10.1175%2f1520-0442%282004%29017%3c3666%3aTCCSMV%3e2.0.CO%3b2&partnerID=40&md5=a74576d4d0c28d7adde69a835ab21e28","The Community Climate System Model, version 2 (CCSM2) is briefly described. A 1000-yr control simulation of the present day climate has been completed without flux adjustments. Minor modifications were made at year 350, which included all five components using the same physical constants. There are very small trends in the upper-ocean, sea ice, atmosphere, and land fields after year 150 of the control simulation. The deep ocean has small but significant trends; however, these are not large enough that the control simulation could not be continued much further. The equilibrium climate sensitivity of CCSM2 is 2.2 K, which is slightly larger than the Climate System Model, version 1 (CSM1) value of 2.0 K. Several aspects of the control simulation's mean climate and interannual variability are described, and good and bad properties of the control simulation are documented. In particular, several aspects of the simulation, especially in the Arctic region, are much improved over those obtained in CSM1. Other aspects, such as the tropical Pacific region simulation, have not been improved much compared to those in CSM1. Priorities for further model development are discussed in the conclusions section. © 2004 American Meteorological Society."
"7006518289;7005965757;7004222705;56520921400;6701508272;7202699757;7402207328;55259660400;9845516300;6701581880;","Climate change projections for the twenty-first century and climate change commitment in the CCSM3",2006,"10.1175/JCLI3746.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645214285&doi=10.1175%2fJCLI3746.1&partnerID=40&md5=b2665c6bac2c5facc2d4cac63dd636e2","Climate change scenario simulations with the Community Climate System Model version 3 (CCSM3), a global coupled climate model, show that if concentrations of all greenhouse gases (GHGs) could have been stabilized at the year 2000, the climate system would already be committed to 0.4°C more warming by the end of the twenty-first century. Committed sea level rise by 2100 is about an order of magnitude more, percentage-wise, compared to sea level rise simulated in the twentieth century. This increase in the model is produced only by thermal expansion of seawater, and does not take into account melt from ice sheets and glaciers, which could at least double that number. Several tenths of a degree of additional warming occurs in the model for the next 200 yr in the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) B1 and A1B scenarios after stabilization in the year 2100, but with twice as much sea level rise after 100 yr, and doubling yet again in the next 100 yr to 2300. At the end of the twenty-first century, the warming in the tropical Pacific for the A2, A1B, and B1 scenarios resembles an El Niño-like response, likely due to cloud feedbacks in the model as shown in an earlier version. Greatest warming occurs at high northern latitudes and over continents. The monsoon regimes intensify somewhat in the future warmer climate, with decreases of sea level pressure at high latitudes and increases in the subtropics and parts of the midlatitudes. There is a weak summer midlatitude soil moisture drying in this model as documented in previous models. Sea ice distributions in both hemispheres are somewhat over-extensive, but with about the right ice thickness at the end of the twentieth century. Future decreases in sea ice with global warming are proportional to the temperature response from the forcing scenarios, with the high forcing scenario, A2, producing an ice-free Arctic in summer by the year 2100. © 2006 American Meteorological Society."
"55544443300;15026371500;7005808242;","The tropical response to extratropical thermal forcing in an idealized GCM: The importance of radiative feedbacks and convective parameterization",2009,"10.1175/2009JAS2924.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73549113106&doi=10.1175%2f2009JAS2924.1&partnerID=40&md5=efa56971492d0665a91d1262beb84fc3","The response of tropical precipitation to extratropical thermal forcing is reexamined using an idealized moist atmospheric GCM that has no water vapor or cloud feedbacks, simplifying the analysis while retaining the aquaplanet configuration coupled to a slab ocean from the authors' previous study. As in earlier studies, tropical precipitation in response to high-latitude forcing is skewed toward the warmed hemisphere. Comparisons with a comprehensive GCM in an identical aquaplanet, mixed-layer framework reveal that the tropical responses tend to be much larger in the comprehensive GCM as a result of positive cloud and water vapor feedbacks that amplify the imposed extratropical thermal forcing. The magnitude of the tropical precipitation response in the idealized model is sensitive to convection scheme parameters. This sensitivity as well as the tropical precipitation response can be understood from a simple theory with two ingredients: the changes in poleward energy fluxes are predicted using a onedimensional energy balance model and a measure of the ""total gross moist stability"" [δm, which is defined as the total (mean plus eddy) atmospheric energy transport per unit mass transport] of the model tropics converts the energy flux change into a mass flux and a moisture flux change. The idealized model produces a low level of compensation of about 25% between the imposed oceanic flux and the resulting response in the atmospheric energy transport in the tropics regardless of the convection scheme parameter. Because Geophysical Fluid Dynamics Laboratory Atmospheric Model 2 (AM2) with prescribed clouds and water vapor exhibits a similarly low level of compensation, it is argued that roughly 25% of the compensation is dynamically controlled through eddy energy fluxes. The sensitivity of the tropical response to the convection scheme in the idealized model results from different values of δm: smaller δm leads to larger tropical precipitation changes for the same response in the energy transport. © 2009 American Meteorological Society."
"6701455548;7005513582;7201520140;","Using the radiative kernel technique to calculate climate feedbacks in NCAR's Community Atmospheric Model",2008,"10.1175/2007JCLI2044.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45349091207&doi=10.1175%2f2007JCLI2044.1&partnerID=40&md5=a7f338048abede99cfa5048eb5ca5475","Climate models differ in their responses to imposed forcings, such as increased greenhouse gas concentrations, due to different climate feedback strengths. Feedbacks in NCAR's Community Atmospheric Model (CAM) are separated into two components: the change in climate components in response to an imposed forcing and the ""radiative kernel,"" the effect that climate changes have on the top-of-the-atmosphere (TOA) radiative budget. This technique's usefulness depends on the linearity of the feedback processes. For the case of CO2 doubling, the sum of the effects of water vapor, temperature, and surface albedo changes on the TOA clear-sky flux is similar to the clear-sky flux changes directly calculated by CAM. When monthly averages are used rather than values from every time step. the global-average TOA shortwave change is underestimated by a quarter, partially as a result of intramonth correlations of surface albedo with the radiative kernel. The TOA longwave flux changes do not depend on the averaging period. The longwave zonal averages are within 10% of the model-calculated values, while the global average differs by only 2%. Cloud radiative forcing (ΔCRF) is often used as a diagnostic of cloud feedback strength. The net effect of the water vapor, temperature, and surface albedo changes on ΔCRF is -1.6 W m-2 , based on the kernel technique, While the total ΔCRF from CAM is -1.3 W m-2, indicating these components contribute significantly to ΔCRF and make it more negative. Assuming linearity of the ΔCRF contributions, these results indicate that the net cloud feedback in CAM is positive. © 2008 American Meteorological Society."
"38863214100;16309079300;6507224579;","Stabilizing cloud feedback dramatically expands the habitable zone of tidally locked planets",2013,"10.1088/2041-8205/771/2/L45","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879671188&doi=10.1088%2f2041-8205%2f771%2f2%2fL45&partnerID=40&md5=c0575f8a27381d0ec386a61e76ebdeea","The habitable zone (HZ) is the circumstellar region where a planet can sustain surface liquid water. Searching for terrestrial planets in the HZ of nearby stars is the stated goal of ongoing and planned extrasolar planet surveys. Previous estimates of the inner edge of the HZ were based on one-dimensional radiative-convective models. The most serious limitation of these models is the inability to predict cloud behavior. Here we use global climate models with sophisticated cloud schemes to show that due to a stabilizing cloud feedback, tidally locked planets can be habitable at twice the stellar flux found by previous studies. This dramatically expands the HZ and roughly doubles the frequency of habitable planets orbiting red dwarf stars. At high stellar flux, strong convection produces thick water clouds near the substellar location that greatly increase the planetary albedo and reduce surface temperatures. Higher insolation produces stronger substellar convection and therefore higher albedo, making this phenomenon a stabilizing climate feedback. Substellar clouds also effectively block outgoing radiation from the surface, reducing or even completely reversing the thermal emission contrast between dayside and nightside. The presence of substellar water clouds and the resulting clement surface conditions will therefore be detectable with the James Webb Space Telescope. © 2013. The American Astronomical Society. All rights reserved.."
"7006518289;7005965757;6701508272;7202699757;55259660400;57206487279;23486332900;7102976560;15724543600;6701581880;56330348400;","Climate system response to external forcings and climate change projections in CCSM4",2012,"10.1175/JCLI-D-11-00240.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859364881&doi=10.1175%2fJCLI-D-11-00240.1&partnerID=40&md5=d607e1860cbec8412ab88816df819dc4","Results are presented from experiments performed with the Community Climate System Model, version 4 (CCSM4) for the Coupled Model Intercomparison Project phase 5 (CMIP5). These include multiple ensemble members of twentieth-century climate with anthropogenic and natural forcings as well as single-forcing runs, sensitivity experiments with sulfate aerosol forcing, twenty-first-century representative concentration pathway (RCP) mitigation scenarios, and extensions for those scenarios beyond 2100-2300. Equilibrium climate sensitivity of CCSM4 is 3.20°C, and the transient climate response is 1.73°C. Global surface temperatures averaged for the last 20 years of the twenty-first century compared to the 1986-2005 reference period for sixmember ensembles from CCSM4 are +0.85°, +1.64°, +2.09°, and +3.53°C for RCP2.6, RCP4.5, RCP6.0, and RCP8.5, respectively. The ocean meridional overturning circulation (MOC) in the Atlantic, which weakens during the twentieth century in the model, nearly recovers to early twentieth-century values in RCP2.6, partially recovers in RCP4.5 and RCP6, and does not recover by 2100 in RCP8.5. Heat wave intensity is projected to increase almost everywhere in CCSM4 in a future warmer climate, with the magnitude of the increase proportional to the forcing. Precipitation intensity is also projected to increase, with dry days increasing in most subtropical areas. For future climate, there is almost no summer sea ice left in the Arctic in the high RCP8.5 scenario by 2100, but in the low RCP2.6 scenario there is substantial sea ice remaining in summer at the end of the century. © 2012 American Meteorological Society."
"13406672500;7004303501;7005070958;7404334532;7003927831;7202988622;7006399110;7004832016;7004696542;13102593000;7202496599;","Climate‐chemical interactions and effects of changing atmospheric trace gases",1987,"10.1029/RG025i007p01441","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0023480782&doi=10.1029%2fRG025i007p01441&partnerID=40&md5=cc136f33e770d709341f3b9d3f73a101","The problem concerning the greenhouse effects of human activities has broadened in scope from the CO2‐climate problem to the trace gas‐climate problem. The climate effects of non‐CO2 trace gases are strongly governed by interactions between chemistry, radiation, and dynamics. We discuss in detail the nature of the trace gas radiative heating and describe the importance of radiative‐chemical interactions within the troposphere and the stratosphere. We make an assessment of the trace gas effects on troposphere‐stratosphere temperature trends for the period covering the preindustrial era to the present and for the next several decades. Non‐CO2 greenhouse gases in the atmosphere are now adding to the greenhouse effect by an amount comparable to the effect of CO2. The rate of decadal increase of the total greenhouse forcing is now 3–6 times greater than the mean rate for the period 1850–1960, Time‐dependent calculations with a simplified one‐dimensional diffusive ocean model suggest that a surface warming about 0.4–0.8 K should have occurred during 1850 to 1980. For the various trace gas scenarios considered in this study, the equilibrium surface warming for the period 1980 to 2030 ranges from 0.8 to 4.1 K. This wide range in the projected warming is due to the range in the assumed scenario as well as due to the threefold uncertainty in the sensitivity of climate models. For the 180‐year period from 1850 to 2030, our analysis suggests a trace gas‐induced cumulative equilibrium surface warming in the range of 1.5 to 6.1 K. The important non‐CO2 greenhouse gases are CFCl3, CF2Cl2, CH4, N2O, O3, and stratospheric H2O. Chlorofluorocarbons (CFCs) (mainly CFCl3 and CF2Cl2), through their indirect chemical effects on O3, have a potentially large stratospheric cooling effect, as large as that due to a CO2 increase. In addition to the direct radiative effect, many of the trace gases have indirect effects on climate. For example, addition of gases such as CH4, CO, and NOx can alter tropospheric O3, which is a radiatively active gas. Within the troposphere the indirect climate effects can be as large as the direct effects. On the other hand, within the stratosphere, temperature changes are largely determined by indirect effects of CFCs. Trace gases can also influence stratospheric H2O through their effect on tropical tropopause temperatures. Furthermore, increases in tropospheric H2O, through the temperature‐H2O feedback, can perturb tropospheric chemistry and alter the concentration of CH4 and O3. The fundamental issue that needs to be addressed within the context of the trace gas‐climate problem is the relative importance of transport, chemistry, and the indirect effects of trace gases in governing the long‐term trends of tropospheric and stratospheric O3, CH4, and stratospheric H2O. Cloud feedback continues to be the major source of uncertainty in the surface temperature sensitivity of climate models. At present, the sign of this feedback is not known. The ocean sequesters the trace gas radiative heating into its interior and thus delays the equilibrium warming. The estimated e‐folding time for the approach to equilibrium varies from a few decades to a century and depends nonlinearly on λ−1 and linearly on κ where λ is the climate feedback parameter and κ is the effective ocean thermal diffusivity. The magnitude of λ, which also governs the equilibrium surface warming, is governed strongly by radiative and dynamical processes in the atmosphere, and hence the effect of oceans on transient climate change is determined by the interactions between atmospheric and oceanic dynamical as well as radiative processes. The next crucial issue concerns accurate determination of decadal trends in radiative forcings, trace gases, planetary albedo (to determine effects of aerosols and cloud feedback), and surface‐troposphere‐stratosphere temperatures. The observational challenges are formidable and must be overcome for a scientifically credible interpretation of the human impacts on climate. Copyright 1987 by the American Geophysical Union."
"55339081600;35509639400;7004714030;6603925960;","The too few, too bright tropical low-cloud problem in CMIP5 models",2012,"10.1029/2012GL053421","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868620896&doi=10.1029%2f2012GL053421&partnerID=40&md5=10ec9b4b3b42a49aeb0d3ef417ccbedb","Previous generations of climate models have been shown to under-estimate the occurrence of tropical low-level clouds and to over-estimate their radiative effects. This study analyzes outputs from multiple climate models participating in the Fifth phase of the Coupled Model Intercomparison Project (CMIP5) using the Cloud Feedback Model Intercomparison Project Observations Simulator Package (COSP), and compares them with different satellite data sets. Those include CALIPSO lidar observations, PARASOL mono-directional reflectances and CERES radiative fluxes at the top of the atmosphere. We show that current state-of-the-art climate models predict overly bright low-clouds, even for a correct low-cloud cover. The impact of these biases on the Earth' radiation budget, however, is reduced by compensating errors. Those include the tendency of models to under-estimate the low-cloud cover and to over-estimate the occurrence of mid-and high-clouds above low-clouds. Finally, we show that models poorly represent the dependence of the vertical structure of low-clouds on large-scale environmental conditions. The implications of this too few, too bright low-cloud problem for climate sensitivity and model development are discussed. © 2012. American Geophysical Union. All Rights Reserved."
"7003543851;7003922138;6701618837;","On the use of cloud forcing to estimate cloud feedback",2004,"10.1175/1520-0442(2004)017<3661:OTUOCF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-6044251401&doi=10.1175%2f1520-0442%282004%29017%3c3661%3aOTUOCF%3e2.0.CO%3b2&partnerID=40&md5=357a27656c1d07c486ee737b840e4067","Uncertainty in cloud feedback is the leading cause of discrepancy in model predictions of climate change. The use of observed or model-simulated radiative fluxes to diagnose the effect of clouds on climate sensitivity requires an accurate understanding of the distinction between a change in cloud radiative forcing and a cloud feedback. This study compares simulations from different versions of the GFDL Atmospheric Model 2 (AM2) that have widely varying strengths of cloud feedback to illustrate the differences between the two and highlight the potential for changes in cloud radiative forcing to be misinterpreted. © 2004 American Meteorological Society."
"57203030873;55338676800;7402064802;52464731300;8866821900;57205867148;25031430500;7102645933;7401974644;7101959253;7005626683;","Exposing global cloud biases in the Community Atmosphere Model (CAM) using satellite observations and their corresponding instrument simulators",2012,"10.1175/JCLI-D-11-00469.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859950845&doi=10.1175%2fJCLI-D-11-00469.1&partnerID=40&md5=4006f69b6d5d824f9b350e99368defb0","Satellite observations and their corresponding instrument simulators are used to document global cloud biases in the Community Atmosphere Model (CAM) versions 4 and 5. The model-observation comparisons show that, despite having nearly identical cloud radiative forcing, CAM5 has a much more realistic representation of cloud properties than CAM4. In particular, CAM5 exhibits substantial improvement in three long-standing climate model cloud biases: 1) the underestimation of total cloud, 2) the overestimation of optically thick cloud, and 3) the underestimation of midlevel cloud. While the increased total cloud and decreased optically thick cloud in CAM5 result from improved physical process representation, the increased midlevel cloud in CAM5 results from the addition of radiatively active snow. Despite these improvements, both CAM versions have cloud deficiencies. Of particular concern, both models exhibit large but differing biases in the subtropical marine boundary layer cloud regimes that are known to explain intermodel differences in cloud feedbacks and climate sensitivity. More generally, this study demonstrates that simulatorfacilitated evaluation of cloud properties, such as amount by vertical level and optical depth, can robustly expose large and at times radiatively compensating climate model cloud biases. © 2012 American Meteorological Society."
"7006518289;7005965757;6701508272;7202699757;55259660400;57203030873;25031430500;7402207328;23486332900;6701581880;","Climate change projections in CESM1(CAM5) compared to CCSM4",2013,"10.1175/JCLI-D-12-00572.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883150442&doi=10.1175%2fJCLI-D-12-00572.1&partnerID=40&md5=a2d85924dd7d28b2a15322a7ecaf72cc","Future climate change projections for phase 5 of the Coupled Model Intercomparison Project (CMIP5) are presented for the Community Earth System Model version 1 that includes the Community Atmospheric Model version 5 [CESM1(CAM5)]. These results are compared to the Community Climate System Model, version 4 (CCSM4) and include simulations using the representative concentration pathway (RCP) mitigation scenarios, and extensions for those scenarios beyond 2100 to 2300. Equilibrium climate sensitivity of CESM1 (CAM5) is 4.108C, which is higher than the CCSM4 value of 3.208C. The transient climate response is 2.338C, compared to the CCSM4 value of 1.738C. Thus, even though CESM1(CAM5) includes both the direct and indirect effects of aerosols (CCSM4 had only the direct effect), the overall climate system response including forcing and feedbacks is greater in CESM1(CAM5) compared to CCSM4. The Atlantic Ocean meridional overturning circulation (AMOC) in CESM1(CAM5) weakens considerably in the twenty-first century in all the RCP scenarios, and recovers more slowly in the lower forcing scenarios. The total aerosol optical depth (AOD) changes from ;0.12 in 2006 to ;0.10 in 2100, compared to a preindustrial 1850 value of 0.08, so there is less negative forcing (a net positive forcing) from that source during the twenty-first century. Consequently, the change from 2006 to 2100 in aerosol direct forcing in CESM1(CAM5) contributes to greater twenty-first century warming relative to CCSM4. There is greater Arctic warming and sea ice loss in CESM1(CAM5), with an ice-free summer Arctic occurring by about 2060 in RCP8.5 (2040s in September) as opposed to about 2100 in CCSM4 (2060s in September). © 2013 American Meteorological Society."
"7004764167;7406514318;","The time-dependence of climate sensitivity",2000,"10.1029/2000GL011373","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034352606&doi=10.1029%2f2000GL011373&partnerID=40&md5=34f71f376e48e9657903301af6543e5f","A doubled CO<inf>2</inf> coupled ocean-atmosphere experiment has been run for over 800 years. The 'effective' equilibrium climate sensitivity to a doubling of CO<inf>2</inf> (the equilibrium response of the model assuming the feedbacks remained constant at the value found at any given point of the transient response) is calculated throughout the run and found to increase by around 40%. The time-dependence is associated with differences in cloud feedback arising from inter-hemispheric temperature differences due to the slower warming rate of the Southern Ocean. The time-dependence of the climate response has implications for the use of simpler models in scaling GCM results to different scenarios of forcing."
"7102010848;7402803216;7406500188;55917306900;8871497700;26643041500;57131535300;56500974300;9846154100;55917847100;8438057200;56997768500;22942638300;35461255500;","Intense atmospheric pollution modifies weather: A case of mixed biomass burning with fossil fuel combustion pollution in eastern China",2013,"10.5194/acp-13-10545-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887055645&doi=10.5194%2facp-13-10545-2013&partnerID=40&md5=1138845fe34e3c2f371581c865f9ed9c","The influence of air pollutants, especially aerosols, on regional and global climate has been widely investigated, but only a very limited number of studies report their impacts on everyday weather. In this work, we present for the first time direct (observational) evidence of a clear effect of how a mixed atmospheric pollution changes the weather with a substantial modification in the air temperature and rainfall. By using comprehensive measurements in Nanjing, China, we found that mixed agricultural burning plumes with fossil fuel combustion pollution resulted in a decrease in the solar radiation intensity by more than 70 %, a decrease in the sensible heat by more than 85 %, a temperature drop by almost 10 K, and a change in rainfall during both daytime and nighttime. Our results show clear air pollution-weather interactions, and quantify how air pollution affects weather via air pollution-boundary layer dynamics and aerosol-radiation-cloud feedbacks. This study highlights cross-disciplinary needs to investigate the environmental, weather and climate impacts of the mixed biomass burning and fossil fuel combustion sources in East China. © Author(s) 2013. CC Attribution 3.0 License."
"7005890514;51360903200;","Climate sensitivity and response",2003,"10.1007/s00382-002-0283-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037302663&doi=10.1007%2fs00382-002-0283-3&partnerID=40&md5=6cd9bbd3c77babb229d377efdb1f4bd8","Results from climate change simulations indicate a reasonably robust proportionality between global mean radiative forcing and global mean surface air temperature response. The ""constant"" of proportionality is a measure of the overall strength of climate feedback processes and hence of global climate sensitivity. Geographically, however, temperature response patterns are generally not proportional to, nor do they resemble, their parent forcing patterns. Temperature response patterns, nevertheless, exhibit a remarkable additivity whereby the sum of response patterns for different forcings closely resembles the response pattern for the sum of the forcings. The geographical distribution of contributions to the climate sensitivity/feedback are obtained diagnostically from simulations with the Canadian Centre for Climate Modelling and Analysis (CCCma) coupled global climate model (GCM). There is positive feedback over high-latitude oceans, over northern land areas, and over the equatorial Pacific. The remaining regions over oceans and tropical land areas exhibit negative feedback. The feedback results are decomposed into components associated with short-and longwave radiative processes and in terms of cloud-free atmosphere/surface and cloud feedbacks. While the geographic pattern of the feedbacks may generally be linked to local processes, all feedback processes display regions of both positive and negative values (except for the solar atmosphere/surface feedback associated with the retreat of ice and snow which is positive) and all vary from place to place so that there is no simple physical picture that operates everywhere. The stable geographical pattern of the feedback is a consequence of the balance between local physical processes rather than the dominance of a particular process. The feedback results indicate that, to first order, temperature response patterns are determined by the geographical pattern of local feedback processes. The feedback processes act to localize forcing changes and to generate temperature response patterns which depend firstly on the pattern of feedbacks and only secondarily on the pattern of the forcing. The geographical distribution of feedback processes can be regarded as a feature of the climate model (and by inference of the climate system) and not (or only comparatively weak) functions of forcing and climate state. An illustrative model is able to reproduce qualitatively the kinds of forcing/temperature response behavior seen in the CCCma GCM including the quasi-independence of forcing and response patterns, the additivity of temperature response patterns, and the resulting ""nonconstancy"" of the global climate sensitivity."
"7202899330;26031402600;","Controls of global-mean precipitation increases in global warming GCM experiments",2008,"10.1175/2008JCLI2144.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60749094247&doi=10.1175%2f2008JCLI2144.1&partnerID=40&md5=8fea54b5a13e99b84dabb7d1d7ad31ae","This paper examines the controls on global precipitation that are evident in the transient experiments conducted using coupled climate models collected for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). The change in precipitation, water vapor clouds, and radiative heating of the atmosphere evident in the 1% increase in carbon dioxide until doubled (1pctto2x) scenario is examined. As noted in other studies, the ensemble-mean changes in water vapor as carbon dioxide is doubled occur at a rate similar to that predicted by the Clausius - Clapeyron relationship. The ratio of global changes in precipitation to global changes in water vapor offers some insight on how readily increased water vapor is converted into precipitation in modeled climate change. This ratio ε is introduced in this paper as, a gross indicator of the global precipitation efficiency under global warming. The main findings of this paper are threefold. First, increases in the global precipitation track increase atmospheric radiative energy loss and the ratio of precipitation sensitivity to water vapor sensitivity is primarily determined by changes to this atmospheric column energy loss. A reference limit to this ratio is introduced as the rate at which the emission of radiation from the clear-sky atmosphere increases as water vapor increases. It is shown that the derived efficiency based on the simple ratio of precipitation to water vapor sensitivities of models in fact closely matches the sensitivity derived from simple energy balance arguments involving changes to water vapor emission alone. Second, although the rate of increase of clear-sky emission is the dominant factor in the change to the energy balance of the atmosphere, there are two important and offsetting processes that contribute to ε in the model simulations studied: One involves a negative feedback through cloud radiative heating that acts to reduce the efficiency; the other is the global reduction in sensible heating that counteracts the effects of the cloud feedback and increases the efficiency. These counteracting feedbacks only apply on the global scale. Third, the negative cloud radiative heating feedback occurs through reductions of cloud amount in the middle troposphere, defined as the layer between 680 and 440 hPa, and by slight global cloud decreases in the lower troposphere. These changes act, in a manner to expose the warmer atmosphere below to high clouds, thus resulting in a net warming of the atmospheric column by clouds and a negative feedback on the precipitation. © 2008 American Meteorological Society."
"26645289600;7402064802;57210518852;24329376600;7201485519;57203049177;35547807400;","Contributions of different cloud types to feedbacks and rapid adjustments in CMIP5",2013,"10.1175/JCLI-D-12-00555.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879994254&doi=10.1175%2fJCLI-D-12-00555.1&partnerID=40&md5=6dffacc57679602073af10c7645bcba2","Using five climate model simulations of the response to an abrupt quadrupling of CO2, the authors perform the first simultaneous model intercomparison of cloud feedbacks and rapid radiative adjustments with cloud masking effects removed, partitioned among changes in cloud types and gross cloud properties. Upon CO2 quadrupling, clouds exhibit a rapid reduction in fractional coverage, cloud-top pressure, and optical depth, with each contributing equally to a 1.1 W m22 net cloud radiative adjustment, primarily from shortwave radiation. Rapid reductions in midlevel clouds and optically thick clouds are important in reducing planetary albedo in every model. As the planet warms, clouds become fewer, higher, and thicker, and global mean net cloud feedback is positive in all but onemodel and results primarily fromincreased trapping of longwave radiation. As was true for earliermodels, high cloud changes are the largest contributor to intermodel spread in longwave and shortwave cloud feedbacks, but low cloud changes are the largest contributor to the mean and spread in net cloud feedback. The importance of the negative optical depth feedback relative to the amount feedback at high latitudes is even more marked than in earlier models. The authors show that the negative longwave cloud adjustment inferred in previous studies is primarily caused by a 1.3 W m22 cloud masking of CO2 forcing. Properly accounting for cloudmasking increases net cloud feedback by 0.3 W m22 K21,whereas accounting for rapid adjustments reduces by 0.14 W m22 K21 the ensemble mean net cloud feedback through a combination of smaller positive cloud amount and altitude feedbacks and larger negative optical depth feedbacks. ©2013 American Meteorological Society."
"7003802133;55763471100;7005808242;","Importance of Ocean Heat Uptake Efficacy to Transient Climate Change",2010,"10.1175/2009JCLI3139.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953699667&doi=10.1175%2f2009JCLI3139.1&partnerID=40&md5=5339b9cd63c413815bd45ba99994a1bb","This article proposes a modification to the standard forcing-feedback diagnostic energy balance model to account for 1) differences between effective and equilibrium climate sensitivities and 2) the variation of effective sensitivity over time in climate change experiments with coupled atmosphere-ocean climate models. In the spirit of Hansen et al. an efficacy factor is applied to the ocean heat uptake. Comparing the time evolution of the surface warming in high and low efficacy models demonstrates the role of this efficacy in the transient response to CO2 forcing. Abrupt CO2 increase experiments show that the large efficacy of the Geophysical Fluid Dynamics Laboratory's Climate Model version 2.1 (CM2.1) sets up in the first two decades following the increase in forcing. The use of an efficacy is necessary to fit this model's global mean temperature evolution in periods with both increasing and stable forcing. The intermodel correlation of transient climate response with ocean heat uptake efficacy is greater than its correlation with equilibrium climate sensitivity in an ensemble of climate models used for the third and fourth Intergovernmental Panel on Climate Change (IPCC) assessments. When computed at the time of doubling in the standard experiment with 1% yr-1 increase in CO2, the efficacy is variable amongst the models but is generally greater than 1, averages between 1.3 and 1.4, and is as large as 1.75 in several models. © 2010 American Meteorological Society."
"24329376600;57203049177;7201485519;","The dependence of radiative forcing and feedback on evolving patterns of surface temperature change in climate models",2015,"10.1175/JCLI-D-14-00545.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922774244&doi=10.1175%2fJCLI-D-14-00545.1&partnerID=40&md5=b91b98cac39ae8dd2637668ad0564bfc","Experiments with CO2 instantaneously quadrupled and then held constant are used to show that the relationship between the global-mean net heat input to the climate system and the global-mean surface air temperature change is nonlinear in phase 5 of the Coupled Model Intercomparison Project (CMIP5) atmosphere-ocean general circulation models (AOGCMs). The nonlinearity is shown to arise from a change in strength of climate feedbacks driven by an evolving pattern of surface warming. In 23 out of the 27 AOGCMs examined, the climate feedback parameter becomes significantly (95% confidence) less negative (i.e., the effective climate sensitivity increases) as time passes. Cloud feedback parameters show the largest changes. In the AOGCM mean, approximately 60% of the change in feedback parameter comes from the tropics (30°N-30°S). An important region involved is the tropical Pacific, where the surface warming intensifies in the east after a few decades. The dependence of climate feedbacks on an evolving pattern of surface warming is confirmed using the HadGEM2 and HadCM3 atmosphere GCMs (AGCMs). With monthly evolving sea surface temperatures and sea ice prescribed from its AOGCM counter part, each AGCM reproduces the timevarying feedbacks, but when a fixed pattern of warming is prescribed the radiative response is linear with global temperature change or nearly so. It is also demonstrated that the regression and fixed-SST methods for evaluating effective radiative forcing are in principle different, because rapid SST adjustment when CO2 is changed can produce a pattern of surface temperature change with zero global mean but nonzero change in net radiation at the top of the atmosphere (~-0.5W m-2 in HadCM3). © 2015 American Meteorological Society."
"57203049177;56726831200;9536987500;6602135031;","Quantifying carbon cycle feedbacks",2009,"10.1175/2009JCLI2949.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350006360&doi=10.1175%2f2009JCLI2949.1&partnerID=40&md5=d85e5c15118d2194e65c4c53db9bbcc4","Perturbations to the carbon cycle could constitute large feedbacks on future changes in atmospheric CO2 concentration and climate. This paper demonstrates how carbon cycle feedback can be expressed in formally similar ways to climate feedback, and thus compares their magnitudes. The carbon cycle gives rise to two climate feedback terms: the concentration-carbon feedback, resulting from the uptake of carbon by land and ocean as a biogeochemical response to the atmospheric CO2 concentration, and the climate-carbon feedback, resulting from the effect of climate change on carbon fluxes. In the earth system models of the Coupled Climate-Carbon Cycle Model Intercomparison Project (C4MIP), climate-carbon feedback on warming is positive and of a similar size to the cloud feedback. The concentration-carbon feedback is negative; it has generally received less attention in the literature, but in magnitude it is 4 times larger than the climate-carbon feedback and more uncertain. The concentration-carbon feedback is the dominant uncertainty in the allowable CO2 emissions that are consistent with a given CO2 concentration scenario. In modeling the climate response to a scenario of CO2 emissions, the net carbon cycle feedback is of comparable size and uncertainty to the noncarbon-climate response. To quantify simulated carbon cycle feedbacks satisfactorily, a radiatively coupled experiment is needed, in addition to the fully coupled and biogeochemically coupled experiments, which are referred to as coupled and uncoupled in C4MIP. The concentration-carbon and climate-carbon feedbacks do not combine linearly, and the concentration-carbon feedback is dependent on scenario and time. © 2009 American Meteorological Society."
"56627414400;","The radiative effects of clouds and their impact on climate",1991,"10.1175/1520-0477(1991)072<0795:TREOCA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026272729&doi=10.1175%2f1520-0477%281991%29072%3c0795%3aTREOCA%3e2.0.CO%3b2&partnerID=40&md5=493593b479607c7a4416adf7318aa1de","There is general agreement that the annual global mean effect of clouds is to cool the climate system, but there is significant diasgreement on magnitude, with the two investigations based on recent satellite data indicating a range from 17 to 27 W/m2. Cold sensitivity, which represents the differential response of top-of-the-atmosphere fluxes to changes in cloud cover parameters, is a critical factor in cloud feedback. Two estimates, of the sensitivity to cloud amount, show wide discrepancies. To be useful, future studies of sensitivity will have to separate different cloud types. Sensitivity of clouds to cloud condensation nuclei raises the issue of a more direct role of clouds in climate change, where aerosols associated with SO2 emissions can ultimately lead to brighter clouds and a reduction in solar heating. -from Author"
"26645289600;7402064802;7202145115;","Computing and partitioning cloud feedbacks using cloud property histograms. Part II: Attribution to changes in cloud amount, altitude, and optical depth",2012,"10.1175/JCLI-D-11-00249.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856973124&doi=10.1175%2fJCLI-D-11-00249.1&partnerID=40&md5=73b01742d011979dc04456ac6662e21c","Cloud radiative kernels and histograms of cloud fraction, both as functions of cloud-top pressure and optical depth, are used to quantify cloud amount, altitude, and optical depth feedbacks. The analysis is applied to doubled-CO 2 simulations from11 global climatemodels in the Cloud FeedbackModel Intercomparison Project. Global, annual, and ensemble mean longwave (LW) and shortwave (SW) cloud feedbacks are positive, with the latter nearly twice as large as the former. The robust increase in cloud-top altitude in both the tropics and extratropics is the dominant contributor to the positive LW cloud feedback. The negative impact of reductions in cloud amount offsets more than half of the positive impact of rising clouds onLWcloud feedback, but the magnitude of compensation varies considerably across the models. In contrast, robust reductions in cloud amount make a large and virtually unopposed positive contribution to SWcloud feedback, though the intermodel spread is greater than for any other individual feedback component. Overall reductions in cloud amount have twice as large an impact on SW fluxes as on LWfluxes, such that the net cloud amount feedback is moderately positive, with no models exhibiting a negative value. As a consequence of large but partially offsetting effects of cloud amount reductions onLWandSWfeedbacks, both the mean and intermodel spread in net cloud amount feedback are smaller than those of the net cloud altitude feedback. Finally, the study finds that the large negative cloud feedback at high latitudes results from robust increases in cloud optical depth, not from increases in total cloud amount as is commonly assumed. © 2012 American Meteorological Society."
"6602558284;6701455548;7004890337;57210350827;6602688130;36809017200;57202754759;7005513582;","Climate sensitivity of the community climate system model, version 4",2012,"10.1175/JCLI-D-11-00290.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859369064&doi=10.1175%2fJCLI-D-11-00290.1&partnerID=40&md5=972859d1f498a524cefeee2cef4e68e3","Equilibrium climate sensitivity of the Community Climate System Model, version 4 (CCSM4) is 3.20°C for 1° horizontal resolution in each component. This is about a half degree Celsius higher than in the previous version (CCSM3). The transient climate sensitivity of CCSM4 at 1° resolution is 1.72°C, which is about 0.2°C higher than in CCSM3. These higher climate sensitivities in CCSM4 cannot be explained by the change to a preindustrial baseline climate. This study uses the radiative kernel technique to show that, from CCSM3 to CCSM4, the global mean lapse-rate feedback declines in magnitude and the shortwave cloud feedback increases. These two warming effects are partially canceled by cooling because of slight decreases in the global mean water vapor feedback and longwave cloud feedback from CCSM3 to CCSM4. A new formulation of the mixed layer, slab-ocean model in CCSM4 attempts to reproduce the SST and sea ice climatology from an integration with a full-depth ocean, and it is integrated with a dynamic sea ice model. These new features allow an isolation of the influence of ocean dynamical changes on the climate response when comparing integrations with the slab ocean and full-depth ocean. The transient climate response of the full-depth ocean version is 0.54 of the equilibrium climate sensitivity when estimated with the new slab-ocean model version for both CCSM3 and CCSM4. The authors argue the ratio is the same in both versions because they have about the same zonal mean pattern of change in ocean surface heat flux, which broadly resembles the zonal mean pattern of net feedback strength. © 2012 American Meteorological Society."
"7202155374;7202257430;","Impacts on regional climate of Amazon deforestation",1992,"10.1029/92GL01905","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027036738&doi=10.1029%2f92GL01905&partnerID=40&md5=df65c8f6254492561ee44f082bb409a0","A simulation of the climate response to Amazon deforestation has been carried out. Precipitation is decreased on the average by 25% or 1.4 mm/day, with ET and runoff both decreasing by 0.7 mm/day. Modifications of surface energy balance through change of albedo and roughness are complicated by cloud feedbacks. The initial decrease of the absorption of solar radiation by higher surface albedos is largely cancelled by a reduction in cloud cover, but consequent reduction in downward longwave has a substantial impact on surface energy balance. Smoke aerosols might have an effect comparable to deforestation during burning season. Copyright 1992 by the American Geophysical Union."
"26645289600;7402064802;7202145115;","Computing and partitioning cloud feedbacks using cloud property histograms. Part I: Cloud radiative kernels",2012,"10.1175/JCLI-D-11-00248.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862735793&doi=10.1175%2fJCLI-D-11-00248.1&partnerID=40&md5=6a84290c37bf5624452b4335a41e92ca","This study proposes a novel technique for computing cloud feedbacks using histograms of cloud fraction as a joint function of cloud-top pressure (CTP) and optical depth (τ). These histograms were generated by the International Satellite Cloud Climatology Project (ISCCP) simulator that was incorporated into doubled-CO 2 simulations from 11 global climate models in the Cloud Feedback Model Intercomparison Project. The authors use a radiative transfer model to compute top of atmosphere flux sensitivities to cloud fraction perturbations in each bin of the histogram for each month and latitude. Multiplying these cloud radiative kernels with histograms of modeled cloud fraction changes at each grid point per unit of global warming produces an estimate of cloud feedback. Spatial structures and globally integrated cloud feedbacks computed in this manner agree remarkably well with the adjusted change in cloud radiative forcing. The global and annual mean model-simulated cloud feedback is dominated by contributions from medium thickness (3.6 &lt; τ ≤ 23) cloud changes, but thick (τ &gt; 23) cloud changes cause the rapid transition of cloud feedback values from positive in midlatitudes to negative poleward of 50°S and 70°N. High (CTP ≤ 440 hPa) cloud changes are the dominant contributor to longwave (LW) cloud feedback, but because their LW and shortwave (SW) impacts are in opposition, they contribute less to the net cloud feedback than do the positive contributions from low (CTP &gt; 680 hPa) cloud changes. Midlevel (440 &lt; CTP ≤ 680 hPa) cloud changes cause positive SW cloud feedbacks that are 80% as large as those due to low clouds. Finally, high cloud changes induce wider ranges of LW and SW cloud feedbacks across models than do low clouds. © 2012 American Meteorological Society."
"37032346000;35237545900;7202155374;","Radiative effects of aerosols on the evolution of the atmospheric boundary layer",2002,"10.1029/2001jd000754","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18144439596&doi=10.1029%2f2001jd000754&partnerID=40&md5=dba95c6042bad4fd511422f6657a6a96","This study investigates the impacts of tropospheric aerosols on the evolution of the atmospheric boundary layer (ABL) for dry subsiding regions by conducting simulations with a high-resolution ABL model. The scattering and absorption of aerosols diminish the surface radiation, inhibiting the sensible heat flux and evaporation and inducing feedbacks such as the enhanced stratification and change in relative humidity in the surface layer. The reduced sensible heat due to aerosol backscattering lowers the air temperature and suppresses the growth of the ABL. The resultant reduction of entrainment heating contributes to an additional cooling. The decreased entrainment drying competes with the reduced surface evaporation, so that the net effect can be either an increase or a decrease of the ABL moisture, depending on the soil moisture. Aerosol absorption decreases the turbulent heating but simultaneously increases the solar heating, increasing the air temperature and decreasing the strength of capping inversion. The resultant rise of the top of the ABL compensates the lowering due to the reduced buoyancy flux. With strong aerosol absorption, the increased entrainment heating enhances the ABL warming. Both the increased entrainment drying and the reduced evaporation decrease the ABL moisture. The increased warmth and dryness of the ABL imply that absorbing aerosols within the ABL decrease the probability of formation of boundary layer clouds, causing additional warming through cloud-feedbacks. The results are sensitive to the vertical distribution of absorbing aerosols. Absorbing aerosol above the ABL increases the strength of capping inversion and reduces the top of the ABL, hence decreasing the entrainment drying and moistening the ABL. Copyright 2002 by the American Geophysical Union."
"26645289600;7202145115;","Why is longwave cloud feedback positive?",2010,"10.1029/2010JD013817","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956338119&doi=10.1029%2f2010JD013817&partnerID=40&md5=48d03c48c64370fe655ffc47e3d67116","Longwave cloud feedback is systematically positive and nearly the same magnitude across all global climate models used in the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4). Here it is shown that this robust positive longwave cloud feedback is caused in large part by the tendency for tropical high clouds to rise in such a way as to remain at nearly the same temperature as the climate warms. Furthermore, it is shown that such a cloud response to a warming climate is consistent with well-known physics, specifically the requirement that, in equilibrium, tropospheric heating by convection can only be large in the altitude range where radiative cooling is efficient, following the fixed anvil temperature hypothesis of Hartmann and Larson (2002). Longwave cloud feedback computed assuming that high-cloud temperature follows upper tropospheric convergence-weighted temperature, which we refer to as proportionately higher anvil temperature, gives an excellent prediction of the longwave cloud feedback in the AR4 models. The ensemble-mean feedback of 0.5 W m-2 K-1 is much larger than that calculated assuming clouds remain at fixed pressure, highlighting the large contribution from rising cloud tops to the robustly positive feedback. An important result of this study is that the convergence profile computed from clear-sky energy and mass balance warms slightly as the climate warms, in proportion to the increase in stability, which results in a longwave cloud feedback that is slightly smaller than that calculated assuming clouds remain at fixed temperature. Copyright 2010 by the American Geophysical Union."
"54982705800;7006304904;7006784145;55880185200;55879760100;7401895830;","Modeling of gas and aerosol with WRF/Chem over Europe: Evaluation and sensitivity study",2012,"10.1029/2011JD016302","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856962320&doi=10.1029%2f2011JD016302&partnerID=40&md5=63d7dcfd7dd8ee04834180738cee2193","The ""online"" meteorological and chemical transport Weather Research and Forecasting/Chemistry (WRF/Chem) model has been implemented over a European domain, run without aerosol-cloud feedbacks for the year 2007, and validated against ground-based observations. To this end, we integrated the European Monitoring and Evaluation Programme (EMEP) anthropogenic emission inventory into the model pre-processor. The simulated average temperature shows a very small negative bias, the relative humidity and the wind speed are overpredicted by 1.5% (8%) and 1.0m/s (76%), respectively. Hourly ozone (Oinf3/inf) exhibits a correlation with observations of 0.62 and daily maxima are underestimated by about 4%. A general ozone underestimation (overestimation) is found in spring (fall), probably related to misrepresentation of intercontinental transport with time-invariant boundary conditions. Daily nitrogen dioxide (NOinf2/inf) is reproduced within 15% with a correlation of 0.57. Daily PMinf2.5/inf aerosol mass shows mean bias of about -4.0 g/msup3/sup (-7.3%), mainly attributable to the carbonaceous fraction. The model underpredicts particulate sulphate by a factor of 2, and overpredicts ammonium and nitrate by about factor of 2. Possible reasons for this bias are investigated with sensitivity tests and revealed that the aqueous phase oxidation of sulphur dioxide (SOinf2/inf) by hydrogen peroxide (Hinf2/infOinf2/inf) and Oinf3/inf, missing in the configuration of WRF/Chem without aerosol-cloud feedbacks, explains the discrepancy. Copyright 2012 by the American Geophysical Union."
"8068419200;55660519500;35755764700;7202671706;8954866200;7801340314;54940625500;7003975505;55390548700;12759949700;56033135100;8559604100;","A model-data comparison for a multi-model ensemble of early Eocene atmosphere-ocean simulations: EoMIP",2012,"10.5194/cp-8-1717-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866086717&doi=10.5194%2fcp-8-1717-2012&partnerID=40&md5=f2e66b12860f8c618f80479eee7fb354","The early Eocene (~55 to 50 Ma) is a time period which has been explored in a large number of modelling and data studies. Here, using an ensemble of previously published model results, making up ""EoMIP"" - the Eocene Modelling Intercomparison Project - and syntheses of early Eocene terrestrial and sea surface temperature data, we present a self-consistent inter-model and model-data comparison. This shows that the previous modelling studies exhibit a very wide inter-model variability, but that at high CO2, there is good agreement between models and data for this period, particularly if possible seasonal biases in some of the proxies are considered. An energy balance analysis explores the reasons for the differences between the model results, and suggests that differences in surface albedo feedbacks, water vapour and lapse rate feedbacks, and prescribed aerosol loading are the dominant cause for the different results seen in the models, rather than inconsistencies in other prescribed boundary conditions or differences in cloud feedbacks. The CO 2 level which would give optimal early Eocene model-data agreement, based on those models which have carried out simulations with more than one CO2 level, is in the range of 2500 ppmv to 6500 ppmv. Given the spread of model results, tighter bounds on proxy estimates of atmospheric CO2 and temperature during this time period will allow a quantitative assessment of the skill of the models at simulating warm climates. If it is the case that a model which gives a good simulation of the Eocene will also give a good simulation of the future, then such an assessment could be used to produce metrics for weighting future climate predictions. © Author(s) 2012."
"7006518289;6701508272;57203406068;","A coupled air-sea response mechanism to solar forcing in the Pacific region",2008,"10.1175/2007JCLI1776.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-46449091082&doi=10.1175%2f2007JCLI1776.1&partnerID=40&md5=d863cf757de48f49a69b9bada3f2591d","The 11-yr solar cycle [decadal solar oscillation (DSO)] at its peaks strengthens the climatological precipitation maxima in the tropical Pacific during northern winter. Results from two global coupled climate model ensemble simulations of twentieth-century climate that include anthropogenic (greenhouse gases, ozone, and sulfate aerosols, as well as black carbon aerosols in one of the models) and natural (volcano and solar) forcings agree with observations in the Pacific region, though the amplitude of the response in the models is about half the magnitude of the observations. These models have poorly resolved stratospheres and no 11-yr ozone variations, so the mechanism depends almost entirely on the increased solar forcing at peaks in the DSO acting on the ocean surface in clear sky areas of the equatorial and subtropical Pacific. Mainly due to geometrical considerations and cloud feedbacks, this solar forcing can be nearly an order of magnitude greater in those regions than the globally averaged solar forcing. The mechanism involves the increased solar forcing at the surface being manifested by increased latent heat flux and evaporation. The resulting moisture is carried to the convergence zones by the trade winds, thereby strengthening the intertropical convergence zone (ITCZ) and the South Pacific convergence zone (SPCZ). Once these precipitation regimes begin to intensify, an amplifying set of coupled feedbacks similar to that in cold events (or La Niña events) occurs. There is a strengthening of the trades and greater upwelling of colder water that extends the equatorial cold tongue farther west and reduces precipitation across the equatorial Pacific, while increasing precipitation even more in the ITCZ and SPCZ. Experiments with the atmosphere component from one of the coupled models are performed in which heating anomalies similar to those observed during DSO peaks are specified in the tropical Pacific. The result is an anomalous Rossby wave response in the atmosphere and consequent positive sea level pressure (SLP) anomalies in the North Pacific extending to western North America. These patterns match features that occur during DSO peak years in observations and the coupled models. © 2008 American Meteorological Society."
"7201485519;56575686800;57203049177;","Origins of differences in climate sensitivity, forcing and feedback in climate models",2013,"10.1007/s00382-012-1336-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874816272&doi=10.1007%2fs00382-012-1336-x&partnerID=40&md5=778fe51acc32ac686c04fefbe2c42f82","We diagnose climate feedback parameters and CO2 forcing including rapid adjustment in twelve atmosphere/mixed-layer-ocean (""slab"") climate models from the CMIP3/CFMIP-1 project (the AR4 ensemble) and fifteen parameter-perturbed versions of the HadSM3 slab model (the PPE). In both ensembles, differences in climate feedbacks can account for approximately twice as much of the range in climate sensitivity as differences in CO2 forcing. In the AR4 ensemble, cloud effects can explain the full range of climate sensitivities, and cloud feedback components contribute four times as much as cloud components of CO2 forcing to the range. Non-cloud feedbacks are required to fully account for the high sensitivities of some models however. The largest contribution to the high sensitivity of HadGEM1 is from a high latitude clear-sky shortwave feedback, and clear-sky longwave feedbacks contribute substantially to the highest sensitivity members of the PPE. Differences in low latitude ocean regions (30°N/S) contribute more to the range than those in mid-latitude oceans (30-55°N/S), low/mid latitude land (55°N/S) or high latitude ocean/land (55-90°N/S), but contributions from these other regions are required to account fully for the higher model sensitivities, for example from land areas in IPSL CM4. Net cloud feedback components over the low latitude oceans sorted into percentile ranges of lower tropospheric stability (LTS) show largest differences among models in stable regions, mainly due to their shortwave components, most of which are positive in spite of increasing LTS. Differences in the mid-stability range are smaller, but cover a larger area, contributing a comparable amount to the range in climate sensitivity. These are strongly anti-correlated with changes in subsidence. Cloud components of CO2 forcing also show the largest differences in stable regions, and are strongly anticorrelated with changes in estimated inversion strength (EIS). This is qualitatively consistent with what would be expected from observed relationships between EIS and low-level cloud fraction. We identify a number of cases where individual models show unusually strong forcings and feedbacks compared to other members of the ensemble. We encourage modelling groups to investigate unusual model behaviours further with sensitivity experiments. Most of the models fail to correctly reproduce the observed relationships between stability and cloud radiative effect in the subtropics, indicating that there remains considerable room for model improvements in the future. © 2012 Crown Copyright."
"13402835300;7404142321;7003976079;6603853280;8397494800;7004714030;8918407000;7201504886;22137065500;10241462700;","Origins of the solar radiation biases over the Southern Ocean in CFMIP2 models",2014,"10.1175/JCLI-D-13-00169.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892601126&doi=10.1175%2fJCLI-D-13-00169.1&partnerID=40&md5=ca00241e76b8053c42ff0d3de593e441","Current climate models generally reflect too little solar radiation over the Southern Ocean, which may be the leading cause of the prevalent sea surface temperature biases in climate models. The authors study the role of clouds on the radiation biases in atmosphere-only simulations of the Cloud Feedback Model Intercomparison Project phase 2 (CFMIP2), as clouds have a leading role in controlling the solar radiation absorbed at those latitudes. The authors composite daily data around cyclone centers in the latitude band between 40° and 70°S during the summer. They use cloud property estimates from satellite to classify clouds into different regimes, which allow them to relate the cloud regimes and their associated radiative biases to themeteorological conditions in which they occur. The cloud regimes are defined using cloud properties retrieved using passive sensors and may suffer from the errors associated with this type of retrievals. The authors use information from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar to investigate inmore detail the properties of the ""midlevel"" cloud regime.Most of the model biases occur in the cold-air side of the cyclone composite, and the cyclone composite accounts formost of the climatological error in that latitudinal band. The midlevel regime is themain contributor to reflected shortwave radiation biases. CALIPSO data show that themidlevel cloud regime is dominated by two main cloud types: cloud with tops actually at midlevel and low-level cloud. Improving the simulation of these cloud types should help reduce the biases in the simulation of the solar radiation budget in the Southern Ocean in climate models. © 2014 American Meteorological Society."
"7404142321;7201485519;","A quantitative performance assessment of cloud regimes in climate models",2009,"10.1007/s00382-008-0443-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67349265921&doi=10.1007%2fs00382-008-0443-1&partnerID=40&md5=31a3021d2495c7de3bfc3267715ed9a6","Differences in the radiative feedback from clouds account for much of the variation in climate sensitivity amongst General Circulation Models (GCMs). Therefore metrics of model performance which are demonstrated to be relevant to the cloud response to climate change form an important contribution to the overall evaluation of GCMs. In this paper we demonstrate an alternative method for assigning model data to observed cloud regimes obtained from clustering histograms of cloud amount in joint cloud optical depth-cloud top pressure classes. The method removes some of the subjectivity that exists in previous GCM cloud clustering studies. We apply the method to ten GCMs submitted to the Cloud Feedback Model Intercomparison Project (CFMIP), evaluate the simulated cloud regimes and analyse the climate change response in the context of these regimes. We also propose two cloud regime metrics, one of which is specifically targeted at assessing GCMs for the purpose of obtaining the global cloud radiative response to climate change. Most of the global variance in the cloud radiative response between GCMs is due to low clouds, with 47% arising from the stratocumulus regime and 18% due to the regime characterised by clouds undergoing transition from stratocumulus to cumulus. This result is found to be dominated by two structurally similar GCMs. The shallow cumulus regime, though widespread, has a smaller contribution and reduces the variance. For the stratocumulus and transition regimes, part of the variance results from a large model spread in the radiative properties of the regime in the control simulation. Comparison with observations reveals a systematic bias for both the stratocumulus and transition regimes to be overly reflective. If this bias was corrected with all other aspects of the response unchanged, the variance in the low cloud response would reduce. The response of some regimes with high cloud tops differ between the GCMs. These regimes are simulated too infrequently in a few of the models. If the frequency in the control simulation were more realistic and changes within the regimes were unaltered, the variance in the cloud radiative response from high-top clouds would increase. As a result, use of observations of the mean present-day cloud regimes suggests that whilst improvements in the simulation of the cloud regimes would impact the climate sensitivity, the inter-model variance may not reduce. When the cloud regime metric is calculated for the GCMs analysed here, only one model is on average consistent with observations within their uncertainty (and even this model is not consistent with the observations for all regimes), indicating scope for improvement in the simulation of cloud regimes. © Crown copyright 2008."
"57205867148;8731430700;35220400000;57210518852;8875844200;","Evaluating the present-day simulation of clouds, precipitation, and radiation in climate models",2008,"10.1029/2007JD009334","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71949105949&doi=10.1029%2f2007JD009334&partnerID=40&md5=db0a1cc845bcaeb7d9f18f50a139d2c9","This paper describes a set of metrics for evaluating the simulation of clouds, radiation, and precipitation in the present-day climate. As with the skill scores used to measure the accuracy of short-term weather forecasts, these metrics are low-order statistical measures of agreement with relevant, well-observed physical quantities. The metrics encompass five statistical summaries computed for five physical quantities (longwave, shortwave, and net cloud radiative effect, projected cloud fraction, and surface precipitation rate) over the global climatological annual cycle. Agreement is measured against two independent observational data sets. The metrics are computed for the models that participated in the Coupled Model Intercomparison Project phase 3, which formed the basis for the Fourth Assessment of the IPCC. Model skill does not depend strongly on the data set used for verification, indicating that observational uncertainty does not limit the ability to assess model simulations of these fields. No individual model excels in all scores though the ""IPCC mean model,"" constructed by averaging the fields produced by all the CMIP models, performs particularly well across the board. This skill is due primarily to the individual model errors being distributed on both sides of the observations, and to a lesser degree to the models having greater skill at simulating large-scale features than those near the grid scale. No measure of model skill considered here is a good predictor of the strength of cloud feedbacks under climate change. The model climatologies, observational data sets, and metric scores are available on-line."
"7003922138;7102875645;","Can existing climate models be used to study anthropogenic changes in tropical cyclone climate?",1990,"10.1029/GL017i011p01917","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025592062&doi=10.1029%2fGL017i011p01917&partnerID=40&md5=c299ac57d4b30a1bd1a48756f6f1fd8a","The utility of current generation climate models for studying the influence of greenhouse warming on the tropical storm climatology is examined. A method developed to identify tropical cyclones is applied to a series of model integrations. The global distribution of tropical storms is simulated by these models in a generally realistic manner. While the model resolution is insufficient to reproduce the fine structure of tropical cyclones, the simulated storms become more realistic as resolution is increased. To obtain a preliminary estimate of the response of the tropical cyclone climatology, CO2 was doubled using models with varying cloud treatments and different horizontal resolutions. In the experiment with prescribed cloudiness, the number of storm‐days, a combined measure of the number and duration of tropical storms, undergoes a statistically significant increase in the doubled‐CO2 climate. In contrast, a smaller but significant reduction of the number of storm‐days is indicated in the experiment with cloud feedback. In both cases the response is independent of horizontal resolution. While the inconclusive nature of these experimeital results highlights the uncertainties that remain in examining the details of greenhouse gas induced climate change, the ability of the models to qualitatively simulate the tropical storm climatology suggests that they are appropriate tools for this problem. Copyright 1990 by the American Geophysical Union."
"57202891769;","The impact of cloud feedbacks on Arctic climate under Greenhouse forcing",2004,"10.1175/1520-0442(2004)017<0603:TIOCFO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642339807&doi=10.1175%2f1520-0442%282004%29017%3c0603%3aTIOCFO%3e2.0.CO%3b2&partnerID=40&md5=1faa3f8fb56b4724e181525890b64042","The simulation of Arctic cloud cover and the sensitivity of Arctic climate to cloud changes are investigated using an atmosphere-mixed-layer ocean GCM (GENESIS2). The model is run with and without changes in three-dimensional cloud fraction under 2 × CO2, radiative forcing. This model was chosen in part because of its relatively successful representation of modern Arctic cloud cover, a trait attributable to the parameterized treatment of mixed-phase microphysics. Simulated modern Arctic cloud fraction is insensitive to model biases in surface boundary conditions (SSTs and sea ice distribution), but the modeled Arctic climate is sensitive to high-frequency cloud variability. When forced with increased CO2, the model generally simulates more (less) vertically integrated cloudiness in high (low) latitudes. In the simulation without cloud feedbacks, cloud fraction is fixed at its modern control value at all grid points and all levels while CO2, is doubled. Compared with this fixed-cloud experiment, the simulated cloud changes enhance greenhouse warming at all latitudes, accounting for one-third of the global warming signal. This positive feedback is most pronounced in the Arctic, where approximately 40% of the warming is due to cloud changes. The strong cloud feedback in the Arctic is caused not only by local processes but also by cloud changes in lower latitudes, where positive top-of-the-atmosphere cloud radiative forcing anomalies are larger. The extra radiative energy gained in lower latitudes is transported dynamically to the Arctic via moist static energy flux convergence. The results presented here demonstrate the importance of remote impacts from low and midlatitudes for Arctic climate change. © 2004 American Meteorological Society."
"35765781400;26027624700;7004423053;12647541100;23016793700;9534656400;57202945421;7409960514;7005712332;","Multiple greenhouse-gas feedbacks from the land biosphere under future climate change scenarios",2013,"10.1038/nclimate1864","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879755362&doi=10.1038%2fnclimate1864&partnerID=40&md5=99fead57586e1c6e0311b0cc29b55496","Atmospheric concentrations of the three important greenhouse gases (GHGs) CO2, CH4 and N2 O are mediated by processes in the terrestrial biosphere that are sensitive to climate and CO2. This leads to feedbacks between climate and land and has contributed to the sharp rise in atmospheric GHG concentrations since pre-industrial times. Here, we apply a process-based model to reproduce the historical atmospheric N 2 O and CH4 budgets within their uncertainties and apply future scenarios for climate, land-use change and reactive nitrogen (Nr) inputs to investigate future GHG emissions and their feedbacks with climate in a consistent and comprehensive framework. Results suggest that in a business-as-usual scenario, terrestrial N2 O and CH4 emissions increase by 80 and 45%, respectively, and the land becomes a net source of C by AD 2100. N2 O and CH4 feedbacks imply an additional warming of 0.4-0.5C by AD 2300; on top of 0.8-1.0C caused by terrestrial carbon cycle and Albedo feedbacks. The land biosphere represents an increasingly positive feedback to anthropogenic climate change and amplifies equilibrium climate sensitivity by 22-27%. Strong mitigation limits the increase of terrestrial GHG emissions and prevents the land biosphere from acting as an increasingly strong amplifier to anthropogenic climate change. © 2013 Macmillan Publishers Limited. All rights reserved."
"7004479957;8882641700;57203288317;","Mechanisms of marine low cloud sensitivity to idealized climate perturbations: A single-LES exploration extending the CGILS cases",2013,"10.1002/jame.20019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880790152&doi=10.1002%2fjame.20019&partnerID=40&md5=0a0a7afaf8fd67c8c22e8978d4bb1577","Climate change sensitivities of subtropical cloud-topped marine boundary layers are analyzed using large-eddy simulation (LES) of three CGILS cases of well-mixed stratocumulus, cumulus under stratocumulus, and shallow cumulus cloud regimes, respectively. For each case, a steadily forced control simulation on a small horizontally doubly periodic domain is run 10-20 days into quasi-steady state. The LES is rerun to steady state with forcings perturbed by changes in temperature, free-tropospheric relative humidity (RH), CO<inf>2</inf> concentration, subsidence, inversion stability, and wind speed; cloud responses to combined forcings superpose approximately linearly. For all three cloud regimes and 2× CO<inf>2</inf> forcing perturbations estimated from the CMIP3 multimodel mean, the LES predicts positive shortwave cloud feedback, like most CMIP3 global climate models. At both stratocumulus locations, the cloud remains overcast but thins in the warmer, moister, CO<inf>2</inf>-enhanced climate, due to the combined effects of an increased lower-tropospheric vertical humidity gradient and an enhanced free-tropospheric greenhouse effect that reduces the radiative driving of turbulence. Reduced subsidence due to weakening of tropical overturning circulations partly counteracts these two factors by raising the inversion and allowing the cloud layer to deepen. These compensating mechanisms may explain the large scatter in low cloud feedbacks predicted by climate models. CMIP3-predicted changes in wind speed, inversion stability, and free-tropospheric RH have lesser impacts on the cloud thickness. In the shallow cumulus regime, precipitation regulates the simulated boundary-layer depth and vertical structure. Cloud-droplet (aerosol) concentration limits the boundary-layer depth and affects the simulated cloud feedbacks. Key Points LES low-cloud feedbacks positive due to enhanced vertical humidity gradients Less subsidence in warmer climate counteracts positive low cloud feedbacks Precipitation and cloud droplet number affect cumulus depth, climate feedbacks ©2013. American Geophysical Union. All Rights Reserved."
"55537426400;7003922138;","Equilibrium response of an atmosphere-mixed layer ocean model to different radiative forcing agents: Global and zonal mean response",2008,"10.1175/2008JCLI2172.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53649091289&doi=10.1175%2f2008JCLI2172.1&partnerID=40&md5=700865b72de027b943ed2a78ba3b645a","The equilibrium response to various forcing agents, including CO2 solar irradiance, tropospheric ozone, black carbon, organic carbon, sulfate, and volcanic aerosols, is investigated using an atmospheric general circulation model coupled to a mixed layer ocean model. The experiments are carried out by altering each forcing agent separately. Realistic spatial patterns of forcing constituents are applied but the magnitude of the forcing is adjusted so that each forcing constituent yields approximately the same strength of radiative forcing. It is demonstrated that the global mean temperature response depends on the types of forcing agents and the efficacy with respect to CO2 forcing ranges from 58% to 100%. The smallest efficacy is seen in one of the black carbon experiments and is associated with negative cloud feedback. The sign of the cloud feedback is shown to be sensitive to the vertical distribution of black carbon. The feedback analysis suggests that the small efficacy in tropospheric ozone is due to a large negative lapse rate feedback. Global mean precipitation increases when the earth warms except for the case of black carbon in which precipitation decreases. In all experiments, the global mean convective mass flux decreases when the earth's surface warms. When the applied radiative forcing resulting from a particular forcing agent is stronger in one hemisphere, anomalous heat exchange between the hemispheres results in conjunction with changes in the Hadley circulation. The magnitude of interhemispheric heat transport is little sensitive to the details of the forcing, but is determined primarily by the interhemispheric contrast in forcing. The change in the Hadley circulation strongly impacts the precipitation changes in low latitudes. © 2008 American Meteorological Society."
"35547807400;57203049177;","The climate sensitivity and its components diagnosed from earth radiation budget data",2006,"10.1175/JCLI3611.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846135845&doi=10.1175%2fJCLI3611.1&partnerID=40&md5=c94728a9f799dc0cd20c9119921a42ac","One of the major uncertainties in the ability to predict future climate change, and hence its impacts, is the lack of knowledge of the earth's climate sensitivity. Here, data are combined from the 1985-96 Earth Radiation Budget Experiment (ERBE) with surface temperature change information and estimates of radiative forcing to diagnose the climate sensitivity. Importantly, the estimate is completely independent of climate model results. A climate feedback parameter of 2.3 ± 1.4 W m -2 K -1 is found. This corresponds to a 1.0-4.1-K range for the equilibrium warming due to a doubling of carbon dioxide (assuming Gaussian errors in observable parameters, which is approximately equivalent to a uniform ""prior"" in feedback parameter). The uncertainty range is due to a combination of the short time period for the analysis as well as uncertainties in the surface temperature time series and radiative forcing time series, mostly the former. Radiative forcings may not all be fully accounted for; however, an argument is presented that the estimate of climate sensitivity is still likely to be representative of longer-term climate change. The methodology can be used to 1) retrieve shortwave and longwave components of climate feedback and 2) suggest clear-sky and cloud feedback terms. There is preliminary evidence of a neutral or even negative longwave feedback in the observations, suggesting that current climate models may not be representing some processes correctly if they give a net positive longwave feedback. © 2006 American Meteorological Society."
"7102875574;36809017200;7003971889;9246029600;37861539400;","The dependence of transient climate sensitivity and radiative feedbacks on the spatial pattern of ocean heat uptake",2014,"10.1002/2013GL058955","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893852494&doi=10.1002%2f2013GL058955&partnerID=40&md5=56ea0b2b85224cefce8ab62c1205da93","The effect of ocean heat uptake (OHU) on transient global warming is studied in a multimodel framework. Simple heat sinks are prescribed in shallow aquaplanet ocean mixed layers underlying atmospheric general circulation models independently and combined with CO2 forcing. Sinks are localized to either tropical or high latitudes, representing distinct modes of OHU found in coupled simulations. Tropical OHU produces modest cooling at all latitudes, offsetting only a fraction of CO2 warming. High-latitude OHU produces three times more global mean cooling in a strongly polar-amplified pattern. Global sensitivities in each scenario are set primarily by large differences in local shortwave cloud feedbacks, robust across models. Differences in atmospheric energy transport set the pattern of temperature change. Results imply that global and regional warming rates depend sensitively on regional ocean processes setting the OHU pattern, and that equilibrium climate sensitivity cannot be reliably estimated from transient observations. Key Points Climate response depends strongly on spatial pattern of ocean heat uptake Different radiative feedbacks govern transient and equilibrium CO2 warming Results are robust across an ensemble of aquaplanet climate models ©2014. American Geophysical Union. All Rights Reserved."
"55924208000;","Towards the probabilistic Earth-system simulator: A vision for the future of climate and weather prediction",2012,"10.1002/qj.1923","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862160611&doi=10.1002%2fqj.1923&partnerID=40&md5=4ddc88682af65d393e6a91d4c3983da4","There is no more challenging problem in computational science than that of estimating, as accurately as science and technology allows, the future evolution of Earth's climate; nor indeed is there a problem whose solution has such importance and urgency. Historically, the simulation tools needed to predict climate have been developed, somewhat independently, at a number of weather and climate institutes around the world. While these simulators are individually deterministic, it is often assumed that the resulting diversity provides a useful quantification of uncertainty in global or regional predictions. However, this notion is not well founded theoretically and corresponding 'multi-simulator' estimates of uncertainty can be prone to systemic failure. Separate to this, individual institutes are now facing considerable challenges in finding the human and computational resources needed to develop more accurate weather and climate simulators with higher resolution and full Earth-system complexity. A new approach, originally designed to improve reliability in ensemble-based numerical weather prediction, is introduced to help solve these two rather different problems. Using stochastic mathematics, this approach recognizes uncertainty explicitly in the parametrized representation of unresolved climatic processes. Stochastic parametrization is shown to be more consistent with the underlying equations of motion and, moreover, provides more skilful estimates of uncertainty when compared with estimates from traditional multi-simulator ensembles, on time-scales where verification data exist. Stochastic parametrization can also help reduce long-term biases which have bedevilled numerical simulations of climate from the earliest days to the present. As a result, it is suggested that the need to maintain a large 'gene pool' of quasi-independent deterministic simulators may be obviated by the development of probabilistic Earth-system simulators. Consistent with the conclusions of the World Summit on Climate Modelling, this in turn implies that individual institutes will be able to pool human and computational resources in developing future-generation simulators, thus benefitting from economies of scale; the establishment of the Airbus consortium provides a useful analogy here. As a further stimulus for such evolution, discussion is given to a potential new synergy between the development of dynamical cores, and stochastic processing hardware. However, it is concluded that the traditional challenge in numerical weather prediction, of reducing deterministic measures of forecast error, may increasingly become an obstacle to the seamless development of probabilistic weather and climate simulators, paradoxical as that may appear at first sight. Indeed, going further, it is argued that it may be time to consider focusing operational weather forecast development entirely on high-resolution ensemble prediction systems. Finally, by considering the exceptionally challenging problem of quantifying cloud feedback in climate change, it is argued that the development of the probabilistic Earth-system simulator may actually provide a route to reducing uncertainty in climate prediction. © 2012 Royal Meteorological Society."
"35547807400;57210518852;","Climate forcings and climate sensitivities diagnosed from coupled climate model integration",2006,"10.1175/JCLI3974.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845387289&doi=10.1175%2fJCLI3974.1&partnerID=40&md5=cc7b4a51d8da78613d5185d595de35a8","A simple technique is proposed for calculating global mean climate forcing from transient integrations of coupled atmosphere-ocean general circulation models (AOGCMs). This ""climate forcing"" differs from the conventionally defined radiative forcing as it includes semidirect effects that account for certain short time scale responses in the troposphere. First, a climate feedback term is calculated from reported values of 2 × CO2 radiative forcing and surface temperature time series from 70-yr simulations by 20 AOGCMs. In these simulations carbon dioxide is increased by 1% yr-1. The derived climate feedback agrees well with values that are diagnosed from equilibrium climate change experiments of slab-ocean versions of the same models. These climate feedback terms are associated with the fast, quasi-linear response of lapse rate, clouds, water vapor, and albedo to global surface temperature changes. The importance of the feedbacks is gauged by their impact on the radiative fluxes at the top of the atmosphere. Partial compensation is found between longwave and shortwave feedback terms that lessens the intermodel differences in the equilibrium climate sensitivity. There is also some indication that the AOGCMs overestimate the strength of the positive longwave feedback. These feedback terms are then used to infer the shortwave and longwave time series of climate forcing in twentieth- and twenty-first-century simulations in the AOGCMs. The technique is validated using conventionally calculated forcing time series from four AOGCMs. In these AOGCMs the shortwave and longwave climate forcings that are diagnosed agree with the conventional forcing time series within ∼10%. The shortwave forcing time series exhibit order of magnitude variations between the AOGCMs, differences likely related to how both natural forcings and/or anthropogenic aerosol effects are included. There are also factor of 2 differences in the longwave climate forcing time series, which may indicate problems with the modeling of well-mixed greenhouse gas changes. The simple diagnoses presented provides an important and useful first step for understanding differences in AOGCM integrations, indicating that some of the differences in model projections can be attributed to different prescribed climate forcing, even for so-called standard climate change scenarios. © 2006 American Meteorological Society."
"7005415069;","The 100 000-yr cycle in tropical SST, greenhouse forcing, and climate sensitivity",2004,"10.1175/1520-0442(2004)017<2170:TYCITS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042792394&doi=10.1175%2f1520-0442%282004%29017%3c2170%3aTYCITS%3e2.0.CO%3b2&partnerID=40&md5=a1cf71456f0d49de538642cb17f9d79e","The key scientific uncertainty in the global warming debate is the equilibrium climate sensitivity. Coupled atmosphere-ocean general circulation models predict a wide range of equilibrium climate sensitivities, with a consequently large spread of societal implications. Comparison of models with instrumental data has not been able to reduce the uncertainty in climate sensitivity. An alternative way to gauge equilibrium climate sensitivity is to use paleoclimatic data. Two recent advances. the development and application of proxy recorders of tropical sea surface temperature (SST) and the synchronization of the deep-sea and Antarctic ice-core time scales, make it possible to directly relate past changes in tropical SST to atmospheric carbon dioxide (CO2) levels. The strong correspondence of a proxy SST record from the eastern equatorial Pacific and the Vostok CO2 record suggests that varying atmospheric carbon dioxide is the dominant control on tropical climate on orbital time scales. This effect is especially pronounced at the 100 000-yr cycle. Calibration of the CO2 influence via tropical SST variability indicates a tropical climate sensitivity of 4.4°-5.6°C (errors estimated at ± 1.0°C) for a doubling of atmospheric CO2 concentration. This result suggests that the equilibrium response of tropical climate to atmospheric CO2 changes is likely to be similar to the upper end of available global predictions from coupled models. © 2004 American Meteorological Society."
"25031430500;57203030873;6701455548;","The evolution of climate sensitivity and climate feedbacks in the community atmosphere model",2012,"10.1175/JCLI-D-11-00197.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858256367&doi=10.1175%2fJCLI-D-11-00197.1&partnerID=40&md5=88fe9b919c95f0a1906f7cab941b85f4","The major evolution of the National Center for Atmospheric Research Community Atmosphere Model (CAM) is used to diagnose climate feedbacks, understand how climate feedbacks change with different physical parameterizations, and identify the processes and regions that determine climate sensitivity. In the evolution of CAM from version 4 to version 5, the water vapor, temperature, surface albedo, and lapse rate feedbacks are remarkably stable across changes to the physical parameterization suite. However, the climate sensitivity increases from 3.2 K in CAM4 to 4.0 K in CAM5. The difference is mostly due to (i) more positive cloud feedbacks and (ii) higher CO 2 radiative forcing in CAM5. The intermodel differences in cloud feedbacks are largest in the tropical trade cumulus regime and in the midlatitude storm tracks. The subtropical stratocumulus regions do not contribute strongly to climate feedbacks owing to their small area coverage. A ""modified Cess"" configuration for atmosphere-only model experiments is shown to reproduce slab ocean model results. Several parameterizations contribute to changes in tropical cloud feedbacks between CAM4 and CAM5, but the new shallow convection scheme causes the largest midlatitude feedback differences and the largest change in climate sensitivity. Simulations with greater cloud forcing in the mean state have lower climate sensitivity. This work provides a methodology for further analysis of climate sensitivity across models and a framework for targeted comparisons with observations that can help constrain climate sensitivity to radiative forcing. © 2012 American Meteorological Society."
"8696069500;7201504886;","Missing iris effect as a possible cause of muted hydrological change and high climate sensitivity in models",2015,"10.1038/ngeo2414","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928632181&doi=10.1038%2fngeo2414&partnerID=40&md5=10e9ca7e4eb37c5aa6cf4175fc419a6a","Equilibrium climate sensitivity to a doubling of CO 2 falls between 2.0 and 4.6 K in current climate models, and they suggest a weak increase in global mean precipitation. Inferences from the observational record, however, place climate sensitivity near the lower end of this range and indicate that models underestimate some of the changes in the hydrological cycle. These discrepancies raise the possibility that important feedbacks are missing from the models. A controversial hypothesis suggests that the dry and clear regions of the tropical atmosphere expand in a warming climate and thereby allow more infrared radiation to escape to space. This so-called iris effect could constitute a negative feedback that is not included in climate models. We find that inclusion of such an effect in a climate model moves the simulated responses of both temperature and the hydrological cycle to rising atmospheric greenhouse gas concentrations closer to observations. Alternative suggestions for shortcomings of models-such as aerosol cooling, volcanic eruptions or insufficient ocean heat uptake-may explain a slow observed transient warming relative to models, but not the observed enhancement of the hydrological cycle. We propose that, if precipitating convective clouds are more likely to cluster into larger clouds as temperatures rise, this process could constitute a plausible physical mechanism for an iris effect. © 2015 Macmillan Publishers Limited. All rights reserved."
"7003876681;7202367208;55446099200;23010937900;6603196127;37560988200;25721798900;6701773156;24490844700;7004372110;6602866981;7003941060;7004390019;7003494572;7006622255;7004423053;6603378233;6603810350;55512595000;55446458900;7006689582;27968009900;8640840300;7401515841;36617794600;36018660100;6602583456;8212589800;13905742000;7005796300;55727417500;12647541100;7402612084;23016793700;14049512800;7801506629;55537426400;7004390586;55823446500;","Historical and idealized climate model experiments: An intercomparison of Earth system models of intermediate complexity",2013,"10.5194/cp-9-1111-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881409906&doi=10.5194%2fcp-9-1111-2013&partnerID=40&md5=17ba4e52ed44eb55b8a81536cb159097","Both historical and idealized climate model experiments are performed with a variety of Earth system models of intermediate complexity (EMICs) as part of a community contribution to the Intergovernmental Panel on Climate Change Fifth Assessment Report. Historical simulations start at 850 CE and continue through to 2005. The standard simulations include changes in forcing from solar luminosity, Earth's orbital configuration, CO2, additional greenhouse gases, land use, and sulphate and volcanic aerosols. In spite of very different modelled pre-industrial global surface air temperatures, overall 20th century trends in surface air temperature and carbon uptake are reasonably well simulated when compared to observed trends. Land carbon fluxes show much more variation between models than ocean carbon fluxes, and recent land fluxes appear to be slightly underestimated. It is possible that recent modelled climate trends or climate-carbon feedbacks are overestimated resulting in too much land carbon loss or that carbon uptake due to CO2 and/or nitrogen fertilization is underestimated. Several one thousand year long, idealized, 2 and 4CO2 experiments are used to quantify standard model characteristics, including transient and equilibrium climate sensitivities, and climate-carbon feedbacks. The values from EMICs generally fall within the range given by general circulation models. Seven additional historical simulations, each including a single specified forcing, are used to assess the contributions of different climate forcings to the overall climate and carbon cycle response. The response of surface air temperature is the linear sum of the individual forcings, while the carbon cycle response shows a non-linear interaction between land-use change and CO2 forcings for some models. Finally, the preindustrial portions of the last millennium simulations are used to assess historical model carbon-climate feedbacks. Given the specified forcing, there is a tendency for the EMICs to underestimate the drop in surface air temperature and CO2 between the Medieval Climate Anomaly and the Little Ice Age estimated from palaeoclimate reconstructions. This in turn could be a result of unforced variability within the climate system, uncertainty in the reconstructions of temperature and CO2, errors in the reconstructions of forcing used to drive the models, or the incomplete representation of certain processes within the models. Given the forcing datasets used in this study, the models calculate significant land-use emissions over the pre-industrial period. This implies that landuse emissions might need to be taken into account, when making estimates of climate-carbon feedbacks from palaeoclimate reconstructions. © Author(s) 2013. CC Attribution 3.0 License."
"57210518852;6602665711;6603875926;7202923875;6602963031;7003922138;7406514318;7201485519;","Estimating shortwave radiative forcing and response in climate models",2007,"10.1175/JCLI4143.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250157338&doi=10.1175%2fJCLI4143.1&partnerID=40&md5=98d5f220f525a48e5533c69a4929e50b","Feedback analysis in climate models commonly involves decomposing any change in the system's energy balance into radiative forcing terms due to prescribed changes, and response terms due to the radiative effects of changes in model variables such as temperature, water vapor, clouds, sea ice, and snow. The established ""partial radiative perturbation"" (PRP) method allows an accurate separation of these terms, but requires processing large volumes of model output with an offline version of the model's radiation code. Here, we propose an ""approximate PRP (APRP) method for the shortwave that provides an accurate estimate of the radiative perturbation, but derived from a quite modest amount of monthly mean model output. The APRP method is based on a simplified sho rtwave radiative model of the atmosphere, where surface absorption and atmospheric scattering and absorption are represented by means of three parameters that are diagnosed for overcast and clear-sky portions of each model grid cell. The accuracy of the method is gauged relative to full PRP calculations in two experiments: one in which carbon dioxide concentration is doubled and another in which conditions of the Last Glacial Maximum (LGM) are simulated. The approximate PRP method yields a shortwave cloud feedback accurate in the global mean to within 7%. Forcings and feedbacks due to surface albedo and noncloud atmospheric constituents are also well approximated with errors of order 5%-10%. Comparison of two different model simulations of the LGM shows that the regional and global differences in their ice sheet albedo forcing fields are clearly captured by the APRP method. Hence this method is an efficient and satisfactory tool for studying and intercomparing shortwave forcing and feedbacks in climate models. © 2007 American Meteorological Society."
"26643043700;6701853567;57203030873;6508089485;","Sensitivity to glacial forcing in the CCSM4",2013,"10.1175/JCLI-D-11-00416.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874849545&doi=10.1175%2fJCLI-D-11-00416.1&partnerID=40&md5=c70f432ae5dc3b24a9601c1429bdc522","Results are presented from the Community Climate System Model, version 4 (CCSM4), simulation of the Last Glacial Maximum (LGM) from phase 5 of the Coupled Model Intercomparison Project (CMIP5) at the standard 18 resolution, the same resolution as the majority of the CCSM4 CMIP5 long-term simulations for the historical and future projection scenarios. The forcings and boundary conditions for this simulation follow the protocols of the Paleoclimate Modeling Intercomparison Project, version 3 (PMIP3). Two additional CCSM4 CO2 sensitivity simulations, in which the concentrations are abruptly changed at the start of the simulation to the low 185 ppm LGM concentrations (LGMCO2) and to a quadrupling of the preindustrial concentration (4×CO2), are also analyzed. For the full LGM simulation, the estimated equilibriumcooling of the global mean annual surface temperature is 5.5°C with an estimated radiative forcing of -6.2 W m-2. The radiative forcing includes the effects of the reduced LGM greenhouse gases, ice sheets, continental distribution with sea level lowered by approximately 120 m from the present, and orbital parameters, but not changes to atmospheric aerosols or vegetation biogeography. The LGM simulation has an equilibrium climate sensitivity (ECS) of 3.1(±0.3)°C, comparable to the CCSM4 4×CO2 result. The LGMCO2 simulation shows a greater ECS of 4.2°C. Other responses found at the LGM in CCSM4 include a global precipitation rate decrease at a rate of ~2% °C-1, similar to climate change simulations in the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4); a strengthening of the Atlantic meridional overturning circulation (AMOC) with a shoaling of North Atlantic Deep Water and a filling of the deep basin up to sill depth with Antarctic Bottom Water; and an enhanced seasonal cycle accompanied by reduced ENSO variability in the eastern Pacific Ocean,s SSTs. © 2013 American Meteorological Society."
"7003543851;7006354215;","The vertical distribution of cloud feedback in coupled ocean-atmosphere models",2011,"10.1029/2011GL047632","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959689422&doi=10.1029%2f2011GL047632&partnerID=40&md5=acbd8cb5878431508b52c741b6893918","We assess the vertical distribution of cloud feedbacks in coupled climate models, taking care to distinguish between cloud feedbacks and a change in cloud forcing. We show that the effect of cloud changes on the longwave fluxes provides a strong positive feedback that is broadly consistent across models. In contrast, the effect of cloud changes on the shortwave fluxes ranges from a modest negative to a strong positive feedback, and is responsible for most of the intermodel spread in net cloud feedback. The feedback from high clouds is positive in all models, and is consistent with that anticipated by the Proportionately Higher Anvil Temperature hypothesis over the tropics. In contrast, low cloud cover is responsible for roughly three-quarters of the difference in global mean net cloud feedback among models, with the largest contributions from regions associated with low-level subtropical marine cloud systems. Copyright 2011 by the American Geophysical Union."
"7102284923;57206526682;55453681500;7004423053;15071907100;7005978899;57202733911;","What caused Earth's temperature variations during the last 800,000 years? Data-based evidence on radiative forcing and constraints on climate sensitivity",2010,"10.1016/j.quascirev.2009.09.026","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73549097426&doi=10.1016%2fj.quascirev.2009.09.026&partnerID=40&md5=68cb50e9f38f9ab990ec62a8f0b3b98b","The temperature on Earth varied largely in the Pleistocene from cold glacials to interglacials of different warmths. To contribute to an understanding of the underlying causes of these changes we compile various environmental records (and model-based interpretations of some of them) in order to calculate the direct effect of various processes on Earth's radiative budget and, thus, on global annual mean surface temperature over the last 800,000 years. The importance of orbital variations, of the greenhouse gases CO2, CH4 and N2O, of the albedo of land ice sheets, annual mean snow cover, sea ice area and vegetation, and of the radiative perturbation of mineral dust in the atmosphere are investigated. Altogether we can explain with these processes a global cooling of 3.9 ± 0.8 K in the equilibrium temperature for the Last Glacial Maximum (LGM) directly from the radiative budget using only the Planck feedback that parameterises the direct effect on the radiative balance, but neglecting other feedbacks such as water vapour, cloud cover, and lapse rate. The unaccounted feedbacks and related uncertainties would, if taken at present day feedback strengths, decrease the global temperature at the LGM by -8.0 ± 1.6 K. Increased Antarctic temperatures during the Marine Isotope Stages 5.5, 7.5, 9.3 and 11.3 are in our conceptual approach difficult to explain. If compared with other studies, such as PMIP2, this gives supporting evidence that the feedbacks themselves are not constant, but depend in their strength on the mean climate state. The best estimate and uncertainty for our reconstructed radiative forcing and LGM cooling support a present day equilibrium climate sensitivity (excluding the ice sheet and vegetation components) between 1.4 and 5.2 K, with a most likely value near 2.4 K, somewhat smaller than other methods but consistent with the consensus range of 2-4.5 K derived from other lines of evidence. Climate sensitivities above 6 K are difficult to reconcile with Last Glacial Maximum reconstructions. © 2009 Elsevier Ltd. All rights reserved."
"12769875100;26324818700;7202699757;7006518289;7005965757;55738957800;","A decomposition of feedback contributions to polar warming amplification",2013,"10.1175/JCLI-D-12-00696.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884252126&doi=10.1175%2fJCLI-D-12-00696.1&partnerID=40&md5=402313b582945f3f4bbcc6c18640a366","Polar surface temperatures are expected to warm 2-3 times faster than the global-mean surface temperature: a phenomenon referred to as polar warming amplification. Therefore, understanding the individual process contributions to the polar warming is critical to understanding global climate sensitivity. The Coupled Feedback Response Analysis Method (CFRAM) is applied to decompose the annual-and zonal-mean vertical temperature response within a transient 1% yr21 CO2 increase simulation of the NCAR Community Climate System Model, version 4 (CCSM4), into individual radiative and nonradiative climate feedback process contributions. The total transient annual-mean polar warming amplification (amplification factor) at the time of CO2 doubling is 12.12 (2.3) and 10.94K (1.6) in the Northern and Southern Hemisphere, respectively. Surface albedo feedback is the largest contributor to the annual-mean polar warming amplification accounting for 11.82 and 11.04K in the Northern and Southern Hemisphere, respectively. Net cloud feedback is found to be the second largest contributor to polar warming amplification (about 10.38K in both hemispheres) and is driven by the enhanced downward longwave radiation to the surface resulting from increases in low polar water cloud. The external forcing and atmospheric dynamic transport also contribute positively to polar warming amplification:10.29 and10.32 K, respectively. Water vapor feedback contributes negatively to polar warming amplification because its induced surface warming is stronger in low latitudes. Ocean heat transport storage and surface turbulent flux feedbacks also contribute negatively to polar warming amplification. Ocean heat transport and storage terms play an important role in reducing the warming over the Southern Ocean and Northern Atlantic Ocean. © 2013 American Meteorological Society."
"56005630600;23082420800;56005518700;","The south pacific meridional mode: A mechanism for ENSO-like variability",2014,"10.1175/JCLI-D-13-00082.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892516499&doi=10.1175%2fJCLI-D-13-00082.1&partnerID=40&md5=e0de8ef47396886181c9ba7fe9bac874","In this study, the authors investigate the connection between the South Pacific atmospheric variability and the tropical Pacific climate in models of different degrees of coupling between the atmosphere and ocean. A robust mode of variability, defined as the South Pacific meridional mode (SPMM), is identified in a multimodel ensemble of climate model experiments where the atmosphere is only thermodynamically coupled to a slab ocean mixed layer. The physical interpretation of the SPMM is nearly identical to the North Pacific meridional mode (NPMM) with the off-equatorial southeast trade wind variability altering the latent heat flux and sea surface temperature (SST) and initiating a wind-evaporation-SST feedback that propagates signals into the tropics. The authors also show that a positive cloud feedback plays a role in the development of this mode, but this effect is model dependent. While physically analogous to the NPMM, theSPMMhas a stronger expression in the equatorial Pacific and directly perturbs the zonal gradients of SST and sea level pressure (SLP) on the equator, thus leading to ENSO-like variability despite the lack of ocean-atmosphere dynamical coupling. Further analysis suggests that the SPMM is also active in fully coupled climate models and observations. This study highlights the important role of the Southern Hemisphere in tropical climate variability and suggests that including observations from the data-poor South Pacific could improve the ENSO predictability. © 2014 American Meteorological Society."
"57203030873;57202754759;6602558284;36871512800;25031430500;15724543600;57210350827;","The influence of local feedbacks and northward heat transport on the equilibrium arctic climate response to increased greenhouse gas forcing",2012,"10.1175/JCLI-D-11-00622.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859966114&doi=10.1175%2fJCLI-D-11-00622.1&partnerID=40&md5=793dc5e14b3f33e4173b6fb8392018e0","This study uses coupled climate model experiments to identify the influence of atmospheric physics [Community Atmosphere Model, versions 4 and 5 (CAM4; CAM5)] and ocean model complexity (slab ocean, full-depth ocean) on the equilibrium Arctic climate response to an instantaneous CO2 doubling. In slab ocean model (SOM) experiments using CAM4 and CAM5, local radiative feedbacks, not atmospheric heat flux convergence, are the dominant control on the Arctic surface response to increased greenhouse gas forcing. Equilibrium Arctic surface air temperature warming and amplification are greater in the CAM5 SOM experiment than in the equivalent CAM4 SOM experiment. Larger 2 3 CO2 radiative forcing, more positive Arctic surface albedo feedbacks, and less negative Arctic shortwave cloud feedbacks all contribute to greater Arctic surface warming and sea ice loss in CAM5 as compared to CAM4. When CAM4 is coupled to an active full-depth ocean model, Arctic Ocean horizontal heat flux convergence increases in response to the instantaneous CO2 doubling. Though this increased ocean northward heat transport slightly enhances Arctic sea ice extent loss, the representation of atmospheric processes (CAM4 versus CAM5) has a larger influence on the equilibrium Arctic surface climate response than the degree of ocean coupling (slab ocean versus fulldepth ocean). These findings underscore that local feedbacks can be more important than northward heat transport for explaining the equilibrium Arctic surface climate response and response differences in coupled climate models. That said, the processes explaining the equilibrium climate response differences here may be different than the processes explaining intermodel spread in transient climate projections. © 2012 American Meteorological Society."
"12801992200;13406672500;6603422104;","Changes in extratropical storm track cloudiness 1983-2008: Observational support for a poleward shift",2012,"10.1007/s00382-011-1065-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860351521&doi=10.1007%2fs00382-011-1065-6&partnerID=40&md5=b21c63272abe9e30f787df6ca717f3aa","Climate model simulations suggest that the extratropical storm tracks will shift poleward as a consequence of global warming. In this study the northern and southern hemisphere storm tracks over the Pacific and Atlantic ocean basins are studied using observational data, primarily from the International Satellite Cloud Climatology Project, ISCCP. Potential shifts in the storm tracks are examined using the observed cloud structures as proxies for cyclone activity. Different data analysis methods are employed, with the objective to address difficulties and uncertainties in using ISCCP data for regional trend analysis. In particular, three data filtering techniques are explored; excluding specific problematic regions from the analysis, regressing out a spurious viewing geometry effect, and excluding specific cloud types from the analysis. These adjustments all, to varying degree, moderate the cloud trends in the original data but leave the qualitative aspects of those trends largely unaffected. Therefore, our analysis suggests that ISCCP data can be used to interpret regional trends in cloudiness, provided that data and instrumental artefacts are recognized and accounted for. The variation in magnitude between trends emerging from application of different data correction methods, allows us to estimate possible ranges for the observational changes. It is found that the storm tracks, here represented by the extent of the midlatitude-centered band of maximum cloud cover over the studied ocean basins, experience a poleward shift as well as a narrowing over the 25 year period covered by ISCCP. The observed magnitudes of these effects are larger than in current generation climate models (CMIP3). The magnitude of the shift is particularly large in the northern hemisphere Atlantic. This is also the one of the four regions in which imperfect data primarily prevents us from drawing firm conclusions. The shifted path and reduced extent of the storm track cloudiness is accompanied by a regional reduction in total cloud cover. This decrease in cloudiness can primarily be ascribed to low level clouds, whereas the upper level cloud fraction actually increases, according to ISCCP. Independent satellite observations of radiative fluxes at the top of the atmosphere are consistent with the changes in total cloud cover. The shift in cloudiness is also supported by a shift in central position of the mid-troposphere meridional temperature gradient. We do not find support for aerosols playing a significant role in the satellite observed changes in cloudiness. The observed changes in storm track cloudiness can be related to local cloud-induced changes in radiative forcing, using ERBE and CERES radiative fluxes. The shortwave and the longwave components are found to act together, leading to a positive (warming) net radiative effect in response to the cloud changes in the storm track regions, indicative of positive cloud feedback. Among the CMIP3 models that simulate poleward shifts in all four storm track areas, all but one show decreasing cloud amount on a global mean scale in response to increased CO2 forcing, further consistent with positive cloud feedback. Models with low equilibrium climate sensitivity to a lesser extent than higher-sensitivity models simulate a poleward shift of the storm tracks. © 2011 Springer-Verlag."
"15071907100;55569698000;57203054070;","Beyond equilibrium climate sensitivity",2017,"10.1038/NGEO3017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030542239&doi=10.1038%2fNGEO3017&partnerID=40&md5=e85d2729df9c31893990f71e5aa54df5","Equilibrium climate sensitivity characterizes the Earth's long-term global temperature response to increased atmospheric CO2 concentration. It has reached almost iconic status as the single number that describes how severe climate change will be. The consensus on the 'likely' range for climate sensitivity of 1.5 °C to 4.5 °C today is the same as given by Jule Charney in 1979, but now it is based on quantitative evidence from across the climate system and throughout climate history. The quest to constrain climate sensitivity has revealed important insights into the timescales of the climate system response, natural variability and limitations in observations and climate models, but also concerns about the simple concepts underlying climate sensitivity and radiative forcing, which opens avenues to better understand and constrain the climate response to forcing. Estimates of the transient climate response are better constrained by observed warming and are more relevant for predicting warming over the next decades. Newer metrics relating global warming directly to the total emitted CO2 show that in order to keep warming to within 2 °C, future CO2 emissions have to remain strongly limited, irrespective of climate sensitivity being at the high or low end. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved."
"56272964700;15124698700;","An energetic perspective on the regional response of precipitation to climate change",2011,"10.1038/nclimate1169","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856948972&doi=10.1038%2fnclimate1169&partnerID=40&md5=a58f98f395664be6b48092c3ffdf835d","Understanding and predicting the response of the hydrological cycle to climate change is a major challenge with important societal implications. Much progress has been made in understanding the response of global average precipitation by considering the energy balances of the atmosphere and the surface. This energetic perspective reveals that changes in temperature, greenhouse gases, aerosols, solar forcing and cloud feedbacks can all affect the global average rate of precipitation. Local precipitation changes have conventionally been analysed using the water vapour budget, but here we show that the energetic approach can be extended to local changes in precipitation by including changes in horizontal energy transport. In simulations of twenty-first century climate change, this energy transport accounts for much of the spatial variability in precipitation change. We show that changes in radiative and surface sensible heat fluxes are a guide to the local precipitation response over land and at large scales, but not at small scales over the ocean, where cloud and water vapour radiative feedbacks dampen the response. The energetic approach described here helps bridge the gap between our understanding of global and regional precipitation changes. It could be applied to better understand the response of regional precipitation to different radiative forcings, including geo-engineering schemes, as well as to understand the differences between the fast and slow responses of regional precipitation to such forcings. © 2011 Macmillan Publishers Limited. All rights reserved."
"6602688130;7004890337;","Equilibrium climate sensitivity: Is it accurate to use a slab ocean model?",2009,"10.1175/2008JCLI2596.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66849097946&doi=10.1175%2f2008JCLI2596.1&partnerID=40&md5=5eacf8a582cb4d4f0aed1e31f453dc64","The equilibrium climate sensitivity of a climate model is usually defined as the globally averaged equilibrium surface temperature response to a doubling of carbon dioxide. This is virtually always estimated in a version with a slab model for the upper ocean. The question is whether this estimate is accurate for the full climate model version, which includes a full-depth ocean component. This question has been answered for the low-resolution version of the Community Climate System Model, version 3 (CCSM3). The answer is that the equilibrium climate sensitivity using the full-depth ocean model is 0.148°C higher than that using the slab ocean model, which is a small increase. In addition, these sensitivity estimates have a standard deviation of nearly 0.18°C because of interannual variability. These results indicate that the standard practice of using a slab ocean model does give a good estimate of the equilibrium climate sensitivity of the full CCSM3. Another question addressed is whether the effective climate sensitivity is an accurate estimate of the equilibrium climate sensitivity. Again the answer is yes, provided that at least 150 yr of data from the doubled carbon dioxide run are used. © 2009 American Meteorological Society."
"6701853567;7403513732;26643043700;57203082758;6603196127;16456768000;6603875926;6602665711;7202923875;7007181954;10143232600;7402489842;6603714917;57203285659;8255576800;7003330033;7406250414;","A comparison of PMIP2 model simulations and the MARGO proxy reconstruction for tropical sea surface temperatures at last glacial maximum",2009,"10.1007/s00382-008-0509-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62549124957&doi=10.1007%2fs00382-008-0509-0&partnerID=40&md5=bfb08579996676cd9cb61bdd75b5cbeb","Results from multiple model simulations are used to understand the tropical sea surface temperature (SST) response to the reduced greenhouse gas concentrations and large continental ice sheets of the last glacial maximum (LGM). We present LGM simulations from the Paleoclimate Modelling Intercomparison Project, Phase 2 (PMIP2) and compare these simulations to proxy data collated and harmonized within the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface Project (MARGO). Five atmosphere-ocean coupled climate models (AOGCMs) and one coupled model of intermediate complexity have PMIP2 ocean results available for LGM. The models give a range of tropical (defined for this paper as 15°S-15°N) SST cooling of 1.0-2.4°C, comparable to the MARGO estimate of annual cooling of 1.7 ± 1°C. The models simulate greater SST cooling in the tropical Atlantic than tropical Pacific, but interbasin and intrabasin variations of cooling are much smaller than those found in the MARGO reconstruction. The simulated tropical coolings are relatively insensitive to season, a feature also present in the MARGO transferred-based estimates calculated from planktonic foraminiferal assemblages for the Indian and Pacific Oceans. These assemblages indicate seasonality in cooling in the Atlantic basin, with greater cooling in northern summer than northern winter, not captured by the model simulations. Biases in the simulations of the tropical upwelling and thermocline found in the preindustrial control simulations remain for the LGM simulations and are partly responsible for the more homogeneous spatial and temporal LGM tropical cooling simulated by the models. The PMIP2 LGM simulations give estimates for the climate sensitivity parameter of 0.67°-0.83°C per Wm-2, which translates to equilibrium climate sensitivity for doubling of atmospheric CO2 of 2.6-3.1°C. © Springer-Verlag 2009."
"7202145115;13406672500;6507378862;7202673976;","Earth Radiation Budget data and climate research",1986,"10.1029/RG024i002p00439","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84995114587&doi=10.1029%2fRG024i002p00439&partnerID=40&md5=b47390fa428d8992758613c1a97ad77c","An overview is presented of the uses of top of the atmosphere radiation budget measurements in studies of climate. The net radiative energy flux at the top of the atmosphere must be balanced by local heat storage in the earth‐atmosphere column or by horizontal transport in the atmosphere and ocean. Regional variations in the components of the radiation balance are significant and place important constraints on regional and global climate. If suitable time averaging is applied, regional net radiation can be used to infer horizontal transport of energy in the atmosphere and ocean. Estimates of equator‐to‐pole transport in the atmosphere and ocean based upon currently available top‐of‐atmosphere radiation budget measurements contain unacceptably large uncertainties associated with uncertainties in the radiation budget measurements themselves. Diurnal and interannual variations in regional radiation balances are large and important but have not yet been properly sampled with broadband instruments. Both have the potential for providing important insights into climate. The role of cloudiness in climate sensitivity remains one of the major uncertainties in quantitative estimates of climate changes associated with particular perturbing influences. Radiation budget data can be used to estimate the effects of actual cloudiness on the top‐of‐atmosphere heat balance and the dependence of these effects on location and season. The observational studies of the effect of cloudiness on the radiation balance at the top of the atmosphere that have been completed to date all suffer from one or more of three fundamental problems. These are that the parameters of the cloudiness are not accurately known, the radiation budget data are not based on measurements whose frequency response is unbiased in relation to the emissions of the sun and the earth, and the diurnal sampling of the measurements is not complete. The uncertainties associated with each of these problems are expected to be reduced as a result of analyses based on data from the Earth Radiation Budget Experiment. In order that quantitative estimates of climate change be as accurate as possible the general circulation models (GCMs) which produce these forecasts must be critically evaluated with observed data. Many of the most important mechanisms for perturbing climate (e.g., CO2, volcanic aerosols, surface albedo changes) and many of the most important feedback processes (e.g., relative humidity feedback, cloud feedback, ice‐albedo feedback) directly involve the radiation balance at the top of the atmosphere and its relation to surface climate. Since the radiation balance at the top of the atmosphere can, in principle, be measured very accurately from space, it is natural that the simulation of top‐of‐atmosphere energy fluxes by GCMs should be carefully validated against observations. Because of the complexities introduced by clouds, a complete validation of the radiation budget of a GCM is a long and difficult task. A strategy is suggested here in which the clear‐sky fluxes of the model are first compared with a clear‐sky radiation budget climatology derived from observations. The radiation budgets with clouds included can then also be compared. This procedure should isolate problems not associated with cloudiness and indicate whether, in the grossest sense, the model clouds are correctly influencing the radiation balance. Comparisons between instantaneous synoptic maps of the radiation budget components and numerical forecasts can also be used to diagnose the performance of models. Copyright 1986 by the American Geophysical Union."
"6701752471;36856321600;26023913800;12760240500;25629055800;57198379031;57209781901;8278450900;6507890706;7102450474;57191737914;8642592500;6506848305;6507492100;7003361863;56604888300;22953153500;9434771700;55914364600;57208304879;7006270084;15044268700;7404544551;8570871900;57209779308;15729547600;23392868000;36876405100;55418728800;57192398469;6602817609;55165863400;54894032100;36056399500;55271577800;24534445300;7402064802;7005920812;7202048112;57206716460;8859530100;57210230785;15755995900;25637373000;6602075440;35617453500;7004687638;18936046300;7102696626;7202475536;55802246600;7006705919;57194773664;7101610644;6602858513;55464772600;57188758598;7004245252;57193608086;36982280200;55544607500;36352387000;57202522440;7101791974;36338065200;23037063200;57202299549;55688930000;36931958000;56161781600;54582960000;7004403539;7401936984;55720018700;55317177900;26645289600;6603400519;7403247998;57201123684;56384704800;52464731300;36183647300;57111263900;56583139400;","The DOE E3SM Coupled Model Version 1: Overview and Evaluation at Standard Resolution",2019,"10.1029/2018MS001603","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065411121&doi=10.1029%2f2018MS001603&partnerID=40&md5=ee99e5d2d79a28ec657d1eff722076dc","This work documents the first version of the U.S. Department of Energy (DOE) new Energy Exascale Earth System Model (E3SMv1). We focus on the standard resolution of the fully coupled physical model designed to address DOE mission-relevant water cycle questions. Its components include atmosphere and land (110-km grid spacing), ocean and sea ice (60 km in the midlatitudes and 30 km at the equator and poles), and river transport (55 km) models. This base configuration will also serve as a foundation for additional configurations exploring higher horizontal resolution as well as augmented capabilities in the form of biogeochemistry and cryosphere configurations. The performance of E3SMv1 is evaluated by means of a standard set of Coupled Model Intercomparison Project Phase 6 (CMIP6) Diagnosis, Evaluation, and Characterization of Klima simulations consisting of a long preindustrial control, historical simulations (ensembles of fully coupled and prescribed SSTs) as well as idealized CO2 forcing simulations. The model performs well overall with biases typical of other CMIP-class models, although the simulated Atlantic Meridional Overturning Circulation is weaker than many CMIP-class models. While the E3SMv1 historical ensemble captures the bulk of the observed warming between preindustrial (1850) and present day, the trajectory of the warming diverges from observations in the second half of the twentieth century with a period of delayed warming followed by an excessive warming trend. Using a two-layer energy balance model, we attribute this divergence to the model's strong aerosol-related effective radiative forcing (ERFari+aci = −1.65 W/m2) and high equilibrium climate sensitivity (ECS = 5.3 K). © 2019. The Authors."
"54893098900;35509639400;","Interpretation of the positive low-cloud feedback predicted by a climate model under global warming",2013,"10.1007/s00382-011-1279-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876877680&doi=10.1007%2fs00382-011-1279-7&partnerID=40&md5=cbee3a5224b918bff0b5b74400717070","The response of low-level clouds to climate change has been identified as a major contributor to the uncertainty in climate sensitivity estimates among climate models. By analyzing the behaviour of low-level clouds in a hierarchy of models (coupled ocean-atmosphere model, atmospheric general circulation model, aqua-planet model, single-column model) using the same physical parameterizations, this study proposes an interpretation of the strong positive low-cloud feedback predicted by the IPSL-CM5A climate model under climate change. In a warmer climate, the model predicts an enhanced clear-sky radiative cooling, stronger surface turbulent fluxes, a deepening and a drying of the planetary boundary layer, and a decrease of tropical low-clouds in regimes of weak subsidence. We show that the decrease of low-level clouds critically depends on the change in the vertical advection of moist static energy from the free troposphere to the boundary-layer. This change is dominated by variations in the vertical gradient of moist static energy between the surface and the free troposphere just above the boundary-layer. In a warmer climate, the thermodynamical relationship of Clausius-Clapeyron increases this vertical gradient, and then the import by large-scale subsidence of low moist static energy and dry air into the boundary layer. This results in a decrease of the low-level cloudiness and in a weakening of the radiative cooling of the boundary layer by low-level clouds. The energetic framework proposed in this study might help to interpret inter-model differences in low-cloud feedbacks under climate change. © 2012 The Author(s)."
"24329376600;35547807400;","CO2 forcing induces semi-direct effects with consequences for climate feedback interpretations",2008,"10.1029/2007GL032273","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44249117154&doi=10.1029%2f2007GL032273&partnerID=40&md5=21d6a3acfb608246173f5f59414d4c47","Climate forcing and feedbacks are diagnosed from seven slab-ocean GCMs for 2 × CO2 using a regression method. Results are compared to those using conventional methodologies to derive a semi-direct forcing due to tropospheric adjustment, analogous to the semi-direct effect of absorbing aerosols. All models show a cloud semi-direct effect, indicating a rapid cloud response to CO2; cloud typically decreases, enhancing the warming. Similarly there is evidence of semi-direct effects from water-vapour, lapse-rate, ice and snow. Previous estimates of climate feedbacks are unlikely to have taken these semi-direct effects into account and so misinterpret processes as feedbacks that depend only on the forcing, but not the global surface temperature. We show that the actual cloud feedback is smaller than what previous methods suggest and that a significant part of the cloud response and the large spread between previous model estimates of cloud feedback is due to the semi-direct forcing. Copyright 2008 by the American Geophysical Union."
"7202923875;7406514318;","Radiative forcing and response of a GCM to ice age boundary conditions: Cloud feedback and climate sensitivity",1997,"10.1007/s003820050199","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031408639&doi=10.1007%2fs003820050199&partnerID=40&md5=4d8ea2e16b234ce61a37379f9caba128","A general circulation model is used to examine the effects of reduced atmospheric CO2, insolation changes and an updated reconstruction of the continental ice sheets at the Last Glacial Maximum (LGM). A set of experiments is performed to estimate the radiative forcing from each of the boundary conditions. These calculations are used to estimate a total radiative forcing for the climate of the LGM. The response of the general circulation model to the forcing from each of the changed boundary conditions is then investigated. About two-thirds of the simulated glacial cooling is due to the presence of the continental ice sheets. The effect of the cloud feedback is substantially modified where there are large changes to surface albedo. Finally, the climate sensitivity is estimated based on the global mean LGM radiative forcing and temperature response, and is compared to the climate sensitivity calculated from equilibrium experiments with atmospheric CO2 doubled from present day concentration. The calculations here using the model and palaeodata support a climate sensitivity of about 1 Wm-2K-1 which is within the conventional range."
"26645289600;7202145115;","Climate feedbacks and their implications for poleward energy flux changes in a warming climate",2012,"10.1175/JCLI-D-11-00096.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856952465&doi=10.1175%2fJCLI-D-11-00096.1&partnerID=40&md5=015c73c7751d2e17a2df1fd8558e9c5b","Feedbacks determine the efficiency with which the climate system comes back into equilibrium in response to a radiative perturbation. Although feedbacks are integrated quantities, the processes from which they arise have rich spatial structures that alter the distribution of top of atmosphere (TOA) net radiation. Here, the authors investigate the implications of the structure of climate feedbacks for the change in poleward energy transport as the planet warms over the twenty-first century in a suite of GCMs. Using radiative kernels that describe the TOA radiative response to small perturbations in temperature, water vapor, and surface albedo, the change in poleward energy flux is partitioned into the individual feedbacks that cause it. This study finds that latitudinal gradients in the sum of climate feedbacks reinforce the preexisting latitudinal gradient in TOA net radiation, requiring that the climate system transport more energy to the poles on a warming planet. This is primarily due to structure of the water vapor and cloud feedbacks, which are strongly positive at low latitudes and decrease dramatically with increasing latitude. Using the change in surface fluxes, the authors partition the anomalous poleward energy flux between the atmosphere and ocean and find that reduced heat flux from the high-latitude ocean further amplifies the equator-to-pole gradient in atmospheric energy loss. This implied reduction in oceanic poleward energy flux requires the atmosphere to increase its share of the total poleward energy transport. As is the case for climate sensitivity, the largest source of intermodel spread in the change in poleward energy transport can be attributed to the shortwave cloud feedback. © 2012 American Meteorological Society."
"6603144464;7005137442;55165863400;6603374472;","Modelling the primary control of paleogeography on Cretaceous climate",2006,"10.1016/j.epsl.2006.06.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746481737&doi=10.1016%2fj.epsl.2006.06.007&partnerID=40&md5=7f9807ff7a8fcfe6268df91b23c4b512","The low thermal gradients and clement winters characterizing climates of the Cretaceous period reveal that the climate system has modes of behaviour quite different from the present. Recent proxy data analyses suggest that some aspects of climate change within the Cretaceous appear to be decoupled from CO2 evolution at the geological time scale. Here, we investigate the impact of paleogeography on the global climate with the climate model FOAM, using a Early, Mid and Late Cretaceous continental configuration. We find that changes in geography from the Early to Mid-to-Late Cretaceous cause a large decrease of the seasonal cycle. First order identified processes are the decreased continentality of the mid-to-high latitudes from the Mid Cretaceous and the increase of the latent heat transport into the winter hemisphere which induce a wetter and a cloudier atmosphere capable of diminishing the winter cooling of the continents. Owing to the modifications of the seasonal cycle in response to the tectonic forcing, the equator-to-pole thermal gradient is reduced from the Early to Mid-to-Late Cretaceous. We nevertheless still do not succeed in simulating warm enough polar temperatures and a definitive theory still waits for an integrated approach explicitly accounting for each factor influencing the thermal gradient (ocean dynamics, stratospheric clouds, and vegetation). Our study also suggests a mechanism that can weaken the correlation between CO2 and climate changes during the Cretaceous as evolving geography from the Early to Late Cretaceous, through the response of the water cycle and the changes in the thermal gradient, results in a 3.8 °C global warming at a constant atmospheric CO2 level. This demonstrates that the paleogeography may affect the relation between pCO2 and the climate history and consequently has to be accounted for when linking the atmospheric CO2 evolution and the climate record at geological time scales. © 2006 Elsevier B.V. All rights reserved."
"55332348600;26645289600;7402064802;","Impact of decadal cloud variations on the Earth's energy budget",2016,"10.1038/ngeo2828","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85001086925&doi=10.1038%2fngeo2828&partnerID=40&md5=8466cc3c3672bd6b4820620164c792b5","Feedbacks of clouds on climate change strongly influence the magnitude of global warming. Cloud feedbacks, in turn, depend on the spatial patterns of surface warming, which vary on decadal timescales. Therefore, the magnitude of the decadal cloud feedback could deviate from the long-term cloud feedback. Here we present climate model simulations to show that the global mean cloud feedback in response to decadal temperature fluctuations varies dramatically due to time variations in the spatial pattern of sea surface temperature. We find that cloud anomalies associated with these patterns significantly modify the Earth's energy budget. Specifically, the decadal cloud feedback between the 1980s and 2000s is substantially more negative than the long-term cloud feedback. This is a result of cooling in tropical regions where air descends, relative to warming in tropical ascent regions, which strengthens low-level atmospheric stability. Under these conditions, low-level cloud cover and its reflection of solar radiation increase, despite an increase in global mean surface temperature. These results suggest that sea surface temperature pattern-induced low cloud anomalies could have contributed to the period of reduced warming between 1998 and 2013, and offer a physical explanation of why climate sensitivities estimated from recently observed trends are probably biased low."
"7102015136;6602112847;","The CLAW hypothesis: A review of the major developments",2007,"10.1071/EN07080","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36849015158&doi=10.1071%2fEN07080&partnerID=40&md5=8729219a986b3bdd28cb0e41f169a6fd","The CLAW hypothesis has for 20 years provided the intriguing prospect of oceanic and atmospheric systems exhibiting in an intimately coupled way a capacity to react to changing climate in a manner that opposes the change. A great number of quality scientific papers has resulted, many confirming details of specific links between oceanic phytoplankton and dimethylsulfide (DMS) emission to the atmosphere, the importance of DMS oxidation products in regulation of marine atmospheric cloud condensation nucleus (CCN) populations, and a concomitant influence on marine stratocumulus cloud properties. However, despite various links in the proposed phytoplankton?DMS?CCN?cloud albedo climate feedback loop being affirmed, there has been no overall scientific synthesis capable of adequately testing the hypothesis at a global scale. Moreover, significant gaps and contradictions remain, such as a lack of quantitative understanding of new particle formation processes in the marine atmospheric boundary layer, and of the extent to which dynamical, rather than microphysical, cloud feedbacks exist. Nevertheless, considerable progress has been made in understanding ?Earth System Science' involving the integration of ocean and atmospheric systems inherent in the CLAW hypothesis. We present here a short review of this progress since the publication of the CLAW hypothesis."
"7403288995;7102875645;","The role of water vapor feedback in unperturbed climate variability and global warming",1999,"10.1175/1520-0442(1999)012<2327:trowvf>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033172671&doi=10.1175%2f1520-0442%281999%29012%3c2327%3atrowvf%3e2.0.co%3b2&partnerID=40&md5=90c159d8a4881c1bd48aef2b75e39a69","To understand the role of water vapor feedback in unperturbed surface temperature variability, a version of the Geophysical Fluid Dynamics Laboratory coupled ocean-atmosphere model is integrated for 1000 yr in two configurations, one with water vapor feedback and one without. For all spatial scales, the model with water vapor feedback has more low-frequency (timescale ≥ 2 yr) surface temperature variability than the one without. Thus water vapor feedback is positive in the context of the model's unperturbed variability. In addition, water vapor feedback is more effective the longer the timescale of the surface temperature anomaly and the larger its spatial scale. To understand the role of water vapor feedback in global warming, two 500-yr integrations were also performed in which CO2 was doubled in both model configurations. The final surface global warming in the model with water vapor feedback is 3.38°C, while in the one without it is only 1.05°C. However, the model's water vapor feedback has a larger impact on surface warming in response to a doubling of CO2 than it does on internally generated, low-frequency, global-mean surface temperature anomalies. Water vapor feedback's strength therefore depends on the type of temperature anomaly it affects. The authors found that the degree to which a surface temperature anomaly penetrates into the troposphere is a critical factor in determining the effectiveness of its associated water vapor feedback. The more the anomaly penetrates, the stronger the feedback. It is also shown that the apparent impact of water vapor feedback is altered by other feedback mechanisms, such as albedo and cloud feedback. The sensitivity of the results to this fact is examined. Finally, the authors compare the local and global-mean surface temperature time series from both unperturbed variability experiments to the observed record. The experiment without water vapor feedback does not have enough global-scale variability to reproduce the magnitude of the variability in the observed global-mean record, whether or not one removes the warming trend observed over the past century. In contrast, the amount of variability in the experiment with water vapor feedback is comparable to that of the global-mean record, provided the observed warming trend is removed. Thus, the authors are unable to simulate the observed levels of variability without water vapor feedback."
"7404183672;6602080205;","Climate response to tropospheric absorbing aerosols in an intermediate general-circulation model",2004,"10.1256/qj.03.64","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0442280914&doi=10.1256%2fqj.03.64&partnerID=40&md5=cda2d7266de304e5983eed326ad5e827","This study uses idealized aerosol distributions with the Reading Intermediate General-Circulation Model (IGCM) to assess and explain the climate response in that model to absorbing tropospheric aerosol. We find that the sign of the direct aerosol radiative forcing is not a good indication of the sign of the resulting global and annual mean surface temperature change. The climate sensitivity parameter for aerosols which absorb some solar radiation is much larger than that for CO2 or solar experiments with the same model. Reasons for the enhanced surface temperature response in the presence of aerosol are examined. Significant changes in cloud amount occur, some of which appear most influenced by the change in surface temperature and may be generic to any mechanism that warms the surface. A reduction in low cloud amount occurs when the aerosol single-scattering albedo is less than 0.95; the so-called 'semi-direct' effect of aerosols is clearly evident in this model. We suggest that this aerosol-cloud feedback is present in all GCMs which include absorbing tropospheric aerosol but remains largely undiagnosed. Comparisons with a previous study and further sensitivity tests suggest that the magnitude of this effect and the mechanisms behind it are strongly dependent on the cloud scheme employed."
"8882641700;7004479957;55745955800;8977001000;55272477500;24173130300;56611366900;7005056279;6603606681;7403282069;","Marine low cloud sensitivity to an idealized climate change: The CGILS les intercomparison",2013,"10.1002/jame.20025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880812843&doi=10.1002%2fjame.20025&partnerID=40&md5=4a00dc8fca01a79f4c3c556826e4d4e0","Subtropical marine low cloud sensitivity to an idealized climate change is compared in six large-eddy simulation (LES) models as part of CGILS. July cloud cover is simulated at three locations over the subtropical northeast Pacific Ocean, which are typified by cold sea surface temperatures (SSTs) under well-mixed stratocumulus, cool SSTs under decoupled stratocumulus, and shallow cumulus clouds overlying warmer SSTs. The idealized climate change includes a uniform 2 K SST increase with corresponding moist-adiabatic warming aloft and subsidence changes, but no change in free-tropospheric relative humidity, surface wind speed, or CO<inf>2</inf>. For each case, realistic advective forcings and boundary conditions are generated for the control and perturbed states which each LES runs for 10 days into a quasi-steady state. For the control climate, the LESs correctly produce the expected cloud type at all three locations. With the perturbed forcings, all models simulate boundary-layer deepening due to reduced subsidence in the warmer climate, with less deepening at the warm-SST location due to regulation by precipitation. The models do not show a consistent response of liquid water path and albedo in the perturbed climate, though the majority predict cloud thickening (negative cloud feedback) at the cold-SST location and slight cloud thinning (positive cloud feedback) at the cool-SST and warm-SST locations. In perturbed climate simulations at the cold-SST location without the subsidence decrease, cloud albedo consistently decreases across the models. Thus, boundary-layer cloud feedback on climate change involves compensating thermodynamic and dynamic effects of warming and may interact with patterns of subsidence change. ©2013. American Geophysical Union. All Rights Reserved."
"36720934300;15026371500;57203030873;","Coupling between Arctic feedbacks and changes in poleward energy transport",2011,"10.1029/2011GL048546","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052768870&doi=10.1029%2f2011GL048546&partnerID=40&md5=85067b5ef298b6907d3e4a160cc6ffa5","The relationship between poleward energy transport and Arctic amplification is examined using climate models and an energy balance model. In 21st century projections, models with large Arctic amplification have strong surface albedo and longwave cloud feedbacks, but only weak increases (or even decreases) in total energy transport into the Arctic. Enhanced Arctic warming weakens the equator-to-pole temperature gradient and decreases atmospheric dry static energy transport, a decrease that often outweighs increases from atmospheric moisture transport and ocean heat transport. Model spread in atmospheric energy transport cannot explain model spread in polar amplification; models with greater polar amplification must instead have stronger local feedbacks. Because local feedbacks affect temperature gradients, coupling between energy transports and Arctic feedbacks cannot be neglected when studying Arctic amplification. Copyright 2011 by the American Geophysical Union."
"6602878057;7004479957;6701431208;7005513582;7005808242;57218978147;7402064802;7003543851;","A comparison of low-latitude cloud properties and their response to climate change in three AGCMs sorted into regimes using mid-tropospheric vertical velocity",2006,"10.1007/s00382-006-0138-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646440016&doi=10.1007%2fs00382-006-0138-4&partnerID=40&md5=c67367343b23e76b62fbb04f04cde3d4","Low-latitude cloud distributions and cloud responses to climate perturbations are compared in near-current versions of three leading U.S. AGCMs, the NCAR CAM 3.0, the GFDL AM2.12b, and the NASA GMAO NSIPP-2 model. The analysis technique of Bony et al. (Clim Dyn 22:71-86, 2004) is used to sort cloud variables by dynamical regime using the monthly mean pressure velocity ω at 500 hPa from 30S to 30N. All models simulate the climatological monthly mean top-of-atmosphere longwave and shortwave cloud radiative forcing (CRF) adequately in all ω-regimes. However, they disagree with each other and with ISCCP satellite observations in regime-sorted cloud fraction, condensate amount, and cloud-top height. All models have too little cloud with tops in the middle troposphere and too much thin cirrus in ascent regimes. In subsidence regimes one model simulates cloud condensate to be too near the surface, while another generates condensate over an excessively deep layer of the lower troposphere. Standardized climate perturbation experiments of the three models are also compared, including uniform SST increase, patterned SST increase, and doubled CO2 over a mixed layer ocean. The regime-sorted cloud and CRF perturbations are very different between models, and show lesser, but still significant, differences between the same model simulating different types of imposed climate perturbation. There is a negative correlation across all general circulation models (GCMs) and climate perturbations between changes in tropical low cloud cover and changes in net CRF, suggesting a dominant role for boundary layer cloud in these changes. For some of the cases presented, upper-level clouds in deep convection regimes are also important, and changes in such regimes can either reinforce or partially cancel the net CRF response from the boundary layer cloud in subsidence regimes. This study highlights the continuing uncertainty in both low and high cloud feedbacks simulated by GCMs. © Springer-Verlag 2006."
"7402064802;7403288995;","Emergent Constraints for Cloud Feedbacks",2015,"10.1007/s40641-015-0027-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983569811&doi=10.1007%2fs40641-015-0027-1&partnerID=40&md5=f333e18572465993b884afd6defdf391","Emergent constraints are physically explainable empirical relationships between characteristics of the current climate and long-term climate prediction that emerge in collections of climate model simulations. With the prospect of constraining long-term climate prediction, scientists have recently uncovered several emergent constraints related to long-term cloud feedbacks. We review these proposed emergent constraints, many of which involve the behavior of low-level clouds, and discuss criteria to assess their credibility. With further research, some of the cases we review may eventually become confirmed emergent constraints, provided they are accompanied by credible physical explanations. Because confirmed emergent constraints identify a source of model error that projects onto climate predictions, they deserve extra attention from those developing climate models and climate observations. While a systematic bias cannot be ruled out, it is noteworthy that the promising emergent constraints suggest larger cloud feedback and hence climate sensitivity. © 2015, Springer International Publishing AG."
"55170561300;8633784600;26323066900;6603415703;8633783900;7201582802;35204593500;16635813000;7004390019;35221443100;55173596300;6602080205;7004169476;18233458200;57198346163;14421382400;55169361300;55884295300;6603749140;6602170016;23486332900;23045537300;7403159332;7006685152;55171972400;35725510400;7404105326;","Broad range of 2050 warming from an observationally constrained large climate model ensemble",2012,"10.1038/ngeo1430","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859329332&doi=10.1038%2fngeo1430&partnerID=40&md5=ad18dadb57a6be625240e0731d7ec1d0","Incomplete understanding of three aspects of the climate system-equilibrium climate sensitivity, rate of ocean heat uptake and historical aerosol forcing-and the physical processes underlying them lead to uncertainties in our assessment of the global-mean temperature evolution in the twenty-first century 1,2. Explorations of these uncertainties have so far relied on scaling approaches 3,4, large ensembles of simplified climate models 1,2, or small ensembles of complex coupled atmosphere-ocean general circulation models 5,6 which under-represent uncertainties in key climate system properties derived from independent sources 7,9. Here we present results from a multi-thousand-member perturbed-physics ensemble of transient coupled atmosphere-ocean general circulation model simulations. We find that model versions that reproduce observed surface temperature changes over the past 50 years show global-mean temperature increases of 1.4-3 K by 2050, relative to 1961-1990, under a mid-range forcing scenario. This range of warming is broadly consistent with the expert assessment provided by the Intergovernmental Panel on Climate Change Fourth Assessment Report, but extends towards larger warming than observed in ensembles-of-opportunity 5 typically used for climate impact assessments. From our simulations, we conclude that warming by the middle of the twenty-first century that is stronger than earlier estimates is consistent with recent observed temperature changes and a mid-range 'no mitigation' scenario for greenhouse-gas emissions. © 2012 Macmillan Publishers Limited. All rights reserved."
"16024614000;7401491382;56252968200;","Variations in cloud cover and cloud types over the Ocean from surface observations, 1954-2008",2011,"10.1175/2011JCLI3972.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-83755182932&doi=10.1175%2f2011JCLI3972.1&partnerID=40&md5=c9e45f95c896d67df2d825c00c8c4fea","Synoptic weather observations from ships throughout the World Ocean have been analyzed to produce a climatology of total cloud cover and the amounts of nine cloud types. About 54 million observations contributed to the climatology, which now covers 55 years from 1954 to 2008. In this work, interannual variations of seasonal cloud amounts are analyzed in 10° grid boxes. Long-term variations O(5-10 yr), coherent across multiple latitude bands, remain present in the updated cloud data. Acomparison to coincident data on islands indicates that the coherent variations are probably spurious. An exact cause for this behavior remains elusive. The globally coherent variations are removed from the gridbox time series using a Butterworth filter before further analysis. Before removing the spurious variation, the global average time series of total cloud cover over the ocean shows low-amplitude, long-term variations O(2%) over the 55-yr span. High-frequency, year-to-year variation is seen O(1%-2%). Among the cloud types, the most widespread and consistent relationship is found for the extensive marine stratus and stratocumulus clouds (MSC) over the eastern parts of the subtropical oceans. Substantiating and expanding upon previous work, strong negative correlation is found between MSC and sea surface temperature (SST) in the eastern North Pacific, eastern South Pacific, eastern South Atlantic, eastern North Atlantic, and the Indian Ocean west of Australia. By contrast, a positive correlation between cloud cover and SST is seen in the central Pacific. High clouds show a consistent low-magnitude positive correlation with SST over the equatorial ocean. In regions of persistent MSC, time series show decreasing MSC amount. This decrease could be due to further spurious variation within the data. However, the decrease combined with observed increases in SST and the negative correlation between marine stratus and sea surface temperature suggests a positive cloud feedback to the warming sea surface. The observed decrease of MSChas been partly but not completely offset by increasing cumuliform clouds in these regions; a similar decrease in stratiform and increase in cumuliform clouds had previously been seen over land. Interannual variations of cloud cover in the tropics show strong correlation with an ENSO index. © 2011 American Meteorological Society."
"55745955800;7004479957;8882641700;7101795549;6701431208;35509639400;54893098900;57195644113;8977001000;57193132723;6603606681;55272477500;8877858700;6701752471;36876405100;24173130300;25927181300;7004714030;7203062717;13405561000;56865378100;7005920812;56611366900;7005056279;57203053317;6701346974;6603371044;6602364115;7006705919;23768540500;55536607600;6603566335;56039057300;7201504886;35497573900;7403282069;6603613067;7201485519;7403174207;55286185400;","CGILS: Results from the first phase of an international project to understand the physical mechanisms of low cloud feedbacks in single column models",2013,"10.1002/2013MS000246","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85006568652&doi=10.1002%2f2013MS000246&partnerID=40&md5=b171fa23582f1967fe02b0e35904ae26","CGILS-the CFMIP-GASS Intercomparison of Large Eddy Models (LESs) and single column models (SCMs)-investigates the mechanisms of cloud feedback in SCMs and LESs under idealized climate change perturbation. This paper describes the CGILS results from 15 SCMs and 8 LES models. Three cloud regimes over the subtropical oceans are studied: shallow cumulus, cumulus under stratocumulus, and well-mixed coastal stratus/stratocumulus. In the stratocumulus and coastal stratus regimes, SCMs without activated shallow convection generally simulated negative cloud feedbacks, while models with active shallow convection generally simulated positive cloud feedbacks. In the shallow cumulus alone regime, this relationship is less clear, likely due to the changes in cloud depth, lateral mixing, and precipitation or a combination of them. The majority of LES models simulated negative cloud feedback in the well-mixed coastal stratus/stratocumulus regime, and positive feedback in the shallow cumulus and stratocumulus regime. A general framework is provided to interpret SCM results: in a warmer climate, the moistening rate of the cloudy layer associated with the surface-based turbulence parameterization is enhanced; together with weaker large-scale subsidence, it causes negative cloud feedback. In contrast, in the warmer climate, the drying rate associated with the shallow convection scheme is enhanced. This causes positive cloud feedback. These mechanisms are summarized as the ""NESTS"" negative cloud feedback and the ""SCOPE"" positive cloud feedback (Negative feedback from Surface Turbulence under weaker Subsidence-Shallow Convection PositivE feedback) with the net cloud feedback depending on how the two opposing effects counteract each other. The LES results are consistent with these interpretations. © American Geophysical Union."
"7402612084;57206416522;","A flexible climate model for use in integrated assessments",1998,"10.1007/s003820050224","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031846054&doi=10.1007%2fs003820050224&partnerID=40&md5=ceab4084574c3a274e500a357a0c4be9","Because of significant uncertainty in the behavior of the climate system, evaluations of the possible impact of an increase in greenhouse gas concentrations in the atmosphere require a large number of long-term climate simulations. Studies of this kind are impossible to carry out with coupled atmosphere ocean general circulation models (AOGCMs) because of their tremendous computer resource requirements. Here we describe a two dimensional (zonally averaged) atmospheric model coupled with a diffusive ocean model developed for use in the integrated framework of the Massachusetts Institute of Technology (MIT) Joint Program on the Science and Policy of Global Change. The 2-D model has been developed from the Goddard Institute for Space Studies (GISS) GCM and includes parametrizations of all the main physical processes. This allows it to reproduce many of the nonlinear interactions occurring in simulations with GCMs. Comparisons of the results of present-day climate simulations with observations show that the model reasonably reproduces the main features of the zonally averaged atmospheric structure and circulation. The model's sensitivity can be varied by changing the magnitude of an inserted additional cloud feedback. Equilibrium responses of different versions of the 2-D model to an instantaneous doubling of atmospheric CO2 are compared with results of similar simulations with different AGCMs. It is shown that the additional cloud feedback does not lead to any physically inconsistent results. On the contrary, changes in climate variables such as precipitation and evaporation, and their dependencies on surface warming produced by different versions of the MIT 2-D model are similar to those shown by GCMs. By choosing appropriate values of the deep ocean diffusion coefficients, the transient behavior of different AOGCMs can be matched in simulations with the 2-D model, with a unique choice of diffusion coefficients allowing one to match the performance of a given AOGCM for a variety of transient forcing scenarios. Both surface warming and sea level rise due to thermal expansion of the deep ocean in response to a gradually increasing forcing are reasonably reproduced on time scales of 100-150 y. However a wide range of diffusion coefficients is needed to match the behavior of different AOGCMs. We use results of simulations with the 2-D model to show that the impact on climate change of the implied uncertainty in the rate of heat penetration into the deep ocean is comparable with that of other significant uncertainties."
"55437010000;23492864500;7201504886;","Marine boundary layer cloud feedbacks in a constant relative humidity atmosphere",2012,"10.1175/JAS-D-11-0203.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867966133&doi=10.1175%2fJAS-D-11-0203.1&partnerID=40&md5=ea60d5413e08b311d9bf3968f2e3b7ab","The mechanisms that govern the response of shallow cumulus, such as found in the trade wind regions, to a warming of the atmosphere in which large-scale atmospheric processes act to keep relative humidity constant are explored. Two robust effects are identified. First, and as is well known, the liquid water lapse rate increases with temperature and tends to increase the amount of water in clouds, making clouds more reflective of solar radiation. Second, and less well appreciated, the surface fluxes increase with the saturation specific humidity, which itself is a strong function of temperature. Using large-eddy simulations it is shown that the liquid water lapse rate acts as a negative feedback: a positive temperature increase driven by radiative forcing is reduced by the increase in cloud water and hence cloud albedo. However, this effect is more than compensated by a reduction of cloudiness associated with the deepening and relative drying of the boundary layer, driven by larger surface moisture fluxes. Because they are so robust, these effects are thought to underlie changes in the structure of the marine boundary layer as a result of global warming. © 2012 American Meteorological Society."
"36339753800;57205867148;6602600408;","On constraining estimates of climate sensitivity with present-day observations through model weighting",2011,"10.1175/2011JCLI4193.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960351865&doi=10.1175%2f2011JCLI4193.1&partnerID=40&md5=91ecf954d348e0215e47a0ebb089b122","The distribution of model-based estimates of equilibrium climate sensitivity has not changed substantially in more than 30 years. Efforts to narrow this distribution by weighting projections according to measures of model fidelity have so far failed, largely because climate sensitivity is independent of current measures of skill in current ensembles of models. This work presents a cautionary example showing that measures of model fidelity that are effective at narrowing the distribution of future projections (because they are systematically related to climate sensitivity in an ensemble of models) may be poor measures of the likelihood that a model will provide an accurate estimate of climate sensitivity (and thus degrade distributions of projections if they are used as weights). Furthermore, it appears unlikely that statistical tests alone can identify robust measures of likelihood. The conclusions are drawn from two ensembles: one obtained by perturbing parameters in a single climate model and a second containing the majority of the world's climate models. The simple ensemble reproduces many aspects of the multimodel ensemble, including the distributions of skill in reproducing the present-day climatology of clouds and radiation, the distribution of climate sensitivity, and the dependence of climate sensitivity on certain cloud regimes. Weighting by error measures targeted on those regimes permits the development of tighter relationships between climate sensitivity and model error and, hence, narrower distributions of climate sensitivity in the simple ensemble. These relationships, however, do not carry into the multimodel ensemble. This suggests that model weighting based on statistical relationships alone is unfounded and perhaps that climate model errors are still large enough that model weighting is not sensible. © 2011 American Meteorological Society."
"7404142321;7004169476;57203049177;","Time variation of effective climate sensitivity in GCMs",2008,"10.1175/2008JCLI2371.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-52949139265&doi=10.1175%2f2008JCLI2371.1&partnerID=40&md5=a296b5801db1197d0fbf04c5ba60cae9","Effective climate sensitivity is often assumed to be constant (if uncertain), but some previous studies of general circulation model (GCM) simulations have found it varying as the simulation progresses. This complicates the fitting of simple models to such simulations, as well as having implications for the estimation of climate sensitivity from observations. This study examines the evolution of the feedbacks determining the climate sensitivity in GCMs submitted to the Coupled Model Intercomparison Project. Apparent centennial- time-scale variations of effective climate sensitivity during stabilization to a forcing can be considered an artifact of using conventional forcings, which only allow for instantaneous effects and stratospheric adjustment. If the forcing is adjusted for processes occurring on time scales that are short compared to the climate stabilization time scale, then there is little centennial-time-scale evolution of effective climate sensitivity in any of the GCMs. Here it is suggested that much of the apparent variation in effective climate sensitivity identified in previous studies is actually due to the comparatively fast forcing adjustment. Persistent differences are found in the strength of the feedbacks between the coupled atmosphere-ocean (AO) versions and their atmosphere-mixed layer ocean (AML) counterparts (the latter are often assumed to give the equilibrium climate sensitivity of the AOGCM). The AML model can typically only estimate the equilibrium climate sensitivity of the parallel AO version to within about 0.5 K. The adjustment to the forcing to account for comparatively fast processes varies in magnitude and sign between GCMs, as well as differing between AO and AML versions of the same model. There is evidence from one AOGCM that the forcing adjustment may take a couple of decades, with implications for observationally based estimates of equilibrium climate sensitivity. It is suggested that at least some of the spread in twenty-first-century global temperature predictions between GCMs is due to differing adjustment processes, hence work to understand these differences should be a priority."
"16645242800;7003802133;7005720211;","Continued global warming after CO2 emissions stoppage",2014,"10.1038/nclimate2060","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890904709&doi=10.1038%2fnclimate2060&partnerID=40&md5=ba5159da74f9be2b559d9bac000bb9f1","Recent studies have suggested that global mean surface temperature would remain approximately constant on multi-century timescales after CO2 emissions are stopped. Here we use Earth system model simulations of such a stoppage to demonstrate that in some models, surface temperature may actually increase on multi-century timescales after an initial century-long decrease. This occurs in spite of a decline in radiative forcing that exceeds the decline in ocean heat uptake - a circumstance that would otherwise be expected to lead to a decline in global temperature. The reason is that the warming effect of decreasing ocean heat uptake together with feedback effects arising in response to the geographic structure of ocean heat uptake overcompensates the cooling effect of decreasing atmospheric CO2 on multi-century timescales. Our study also reveals that equilibrium climate sensitivity estimates based on a widely used method of regressing the Earth's energy imbalance against surface temperature change are biased. Uncertainty in the magnitude of the feedback effects associated with the magnitude and geographic distribution of ocean heat uptake therefore contributes substantially to the uncertainty in allowable carbon emissions for a given multi-century warming target. © 2014 Macmillan Publishers Limited. All rights reserved."
"7403508241;7004325649;7102731389;7407116104;7403282069;","The Iris hypothesis: A negative or positive cloud feedback?",2002,"10.1175/1520-0442(2002)015<0003:tihano>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036465051&doi=10.1175%2f1520-0442%282002%29015%3c0003%3atihano%3e2.0.co%3b2&partnerID=40&md5=40fa5c52c42b03fb5535bc78260ce775","Using the Tropical Rainfall Measuring Mission (TRMM) satellite measurements over tropical oceans, this study evaluates the iris hypothesis recently proposed by Lindzen et al. that tropical upper-tropospheric anvils act as a strong negative feedback in the global climate system. The modeled radiative fluxes of Lindzen et al. are replaced by the Clouds and the Earth's Radiant Energy System (CERES) directly observed broadband radiation fields. The observations show that the clouds have much higher albedos and moderately larger longwave fluxes than those assumed by Lindzen et al. As a result, decreases in these clouds would cause a significant but weak positive feedback to the climate system, instead of providing a strong negative feedback."
"55758496500;7202162685;","The implications for climate sensitivity of AR5 forcing and heat uptake estimates",2015,"10.1007/s00382-014-2342-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84932194317&doi=10.1007%2fs00382-014-2342-y&partnerID=40&md5=b429b7b7fd3773f19e5b34a0d6b06b1f","Energy budget estimates of equilibrium climate sensitivity (ECS) and transient climate response (TCR) are derived using the comprehensive 1750–2011 time series and the uncertainty ranges for forcing components provided in the Intergovernmental Panel on Climate Change Fifth Assessment Working Group I Report, along with its estimates of heat accumulation in the climate system. The resulting estimates are less dependent on global climate models and allow more realistically for forcing uncertainties than similar estimates based on forcings diagnosed from simulations by such models. Base and final periods are selected that have well matched volcanic activity and influence from internal variability. Using 1859–1882 for the base period and 1995–2011 for the final period, thus avoiding major volcanic activity, median estimates are derived for ECS of 1.64 K and for TCR of 1.33 K. ECS 17–83 and 5–95 % uncertainty ranges are 1.25–2.45 and 1.05–4.05 K; the corresponding TCR ranges are 1.05–1.80 and 0.90–2.50 K. Results using alternative well-matched base and final periods provide similar best estimates but give wider uncertainty ranges, principally reflecting smaller changes in average forcing. Uncertainty in aerosol forcing is the dominant contribution to the ECS and TCR uncertainty ranges. © 2014, Springer-Verlag Berlin Heidelberg."
"55207447000;","Heat capacity, time constant, and sensitivity of Earth's climate system",2007,"10.1029/2007JD008746","https://www.scopus.com/inward/record.uri?eid=2-s2.0-49249084300&doi=10.1029%2f2007JD008746&partnerID=40&md5=d38764042f972de418af9bf84e6f1589","The equilibrium sensitivity of Earth's climate is determined as the quotient of the relaxation time constant of the system and the pertinent global heat capacity. The heat capacity of the global ocean, obtained from regression of ocean heat content versus global mean surface temperature, GMST, is 14 ± 6 W a m-2 K-1, equivalent to 110 m of ocean water; other sinks raise the effective planetary heat capacity to 17 ± 7 W a m-2 K-1 (all uncertainties are 1-sigma estimates). The time constant pertinent to changes in GMST is determined from autocorrelation of that quantity over 1880-2004 to be 5 ± 1 a. The resultant equilibrium climate sensitivity, 0.30 ± 0.14 K/(W m-2), corresponds to an equilibrium temperature increase for doubled CO<inf>2</inf> of 1.1 ± 0.5 K. The short time constant implies that GMST is in near equilibrium with applied forcings and hence that net climate forcing over the twentieth century can be obtained from the observed temperature increase over this period, 0.57 ± 0.08 K, as 1.9 ± 0.9 W m-2. For this forcing considered the sum of radiative forcing by incremental greenhouse gases, 2.2 ± 0.3 W m-2, and other forcings, other forcing agents, mainly incremental tropospheric aerosols, are inferred to have exerted only a slight forcing over the twentieth century of -0.3 ± 1.0 W m-2. Copyright 2007 by the American Geophysical Union."
"57193132723;6507993848;7403318365;16304488000;","Cumulus microphysics and climate sensitivity",2005,"10.1175/JCLI3413.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25844503623&doi=10.1175%2fJCLI3413.1&partnerID=40&md5=c36adb3f504b938b99d45ec43b488472","Precipitation processes in convective storms are potentially a major regulator of cloud feedback. An unresolved issue is how the partitioning of convective condensate between precipitation-size particles that fall out of updrafts and smaller particles that are detrained to form anvil clouds will change as the climate warms. Tropical Rainfall Measuring Mission (TRMM) observations of tropical oceanic convective storms indicate higher precipitation efficiency at warmer sea surface temperature (SST) but also suggest that cumulus anvil sizes, albedos, and ice water paths become insensitive to warming at high temperatures. International Satellite Cloud Climatology Project (ISCCP) data show that instantaneous cirrus and deep convective cloud fractions are positively correlated and increase with SST except at the highest temperatures, but are sensitive to variations in large-scale vertical velocity. A simple conceptual model based on a Marshall-Palmer drop size distribution, empirical terminal velocity-particle size relationships, and assumed cumulus updraft speeds reproduces the observed tendency for detrained condensate to approach a limiting value at high SST. These results suggest that the climatic behavior of observed tropical convective clouds is intermediate between the extremes required to support the thermostat and adaptive iris hypotheses."
"44061090200;35547807400;8326850700;","Spatial patterns of modeled climate feedback and contributions to temperature response and polar amplification",2011,"10.1175/2011JCLI3863.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960675006&doi=10.1175%2f2011JCLI3863.1&partnerID=40&md5=9de4abe7030e90b13f3df5add6194bb4","Spatial patterns of local climate feedback and equilibriumpartial temperature responses are produced from eight general circulation models with slab oceans forced by doubling carbon dioxide (CO2). The analysis is extended to other forcing mechanisms with the Met Office Hadley Centre slab ocean climate model version 3 (HadSM3). In agreement with previous studies, the greatest intermodel differences are in the tropical cloud feedbacks. However, the greatest intermodel spread in the equilibrium temperature response comes from the water vapor plus lapse rate feedback, not clouds, disagreeing with a previous study. Although the surface albedo feedback contributes most in the annual mean to the greater warming of high latitudes, compared to the tropics (polar amplification), its effect is significantly ameliorated by shortwave cloud feedback. In different seasons the relative importance of the contributions varies considerably, with longwave cloudy-sky feedback and horizontal heat transport plus ocean heat release playing a major role during winter and autumn when polar amplification is greatest. The greatest intermodel spread in annual mean polar amplification is due to variations in horizontal heat transport and shortwave cloud feedback. Spatial patterns of local climate feedback for HadSM3 forced with 2 × CO2, 12% solar, low-level scattering aerosol and high-level absorbing aerosol are more similar than those for different models forced with 2 × CO2. However, the equilibrium temperature response to high-level absorbing aerosol shows considerably enhanced polar amplification compared to the other forcing mechanisms, largely due to differences in horizontal heat transport and water vapor plus lapse rate feedback, with the forcing itself acting to reduce amplification. Such variations in highlatitude response between models and forcing mechanisms make it difficult to infer specific causes of recent Arctic temperature change. © 2011 American Meteorological Society."
"56575686800;7201485519;","Dependency of global mean precipitation on surface temperature",2008,"10.1029/2008GL034838","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56449120333&doi=10.1029%2f2008GL034838&partnerID=40&md5=1cc2d3a5a89246229febdb53dce66b3a","We investigate the causes of temperature dependent changes in global precipitation in contemporary General Circulation Models (GCMs) subjected to a doubling of atmospheric CO2 concentration. By analyzing the energy budget of the troposphere, we find that changes are dominated by processes robustly simulated by GCMs. Importantly, shortwave cloud feedbacks, whose uncertainty is largely responsible for the wide range of GCM temperature climate sensitivities, are shown to have little effect. This is because these mainly arise from the scattering of shortwave radiation that has little impact on the tropospheric heating that controls precipitation. Hence, we expect that the range of simulated precipitation sensitivities to temperature will not change greatly in future GCMs, despite the recent suggestion that satellite observations indicate that GCM precipitation changes are significantly in error."
"57112070700;23012746800;12761291000;55885528600;6602414959;12242312400;","Transient climate response in a two-layer energy-balance model. Part II: Representation of the efficacy of deep-ocean heat uptake and validation for CMIP5 AOGCMs",2013,"10.1175/JCLI-D-12-00196.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871537248&doi=10.1175%2fJCLI-D-12-00196.1&partnerID=40&md5=50d1e099faf54c15856ed8e20a2dc595","In this second part of a series of two articles analyzing the global thermal properties of atmosphere-ocean coupled general circulation models (AOGCMs) within the framework of a two-layer energy-balance model (EBM), the role of the efficacy of deep-ocean heat uptake is investigated. Taking into account such an efficacy factor is shown to amount to representing the effect of deep-ocean heat uptake on the local strength of the radiative feedback in the transient regime. It involves an additional term in the formulation of the radiative imbalance at the top of the atmosphere (TOA), which explains the nonlinearity between radiative imbalance and the mean surface temperature observed in some AOGCMs. An analytical solution of this system is given and this simple linear EBM is calibrated for the set of 16 AOGCMs of phase 5 of the Coupled Model Intercomparison Project (CMIP5) studied in Part I. It is shown that both the net radiative fluxes at TOAand the global surface temperature transient response are well represented by the simple EBM over the available period of simulations. Differences between this two-layer EBM and the previous version without an efficacy factor are analyzed and relationships between parameters are discussed. The simple model calibration applied to AOGCMs constitutes a new method for estimating their respective equilibrium climate sensitivity and adjusted radiative forcing amplitude from short-term step-forcing simulations and more generally a method to compute their global thermal properties. © 2013 American Meteorological Society."
"55885528600;23012746800;7005806315;10339477400;55597087360;36159440000;26634988200;6507659985;6506553245;53865439800;55802221900;36187387300;15828193000;55240165900;6602240885;6603853280;6507121903;57041028000;26031912400;26645901500;22134074500;7004468723;6507151484;6507882912;57112070700;7202219277;57194045072;57193170776;36599032700;26635870100;25227989500;6701659989;57190880798;","Evaluation of CMIP6 DECK Experiments With CNRM-CM6-1",2019,"10.1029/2019MS001683","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068081500&doi=10.1029%2f2019MS001683&partnerID=40&md5=3df91945a92219535ec8b6845d19335e","This paper describes the main characteristics of CNRM-CM6-1, the fully coupled atmosphere-ocean general circulation model of sixth generation jointly developed by Centre National de Recherches Météorologiques (CNRM) and Cerfacs for the sixth phase of the Coupled Model Intercomparison Project 6 (CMIP6). The paper provides a description of each component of CNRM-CM6-1, including the coupling method and the new online output software. We emphasize where model's components have been updated with respect to the former model version, CNRM-CM5.1. In particular, we highlight major improvements in the representation of atmospheric and land processes. A particular attention has also been devoted to mass and energy conservation in the simulated climate system to limit long-term drifts. The climate simulated by CNRM-CM6-1 is then evaluated using CMIP6 historical and Diagnostic, Evaluation and Characterization of Klima (DECK) experiments in comparison with CMIP5 CNRM-CM5.1 equivalent experiments. Overall, the mean surface biases are of similar magnitude but with different spatial patterns. Deep ocean biases are generally reduced, whereas sea ice is too thin in the Arctic. Although the simulated climate variability remains roughly consistent with CNRM-CM5.1, its sensitivity to rising CO2 has increased: the equilibrium climate sensitivity is 4.9 K, which is now close to the upper bound of the range estimated from CMIP5 models. ©2019. The Authors."
"7201485519;24329376600;13402835300;35509639400;7004479957;35742922300;6603925960;7004468723;36010237000;57203030873;7402064802;7101959253;8866821900;6603566335;36135047900;7201504886;6603422104;7007021059;55686667100;","The Cloud Feedback Model Intercomparison Project (CFMIP) contribution to CMIP6",2017,"10.5194/gmd-10-359-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85010764262&doi=10.5194%2fgmd-10-359-2017&partnerID=40&md5=13058d8755fbdbf7455ba0fce44048ba","The primary objective of CFMIP is to inform future assessments of cloud feedbacks through improved understanding of cloud-climate feedback mechanisms and better evaluation of cloud processes and cloud feedbacks in climate models. However, the CFMIP approach is also increasingly being used to understand other aspects of climate change, and so a second objective has now been introduced, to improve understanding of circulation, regional-scale precipitation, and non-linear changes. CFMIP is supporting ongoing model inter-comparison activities by coordinating a hierarchy of targeted experiments for CMIP6, along with a set of cloud-related output diagnostics. CFMIP contributes primarily to addressing the CMIP6 questions ""How does the Earth system respond to forcing?"" and ""What are the origins and consequences of systematic model biases?"" and supports the activities of the WCRP Grand Challenge on Clouds, Circulation and Climate Sensitivity. A compact set of Tier 1 experiments is proposed for CMIP6 to address this question: (1) what are the physical mechanisms underlying the range of cloud feedbacks and cloud adjustments predicted by climate models, and which models have the most credible cloud feedbacks? Additional Tier 2 experiments are proposed to address the following questions. (2) Are cloud feedbacks consistent for climate cooling and warming, and if not, why? (3) How do cloud-radiative effects impact the structure, the strength and the variability of the general atmospheric circulation in present and future climates? (4) How do responses in the climate system due to changes in solar forcing differ from changes due to CO2, and is the response sensitive to the sign of the forcing? (5) To what extent is regional climate change per CO2 doubling state-dependent (non-linear), and why? (6) Are climate feedbacks during the 20th century different to those acting on long-term climate change and climate sensitivity? (7) How do regional climate responses (e.g. in precipitation) and their uncertainties in coupled models arise from the combination of different aspects of CO2 forcing and sea surface warming? CFMIP also proposes a number of additional model outputs in the CMIP DECK, CMIP6 Historical and CMIP6 CFMIP experiments, including COSP simulator outputs and process diagnostics to address the following questions. 1. How well do clouds and other relevant variables simulated by models agree with observations? 2. What physical processes and mechanisms are important for a credible simulation of clouds, cloud feedbacks and cloud adjustments in climate models? 3. Which models have the most credible representations of processes relevant to the simulation of clouds? 4. How do clouds and their changes interact with other elements of the climate system. © Author(s) 2017."
"55932195300;8696069500;28367935500;","Robust increase in equilibrium climate sensitivity under global warming",2013,"10.1002/2013GL058118","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887879771&doi=10.1002%2f2013GL058118&partnerID=40&md5=3e4164aa83628c138cd2e00b8426dd88","Equilibrium climate sensitivity (ECS) is a widely accepted measure of Earth's susceptibility to radiative forcing. While ECS is often assumed to be constant to a first order of approximation, recent studies suggested that ECS might depend on the climate state. Here it is shown that the latest generation of climate models consistently exhibits an increasing ECS in warmer climates due to a strengthening of the water-vapor feedback with increasing surface temperatures. The increasing ECS is replicated by a one-dimensional radiative-convective equilibrium model, which further shows that the enhanced water-vapor feedback follows from the rising of the tropopause in a warming climate. This mechanism is potentially important for understanding both warm climates of Earth's past and projections of future high-emission scenarios."
"6505568138;24511929800;6506101358;","Sensitivity of the LMD general circulation model to greenhouse forcing associated with two different cloud water parameterizations",1994,"10.1175/1520-0442(1994)007<1827:sotlgc>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028599228&doi=10.1175%2f1520-0442%281994%29007%3c1827%3asotlgc%3e2.0.co%3b2&partnerID=40&md5=18d89d88674d142bdf80c5fabc0c0e7c","The atmospheric general circulation model is coupled to a slab ocean model and is used to investigate the climatic impact of a CO2 doubling. Two versions of the model are used with two different representations of the cloud-radiation interaction. The annual and global mean of the surface warming is similar in the two experiments in spite of regional differences. The results show that, in the second model version, the cloud feedback decreases significantly, especially at high latitudes, due to an increase of low-level clouds in the 2 × CO2 simulation. The modification of the cloud scheme influences also the water vapor variation and the associated feedback is reduced, in particular, over the subtropical regions. -from Authors"
"7103010852;56264191700;7102708039;57191367079;7003854810;6701412834;57206924573;7004171611;55902566200;","The far-infrared earth",2008,"10.1029/2007RG000233","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60849118390&doi=10.1029%2f2007RG000233&partnerID=40&md5=47859586aa1b1af6b6bc9712282a1988","The paper presents a review of the far-infrared (FIR) properties of the Earth's atmosphere and their role in climate. These properties have been relatively poorly understood, and it is one of the purposes of this review to demonstrate that in recent years we have made great strides in improving this understanding. Seen from space, the Earth is a cool object, with an effective emitting temperature of about 255 K. This contrasts with a global mean surface temperature of ∼288 K and is due primarily to strong absorption of outgoing longwave energy by water vapor, carbon dioxide, and clouds (especially ice). A large fraction of this absorption occurs in the FIR, and so the Earth is effectively a FIR planet. The FIR is important in a number of key climate processes, for example, the water vapor and cloud feedbacks (especially ice clouds). The FIR is also a spectral region which can be used to remotely sense and retrieve atmospheric composition in the presence of ice clouds. Recent developments in instrumentation have allowed progress in each of these areas, which are described, and proposals for a spaceborne FIR instrument are being formulated. It is timely to review the FIR properties of the clear and cloudy atmosphere, the role of FIR processes in climate, and its use in observing our planet from space. Copyright 2008 by the American Geophysical Union."
"7401776640;7601332830;7402966758;","Role of low clouds in summertime atmosphere-ocean interactions over the North Pacific",1998,"10.1175/1520-0442(1998)011<2482:ROLCIS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032194342&doi=10.1175%2f1520-0442%281998%29011%3c2482%3aROLCIS%3e2.0.CO%3b2&partnerID=40&md5=171fc3a12c7967db9697de8693d24b16","The summer-to-summer variability of the areal extent of marine stratiform cloudiness (MSC; stratus, stratocumulus, and fog) over the North Pacific is examined for the period of record 1952-92 using a dataset based on surface observations. Variability is largest in two regions: the central and western Pacific along 35°N coincident with a strong meridional gradient in climatological MSC amount, and the eastern Pacific near 15°N downstream of the persistent stratocumulus deck off Baja California. The MSC amount in both regions tends to be negatively correlated with local sea surface temperature (SST), suggestive of a positive cloud feedback on SST. The MSC amounts in the two regions also tend to be negatively correlated by virtue of their relationship to the basin-wide sea level pressure (SLP) field: a strengthening of the seasonal mean subtropical anticyclone is accompanied by increased cloudiness in the trade wind regime and decreased cloudiness in the southerly flow farther toward the west. These relationships are reflected in the leading modes derived from empirical orthogonal function analysis and singular value decomposition analysis of the MSC, SST, and SLP fields. From the 1950s to the 1980s, summertime MSC amounts increased in the central and western Pacific and decreased in the trade wind region, while SST exhibited the opposite tendencies. Although these trends contributed to the relationships described above, similar patterns are obtained when the analysis is performed on 1-yr difference fields (e.g., 1953 minus 1952, 1954 minus 1953, etc.). Hence, it appears that MSC plays an important role in atmosphere-ocean coupling over the North Pacific during the summer season when latent and sensible heat fluxes are not as dominant and the coupling between atmospheric circulation and SST is not as strong as in winter.The summer-to-summer variability of the areal extent of marine stratiform cloudiness (MSC) over the North Pacific was examined for the period of record 1952-1992 using a dataset based on surface observations. The variability was largest in the central and western Pacific along 35°N coincident with a strong meridional gradient in climatological MSC amount, and the eastern Pacific near 15°N downstream of the persistent stratocumulus deck off Baja, California. The MSC amount in both regions negatively-correlate with local sea surface temperature, and to the basin-wide sea level pressure field."
"26645289600;55894937000;56457851700;18635208300;36856321600;54897465300;7402064802;57210518852;","Causes of Higher Climate Sensitivity in CMIP6 Models",2020,"10.1029/2019GL085782","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078245843&doi=10.1029%2f2019GL085782&partnerID=40&md5=5568b6e937a543e6497d3829e7c583c7","Equilibrium climate sensitivity, the global surface temperature response to CO CO2 doubling, has been persistently uncertain. Recent consensus places it likely within 1.5–4.5 K. Global climate models (GCMs), which attempt to represent all relevant physical processes, provide the most direct means of estimating climate sensitivity via CO2 quadrupling experiments. Here we show that the closely related effective climate sensitivity has increased substantially in Coupled Model Intercomparison Project phase 6 (CMIP6), with values spanning 1.8–5.6 K across 27 GCMs and exceeding 4.5 K in 10 of them. This (statistically insignificant) increase is primarily due to stronger positive cloud feedbacks from decreasing extratropical low cloud coverage and albedo. Both of these are tied to the physical representation of clouds which in CMIP6 models lead to weaker responses of extratropical low cloud cover and water content to unforced variations in surface temperature. Establishing the plausibility of these higher sensitivity models is imperative given their implied societal ramifications. ©2020. The Authors."
"7003266014;","Observations of climate feedbacks over 2000-10 and comparisons to climate models",2013,"10.1175/JCLI-D-11-00640.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872946004&doi=10.1175%2fJCLI-D-11-00640.1&partnerID=40&md5=d65ee2550f654c92f9ea1a00a8f63be8","Feedbacks in response to climate variations during the period 2000-10 have been calculated using reanalysis meteorological fields and top-of-atmosphere flux measurements. Over this period, the climate was stabilized by a strongly negative temperature feedback (̃-3 W m2 K1); climate variations were also amplified by a strong positive water vapor feedback (̃+1.2 W m2 K1) and smaller positive albedo and cloud feedbacks (̃+0.3 and 10.5 W m2 K1, respectively). These observations are compared to two climate model ensembles, one dominated by internal variability (the control ensemble) and the other dominated by long-term global warming (the A1B ensemble). The control ensemble produces global average feedbacks that agree within uncertainties with the observations, as well as producing similar spatial patterns. The most significant discrepancy was in the spatial pattern for the total (shortwave + longwave) cloud feedback. Feedbacks calculated from the A1B ensemble show a stronger negative temperature feedback (due to a stronger lapse-rate feedback), but that is cancelled by a stronger positive water vapor feedback. The feedbacks in the A1B ensemble tend to be more smoothly distributed in space, which is consistent with the differences between El Niñ o-Southern Oscillation (ENSO) climate variations and long-term global warming. The sum of all of the feedbacks, sometimes referred to as the thermal damping rate, is-1.15±0.88 W m2 K1 in the observations and-0.60±0.37 W m2 K1 in the control ensemble.Within the control ensemble, models that more accurately simulate ENSO tend to produce thermal damping rates closer to the observations. The A1B ensemble average thermal damping rate is -1.26 ± 0.45 W m2 K1. © 2013 American Meteorological Society."
"55660926800;7201504886;28367935500;","Climate and climate change in a radiative-convective equilibrium version of ECHAM6",2013,"10.1029/2012MS000191","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876725239&doi=10.1029%2f2012MS000191&partnerID=40&md5=ed1ca72bf5ee40c74531b6324cf3683b","A radiative-convective equilibrium (RCE) configuration of a comprehensive atmospheric general circulation model, ECHAM6, is coupled to a mixed-layer ocean for the purpose of advancing understanding of climate and climate change. This configuration differs from a standard configuration only through the removal of land-surface processes, spatial gradients in solar insolation, and the effects of rotation. Nonetheless, the model produces a climate that resembles the tropical climate in a control simulation of Earth's atmosphere. In the RCE configuration, regional inhomogeneities in surface temperature develop. These inhomogeneities are transient in time but sufficiently long-lived to establish large-scale overturning circulations with a distribution similar to the preindustrial tropics in the standard configuration. The vertical structure of the atmosphere, including profiles of clouds and condensate conditioned on the strength of overturning, also resembles those produced by a control simulation of Earth's tropical atmosphere. The equilibrium climate sensitivity of the RCE atmosphere can explain 50% of the global climate sensitivity of a realistic configuration of ECHAM6. Part of the difference is attributed to the lack of polar amplification in RCE. The remainder appears to be related to a less positive cloud shortwave feedback, which results from an increase in low cloudiness with increasing surface temperatures in the RCE configuration. The RCE configuration shows an increase of climate sensitivity in a warmer climate. The increase in climate sensitivity scales with the degree to which the upper-troposphere temperature departs from a moist adiabat. © 2012. American Geophysical Union. All Rights Reserved."
"7403968239;7406250414;7404373922;","Tropical water vapor and cloud feedbacks in climate models: A further assessment using coupled simulations",2009,"10.1175/2008JCLI2267.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-64049117621&doi=10.1175%2f2008JCLI2267.1&partnerID=40&md5=22bf19468287087f68e66e7304082faa","By comparing the response of clouds and water vapor to ENSO forcing in nature with that in Atmospheric Model Intercomparison Project (AMIP) simulations by some leading climate models, an earlier evaluation of tropical cloud and water vapor feedbacks has revealed the following two common biases in the models: 1) an underestimate of the strength of the negative cloud albedo feedback and 2) an overestimate of the positive feedback from the greenhouse effect of water vapor. Extending the same analysis to the fully coupled simulations of these models as well as other Intergovernmental Panel on Climate Change (IPCC) coupled models, it is found that these two biases persist. Relative to the earlier estimates from AMIP simulations, the overestimate of the positive feedback from water vapor is alleviated somewhat for most of the coupled simulations. Improvements in the simulation of the cloud albedo feedback are only found in the models whose AMIP runs suggest either a positive or nearly positive cloud albedo feedback. The strength of the negative cloud albedo feedback in all other models is found to be substantially weaker than that estimated from the corresponding AMIP simulations. Consequently, although additional models are found to have a cloud albedo feedback in their AMIP simulations that is as strong as in the observations, all coupled simulations analyzed in this study have a weaker negative feedback from the cloud albedo and therefore a weaker negative feedback from the net surface heating than that indicated in observations. The weakening in the cloud albedo feedback is apparently linked to a reduced response of deep convection over the equatorial Pacific, which is in turn linked to the excessive cold tongue in the mean climate of these models. The results highlight that the feedbacks of water vapor and clouds-the cloud albedo feedback in particular - may depend on the mean intensity of the hydrological cycle. Whether the intermodel variations in the feedback from cloud albedo (water vapor) in the ENSO variability are correlated with the intermodel variations of the feedback from cloud albedo (water vapor) in global warming has also been examined. While a weak positive correlation between the intermodel variations in the feedback of water vapor during ENSO and the intermodel variations in the water vapor feedback during global warming was found, there is no significant correlation found between the intermodel variations in the cloud albedo feedback during ENSO and the intermodel variations in the cloud albedo feedback during global warming. The results suggest that the two common biases revealed in the simulated ENSO variability may not necessarily be carried over to the simulated global warming. These biases, however, highlight the continuing difficulty that models have in simulating accurately the feedbacks of water vapor and clouds on a time scale of the observations available. © 2009 American Meteorological Society."
"7202660824;7403288995;7402064802;55746365900;","Positive tropical marine low-cloud cover feedback inferred from cloud-controlling factors",2015,"10.1002/2015GL065627","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945241933&doi=10.1002%2f2015GL065627&partnerID=40&md5=9ee265d41edaadfa7785fad358cbfefa","Differences in simulations of tropical marine low-cloud cover (LCC) feedback are sources of significant spread in temperature responses of climate models to anthropogenic forcing. Here we show that in models the feedback is mainly driven by three large-scale changes - a strengthening tropical inversion, increasing surface latent heat flux, and an increasing vertical moisture gradient. Variations in the LCC response to these changes alone account for most of the spread in model-projected 21st century LCC changes. A methodology is devised to constrain the LCC response observationally using sea surface temperature (SST) as a surrogate for the latent heat flux and moisture gradient. In models where the current climate's LCC sensitivities to inversion strength and SST variations are consistent with observed, LCC decreases systematically, which would increase absorption of solar radiation. These results support a positive LCC feedback. Correcting biases in the sensitivities will be an important step toward more credible simulation of cloud feedbacks. © 2015 American Geophysical Union. All Rights Reserved."
"54897465300;26645289600;7202145115;","The response of the Southern Hemispheric eddy-driven jet to future changes in shortwave radiation in CMIP5",2014,"10.1002/2014GL060043","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901933770&doi=10.1002%2f2014GL060043&partnerID=40&md5=2b70595a74f0b00f7fa685e4bbae045a","A strong relationship is found between changes in the meridional gradient of absorbed shortwave radiation (ASR) and Southern Hemispheric jet shifts in 21st century climate simulations of CMIP5 (Coupled Model Intercomparison Project phase 5) coupled models. The relationship is such that models with increases in the meridional ASR gradient around the southern midlatitudes, and therefore increases in midlatitude baroclinicity, tend to produce a larger poleward jet shift. The ASR changes are shown to be dominated by changes in cloud properties, with sea ice declines playing a secondary role. We demonstrate that the ASR changes are the cause, and not the result, of the intermodel differences in jet response by comparing coupled simulations with experiments in which sea surface temperature increases are prescribed. Our results highlight the importance of reducing the uncertainty in cloud feedbacks in order to constrain future circulation changes. Key Points Large intermodel spread in SW radiation response to global warming in CMIP5 Spread in SW changes causes spread in SH jet response to global warming Different SW changes cause different changes in midlatitude baroclinicity © 2014. American Geophysical Union. All Rights Reserved."
"56457851700;7202145115;26645289600;54897465300;16444006500;","Mixed-phase cloud physics and Southern Ocean cloud feedback in climate models",2015,"10.1002/2015JD023603","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944930594&doi=10.1002%2f2015JD023603&partnerID=40&md5=8f6366391dfd3995997b51892cd95e0d","Increasing optical depth poleward of 45° is a robust response to warming in global climatemodels. Much of this cloud optical depth increase has been hypothesized to be due to transitions from ice-dominated to liquid-dominated mixed-phase cloud. In this study, the importance of liquid-ice partitioning for the optical depth feedback is quantified for 19 Coupled Model Intercomparison Project Phase 5models. Allmodels show a monotonic partitioning of ice and liquid as a function of temperature, but the temperature at which ice and liquid are equally mixed (the glaciation temperature) varies by as much as 40 K across models. Models that have a higher glaciation temperature are found to have a smaller climatological liquid water path (LWP) and condensedwater path and experience a larger increase in LWP as the climate warms. The ice-liquid partitioning curve of eachmodel may be used to calculate the response of LWP towarming. It is found that the repartitioning between ice and liquid in a warming climate contributes at least 20% to 80% of the increase in LWP as the climate warms, depending onmodel. Intermodel differences in the climatological partitioning between ice and liquid are estimated to contribute at least 20% to the intermodel spread in the high-latitude LWP response in themixed-phase region poleward of 45°S. It is hypothesized that a more thorough evaluation and constraint of global climate model mixed-phase cloud parameterizations and validation of the total condensate and ice-liquid apportionment against observations will yield a substantial reduction in model uncertainty in the high-latitude cloud response to warming. © 2015. American Geophysical Union. All Rights Reserved."
"34979885900;6701751765;23096635200;6603150451;26323026900;6507671561;22936054800;","Exploring the faint young Sun problem and the possible climates of the Archean Earth with a 3-D GCM",2013,"10.1002/jgrd.50808","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886065268&doi=10.1002%2fjgrd.50808&partnerID=40&md5=148d9105ec48a418c20547896c1ed9ea","Different solutions have been proposed to solve the ""faint young Sun problem,"" defined by the fact that the Earth was not fully frozen during the Archean despite the fainter Sun. Most previous studies were performed with simple 1-D radiative convective models and did not account well for the clouds and ice-albedo feedback or the atmospheric and oceanic transport of energy. We apply a global climate model (GCM) to test the different solutions to the faint young Sun problem. We explore the effect of greenhouse gases (CO2 and CH4), atmospheric pressure, cloud droplet size, land distribution, and Earth's rotation rate. We show that neglecting organic haze, 100 mbar of CO2 with 2 mbar of CH4 at 3.8 Ga and 10 mbar of CO 2 with 2 mbar of CH4 at 2.5 Ga allow a temperate climate (mean surface temperature between 10°C and 20°C). Such amounts of greenhouse gases remain consistent with the geological data. Removing continents produces a warming lower than +4°C. The effect of rotation rate is even more limited. Larger droplets (radii of 17 μm versus 12 μm) and a doubling of the atmospheric pressure produce a similar warming of around +7°C. In our model, ice-free water belts can be maintained up to 25°N/S with less than 1 mbar of CO2 and no methane. An interesting cloud feedback appears above cold oceans, stopping the glaciation. Such a resistance against full glaciation tends to strongly mitigate the faint young Sun problem. Key PointsNew constraints on the amount of greenhouse gases to get a temperate climateWaterbelt can be maintained with less than 1 mbar of CO2 and no methaneThe effects of larger cloud droplets and a higher pressure are quantified ©2013. American Geophysical Union. All Rights Reserved."
"6603555567;6701344406;56276813400;26323963700;6602241511;6701792123;6603335688;8915901800;8323981800;","Cloud response to summer temperatures in Fennoscandia over the last thousand years",2011,"10.1029/2010GL046216","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952128868&doi=10.1029%2f2010GL046216&partnerID=40&md5=99445bb64fe6e02e9f1fefb0d1a05ce6","Cloud cover is one of the most important factors controlling the radiation balance of the Earth. The response of cloud cover to increasing global temperatures represents the largest uncertainty in model estimates of future climate because the cloud response to temperature is not well-constrained. Here we present the first regional reconstruction of summer sunshine over the past millennium, based on the stable carbon isotope ratios of pine treerings from Fennoscandia. Comparison with the regional temperature evolution reveals the Little Ice Age (LIA) to have been sunny, with cloudy conditions in the warmest periods of the Medieval at this site. A negative shortwave cloud feedback is indicated at high latitude. A millennial climate simulation suggests that regionally low temperatures during the LIA were mostly maintained by a weaker greenhouse effect due to lower humidity. Simulations of future climate that display a negative shortwave cloud feedback for high-latitudes are consistent with our proxy interpretation. Copyright © 2011 by the American Geophysical Union."
"56652365500;6701843355;","Shifts in ENSO coupling processes under global warming",2006,"10.1029/2006GL026196","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746418902&doi=10.1029%2f2006GL026196&partnerID=40&md5=ed80c513ec04d810d36dba3f4d913192","Global warming may shift the properties and dynamics of El Niño. We study the shifts in ENSO couplings in IPCC-AR4 coupled general circulation climate models. First, we compare period, pattern, amplitude and mean state of the Pacific Ocean between the current climate and a high CO2 climate. Next, shifts in ENSO couplings between sea surface temperature (SST), thermocline depth and wind stress are discussed. Although the mean state shifts, the overall ENSO properties do not change much. Changes in the mean state affect the feedback loop. Higher mean SST provides higher damping through cloud feedback. The shallower thermocline and mixed layer depth increase SST sensitivity to thermocline variability and wind stress. Wind response to SST variability increases where the mean SST has increased the most. However, the higher damping and more stable atmosphere compensate the other changes and the residual change in ENSO properties is relatively small. Copyright 2006 by the American Geophysical Union."
"7401776640;6603568514;","North Pacific cloud feedbacks inferred from synoptic-scale dynamic and thermodynamic relationships",2005,"10.1175/JCLI3558.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30144434489&doi=10.1175%2fJCLI3558.1&partnerID=40&md5=524b4251a6e7c9c835a6c968899d4de5","Daily satellite cloud observations and reanalysis dynamical parameters are analyzed to determine how midtropospheric vertical velocity and advection over the sea surface temperature gradient control midlatitude North Pacific cloud properties. Optically thick clouds with high tops are generated by synoptic ascent, but two different cloud regimes occur under synoptic descent. When vertical motion is downward during summer, extensive stratocumulus cloudiness is associated with near-surface northerly wind, while frequent cloudless pixels occur with southerly wind. Examination of ship-reported cloud types indicates that midlatitude stratocumulus breaks up as the boundary layer decouples when it is advected equatorward over warmer water. Cumulus is prevalent under conditions of synoptic descent and cold advection during winter. Poleward advection of subtropical air over colder water causes stratification of the near-surface layer that inhibits upward mixing of moisture and suppresses cloudiness until a fog eventually forms. Averaging of cloud and radiation data into intervals of 500-hPa vertical velocity and advection over the SST gradient enables the cloud response to changes in temperature and the stratification of the lower troposphere to be investigated independent of the dynamics. Vertically uniform warming results in decreased cloud amount and optical thickness over a large range of dynamical conditions. Further calculations indicate that a decrease in the variance of vertical velocity would lead to a small decrease in mean cloud optical thickness and cloud-top height. These results suggest that reflection of solar radiation back to space by midlatitude oceanic clouds will decrease as a direct response to global warming, thus producing an overall positive feedback on the climate system. An additional decrease in solar reflection would occur were the storm track also to weaken, whereas an intensification of the storm track would partially cancel the cloud response to warming. © 2005 American Meteorological Society."
"57002856000;36161790500;","The role of cloud phase in Earth’s radiation budget",2017,"10.1002/2016JD025951","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85014087612&doi=10.1002%2f2016JD025951&partnerID=40&md5=3c4400021621915cd2a81c67457f4301","The radiative impact of clouds strongly depends on their partitioning between liquid and ice phases. Until recently, however, it has been challenging to unambiguously discriminate cloud phase in a number of important global regimes. CloudSat and CALIPSO supply vertically resolved measurements necessary to identify clouds composed of both liquid and ice that are not easily detected using conventional passive sensors. The capability of these active sensors to discriminate cloud phase has been incorporated into the fifth generation of CloudSat’s 2B-FLXHR-LIDAR algorithm. Comparisons with Clouds and the Earth’s Radiant Energy System fluxes at the top of atmosphere reveal that an improved representation of cloud phase leads to better agreement compared to earlier versions of the algorithm. The RMS differences in annual mean outgoing longwave (LW) radiation gridded at 2.5° resolution are 4.9 W m-2, while RMS differences in outgoing shortwave (SW) are slightly larger at 8.9 W m-2 due to the larger diurnal range of solar insolation. This study documents the relative contributions of clouds composed of only liquid, only ice, and a combination of both phases to global and regional radiation budgets. It is found that mixed-phase clouds exert a global net cloud radiative effect of -3.4Wm-2, with contributions of -8.1Wm-2 and 4.7Wm-2 from SW and LW radiation, respectively. When compared with the effects of warm liquid clouds (-11.8Wm-2), ice clouds (3.5 W m-2), and multilayered clouds consisting of distinct liquid and ice layers (-4.6Wm-2), these results reinforce the notion that accurate representation of mixed-phase clouds is essential for quantifying cloud feedbacks in future climate scenarios. © 2017. American Geophysical Union. All Rights Reserved."
"56537463000;7404829395;22959252400;16553368000;7006417494;7202899330;7005973015;","Weakening and strengthening structures in the Hadley Circulation change under global warming and implications for cloud response and climate sensitivity",2014,"10.1002/2014JD021642","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902839438&doi=10.1002%2f2014JD021642&partnerID=40&md5=b1bb998c9545aaddedfbd0fd3fdddd6f","It has long been recognized that differences in climate model-simulated cloud feedbacks are a primary source of uncertainties for the model-predicted surface temperature change induced by increasing greenhouse gases such as CO2. Large-scale circulation broadly determines when and where clouds form and how they evolve. However, the linkage between large-scale circulation change and cloud radiative effect (CRE) change under global warming has not been thoroughly studied. By analyzing 15 climate models, we show that the change of the Hadley Circulation exhibits meridionally varying weakening and strengthening structures, physically consistent with the cloud changes in distinct cloud regimes. The regions that experience a weakening (strengthening) of the zonal-mean circulation account for 54% (46%) of the multimodel-mean top-of-atmosphere (TOA) CRE change integrated over 45°S-40°N. The simulated Hadley Circulation structure changes per degree of surface warming differ greatly between the models, and the intermodel spread in the Hadley Circulation change is well correlated with the intermodel spread in the TOA CRE change. This correlation underscores the close interactions between large-scale circulation and clouds and suggests that the uncertainties of cloud feedbacks and climate sensitivity reside in the intimate coupling between large-scale circulation and clouds. New model performance metrics proposed in this work, which emphasize how models reproduce satellite-observed spatial variations of zonal-mean cloud fraction and relative humidity associated with the Hadley Circulation, indicate that the models closer to the satellite observations tend to have equilibrium climate sensitivity higher than the multimodel mean. © 2014. American Geophysical Union. All Rights Reserved."
"6602688130;7102976560;6701431208;57210350827;56638409500;57199181531;7004347243;6602098362;7403263977;25031430500;36876405100;57202754759;7006739521;13406399300;7402207328;35490828000;7101816869;57210230785;7201488063;7102696626;6603901951;6701853567;7401658754;7003465505;55893823700;56768110900;6507312147;57215535856;7202979963;7003843648;7402486833;6507386356;57203030873;6701511321;7006735547;7005920812;35368948100;55911314000;57207008613;50561946500;7004060399;7006705919;6701581880;","The Community Earth System Model Version 2 (CESM2)",2020,"10.1029/2019MS001916","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081086192&doi=10.1029%2f2019MS001916&partnerID=40&md5=12159cbcf1024dca112b5c2b42479768","An overview of the Community Earth System Model Version 2 (CESM2) is provided, including a discussion of the challenges encountered during its development and how they were addressed. In addition, an evaluation of a pair of CESM2 long preindustrial control and historical ensemble simulations is presented. These simulations were performed using the nominal 1° horizontal resolution configuration of the coupled model with both the “low-top” (40 km, with limited chemistry) and “high-top” (130 km, with comprehensive chemistry) versions of the atmospheric component. CESM2 contains many substantial science and infrastructure improvements and new capabilities since its previous major release, CESM1, resulting in improved historical simulations in comparison to CESM1 and available observations. These include major reductions in low-latitude precipitation and shortwave cloud forcing biases; better representation of the Madden-Julian Oscillation; better El Niño-Southern Oscillation-related teleconnections; and a global land carbon accumulation trend that agrees well with observationally based estimates. Most tropospheric and surface features of the low- and high-top simulations are very similar to each other, so these improvements are present in both configurations. CESM2 has an equilibrium climate sensitivity of 5.1–5.3 °C, larger than in CESM1, primarily due to a combination of relatively small changes to cloud microphysics and boundary layer parameters. In contrast, CESM2's transient climate response of 1.9–2.0 °C is comparable to that of CESM1. The model outputs from these and many other simulations are available to the research community, and they represent CESM2's contributions to the Coupled Model Intercomparison Project Phase 6. © 2020. The Authors."
"6603362421;7102163440;7003346500;11940188700;7003777747;6603749963;","Bayesian estimation of climate sensitivity based on a simple climate model fitted to observations of hemispheric temperatures and global ocean heat content",2012,"10.1002/env.2140","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859443747&doi=10.1002%2fenv.2140&partnerID=40&md5=d80a63fc2efbfd040fae549853fcdc72","Predictions of climate change are uncertain mainly because of uncertainties in the emissions of greenhouse gases and how sensitive the climate is to changes in the abundance of the atmospheric constituents. The equilibrium climate sensitivity is defined as the temperature increase because of a doubling of the CO 2 concentration in the atmosphere when the climate reaches a new steady state. CO 2 is only one out of the several external factors that affect the global temperature, called radiative forcing mechanisms as a collective term. In this paper, we present a model framework for estimating the climate sensitivity. The core of the model is a simple, deterministic climate model based on elementary physical laws such as energy balance. It models yearly hemispheric surface temperature and global ocean heat content as a function of historical radiative forcing. This deterministic model is combined with an empirical, stochastic model and fitted to observations on global temperature and ocean heat content, conditioned on estimates of historical radiative forcing. We use a Bayesian framework, with informative priors on a subset of the parameters and flat priors on the climate sensitivity and the remaining parameters. The model is estimated by Markov Chain Monte Carlo techniques. © 2012 John Wiley &amp; Sons, Ltd."
"36809017200;","Energy budget constraints on climate sensitivity in light of inconstant climate feedbacks",2017,"10.1038/nclimate3278","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018730337&doi=10.1038%2fnclimate3278&partnerID=40&md5=f3b21e496eeaca2f211fee4f19a79f8e","Global energy budget constraints suggest an equilibrium climate sensitivity around 2 °C, which is lower than estimates from palaeoclimate reconstructions, process-based observational analyses, and global climate model simulations. A key assumption is that the climate sensitivity inferred today also applies to the distant future. Yet, global climate models robustly show that feedbacks vary over time, with a strong tendency for climate sensitivity to increase as equilibrium is approached. Here I consider the implications of inconstant climate feedbacks for energy budget constraints on climate sensitivity. I find that the long-term value of climate sensitivity is, on average, 26% above that inferred during transient warming within global climate models, with a larger discrepancy when climate sensitivity is high. Moreover, model values of climate sensitivity inferred during transient warming are found to be consistent with energy budget observations, indicating that the models are not overly sensitive. Using model-based estimates of how climate feedbacks will change in the future, in conjunction with recent energy budget constraints, produces a current best estimate of equilibrium climate sensitivity of 2.9 °C (1.7-7.1 °C, 90% confidence). These findings suggest that climate sensitivity estimated from global energy budget constraints is in agreement with values derived from other methods and simulated by global climate models."
"56457851700;55683910600;7202145115;26645289600;13403622000;","On the relationships among cloud cover, mixed-phase partitioning, and planetary albedo in GCMs",2016,"10.1002/2015MS000589","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84966415563&doi=10.1002%2f2015MS000589&partnerID=40&md5=867f80a552bfb838b43f52b07a88a0dc","In this study, it is shown that CMIP5 global climate models (GCMs) that convert supercooled water to ice at relatively warm temperatures tend to have a greater mean-state cloud fraction and more negative cloud feedback in the middle and high latitude Southern Hemisphere. We investigate possible reasons for these relationships by analyzing the mixed-phase parameterizations in 26 GCMs. The atmospheric temperature where ice and liquid are equally prevalent (T5050) is used to characterize the mixed-phase parameterization in each GCM. Liquid clouds have a higher albedo than ice clouds, so, all else being equal, models with more supercooled liquid water would also have a higher planetary albedo. The lower cloud fraction in these models compensates the higher cloud reflectivity and results in clouds that reflect shortwave radiation (SW) in reasonable agreement with observations, but gives clouds that are too bright and too few. The temperature at which supercooled liquid can remain unfrozen is strongly anti-correlated with cloud fraction in the climate mean state across the model ensemble, but we know of no robust physical mechanism to explain this behavior, especially because this anti-correlation extends through the subtropics. A set of perturbed physics simulations with the Community Atmospheric Model Version 4 (CAM4) shows that, if its temperature-dependent phase partitioning is varied and the critical relative humidity for cloud formation in each model run is also tuned to bring reflected SW into agreement with observations, then cloud fraction increases and liquid water path (LWP) decreases with T5050, as in the CMIP5 ensemble. © 2016. The Authors."
"6603783890;25030776200;8633783900;56726831200;13905919900;6506421883;6602529747;","Contributions of carbon cycle uncertainty to future climate projection spread",2009,"10.1111/j.1600-0889.2009.00414.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-61849142699&doi=10.1111%2fj.1600-0889.2009.00414.x&partnerID=40&md5=bea3dd42b3034c4ab795cde1fd97af71","We have characterized the relative contributions to uncertainty in predictions of global warming amount by year 2100 in the C4MIP model ensemble (Friedlingstein et al., 2006) due to both carbon cycle process uncertainty and uncertainty in the physical climate properties of the Earth system. We find carbon cycle uncertainty to be important. On average the spread in transient climate response is around 40% of that due to the more frequently debated uncertainties in equilibrium climate sensitivity and global heat capacity. This result is derived by characterizing the influence of different parameters in a global climate-carbon cycle 'box' model that has been calibrated against the 11 General Circulation models (GCMs) and Earth system Models of Intermediate Complexity (EMICs) in the C4MIP ensemble; a collection of current state-of-the-art climate models that include an explicit representation of the global carbon cycle. © 2009 The Author Journal compilation © 2009 Blackwell Munksgaard."
"55113736500;35464731600;7003897194;","Examining feedbacks of aerosols to urban climate with a model that treats 3-D clouds with aerosol inclusions",2007,"10.1029/2007JD008922","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39449113126&doi=10.1029%2f2007JD008922&partnerID=40&md5=eb68a464fbcdf5dabb73d6d757265ad4","Anthropogenic aerosol particles alter clouds, radiation, and precipitation, thereby affecting weather, climate, and air pollution. To examine and understand such feedbacks, a module that simulates the evolution, movement, and microphysics of three-dimensional size-resolved mixed-phase clouds and precipitation and their multicomponent aerosol inclusions was developed and implemented into the GATOR-GCMOM global-through-urban air pollution-weather-climate model. A unique feature of the module is that aerosol particles and their chemical components are tracked in time and space within size-resolved liquid, ice, and graupel and interstitially within clouds. Modeled parameters were evaluated against in situ data, compared with MODIS climatologies, and nested with emission data down to 5 km resolution to study aerosol-cloud feedbacks in Los Angeles. Although updrafts are not resolved during deep convection at this resolution, most convection is shallow in Los Angeles. This resolution is also near the lower limit for which a hydrostatic solution to vertical momentum (used here) is similar to a nonhydrostatic solution. Aerosols in Los Angeles were found to increase cloud optical depth, cloud liquid water, cloud fraction, net downward thermal-infrared radiation, soil moisture, the relative humidity, and (slightly) middle-boundary layer air temperatures. Aerosols also decreased precipitation, surface solar, and near-surface temperatures. Both boundary layer warming due to black carbon and surface cooling due to all aerosol components increased stability, inhibiting cloud top growth under some conditions. Aerosols may feed back to themselves by increasing cloud liquid, gas dissolution, and aerosol volume upon evaporation. They may also decrease visibility by increasing the relative humidity and decrease photolysis below them by enhancing cloud thickness. Copyright 2007 by the American Geophysical Union."
"55286185400;6701752471;7005808242;56744278700;57208455668;7006306835;57208462871;8733579800;7103271625;23486734100;50261552200;","Uncertainty in model climate sensitivity traced to representations of cumulus precipitation microphysics",2016,"10.1175/JCLI-D-15-0191.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957828230&doi=10.1175%2fJCLI-D-15-0191.1&partnerID=40&md5=e46c25d15b4ae702dbae62a6c958af41","Uncertainty in equilibrium climate sensitivity impedes accurate climate projections. While the intermodel spread is known to arise primarily from differences in cloud feedback, the exact processes responsible for the spread remain unclear. To help identify some key sources of uncertainty, the authors use a developmental version of the next-generation Geophysical Fluid Dynamics Laboratory global climate model (GCM) to construct a tightly controlled set of GCMs where only the formulation of convective precipitation is changed. The different models provide simulation of present-day climatology of comparable quality compared to the model ensemble from phase 5 of CMIP (CMIP5). The authors demonstrate that model estimates of climate sensitivity can be strongly affected by the manner through which cumulus cloud condensate is converted into precipitation in a model's convection parameterization, processes that are only crudely accounted for in GCMs. In particular, two commonly used methods for converting cumulus condensate into precipitation can lead to drastically different climate sensitivity, as estimated here with an atmosphere-land model by increasing sea surface temperatures uniformly and examining the response in the top-of-atmosphere energy balance. The effect can be quantified through a bulk convective detrainment efficiency, whichmeasures the ability of cumulus convection to generate condensate per unit precipitation. The model differences, dominated by shortwave feedbacks, come from broad regimes ranging from large-scale ascent to subsidence regions. Given current uncertainties in representing convective precipitation microphysics and the current inability to find a clear observational constraint that favors one version of the authors'model over the others, the implications of this ability to engineer climate sensitivity need to be considered when estimating the uncertainty in climate projections. © 2016 American Meteorological Society."
"7005890514;51360903200;","Climate sensitivity and climate state",2003,"10.1007/s00382-003-0323-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038407006&doi=10.1007%2fs00382-003-0323-7&partnerID=40&md5=39b828699c563d95bdeef85bb88879ee","The effective climate feedback/sensitivity, including its components, is a robust first order feature of the Canadian Centre for Climate Modelling and Analysis (CCCma) coupled global climate model (GCM) and presumably of the climate system. Feedback/sensitivity characterizes the surface air temperature response to changes in radiative forcing and is constant, to first order, independent of the nature, history, and magnitude of the forcing and of the changing climate state. This ""constancy"" can only be approximate, however, and modest second order changes of 10-20% are found in stabilization simulations in which the forcing, based on the IS92a scenario, is fixed (stabilized) at year 2050 and 2100 values and the system is integrated for an additional 1000 years toward a new equilibrium. Both positive and negative feedback mechanisms tend to strengthen, with the balance tilted toward stronger negative feedback and hence weaker climate sensitivity, as the system evolves and warms. Some feedback mechanisms weaken locally, however, and an example of such is the ice/snow albedo feedback which is less effective in areas of the Northern Hemisphere where ice/snow has retreated. Changes in the geographical distribution of the feedbacks are modest and weakening feedback in one region is often counteracted by strengthening feedback in other regions so that global and zonal values do not reflect the dominance of a particular mechanism or region but rather the residual of changes in different components and regions. The overall 10-20% strengthening of the negative feedback (decrease in climate sensitivity) in the CCCma model contrasts with a weakening of negative feedback (increase in climate sensitivity) of over 20% in the Hadley Centre model under similar conditions. The different behaviour in the two models is due primarily to solar cloud feedback with a strengthening of the negative solar cloud feedback in the CCCma model contrasting with a weakening of it in the Hadley Centre model. The importance of processes which determine cloud properties and distribution is again manifest both in determining first order climate feedback/sensitivity and also in determining its second order variation with climate state."
"57212781009;6701715507;","A study of general circulation model climate feedbacks determined from perturbed sea surface temperature experiments",1997,"10.1029/97jd00206","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031401050&doi=10.1029%2f97jd00206&partnerID=40&md5=2451d44cd1b968c37312a05fcfd5e0d2","The response of a general circulation model (GCM) to global perturbations in sea surface temperatures (SSTs) is examined. The feedback strengths in the model are diagnosed by the response of top of atmosphere (TOA) radiative fluxes determined after substitution of fields from the ""perturbed"" climate into the ""control."" Total feedback is divided into terms due to water vapour, lapse rate, surface temperature, and clouds (in turn analysed in terms of cloud amount, height and types). The ""standard experiment"" prescribes a globally uniform SST perturbation with fixed soil moisture. Four additional experiments vary the number of model vertical levels, the pattern of SST changes, the convection scheme, and the soil moisture. The SST pattern change chosen follows that of an equilibrium 2×CO2 experiment, which shows polar amplification of the surface warming. Variations in the clear sky sensitivity of the model are shown to depend primarily on changes in the long wave response due to competing (positive) water vapor and (generally negative) lapse rate feedbacks. Results here indicate that these feedbacks may be very different for differing experimental boundary conditions. The long wave feedback due to cloud amount changes is negative in all experiments, due to a very consistent decrease in high and middle cloud fractions. Conversely, cloud height feedback is positive due to a general increase in the altitude of (particularly high) cloud. Cloud height feedback is very sensitive to the choice of the convection scheme and to the change in vertical resolution. Greatest changes in the strength of the short wave cloud feedback results from modifications to the soil moisture specification and the convection scheme. The results here indicate that large differences in cloud feedback may be diagnosed from a single model, even without changes being made to the cloud parametrization. The value of the sensitivity can thus be expected to be a function not only of the physical parametrizations chosen for the model (e.g. the penetrative convection scheme), but also of the details of the manner in which the experiment was performed (e.g. SST and soil moisture specifications). The TOA radiation perturbation analysis method proves to be a powerful technique for diagnosing and understanding the physical processes responsible for the range in climate sensitivity found between the experiments."
"25031430500;36876405100;6701431208;7102696626;30967646900;6602688130;7102976560;6602098362;57210350827;7402207328;7201488063;","High Climate Sensitivity in the Community Earth System Model Version 2 (CESM2)",2019,"10.1029/2019GL083978","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85069816427&doi=10.1029%2f2019GL083978&partnerID=40&md5=3632e75a55abb7ca5879f8e434dee157","The Community Earth System Model Version 2 (CESM2) has an equilibrium climate sensitivity (ECS) of 5.3 K. ECS is an emergent property of both climate feedbacks and aerosol forcing. The increase in ECS over the previous version (CESM1) is the result of cloud feedbacks. Interim versions of CESM2 had a land model that damped ECS. Part of the ECS change results from evolving the model configuration to reproduce the long-term trend of global and regional surface temperature over the twentieth century in response to climate forcings. Changes made to reduce sensitivity to aerosols also impacted cloud feedbacks, which significantly influence ECS. CESM2 simulations compare very well to observations of present climate. It is critical to understand whether the high ECS, outside the best estimate range of 1.5–4.5 K, is plausible. ©2019. American Geophysical Union. All Rights Reserved."
"36856321600;7004479957;26645289600;7402064802;7004222705;23486332900;","Statistical significance of climate sensitivity predictors obtained by data mining",2014,"10.1002/2014GL059205","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84895643490&doi=10.1002%2f2014GL059205&partnerID=40&md5=f8ca70c87d9de4ef37c49523dcc26a75","Several recent efforts to estimate Earth's equilibrium climate sensitivity (ECS) focus on identifying quantities in the current climate which are skillful predictors of ECS yet can be constrained by observations. This study automates the search for observable predictors using data from phase 5 of the Coupled Model Intercomparison Project. The primary focus of this paper is assessing statistical significance of the resulting predictive relationships. Failure to account for dependence between models, variables, locations, and seasons is shown to yield misleading results. A new technique for testing the field significance of data-mined correlations which avoids these problems is presented. Using this new approach, all 41,741 relationships we tested were found to be explainable by chance. This leads us to conclude that data mining is best used to identify potential relationships which are then validated or discarded using physically based hypothesis testing. Key Points Correlation magnitude is not sufficient proof of predictive skill Significance testing is complicated by model nonindependence in ensembles The best predictors of climate change are related to the Southern Ocean ©2014. American Geophysical Union. All Rights Reserved."
"7004468723;","Relative contribution of soil moisture and snow mass to seasonal climate predictability: A pilot study",2010,"10.1007/s00382-008-0508-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951878461&doi=10.1007%2fs00382-008-0508-1&partnerID=40&md5=f6455ff86ee1241694a0ee65701d0a29","Land surface hydrology (LSH) is a potential source of long-range atmospheric predictability that has received less attention than sea surface temperature (SST). In this study, we carry out ensemble atmospheric simulations driven by observed or climatological SST in which the LSH is either interactive or nudged towards a global monthly re-analysis. The main objective is to evaluate the impact of soil moisture or snow mass anomalies on seasonal climate variability and predictability over the 1986-1995 period. We first analyse the annual cycle of zonal mean potential (perfect model approach) and effective (simulated vs. observed climate) predictability in order to identify the seasons and latitudes where land surface initialization is potentially relevant. Results highlight the influence of soil moisture boundary conditions in the summer mid-latitudes and the role of snow boundary conditions in the northern high latitudes. Then, we focus on the Eurasian continent and we contrast seasons with opposite land surface anomalies. In addition to the nudged experiments, we conduct ensembles of seasonal hindcasts in which the relaxation is switched off at the end of spring or winter in order to evaluate the impact of soil moisture or snow mass initialization. LSH appears as an effective source of surface air temperature and precipitation predictability over Eurasia (as well as North America), at least as important as SST in spring and summer. Cloud feedbacks and large-scale dynamics contribute to amplify the regional temperature response, which is however, mainly found at the lowest model levels and only represents a small fraction of the observed variability in the upper troposphere. © Springer-Verlag 2009."
"56867812800;8211380400;7202839433;","Simulating aerosol-radiation-cloud feedbacks on meteorology and air quality over eastern China under severe haze conditionsin winter",2015,"10.5194/acp-15-2387-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929298697&doi=10.5194%2facp-15-2387-2015&partnerID=40&md5=0e74ed878f5e0f1186a9990a71c89e14","The aerosol-radiation-cloud feedbacks on meteorology and air quality over eastern China under severe winter haze conditions in January 2013 are simulated using the fully coupled online Weather Research and Forecasting/Chemistry (WRF-Chem) model. Three simulation scenarios including different aerosol configurations are undertaken to distinguish the aerosol's radiative (direct and semi-direct) and indirect effects. Simulated spatial and temporal variations of PM2.5 are generally consistent with surface observations, with a mean bias of -18.9 μg m-3 (-15.0%) averaged over 71 big cities in China. Comparisons between different scenarios reveal that aerosol radiative effects (direct effect and semi-direct effects) result in reductions of downward shortwave flux at the surface, 2 m temperature, 10 m wind speed and planetary boundary layer (PBL) height by up to 84.0 W m-2, 3.2°C, 0.8 m s-1, and 268 m, respectively. The simulated impact of the aerosol indirect effects is comparatively smaller. Through reducing the PBL height and stabilizing lower atmosphere, the aerosol effects lead to increases in surface concentrations of primary pollutants (CO and SO<inf>2</inf>). Surface O<inf>3</inf> mixing ratio is reduced by up to 6.9 ppb (parts per billion) due to reduced incoming solar radiation and lower temperature, while the aerosol feedbacks on PM<inf>2.5</inf> mass concentrations show some spatial variations. Comparisons of model results with observations show that inclusion of aerosol feedbacks in the model significantly improves model performance in simulating meteorological variables and improves simulations of PM<inf>2.5</inf> temporal distributions over the North China Plain, the Yangtze River delta, the Pearl River delta, and central China. Although the aerosol-radiation-cloud feedbacks on aerosol mass concentrations are subject to uncertainties, this work demonstrates the significance of aerosol-radiation-cloud feedbacks for real-time air quality forecasting under haze conditions. © Author(s) 2015."
"6701562113;8631239200;6602572031;7005751636;55665687100;55536747200;7006030430;7003495982;","Introducing subgrid-scale cloud feedbacks to radiation for regional meteorological and climate modeling",2012,"10.1029/2012GL054031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871574295&doi=10.1029%2f2012GL054031&partnerID=40&md5=2ee3719f45dd089e5bddafaa275b4a51","Convective systems and associated cloudiness directly influence regional and local atmospheric radiation budgets, as well as dynamics and thermodynamics, through feedbacks. However, most subgrid-scale convective parameterizations in regional weather and climate models do not consider cumulus cloud feedbacks to radiation, resulting in biases in several meteorological parameters. We have incorporated this key feedback process into a convective parameterization and a radiation scheme in the Weather Research and Forecasting model, and evaluated the impacts of including this process in short-term weather and multiyear climate simulations. Introducing subgrid-scale convective cloud-radiation feedbacks leads to a more realistic simulation of attenuation of downward surface shortwave radiation. Reduced surface shortwave radiation moderates the surface forcing for convection and results in a notable reduction in precipitation biases. Our research reveals a need for more in-depth consideration of the effects of subgrid-scale clouds in regional meteorology/climate and air quality models on radiation, photolysis, cloud mixing, and aerosol indirect effects. © 2012. American Geophysical Union. All Rights Reserved."
"55977336000;16637291100;7406671641;7501855361;57202891769;","A cloudier Arctic expected with diminishing sea ice",2012,"10.1029/2012GL051251","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863275739&doi=10.1029%2f2012GL051251&partnerID=40&md5=b1ae5649a94d7da37ffc945412d004e2","Arctic sea ice cover has decreased dramatically over the last three decades. Global climate models under-predicted this decline, most likely a result of the misrepresentation of one or more processes that influence sea ice. The cloud feedback is the primary source of uncertainty in model simulations, especially in the polar regions. A better understanding of the interaction between sea ice and clouds, and specifically the impact of decreased sea ice on cloud cover, will provide valuable insight into the Arctic climate system and may ultimately help in improving climate model parameterizations. In this study, an equilibrium feedback assessment is employed to quantify the relationship between changes in sea ice and clouds, using satellite-derived sea ice concentration and cloud cover over the period 2000-2010. Results show that a 1% decrease in sea ice concentration leads to a 0.36-0.47% increase in cloud cover, suggesting that a further decline in sea ice cover will result in an even cloudier Arctic. Copyright © 2012 by the American Geophysical Union."
"22978151200;7201837768;","Aerosol direct, indirect, semidirect, and surface albedo effects from sector contributions based on the IPCC AR5 emissions for preindustrial and present-day conditions",2012,"10.1029/2011JD016816","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856043564&doi=10.1029%2f2011JD016816&partnerID=40&md5=2bbf80686f0742c18d794e0fb79ec67e","The anthropogenic increase in aerosol concentrations since preindustrial times and its net cooling effect on the atmosphere is thought to mask some of the greenhouse gas-induced warming. Although the overall effect of aerosols on solar radiation and clouds is most certainly negative, some individual forcing agents and feedbacks have positive forcing effects. Recent studies have tried to identify some of those positive forcing agents and their individual emission sectors, with the hope that mitigation policies could be developed to target those emitters. Understanding the net effect of multisource emitting sectors and the involved cloud feedbacks is very challenging, and this paper will clarify forcing and feedback effects by separating direct, indirect, semidirect and surface albedo effects due to aerosols. To this end, we apply the Goddard Institute for Space Studies climate model including detailed aerosol microphysics to examine aerosol impacts on climate by isolating single emission sector contributions as given by the Coupled Model Intercomparison Project Phase 5 (CMIP5) emission data sets developed for Intergovernmental Panel on Climate Change (IPCC) AR5. For the modeled past 150 years, using the climate model and emissions from preindustrial times to present-day, the total global annual mean aerosol radiative forcing is -0.6 W/m2, with the largest contribution from the direct effect (-0.5 W/m2). Aerosol-induced changes on cloud cover often depends on cloud type and geographical region. The indirect (includes only the cloud albedo effect with -0.17 W/m2) and semidirect effects (-0.10 W/m2) can be isolated on a regional scale, and they often have opposing forcing effects, leading to overall small forcing effects on a global scale. Although the surface albedo effects from aerosols are small (0.016 W/m2), triggered feedbacks on top of the atmosphere (TOA) radiative forcing can be 10 times larger. Our results point out that each emission sector has varying impacts by geographical region. For example, the single sector most responsible for a net positive radiative forcing is the transportation sector in the United States, agricultural burning and transportation in Europe, and the domestic emission sector in Asia. These sectors are attractive mitigation targets. Copyright 2012 by the American Geophysical Union."
"7201443624;","Combining satellite data and models to estimate cloud radiative effect at the surface and in the atmosphere",2011,"10.1002/met.285","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051879400&doi=10.1002%2fmet.285&partnerID=40&md5=a7feeda7833aa2321a3129e7bf577eba","Satellite measurements and numerical forecast model reanalysis data are used to compute an updated estimate of the cloud radiative effect on the global multi-annual mean radiative energy budget of the atmosphere and surface. The cloud radiative cooling effect through reflection of short wave radiation dominates over the long wave heating effect, resulting in a net cooling of the climate system of - 21 Wm-2. The short wave radiative effect of cloud is primarily manifest as a reduction in the solar radiation absorbed at the surface of - 53 Wm-2. Clouds impact long wave radiation by heating the moist tropical atmosphere (up to around 40 Wm-2 for global annual means) while enhancing the radiative cooling of the atmosphere over other regions, in particular higher latitudes and sub-tropical marine stratocumulus regimes. While clouds act to cool the climate system during the daytime, the cloud greenhouse effect heats the climate system at night. The influence of cloud radiative effect on determining cloud feedbacks and changes in the water cycle are discussed. © 2011 Royal Meteorological Society."
"54897465300;54893098900;26645289600;7202145115;","Cloud feedback mechanisms and their representation in global climate models",2017,"10.1002/wcc.465","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019160391&doi=10.1002%2fwcc.465&partnerID=40&md5=f41783285b9275b38c876115090cf26b","Cloud feedback—the change in top-of-atmosphere radiative flux resulting from the cloud response to warming—constitutes by far the largest source of uncertainty in the climate response to CO2 forcing simulated by global climate models (GCMs). We review the main mechanisms for cloud feedbacks, and discuss their representation in climate models and the sources of intermodel spread. Global-mean cloud feedback in GCMs results from three main effects: (1) rising free-tropospheric clouds (a positive longwave effect); (2) decreasing tropical low cloud amount (a positive shortwave [SW] effect); (3) increasing high-latitude low cloud optical depth (a negative SW effect). These cloud responses simulated by GCMs are qualitatively supported by theory, high-resolution modeling, and observations. Rising high clouds are consistent with the fixed anvil temperature (FAT) hypothesis, whereby enhanced upper-tropospheric radiative cooling causes anvil cloud tops to remain at a nearly fixed temperature as the atmosphere warms. Tropical low cloud amount decreases are driven by a delicate balance between the effects of vertical turbulent fluxes, radiative cooling, large-scale subsidence, and lower-tropospheric stability on the boundary-layer moisture budget. High-latitude low cloud optical depth increases are dominated by phase changes in mixed-phase clouds. The causes of intermodel spread in cloud feedback are discussed, focusing particularly on the role of unresolved parameterized processes such as cloud microphysics, turbulence, and convection. WIREs Clim Change 2017, 8:e465. doi: 10.1002/wcc.465. For further resources related to this article, please visit the WIREs website. © 2017 Wiley Periodicals, Inc."
"8866821900;7201504886;35509639400;","Using aquaplanets to understand the robust responses of comprehensive climate models to forcing",2015,"10.1007/s00382-014-2138-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939873329&doi=10.1007%2fs00382-014-2138-0&partnerID=40&md5=69761b7cc5058381a2ff428415301b3f","Idealized climate change experiments using fixed sea-surface temperature are investigated to determine whether zonally symmetric aquaplanet configurations are useful for understanding climate feedbacks in more realistic configurations. The aquaplanets capture many of the robust responses of the large-scale circulation and hydrologic cycle to both warming the sea-surface temperature and quadrupling atmospheric CO<inf>2</inf>. The cloud response to both perturbations varies across models in both Earth-like and aquaplanet configurations, and this spread arises primarily from regions of large-scale subsidence. Most models produce a consistent cloud change across the subsidence regimes, and the feedback in trade-wind cumulus regions dominates the tropical response. It is shown that these trade-wind regions have similar cloud feedback in Earth-like and aquaplanet warming experiments. The tropical average cloud feedback of the Earth-like experiment is captured by five of eight aquaplanets, and the three outliers are investigated to understand the discrepancy. In two models, the discrepancy is due to warming induced dissipation of stratocumulus decks in the Earth-like configuration which are not represented in the aquaplanet. One model shows a circulation response in the aquaplanet experiment accompanied by a cloud response that differs from the Earth-like configuration. Quadrupling atmospheric CO<inf>2</inf> in aquaplanets produces slightly greater adjusted forcing than in Earth-like configurations, showing that land-surface effects dampen the adjusted forcing. The analysis demonstrates how aquaplanets, as part of a model hierarchy, help elucidate robust aspects of climate change and develop understanding of the processes underlying them. © 2014, The Author(s)."
"30667558200;6603925960;","Evaluation of the cloud thermodynamic phase in a climate model using CALIPSO-GOCCP",2013,"10.1002/jgrd.50376","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882745774&doi=10.1002%2fjgrd.50376&partnerID=40&md5=7427d05eba35e04c9ea8e6db131e215c","Level 1 measurements, including cross-polarized backscatter, from the Cloud-Aerosol Lidar with Orthogonal Polarization lidar, have been used to document the vertical structure of the cloud thermodynamic phase at global scale. We built a cloud phase identification (liquid, ice, or undefined) in the Global Climate Model (GCM)-oriented Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Cloud Product (GOCCP) and analyzed the spatial distribution of liquid and ice clouds in five January, February, March (JFM) seasons of global-scale observations (2007-2011). We developed a cloud phase diagnosis in the Cloud Feedback Model Intercomparison Program Observation Simulator Package to evaluate the cloud phase description in the LMDZ5B climate model. The diagnosis in the simulator is fully consistent with the CALIPSO-GOCCP observations to ensure that differences between the observations and the ""model + simulator"" ensemble outputs can be attributed to model biases. We compared the liquid and ice cloud vertical distributions simulated by the model with and without the simulator to quantify the impact of the simulator. The model does not produce liquid clouds above 3 km and produces ice instead of liquid at low and middle altitudes in polar regions, as well as along the Intertropical Convergence Zone. The model is unable to replicate the observed coexistence of liquid and ice cloud between 0°C and -40°C. Liquid clouds dominate T > -21°C in the observations, T > -12°C in the model + simulator, and T > -7.5°C in the model parameterization. Even if the simulator shifts the model cloud phase parameterization to colder temperature because of the lidar instrument peculiarities, the cloud phase transition remains too warm compared to the observations. Key Points To document the partition of liquid and ice phase within clouds at global scale To evaluate the description of liquid and ice clouds in a climate model To build a new cloud thermodynamic phase climatology vertically resolved ©2013. American Geophysical Union. All Rights Reserved."
"57212781009;6701715507;","Climate feedbacks under a very broad range of forcing",2009,"10.1029/2008GL036268","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62749101228&doi=10.1029%2f2008GL036268&partnerID=40&md5=1df9d5dd4ab5879e9dec847d3d6904dd","An atmospheric general circulation model, coupled to a mixed layer ocean, is subjected to a broad range of forcing away from the current climate between 1/16 to 32 times current CO2 in halving/doubling steps. As climate warms climate sensitivity weakens (although not monotonically), albedo feedback weakens (driving much of the sensitivity weakening), water vapour feedback strengthens (at a rate slightly larger than it would if relative humidity remained unchanged), and lapse rate feedback increases (negatively); this latter change essentially offsetting the water vapour increases. Longwave cloud feedbacks are relatively stable (moderate and positive) across the full range; shortwave cloud feedback remains relatively weak, apart from under the coldest climates. Cloud optical property related components (from total water content, water/ice fraction and cloud thickness) remain remarkably stable. Cloud 'amount' feedbacks show the greatest trend\s: weakening as temperatures increase. Although cloud feedbacks show an overall consistency of features in different latitudes, precise patterns of changes differ substantially for different baseline Climates. © 2009 by the American Geophysical Union."
"7005955015;24347548900;12139043600;12139310900;6506436908;","Response of the climate system to aerosol direct and indirect forcing: Role of cloud feedbacks",2005,"10.1029/2005JD006299","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31644442337&doi=10.1029%2f2005JD006299&partnerID=40&md5=a7ea4a199463df596341da872a4b3471","In this study, the response of the climate system to aerosol direct and indirect radiative forcing is investigated. Several multidecadal equilibrium simulations are carried out, using the NCAR CCM3 framework coupled to a separately developed aerosol treatment. The aerosol treatment includes, e.g., a life cycle scheme for particulate sulfate and black carbon (natural and anthropogenic), calculations of aerosol size distributions and CCN activation, as well as computations of direct and indirect forcing (1st and 2nd indirect effect). In all the simulations the full aerosol treatment is run online, hence responding interactively to changes in climate. By far the largest response is caused by the indirect forcing, with a globally averaged cooling of -1.25 K due to anthropogenic aerosols. The largest temperature reduction is found in the Northern Hemisphere because of a larger aerosol burden there. As a result of this cooling pattern, the Intertropical Convergence Zone is displaced southward by a few hundred kilometers. Interestingly, a similar, though less significant displacement is also found in the experiments with the direct effect alone, even though the globally averaged aerosol induced cooling is much weaker in that case, i.e., -0.08 K. The direct radiative forcing is much stronger at the surface than at the top of the atmosphere, and this leads to a slight weakening of the hydrological cycle. Comparing simulations with direct and indirect forcing combined to those with indirect and direct forcing separately, a residual, caused by nonlinear model feedbacks, is manifested through a reduction in precipitation. This reduction amounts to -0.5% in a global average and exceeds -2.5% in the Arctic, highlighting the role of high-latitude climate feedbacks. Globally, cloud feedback is negative in the sense that in the colder climate resulting from anthropogenic aerosol forcing, net cloud forcing is reduced by 15% compared to the original climate state. This is caused by a general cloud thinning, especially at high latitudes, while in the most polluted regions, clouds are thicker through the 2nd indirect effect. The 1st indirect effect, on the other hand, remains intact in the presence of climate feedbacks, yielding a similar signature of cloud droplet reduction as in the pure forcing simulations. Copyright 2005 by the American Geophysical Union."
"7401559815;7006329926;7201844203;7202772927;","An inquiry into the cirrus‐cloud thermostat effect for tropical sea surface temperature",1994,"10.1029/94GL00222","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028592859&doi=10.1029%2f94GL00222&partnerID=40&md5=2e5b95c0039bcfb11e2c666477e5ace3","In this paper, we investigate the relative importance of local vs remote control on cloud radiative forcing using a cumulus ensemble model. It is found that cloud and surface radiation forcings are much more sensitive to the mean vertical motion associated with large scale tropical circulation than to the local SST. When the local SST is increased with the mean vertical motion held constant, increased surface latent and sensible heat flux associated with enhanced moisture recycling is found to be the primary mechanism for cooling the ocean surface. Large changes in surface shortwave fluxes are related to changes in cloudiness induced by changes in the large scale circulation. These results are consistent with a number of earlier empirical studies, which raised concerns regarding the validity of the cirrus‐thermostat hypothesis (Ramanathan and Collins, 1991). It is argued that for a better understanding of cloud feedback, both local and remote controls need to be considered and that a cumulus ensemble model is a powerful tool that should be explored for such purpose. Copyright 1994 by the American Geophysical Union."
"26645289600;55332348600;7402064802;","Insights from a refined decomposition of cloud feedbacks",2016,"10.1002/2016GL069917","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84987605289&doi=10.1002%2f2016GL069917&partnerID=40&md5=f49d6dd9a4d8dca6636ea0124b51cb8b","Decomposing cloud feedback into components due to changes in several gross cloud properties provides valuable insights into its physical causes. Here we present a refined decomposition that separately considers changes in free tropospheric and low cloud properties, better connecting feedbacks to individual governing processes and avoiding ambiguities present in a commonly used decomposition. It reveals that three net cloud feedback components are robustly nonzero: positive feedbacks from increasing free tropospheric cloud altitude and decreasing low cloud cover and a negative feedback from increasing low cloud optical depth. Low cloud amount feedback is the dominant contributor to spread in net cloud feedback but its anticorrelation with other components damps overall spread. The ensemble mean free tropospheric cloud altitude feedback is roughly 60% as large as the standard cloud altitude feedback because it avoids aliasing in low cloud reductions. Implications for the “null hypothesis” climate sensitivity from well-understood and robustly simulated feedbacks are discussed. ©2016. American Geophysical Union. All Rights Reserved."
"36856321600;26645289600;57210518852;55575258400;","Quantifying the sources of intermodel spread in equilibrium climate sensitivity",2016,"10.1175/JCLI-D-15-0352.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957824678&doi=10.1175%2fJCLI-D-15-0352.1&partnerID=40&md5=614375d4d9e1241ddbc46eaeee91aced","This study clarifies the causes of intermodel differences in the global-average temperature response to doubled CO2, commonly known as equilibriumclimate sensitivity (ECS). The authors begin by noting several issues with the standard approach for decomposing ECS into a sum of forcing and feedback terms. This leads to a derivation of an alternative method based on linearizing the effect of the net feedback. Consistent with previous studies, the new method identifies shortwave cloud feedback as the dominant source of intermodel spread in ECS. This new approach also reveals that covariances between cloud feedback and forcing, between lapse rate and longwave cloud feedbacks, and between albedo and shortwave cloud feedbacks play an important and previously underappreciated role in determining model differences in ECS. Defining feedbacks based on fixed relative rather than specific humidity (as suggested by Held and Shell) reduces the covariances between processes and leads to more straightforward interpretations of results. © 2016 American Meteorological Society."
"26645289600;7202145115;","The observed sensitivity of high clouds to mean surface temperature anomalies in the tropics",2011,"10.1029/2011JD016459","https://www.scopus.com/inward/record.uri?eid=2-s2.0-82955164959&doi=10.1029%2f2011JD016459&partnerID=40&md5=a6b3183040bd48163c2cc17ee1993e67","Cloud feedback represents the source of largest diversity in projections of future warming. Observational constraints on both the sign and magnitude of the feedback are limited, since it is unclear how the natural variability that can be observed is related to secular climate change, and analyses have rarely been focused on testable physical theories for how clouds should respond to climate change. In this study we use observations from a suite of satellite instruments to assess the sensitivity of tropical high clouds to interannual tropical mean surface temperature anomalies. We relate cloud changes to a physical governing mechanism that is sensitive to the vertical structure of warming. Specifically, we demonstrate that the mean and interannual variability in both the altitude and fractional coverage of tropical high clouds as measured by CloudSat, the Moderate Resolution Imaging Spectroradiometer, the Atmospheric Infrared Sounder, and the International Satellite Cloud Climatology Project are well diagnosed by upper tropospheric convergence computed from the mass and energy budget of the clear-sky atmosphere. Observed high clouds rise approximately isothermally in accordance with theory and exhibit an overall reduction in coverage when the tropics warms, similar to their behavior in global warming simulations. Such cloud changes cause absorbed solar radiation to increase more than does outgoing longwave radiation, resulting in a positive but statistically insignificant net high cloud feedback in response to El Nio-Southern Oscillation. The results suggest that the convergence metric based on simple mass and energy budget constraints may be a powerful tool for understanding observed and modeled high cloud behavior and for evaluating the realism of modeled high cloud changes in response to a variety of forcings. Copyright 2011 by the American Geophysical Union."
"55575258400;35561911800;36705143500;56203249800;","Implications for climate sensitivity from the response to individual forcings",2016,"10.1038/nclimate2888","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84962268472&doi=10.1038%2fnclimate2888&partnerID=40&md5=3fa08719edbb816232aedbbf15bba6ee","Climate sensitivity to doubled CO2 is a widely used metric for the large-scale response to external forcing. Climate models predict a wide range for two commonly used definitions: the transient climate response (TCR: the warming after 70 years of CO2 concentrations that rise at 1% per year), and the equilibrium climate sensitivity (ECS: the equilibrium temperature change following a doubling of CO2 concentrations). Many observational data sets have been used to constrain these values, including temperature trends over the recent past, inferences from palaeoclimate and process-based constraints from the modern satellite era. However, as the IPCC recently reported, different classes of observational constraints produce somewhat incongruent ranges. Here we show that climate sensitivity estimates derived from recent observations must account for the efficacy of each forcing active during the historical period. When we use single-forcing experiments to estimate these efficacies and calculate climate sensitivity from the observed twentieth-century warming, our estimates of both TCR and ECS are revised upwards compared to previous studies, improving the consistency with independent constraints. © 2016 Macmillan Publishers Limited. All rights reserved."
"57034069700;35509639400;","Physical mechanisms controlling the initiation of convective self-aggregation in a General Circulation Model",2015,"10.1002/2015MS000571","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959576864&doi=10.1002%2f2015MS000571&partnerID=40&md5=6d729f7b1ea968f6b4a8a35ef810bf37","Cloud-resolving models have shown that under certain conditions, the Radiative-Convective Equilibrium (RCE) could become unstable and lead to the spontaneous organization of the atmosphere into dry and wet areas, and the aggregation of convection. In this study, we show that this ""self-aggregation"" behavior also occurs in nonrotating RCE simulations performed with the IPSL-CM5A-LR General Circulation Model (GCM), and that it exhibits a strong dependence on sea surface temperature (SST). We investigate the physical mechanisms that control the initiation of self-aggregation in this model, and their dependence on temperature. At low SSTs, the onset of self-aggregation is primarily controlled by the coupling between low-cloud radiative effects and shallow circulations and the formation of ""radiatively driven cold pools"" in areas devoid of deep convection, while at high SSTs it is primarily controlled by the coupling between surface fluxes and circulation within convective areas. At intermediate temperatures, the occurrence of self-aggregation is less spontaneous and depends on initial conditions, but it can arise through a combination of both mechanisms. Through their coupling to circulation and surface fluxes, the radiative effects of low-level clouds play a critical role in both initiation mechanisms, and the sensitivity of boundary layer clouds to surface temperature explains to a large extent the temperature dependence of convective self-aggregation. At any SST, the presence of cloud-radiative effects in the free troposphere is necessary to the initiation, growth, and maintenance of convective aggregation. © 2015. The Authors."
"57212781009;6701715507;","On tropospheric adjustment to forcing and climate feedbacks",2011,"10.1007/s00382-011-1067-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954620930&doi=10.1007%2fs00382-011-1067-4&partnerID=40&md5=4a18c877f4a414413d68ac8101e46e0d","Motivated by findings that major components of so-called cloud 'feedbacks' are best understood as rapid responses to CO2 forcing (Gregory and Webb in J Clim 21:58-71, 2008), the top of atmosphere (TOA) radiative effects from forcing, and the subsequent responses to global surface temperature changes from all 'atmospheric feedbacks' (water vapour, lapse rate, surface albedo, 'surface temperature' and cloud) are examined in detail in a General Circulation Model. Two approaches are used: applying regressions to experiments as they approach equilibrium, and equilibrium experiments forced separately by CO2 and patterned sea surface temperature perturbations alone. Results are analysed using the partial radiative perturbation ('PRP') technique. In common with Gregory and Webb (J Clim 21:58-71, 2008) a strong positive addition to 'forcing' is found in the short wave (SW) from clouds. There is little evidence, however, of significant global scale rapid responses from long wave (LW) cloud, nor from surface albedo, SW water vapour or 'surface temperature'. These responses may be well understood to first order as classical 'feedbacks'-i. e. as a function of global mean temperature alone and linearly related to it. Linear regression provides some evidence of a small rapid negative response in the LW from water vapour, related largely to decreased relative humidity (RH), but the response here, too, is dwarfed by subsequent response to warming. The large rapid SW cloud response is related to cloud fraction changes-and not optical properties-resulting from small cloud decreases ranging from the tropical mid troposphere to the mid latitude lower troposphere, in turn associated with decreased lower tropospheric RH. These regions correspond with levels of enhanced heating rates and increased temperatures from the CO2 increase. The pattern of SW cloud fraction response to SST changes differs quite markedly to this, with large positive radiation responses originating in the upper troposphere, positive contributions in the lowest levels and patterns of positive/negative contributions in mid latitude low levels. Overall SW cloud feedback was diagnosed as negative, due to the substantial negative SW feedback in cloud optical properties more than offsetting these. This study therefore suggests the rapid response to CO2 forcing is (apart from a possible small negative response from LW water vapour) essentially confined to cloud fraction changes affecting SW radiation, and further that significant feedbacks with temperature occur in all cloud components (including this one), and indeed in all other classically understood 'feedbacks'. © 2011 Springer-Verlag."
"55977336000;7101677832;24802640400;16637291100;7201607592;","Errors in cloud detection over the arctic using a satellite imager and implications for observing feedback mechanisms",2010,"10.1175/2009JCLI3386.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953699014&doi=10.1175%2f2009JCLI3386.1&partnerID=40&md5=5c62602e75ffbd24324b77a267705b3f","Arctic sea ice extent has decreased dramatically over the last 30 years, and this trend is expected to continue through the twenty-first century. Changes in sea ice extent impact cloud cover, which in turn influences the surface energy budget. Understanding cloud feedback mechanisms requires an accurate determination of cloud cover over the polar regions, which must be obtained from satellite-based measurements. The accuracy of cloud detection using observations from space varies with surface type, complicating any assessment of climate trends aswell as the understanding of ice-albedo and cloud-radiative feedbackmechanisms. To explore the implications of this dependence on measurement capability, cloud amounts from the Moderate Resolution Imaging Spectroradiometer (MODIS) are compared with those from the CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder (CALIPSO) satellites in both daytime and nighttime during the time period from July 2006 to December 2008. MODIS is an imager that makes observations in the solar and infrared spectrum. The active sensors of CloudSat and CALIPSO, a radar and lidar, respectively, provide vertical cloud structures along a narrow curtain. Results clearly indicate that MODIS cloud mask products perform better over open water than over ice. Regional changes in cloud amount from CloudSat/CALIPSO and MODIS are categorized as a function of independent measurements of sea ice concentration (SIC) from the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E). As SIC increases from 10% to 90%, the mean cloud amounts from MODIS and CloudSat-CALIPSO both decrease; water that is more open is associated with increased cloud amount. However, this dependency on SIC is much stronger for MODIS than for CloudSat-CALIPSO, and is likely due to a low bias in MODIS cloud amount. The implications of this on the surface radiative energy budget using historical satellite measurements are discussed. The quantified ice-water difference in MODIS cloud detection can be used to adjust estimated trends in cloud amount in the presence of changing sea ice cover from an independent dataset. It was found that cloud amount trends in the Arctic might be in error by up to 2.7% per decade. The impact of these errors on the surface net cloud radiative effect (""forcing"") of the Arctic can be significant, as high as 8.5%. © 2010 American Meteorological Society."
"16202694600;7004060399;","Southern hemisphere cloud-dynamics biases in CMIP5 models and their implications for climate projections",2014,"10.1175/JCLI-D-14-00113.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905177906&doi=10.1175%2fJCLI-D-14-00113.1&partnerID=40&md5=df67aa7a7f968525a8c8cab21adcac7a","This study quantifies cloud-radiative anomalies associated with interannual variability in the latitude of the Southern Hemisphere (SH) midlatitude eddy-driven jet, in 20 global climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5). Two distinct model types are found. In the first class of models (type I models), total cloud fraction is reduced at SH midlatitudes as the jet moves poleward, contributing to enhanced shortwave radiative warming. In the second class of models (type II models), this dynamically induced cloud radiative warming effect is largely absent. Type I and type II models have distinct deficiencies in their representation of observed Southern Ocean clouds, but comparison with two independent satellite datasets indicates that the cloud-dynamics behavior of type II models is more realistic. Because the SH midlatitude jet shifts poleward in response to CO2 forcing, the cloud-dynamics biases uncovered from interannual variability are directly relevant for climate change projections. In CMIP5 model experiments with abruptly quadrupled atmospheric CO2 concentrations, the global-mean surface temperature initially warms more in type I models, even though their equilibrium climate sensitivity is not significantly larger. In type I models, this larger initial warming is linked to the rapid adjustment of the circulation and clouds to CO2 forcing in the SH, where a nearly instantaneous poleward shift of the midlatitude jet is accompanied by a reduction in the reflection of solar radiation by clouds. In type II models, the SH jet also shifts rapidly poleward with CO2 quadrupling, but it is not accompanied by cloud radiative warming anomalies, resulting in a smaller initial global-mean surface temperature warming. © 2014 American Meteorological Society."
"55087038900;56979463400;7202145115;","Tropical cirrus and water vapor: An effective Earth infrared iris feedback?",2002,"10.5194/acp-2-31-2002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48749104391&doi=10.5194%2facp-2-31-2002&partnerID=40&md5=ca0d2f80124bbe2f74f9614ecc309c98","We revisit a model of feedback processes proposed by Lindzen et al. (2001), in which an assumed 22% reduction in the area of tropical high clouds per degree increase in sea surface temperature produces negative feedbacks associated with upper tropospheric water vapor and cloud radiative effects. We argue that the water vapor feedback is overestimated in Lindzen et al. (2001) by at least 60%, and that the high cloud feedback is small. Although not mentioned by Lindzen et al. (2001), tropical low clouds make a significant contribution to their negative feedback, which is also overestimated. Using more realistic parameters in the model of Lindzen et al. (2001), we obtain a feedback factor in the range of -0.15 to -0.51, compared to their larger negative feedback factor of -0.45 to -1.03. It is noted that our feedback factor could still be overestimated due to the assumption of constant low cloud cover in the simple radiative-convective model. © European Geophysical Society 2002."
"57201828043;55911178700;6602662282;7403211753;7003642344;55495816500;","Pathways to 1.5 °c and 2 °c warming based on observational and geological constraints",2018,"10.1038/s41561-017-0054-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040763726&doi=10.1038%2fs41561-017-0054-8&partnerID=40&md5=d3324bed4845a8aac5a2fbd4a7ccfd5b","To restrict global warming to below the agreed targets requires limiting carbon emissions, the principal driver of anthropogenic warming. However, there is significant uncertainty in projecting the amount of carbon that can be emitted, in part due to the limited number of Earth system model simulations and their discrepancies with present-day observations. Here we demonstrate a novel approach to reduce the uncertainty of climate projections; using theory and geological evidence we generate a very large ensemble (3 × 104) of projections that closely match records for nine key climate metrics, which include warming and ocean heat content. Our analysis narrows the uncertainty in surface-warming projections and reduces the range in equilibrium climate sensitivity. We find that a warming target of 1.5 °C above the pre-industrial level requires the total emitted carbon from the start of year 2017 to be less than 195-205 PgC (in over 66% of the simulations), whereas a warming target of 2 °C is only likely if the emitted carbon remains less than 395-455 PgC. At the current emission rates, these warming targets are reached in 17-18 years and 35-41 years, respectively, so that there is a limited window to develop a more carbon-efficient future. © 2018 The Author(s)."
"54897465300;7202145115;7201485519;","Mechanisms of the negative shortwave cloud feedback in middle to high latitudes",2016,"10.1175/JCLI-D-15-0327.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957673640&doi=10.1175%2fJCLI-D-15-0327.1&partnerID=40&md5=f4724f3fb3266e86ee3a697ca8bef616","Increases in cloud optical depth and liquid water path (LWP) are robust features of global warming model simulations in high latitudes, yielding a negative shortwave cloud feedback, but the mechanisms are still uncertain. Here the importance of microphysical processes for the negative optical depth feedback is assessed by perturbing temperature in the microphysics schemes of two aquaplanet models, both of which have separate prognostic equations for liquid water and ice. It is found that most of the LWP increase with warming is caused by a suppression of ice microphysical processes in mixed-phase clouds, resulting in reduced conversion efficiencies of liquid water to ice and precipitation. Perturbing the temperature-dependent phase partitioning of convective condensate also yields a small LWP increase. Together, the perturbations in large-scale microphysics and convective condensate partitioning explain more than two-thirds of the LWP response relative to a reference case with increased SSTs, and capture all of the vertical structure of the liquid water response. In support of these findings, a very robust positive relationship between monthly mean LWP and temperature in CMIP5 models and observations is shown to exist in mixed-phase cloud regions only. In models, the historical LWP sensitivity to temperature is a good predictor of the forced global warming response poleward of about 45°, although models appear to overestimate the LWP response to warming compared to observations. The results indicate that in climate models, the suppression of ice-phase microphysical processes that deplete cloud liquid water is a key driver of the LWP increase with warming and of the associated negative shortwave cloud feedback. © 2016 American Meteorological Society."
"8525144100;","Spread of model climate sensitivity linked to double-Intertropical Convergence Zone bias",2015,"10.1002/2015GL064119","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84931568310&doi=10.1002%2f2015GL064119&partnerID=40&md5=b2011731bac1a6b0f33a1c2e071fffcf","Despite decades of climate research and model development, two outstanding problems still plague the latest global climate models (GCMs): the double-Intertropical Convergence Zone (ITCZ) bias and the 2-5°C spread of equilibrium climate sensitivity (ECS). Here we show that the double-ITCZ bias and ECS in 44 GCMs from Coupled Model Intercomparison Project Phases 3/5 are negatively correlated. The models with weak (strong) double-ITCZ biases have high (low)-ECS values of ∼4.1(2.2)°C. This indicates that the double-ITCZ bias is a new emergent constraint for ECS based on which ECS might be in the higher end of its range (∼4.0°C) and most models might have underestimated ECS. In addition, we argue that the double-ITCZ bias can physically affect both cloud and water vapor feedbacks (thus ECS) and is a more easily measured emergent constraint for ECS than previous ones. It can be used as a performance metric for evaluating and comparing different GCMs. ©2015. This article is a U.S. Government work and is in the public domain in the USA."
"55286185400;","An investigation of the connections among convection, clouds, and climate sensitivity in a global climate model",2014,"10.1175/JCLI-D-13-00145.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897635713&doi=10.1175%2fJCLI-D-13-00145.1&partnerID=40&md5=3dd5992de7ee02a6fa9aeda8808d35e9","This study explores connections between process-level modeling of convection and global climate model (GCM) simulated clouds and cloud feedback to global warming through a set of perturbed-physics and perturbed sea surface temperature experiments. A bulk diagnostic approach is constructed, and a set of variables is derived and demonstrated to be useful in understanding the simulated relationship. In particular, a novel bulk quantity, the convective precipitation efficiency or equivalently the convective detrainment efficiency, is proposed as a simple measure of the aggregated properties of parameterized convection important to the GCM simulated clouds. As the convective precipitation efficiency increases in the perturbedphysics experiments, both liquid and ice water path decrease, with low and middle cloud fractions diminishing at a faster rate than high cloud fractions. This asymmetry results in a large sensitivity of top-of-atmosphere net cloud radiative forcing to changes in convective precipitation efficiency in this limited set of models. For global warming experiments, intermodel variations in the response of cloud condensate, low cloud fraction, and total cloud radiative forcing are well explained by model variations in response to total precipitation (or detrainment) efficiency. Despite significant variability, all of the perturbed-physics models produce a sizable increase in precipitation efficiency to warming. A substantial fraction of the increase is due to its convective component, which depends on the parameterization of cumulus mixing and convective microphysical processes. The increase in convective precipitation efficiency and associated change in convective cloud height distribution owing to warming explains the increased cloud feedback and climate sensitivity in recently developed Geophysical Fluid Dynamics Laboratory GCMs. The results imply that a cumulus scheme using fractional removal of condensate for precipitation and inverse calculation of the entrainment rate tends to produce a lower climate sensitivity than a scheme using threshold removal for precipitation and the entrainment rate formulated inversely dependent on convective depth. © 2014 American Meteorological Society."
"35580303100;7003420726;55537426400;6603196127;","Can the Last Glacial Maximum constrain climate sensitivity?",2012,"10.1029/2012GL053872","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871571629&doi=10.1029%2f2012GL053872&partnerID=40&md5=48c876a121160d0745863bc236ad5684","We investigate the relationship between the Last Glacial Maximum (LGM) and climate sensitivity across the PMIP2 multi-model ensemble of GCMs, and find a correlation between tropical temperature and climate sensitivity which is statistically significant and physically plausible. We use this relationship, together with the LGM temperature reconstruction of Annan and Hargreaves (2012), to generate estimates for the equilibrium climate sensitivity. We estimate the equilibrium climate sensitivity to be about 2.5C with a high probability of being under 4C, though these results are subject to several important caveats. The forthcoming PMIP3/CMIP5 models were not considered in this analysis, as very few LGM simulations are currently available from these models. We propose that these models will provide a useful validation of the correlation presented here. © 2012. American Geophysical Union. All Rights Reserved."
"54897465300;7202145115;","Clouds and the atmospheric circulation response to warming",2016,"10.1175/JCLI-D-15-0394.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957804102&doi=10.1175%2fJCLI-D-15-0394.1&partnerID=40&md5=5f13669e22184d95dd26a0b636e4b1d8","The authors study the effect of clouds on the atmospheric circulation response to CO2 quadrupling in an aquaplanet model with a slab ocean lower boundary. The cloud effect is isolated by locking the clouds to either the control or 4xCO2 state in the shortwave (SW) or longwave (LW) radiation schemes. In the model, cloud radiative changes explain more than half of the total poleward expansion of the Hadley cells, midlatitude jets, and storm tracks under CO2 quadrupling, even though they cause only one-fourth of the total global-mean surface warming. The effect of clouds on circulation results mainly from the SW cloud radiative changes, which strongly enhance the equator-to-pole temperature gradient at all levels in the troposphere, favoring stronger and poleward-shifted midlatitude eddies. By contrast, quadrupling CO2 while holding the clouds fixed causes strong polar amplification and weakened midlatitude baroclinicity at lower levels, yielding only a small poleward expansion of the circulation. The results show that 1) the atmospheric circulation responds sensitively to cloud-driven changes in meridional and vertical temperature distribution and 2) the spatial structure of cloud feedbacks likely plays a dominant role in the circulation response to greenhouse gas forcing. While the magnitude and spatial structure of the cloud feedback are expected to be highly model dependent, an analysis of 4xCO2 simulations of CMIP5 models shows that the SW cloud feedback likely forces a poleward expansion of the tropospheric circulation in most climate models. © 2016 American Meteorological Society."
"7005808242;57218978147;8733579800;","Dynamic radiative-convective equilibria using GCM column physics",2007,"10.1175/JAS3825.11","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846485149&doi=10.1175%2fJAS3825.11&partnerID=40&md5=1838da7ddcb99f49c3877c59b2d41c6c","The behavior of a GCM column physics package in a nonrotating, doubly periodic, homogeneous setting with prescribed SSTs is examined. This radiative-convective framework is proposed as a useful tool for studying some of the interactions between convection and larger-scale dynamics and the effects of differing modeling assumptions on convective organization and cloud feedbacks. For the column physics utilized here, from the Geophysical Fluid Dynamics Laboratory (GFDL) AM2 model, many of the properties of the homogeneous, nonrotating model are closely tied to the fraction of precipitation that is large-scale, rather than convective. Significant large-scale precipitation appears above a critical temperature and then increases with further increases in temperature. The amount of large-scale precipitation is a function of horizontal resolution and can also be controlled by modifying the convection scheme, as is illustrated here by modifying assumptions concerning entrainment into convective plumes. Significant similarities are found between the behavior of the homogeneous model and that of the Tropics of the parent GCM when ocean temperatures are increased and when the convection scheme is modified."
"7403318365;57193132723;","Effects of cloud parameterization on the simulation of climate changes in the GISS GCM",1999,"10.1175/1520-0442(1999)012<0761:eocpot>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033102334&doi=10.1175%2f1520-0442%281999%29012%3c0761%3aeocpot%3e2.0.co%3b2&partnerID=40&md5=ac444882946b07ffd277b3b8147611a3","Climate changes obtained from five doubled CO2 experiments with different parameterizations of large-scale clouds and moist convection are studied by use of the Goddard Institute for Space Studies (GISS) GCM at 4° lat × 5° long resolution. The baseline for the experiments is GISS Model II, which uses a diagnostic cloud scheme with fixed optical properties and a convection scheme with fixed cumulus mass fluxes and no downdrafts. The global and annual mean surface air temperature change (ΔTs) of 4.2°C obtained by Hansen et al. using the Model II physics at 8° lat × 10° long resolution is reduced to 3.55°C at the finer resolution. This is due to a significant reduction of tropical cirrus clouds in the warmer climate when a finer resolution is used, despite the fact that the relative humidity increases there with a doubling of CO2. When the new moist convection parameterization of Del Genio and Yao and prognostic large-scale cloud parameterization of Del Genio et al. are used, ΔTs is reduced to 3.09°C from 3.55°C. This is the net result of the inclusion of the feedback of cloud optical thickness and phase change of cloud water, and the presence of areally extensive cumulus anvil clouds. Without the optical thickness feedback, ΔTs is further reduced to 2.74°C, suggesting that this feedback is positive overall. Without anvil clouds, ΔTs is increased from 3.09° to 3.7°C, suggesting that anvil clouds of large optical thickness reduce the climate sensitivity. The net effect of using the new large-scale cloud parameterization without including the detrainment of convective cloud water is a slight increase of ΔT, from 3.56° to 3.7°C. The net effect of using the new moist convection parameterization without anvil clouds is insignificant (from 3.55° to 3.56°C). However, this is a result of a combination of many competing differences in other climate parameters. Despite the global cloud cover decrease simulated in most of the experiments, middle- and high-latitude continental cloudiness generally increases with warming, consistent with the sense of observed twentieth-century cloudiness trends; an indirect aerosol effect may therefore not be the sole explanation of these observations. An analysis of climate sensitivity and changes in cloud radiative forcing (CRF) indicates that the cloud feedback is positive overall in all experiments except the one using the new moist convection and large-scale cloud parameterization with prescribed cloud optical thickness, for which the cloud feedback is nearly neutral. Differences in ΔCRF among the different experiments cannot reliably be anticipated by the analogous differences in current climate CRF. The meridional distribution of ΔCRF suggests that the cloud feedback is positive mostly in the low and midlatitudes, but in the high latitudes, the cloud feedback is mostly negative and the amplification of ΔTs is due to other processes, such as snow/ice-albedo feedback and changes in the lapse rate. The authors' results suggest that when a sufficiently large variety of cloud feedback mechanisms are allowed for, significant cancellations between positive and negative feedbacks result, causing overall climate sensitivity to be less sensitive to uncertainties in poorly understood cloud physics. In particular, the positive low cloud optical thickness correlations with temperature observed in satellite data argue for a minimum climate sensitivity higher than the 1.5°C that is usually assumed."
"55207447000;7006307463;7201463831;7006634316;7004920873;","Why hasn't earth warmed as much as expected?",2010,"10.1175/2009JCLI3461.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952338354&doi=10.1175%2f2009JCLI3461.1&partnerID=40&md5=b73c841138f7a09a5b7e1212d6f269a3","The observed increase in global mean surface temperature (GMST) over the industrial era is less than 40% of that expected from observed increases in long-lived greenhouse gases together with the best-estimate equilibrium climate sensitivity given by the 2007 Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Possible reasons for this warming discrepancy are systematically examined here. The warming discrepancy is found to be due mainly to some combination of two factors: the IPCC best estimate of climate sensitivity being too high and/or the greenhouse gas forcing being partially offset by forcing by increased concentrations of atmospheric aerosols; the increase in global heat content due to thermal disequilibrium accounts for less than 25% of the discrepancy, and cooling by natural temperature variation can account for only about 15%. Current uncertainty in climate sensitivity is shown to preclude determining the amount of future fossil fuel CO2 emissions that would be compatible with any chosen maximum allowable increase in GMST; even the sign of such allowable future emissions is unconstrained. Resolving this situation, by empirical determination of the earth's climate sensitivity from the historical record over the industrial period or through use of climate models whose accuracy is evaluated by their performance over this period, is shown to require substantial reduction in the uncertainty of aerosol forcing over this period. © 2010 American Meteorological Society."
"7003976079;6701715507;7004033942;9845516300;6701689939;7004169476;26643217800;13609930400;7003979342;7004764167;7003543851;7003532926;7201485519;7404142321;","Global mean cloud feedbacks in idealized climate change experiments",2006,"10.1029/2005GL025370","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646844490&doi=10.1029%2f2005GL025370&partnerID=40&md5=4657faca8eca270a84796d2b96c591bf","Global mean cloud feedbacks in ten atmosphere-only climate models are estimated in perturbed sea surface temperature (SST) experiments and the results compared to doubled CO2 experiments using mixed-layer ocean versions of these same models. The cloud feedbacks in any given model are generally not consistent: the sign of the net cloud radiative feedback may vary according to the experimental design. However, both sets of experiments indicate that the variation of the total climate feedback across the models depends primarily on the variation of the net cloud feedback. Changes in different cloud types show much greater consistency between the two experiments for any individual model and amongst the set of models analyzed here. This suggests that the SST perturbation experiments may provide useful information on the processes associated with cloud changes which is not evident when analysis is restricted to feedbacks defined in terms of the change in cloud radiative forcing."
"35547807400;","Inference of Climate Sensitivity from Analysis of Earth's Energy Budget",2016,"10.1146/annurev-earth-060614-105156","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977139562&doi=10.1146%2fannurev-earth-060614-105156&partnerID=40&md5=0f9318ceeff37fd14585d733426b058e","Recent attempts to diagnose equilibrium climate sensitivity (ECS) from changes in Earth's energy budget point toward values at the low end of the Intergovernmental Panel on Climate Change Fifth Assessment Report (AR5)'s likely range (1.5-4.5 K). These studies employ observations but still require an element of modeling to infer ECS. Their diagnosed effective ECS over the historical period of around 2 K holds up to scrutiny, but there is tentative evidence that this underestimates the true ECS from a doubling of carbon dioxide. Different choices of energy imbalance data explain most of the difference between published best estimates, and effective radiative forcing dominates the overall uncertainty. For decadal analyses the largest source of uncertainty comes from a poor understanding of the relationship between ECS and decadal feedback. Considerable progress could be made by diagnosing effective radiative forcing in models. Copyright © 2016 by Annual Reviews. All rights reserved."
"7201606127;7402064802;","Low-cloud optical depth feedback in climate models",2014,"10.1002/2013JD021052","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902815940&doi=10.1002%2f2013JD021052&partnerID=40&md5=093a0a4a7706a80527033818d3e7ffbe","The relationship between low-level cloud optical depth and atmospheric and surface air temperature is examined in the control climate of 13 climate models to determine if cloud optical depth-temperature relationships found in observations are replicated in climate models and if climate model behavior found in control climate simulations provides information about the optical depth feedback in climate warming simulations forced by increasing carbon dioxide. A positive relationship between cloud optical depth and cloud temperature exists in allmodels for low clouds with relatively cold temperatures atmiddle and high latitudes, whereas a negative relationship exists for warmer low clouds in the tropics and subtropics. This relationship is qualitatively similar to that in an earlier analysis of satellite observations, although modeled regression slopes tend to be too positive and their intermodel spread is large. In the models, the cold cloud response comes from increases in cloud water content with increasing temperature, while the warm cloud response comes from decreases in physical thickness with increasing cloud temperature. The intermodel and interregional spread of low-cloud optical depth feedback in climate warming simulations is well predicted by the corresponding spread in the relationships between optical depth and temperature for the current climate, suggesting that this aspect of cloud feedback may be constrained by observations. Because models have a positive bias relative to observations in the optical depth-temperature relationship, shortwave cloud feedback for climate changes may be more positive than climate models currently simulate. © 2014. American Geophysical Union. All Rights Reserved"
"24081888700;6603081424;26645289600;57203386948;7401776640;7102517130;57208765879;7401793588;","Positive low cloud and dust feedbacks amplify tropical North Atlantic Multidecadal Oscillation",2016,"10.1002/2016GL067679","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959387760&doi=10.1002%2f2016GL067679&partnerID=40&md5=f48ac0d7378d525442313ff11a864124","The Atlantic Multidecadal Oscillation (AMO) is characterized by a horseshoe pattern of sea surface temperature (SST) anomalies and has a wide range of climatic impacts. While the tropical arm of AMO is responsible for many of these impacts, it is either too weak or completely absent in many climate model simulations. Here we show, using both observational and model evidence, that the radiative effect of positive low cloud and dust feedbacks is strong enough to generate the tropical arm of AMO, with the low cloud feedback more dominant. The feedbacks can be understood in a consistent dynamical framework: weakened tropical trade wind speed in response to a warm middle latitude SST anomaly reduces dust loading and low cloud fraction over the tropical Atlantic, which warms the tropical North Atlantic SST. Together they contribute to the appearance of the tropical arm of AMO. Most current climate models miss both the critical wind speed response and two positive feedbacks though realistic simulations of them may be essential for many climatic studies related to the AMO. © 2016. The Authors."
"7005808242;6701455548;","Using relative humidity as a state variable in climate feedback analysis",2012,"10.1175/JCLI-D-11-00721.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859974350&doi=10.1175%2fJCLI-D-11-00721.1&partnerID=40&md5=b02dca05f21bee15dbc1c468efafc53f","An approach to climate change feedback analysis is described in which tropospheric relative humidity replaces specific humidity as the state variable that, along with the temperature structure, surface albedos, and clouds, controls the magnitude of the response of global mean surface temperature to a radiative forcing. Despite being simply a regrouping of terms in the feedback analysis, this alternative perspective has the benefit of removing most of the pervasive cancellation between water and lapse-rate feedbacks seen in models. As a consequence, the individual feedbacks have less scatter than in the traditional formulation. The role of cloud feedbacks in controlling climate sensitivity is also reflected more clearly in the new formulation. © 2012 American Meteorological Society."
"23486332900;","A multimodel study of parametric uncertainty in predictions of climate response to rising greenhouse gas concentrations",2011,"10.1175/2010JCLI3498.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954998482&doi=10.1175%2f2010JCLI3498.1&partnerID=40&md5=62877a32eae589ab1b5df5cb569149ca","One tool for studying uncertainties in simulations of future climate is to consider ensembles of general circulation models where parameterizations have been sampled within their physical range of plausibility. This study is about simulations from two such ensembles: a subset of the climateprediction.net ensemble using the Met Office Hadley Centre Atmosphere Model, version 3.0 and the new ""CAMcube"" ensemble using the Community Atmosphere Model, version 3.5. The study determines that the distribution of climate sensitivity in the two ensembles is very different: the climateprediction.net ensemble subset range is 1.7-9.9 K, while the CAMcube ensemble range is 2.2-3.2 K. On a regional level, however, both ensembles show a similarly diverse range in their mean climatology. Model radiative flux changes suggest that the major difference between the ranges of climate sensitivity in the two ensembles lies in their clear-sky longwave responses. Large clear-sky feedbacks present only in the climateprediction.net ensemble are found to be proportional to significant biases in upper-tropospheric water vapor concentrations, which are not observed in the CAMcube ensemble. Both ensembles have a similar range of shortwave cloud feedback, making it unlikely that they are causing the larger climate sensitivities in climateprediction.net. In both cases, increased negative shortwave cloud feedbacks at high latitudes are generally compensated by increased positive feedbacks at lower latitudes. © 2011 American Meteorological Society."
"57218150582;55544443300;7005808242;","Sensitivity of climate change induced by the weakening of the Atlantic meridional overturning circulation to cloud feedback",2010,"10.1175/2009JCLI3118.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949337608&doi=10.1175%2f2009JCLI3118.1&partnerID=40&md5=378bf2bf8e09b88bc36890b7142dcc2b","A variety of observational and modeling studies show that changes in the Atlantic meridional overturning circulation (AMOC) can induce rapid global-scale climate change. In particular, a substantially weakened AMOC leads to a southward shift of the intertropical convergence zone (ITCZ) in both the Atlantic and the Pacific Oceans. However, the simulated amplitudes of the AMOC-induced tropical climate change differ substantially among different models. In this paper, the sensitivity to cloud feedback of the climate response to a change in the AMOC is studied using a coupled ocean-atmosphere model [the GFDL Coupled Model, version 2.1 (CM2.1)]. Without cloud feedback, the simulated AMOC-induced climate change in this model is weakened substantially. Low-cloud feedback has a strong amplifying impact on the tropical ITCZ shift in this model, whereas the effects of high-cloud feedback are weaker. It is concluded that cloud feedback is an important contributor to the uncertainty in the global response to AMOC changes. © 2010 American Meteorological Society."
"51360903200;7005890514;","The roles of radiation and dynamical processes in the El Niño-like response to global warming",2002,"10.1007/s00382-002-0244-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036692364&doi=10.1007%2fs00382-002-0244-x&partnerID=40&md5=37f65035cf60155886721c697bf7d9e0","The current understanding of ENSO does not foreshadow how it might change as a consequence of global warming due to an increase in atmospheric greenhouse gas (GHG) concentration. A number of global coupled climate models simulate a ""mean"" El Niño-like change in tropical Pacific temperatures, precipitation, and winds but at least one model exhibits a La Niña-like pattern and others a more or less homogeneous warming in the tropics with little of either pattern. The mechanisms leading to a mean positive El Niño-like pattern (PEP) are studied in simulations with the Canadian Centre for Climate Modeling and Analysis (CCCma) coupled general circulation model. The changes associated with the PEP are compared with, and are shown to closely resemble, those observed for the positive El Niño phase of the ENSO oscillation in the current climate including the anomalies in SST, precipitation and atmospheric circulation, the changes of vertically integrated energy and heat transports in the atmosphere, and changes in the sign and magnitude of radiative energy balance terms. The PEP in the model is supported by changes in oceanic heat transport and surface longwave radiative flux in the face of solar radiative flux and evaporative flux changes which act to damp it away. There is negative cloud-radiation feedback associated with the PEP, as with the observed El Niño. Negative cloud feedback by itself does not, therefore, preclude the existence of a PEP response to GHG forcing. The climatological PEP does not exhibit an oceanic export of energy from the tropical Pacific, as inferred for the regular El Niño event, but rather an oceanic import of energy. Nevertheless the PEP provides an effective means of regulating climate warming and the energy budget in the tropical Pacific which is accomplished through energy transports out of the region by the atmosphere. The PEP is seen as a more or less straightforward manifestation of the feedback mechanism proposed by Bjerknes and as a physically plausible response to GHG-induced climate warming."
"36161386500;8670472000;25652188900;56063791400;7004898784;24339847400;7004966070;8724963200;55451545500;55030720500;23101727900;57217838673;6602893477;23968109800;45761169000;57212940867;7405666962;57189370251;35775264900;56059501400;24329376600;23476421000;56123889200;57202411660;55329994600;7004469744;12806941900;57193920163;9941600400;6602135635;11339675000;35737202600;57213695884;57197016522;7404747615;7407104838;56726831200;55921861500;26967878800;7004587644;55675224272;57212515855;7202391479;57204624240;55727417500;57212513320;24463029300;7202802701;6603589621;","UKESM1: Description and Evaluation of the U.K. Earth System Model",2019,"10.1029/2019MS001739","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074861901&doi=10.1029%2f2019MS001739&partnerID=40&md5=706c748577f59fc940e136d40dfb3db8","We document the development of the first version of the U.K. Earth System Model UKESM1. The model represents a major advance on its predecessor HadGEM2-ES, with enhancements to all component models and new feedback mechanisms. These include a new core physical model with a well-resolved stratosphere; terrestrial biogeochemistry with coupled carbon and nitrogen cycles and enhanced land management; tropospheric-stratospheric chemistry allowing the holistic simulation of radiative forcing from ozone, methane, and nitrous oxide; two-moment, five-species, modal aerosol; and ocean biogeochemistry with two-way coupling to the carbon cycle and atmospheric aerosols. The complexity of coupling between the ocean, land, and atmosphere physical climate and biogeochemical cycles in UKESM1 is unprecedented for an Earth system model. We describe in detail the process by which the coupled model was developed and tuned to achieve acceptable performance in key physical and Earth system quantities and discuss the challenges involved in mitigating biases in a model with complex connections between its components. Overall, the model performs well, with a stable pre-industrial state and good agreement with observations in the latter period of its historical simulations. However, global mean surface temperature exhibits stronger-than-observed cooling from 1950 to 1970, followed by rapid warming from 1980 to 2014. Metrics from idealized simulations show a high climate sensitivity relative to previous generations of models: Equilibrium climate sensitivity is 5.4 K, transient climate response ranges from 2.68 to 2.85 K, and transient climate response to cumulative emissions is 2.49 to 2.66 K TtC−1. ©2019. The Authors."
"7005548544;6507742481;","On the climatic implications of volcanic cooling",1998,"10.1029/98JD00125","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032571196&doi=10.1029%2f98JD00125&partnerID=40&md5=57f4a81dd9311b95f83a08b58ffcee8c","A simple energy balance model is used to investigate the response to a volcanic-type radiative forcing under different assumptions about the climatic sensitivity of the system. Volcanic eruptions are used as control experiments to investigate the role of the ocean-atmosphere coupling and of diffusive heat uptake by the thermocline. The effect of varying equilibrium climate sensitivity by varying the coupling of the atmosphere and ocean is examined, high sensitivity being associated with weak coupling. A model representing a coupled land-ocean system, with a reasonably realistic representation of the large-scale physics is used. It is found that systems with large equilibrium sensitivities not only respond somewhat more strongly to radiative perturbations but also return to equilibrium with much longer timescales. Based on this behavior pattern, we examine the model response to a series of volcanic eruptions following Krakatoa in 1883. Comparison between the model results and past temperature records seems to suggest that use of small sensitivity parameters is more appropriate. Despite the uncertainties associated with both the physics and the quantitative characteristics of the radiative forcing and the temperature anomalies produced by volcanic eruptions, the present study constitutes a possible test of different assumptions about the sensitivity of the climate system."
"7004479957;8882641700;","Low cloud reduction in a greenhouse-warmed climate: Results from Lagrangian les of a subtropical marine cloudiness transition",2014,"10.1002/2013MS000250","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899096387&doi=10.1002%2f2013MS000250&partnerID=40&md5=fac647578cd997136a7a7715847debc9","Lagrangian large-eddy simulations of a composite stratocumulus to cumulus transition case over the subtropical northeast Pacific Ocean are subject to perturbed forcings that isolate the cloud response to CO<inf>2</inf>, to overall tropical warming, and to increased inversion stability over the subtropical subsidence regions. These simulations show that a tropical surface warming of 4 K induces substantial stratocumulus thinning via a thermodynamic mechanism: increased cloud layer humidity flux in a warmer climate induces an entrainment liquid-flux adjustment that dries the stratocumulus cloud layer, whether well mixed or cumulus coupled. A radiative mechanism amplifies this response: increased emissivity of the free troposphere due to increased CO<inf>2</inf> and water vapor reduces radiative driving of turbulence in a stratocumulus-capped boundary layer; a thinner stratocumulus layer accompanies less turbulence. In combination, a 4 K warming and CO<inf>2</inf> quadrupling greatly reduce low cloud and weaken the simulated shortwave cloud radiative effect by over 50%. Large increases in inversion stability in the stratocumulus regions could counter much of this cloudiness reduction. Key Points LES isolates radiative and thermodynamic positive low cloud feedback mechanisms Thermodynamic cloud thinning due to entrainment liquid-flux adjustment ELF thinning mechanism affects all subtropical Sc-topped cloud regimes © 2014. American Geophysical Union. All Rights Reserved."
"10241462700;7201485519;35204593500;7404142321;55537426400;35580303100;7003420726;","Structural similarities and differences in climate responses to CO2 increase between two perturbed physics ensembles",2010,"10.1175/2009JCLI2917.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953653197&doi=10.1175%2f2009JCLI2917.1&partnerID=40&md5=f9e08343da8c3b214bbb16ca307a1a39","The equilibrium climate sensitivity (ECS) of the two perturbed physics ensembles (PPE) generated using structurally different GCMs, Model for Interdisciplinary Research on Climate (MIROC3.2) and the Third Hadley Centre Atmospheric Model with slab ocean (HadSM3), is investigated. A method to quantify the shortwave (SW) cloud feedback by clouds with different cloud-top pressure is developed. It is found that the difference in the ensemble means of the ECS between the two ensembles is mainly caused by differences in the SW low-level cloud feedback. The ensemble mean SW cloud feedback and ECS of the MIROC3.2 ensemble is larger than that of the HadSM3 ensemble. This is likely related to the 1XCO2 low-level cloud albedo of the former being larger than that of the latter. It is also found that the largest contribution to the within-ensemble variation of ECS comes from the SW low-level cloud feedback in both ensembles. The mechanism that causes the within-ensemble variation is different between the two ensembles. In the HadSM3 ensemble, members with large 1XCO2 low-level cloud albedo have large SW cloud feedback and large ECS; ensemble members with large 1XCO2 cloud cover have large negative SW cloud feedback and relatively low ECS. In the MIROC3.2 ensemble, the 1XCO2 low-level cloud albedo is much more tightly constrained, and no relationship is found between it and the cloud feedback. These results indicate that both the parametric uncertainties sampled in PPEs and the structural uncertainties of GCMs are important and worth further investigation. © 2010 American Meteorological Society."
"12139043600;56250250300;12139310900;6506436908;13403622000;7005955015;","Aerosol-cloud-climate interactions in the climate model CAM-Oslo",2008,"10.1111/j.1600-0870.2008.00313.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42549159929&doi=10.1111%2fj.1600-0870.2008.00313.x&partnerID=40&md5=80a7740f3a046d44a684e9d1555402ee","A new aerosol module is integrated on-line in the atmospheric GCM CAM-Oslo coupled to a slab ocean for equilibrium climate response studies. The response to an anthropogenic change in aerosols since pre-industrial times is compared with that of a future 63% increased CO2 level. The aerosol module calculates concentrations of sea-salt, mineral dust, sulphate, black carbon (BC) and particulate organic matter (POM). Look-up tables, constructed from first principles, are used to obtain optical parameters and cloud droplet numbers (CDNC) for any given aerosol composition. Anthropogenic aerosols thus produce a global near-surface cooling of 1.94 K and a 5.5% precipitation decrease, including amplifications by positive cloud feedbacks. In comparison, the CO2 increase gives a warming of 1.98 K and a 3.8% precipitation increase, causing slightly reduced sulphate, BC, POM and sea-salt burdens. A minor increase in mineral dust is ascribed to reduced subtropical precipitation downwind of Sahara over the Atlantic Ocean. The modelled indirect effects are probably overestimated, mainly due to neglected natural aerosol components and the diagnostic scheme for CDNC. Adding 15 cm-3 to CDNC everywhere reduces the indirect forcing from -2.34 to -1.36 Wm-2, whilst solving a prognostic equation for CDNC reduces it from -2.34 to -1.44 Wm-2. © 2008 The Authors Journal compilation © 2008 Blackwell Munksgaard."
"16178435500;8397494800;7006462819;15763329000;6603561402;7006130951;6603356769;35518083800;57203350431;25723368400;7102211934;7407088652;57212023466;7003924213;26650162200;57202512993;57211522729;6602256427;7003365490;6603613067;56138596800;25227858900;","The Canadian Earth System Model version 5 (CanESM5.0.3)",2019,"10.5194/gmd-12-4823-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075761257&doi=10.5194%2fgmd-12-4823-2019&partnerID=40&md5=5e7f2e8c917efb0ea4895bc7c7a64dd4","The Canadian Earth System Model version 5 (CanESM5) is a global model developed to simulate historical climate change and variability, to make centennial-scale projections of future climate, and to produce initialized seasonal and decadal predictions. This paper describes the model components and their coupling, as well as various aspects of model development, including tuning, optimization, and a reproducibility strategy. We also document the stability of the model using a long control simulation, quantify the model's ability to reproduce large-scale features of the historical climate, and evaluate the response of the model to external forcing. CanESM5 is comprised of three-dimensional atmosphere (T63 spectral resolution equivalent roughly to 2.8°) and ocean (nominally 1°) general circulation models, a sea-ice model, a land surface scheme, and explicit land and ocean carbon cycle models. The model features relatively coarse resolution and high throughput, which facilitates the production of large ensembles. CanESM5 has a notably higher equilibrium climate sensitivity (5.6 K) than its predecessor, CanESM2 (3.7 K), which we briefly discuss, along with simulated changes over the historical period. CanESM5 simulations contribute to the Coupled Model Intercomparison Project phase 6 (CMIP6) and will be employed for climate science and service applications in Canada. © 2019 Author(s)."
"13411455700;16644246500;35509639400;56272964700;7006614696;36161790500;7402934750;7005035762;","Observing Convective Aggregation",2017,"10.1007/s10712-017-9419-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85025067879&doi=10.1007%2fs10712-017-9419-1&partnerID=40&md5=3aebb39e19c43f386bec273123bc10c4","Convective self-aggregation, the spontaneous organization of initially scattered convection into isolated convective clusters despite spatially homogeneous boundary conditions and forcing, was first recognized and studied in idealized numerical simulations. While there is a rich history of observational work on convective clustering and organization, there have been only a few studies that have analyzed observations to look specifically for processes related to self-aggregation in models. Here we review observational work in both of these categories and motivate the need for more of this work. We acknowledge that self-aggregation may appear to be far-removed from observed convective organization in terms of time scales, initial conditions, initiation processes, and mean state extremes, but we argue that these differences vary greatly across the diverse range of model simulations in the literature and that these comparisons are already offering important insights into real tropical phenomena. Some preliminary new findings are presented, including results showing that a self-aggregation simulation with square geometry has too broad distribution of humidity and is too dry in the driest regions when compared with radiosonde records from Nauru, while an elongated channel simulation has realistic representations of atmospheric humidity and its variability. We discuss recent work increasing our understanding of how organized convection and climate change may interact, and how model discrepancies related to this question are prompting interest in observational comparisons. We also propose possible future directions for observational work related to convective aggregation, including novel satellite approaches and a ground-based observational network. © 2017, The Author(s)."
"54893098900;7401836526;","Constraints on climate sensitivity from space-based measurements of low-cloud reflection",2016,"10.1175/JCLI-D-15-0897.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983522067&doi=10.1175%2fJCLI-D-15-0897.1&partnerID=40&md5=b742df9f9b0de211dd2718f79c1c5a42","Physical uncertainties in global-warming projections are dominated by uncertainties about how the fraction of incoming shortwave radiation that clouds reflect will change as greenhouse gas concentrations rise. Differences in the shortwave reflection by low clouds over tropical oceans alone account for more than half of the variance of the equilibrium climate sensitivity (ECS) among climate models, which ranges from 2.1 to 4.7 K. Space-based measurements now provide an opportunity to assess how well models reproduce temporal variations of this shortwave reflection on seasonal to interannual time scales. Here such space-based measurements are used to show that shortwave reflection by low clouds over tropical oceans decreases robustly when the underlying surface warms, for example, by -(0.96 ± 0.22)%K-1 (90% confidence level) for deseasonalized variations. Additionally, the temporal covariance of low-cloud reflection with temperature in historical simulations with current climate models correlates strongly (r = -0.67) with the models' ECS. Therefore, measurements of temporal low-cloud variations can be used to constrain ECS estimates based on climate models. An information-theoretic weighting of climate models by how well they reproduce the measured deseasonalized covariance of shortwave cloud reflection with temperature yields a most likely ECS estimate around 4.0 K; an ECS below 2.3 K becomes very unlikely (90% confidence). © 2016 American Meteorological Society."
"55332348600;26645289600;7003266014;7402064802;","The relationship between interannual and long-term cloud feedbacks",2015,"10.1002/2015GL066698","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84953637951&doi=10.1002%2f2015GL066698&partnerID=40&md5=a68eead74737481fa445c86b1b35fbdb","Analyses of Coupled Model Intercomparison Project phase 5 simulations suggest that climate models with more positive cloud feedback in response to interannual climate fluctuations also have more positive cloud feedback in response to long-term global warming. Ensemble mean vertical profiles of cloud change in response to interannual and long-term surface warming are similar, and the ensemble mean cloud feedback is positive on both timescales. However, the average long-term cloud feedback is smaller than the interannual cloud feedback, likely due to differences in surface warming pattern on the two timescales. Low cloud cover (LCC) change in response to interannual and long-term global surface warming is found to be well correlated across models and explains over half of the covariance between interannual and long-term cloud feedback. The intermodel correlation of LCC across timescales likely results from model-specific sensitivities of LCC to sea surface warming. © 2015. American Geophysical Union. All Rights Reserved."
"35069282600;6507731482;7202899330;25953950400;","Radiative impacts of free-tropospheric clouds on the properties of marine stratocumulus",2013,"10.1175/JAS-D-12-0287.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885939468&doi=10.1175%2fJAS-D-12-0287.1&partnerID=40&md5=c922972b7f0bebea3b2beb3e1966621f","Observations from multiple satellites and large-eddy simulations (LESs) from the Regional Atmospheric Modeling System (RAMS) are used to determine the extent to which free-tropospheric clouds (FTCs) affect the properties of stratocumulus. Overlying FTCs decrease the cloud-top radiative cooling in stratocumulus by an amount that depends on the upper-cloud base altitude, cloud optical thickness, and abundance of moisture between the cloud layers. On average, FTCs increase the downward longwave radiative flux above stratocumulus clouds (at 3.5 km) by approximately 30Wm-2. As a consequence, this forcing translates to a relative decrease in stratocumulus cooling rates by about 20%. Overall, the reduced cloud-top radiative cooling decreases the turbulent mixing, vertical development, and precipitation rate in stratocumulus clouds at night. During the day these effects are greatly reduced because the overlying clouds shade the stratocumulus from strong solar radiation, thus reducing the net radiative effect by the upper cloud. Differences in liquid water path are also observed in stratocumulus; however, the response is tied to the diurnal cycle and the time scale of interaction between the FTCs and the stratocumulus. Radiative effects by FTCs tend to be largest in the midlatitudes where the clouds overlying stratocumulus tend to be more frequent, lower, and thicker on average. In conclusion, changes in net radiation and moisture brought about by FTCs can significantly affect the dynamics of marine stratocumulus and these processes should be considered when evaluating cloud feedbacks in the climate system. © 2013 American Meteorological Society."
"24329376600;57203049177;35547807400;7201485519;","Cloud Adjustment and its Role in CO 2 Radiative Forcing and Climate Sensitivity: A Review",2012,"10.1007/s10712-011-9152-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862649741&doi=10.1007%2fs10712-011-9152-0&partnerID=40&md5=e2553662fd3ad5721555b904a8596153","Understanding the role of clouds in climate change remains a considerable challenge. Traditionally, this challenge has been framed in terms of understanding cloud feedback. However, recent work suggests that under increasing levels of atmospheric carbon dioxide, clouds not only amplify or dampen climate change through global feedback processes, but also through rapid (days to weeks) tropospheric temperature and land surface adjustments. In this article, we use the Met Office Hadley Centre climate model HadGSM1 to review these recent developments and assess their impact on radiative forcing and equilibrium climate sensitivity. We estimate that cloud adjustment contributes ~0.8 K to the 4.4 K equilibrium climate sensitivity of this particular model. We discuss the methods used to evaluate cloud adjustments, highlight the mechanisms and processes involved and identify low level cloudiness as a key cloud type. Looking forward, we discuss the outstanding issues, such as the application to transient forcing scenarios. We suggest that the upcoming CMIP5 multi-model database will allow a comprehensive assessment of the significance of cloud adjustments in fully coupled atmosphere-ocean-general-circulation models for the first time, and that future research should exploit this opportunity to understand cloud adjustments/feedbacks in non-idealised transient climate change scenarios. © 2011 The Author(s)."
"35459245100;7004469744;35547807400;15519671300;7201606127;6506718302;","Aerosol climate feedback due to decadal increases in southern hemisphere wind speeds",2010,"10.1029/2009GL041320","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76749090406&doi=10.1029%2f2009GL041320&partnerID=40&md5=20281273d637a24c97c5c73321da59e6","Observations indicate that the westerly jet in the Southern Hemisphere troposphere is accelerating. Using a global aerosol model we estimate that the increase in wind speed of 0.45 ± 0.2 m s-1decade-1 at 50-65°S since the early 1980s caused a higher sea spray flux, resulting in an increase of cloud condensation nucleus concentrations of more than 85% in some regions, and of 22% on average between 50 and 65°S. These fractional increases are similar in magnitude to the decreases over many northern hemisphere land areas due to changes in air pollution over the same period. The change in cloud drop concentrations causes an increase in cloud reflectivity and a summertime radiative forcing between at 50 and 65°S comparable in magnitude but acting against that from greenhouse gas forcing over the same time period, and thus represents a substantial negative climate feedback. However, recovery of Antarctic ozone depletion in the next two decades will likely cause a fall in wind speeds, a decrease in cloud drop concentration and a correspondingly weaker cloud feedback. © Copyright 2010 by the American Geophysical Union."
"6507224579;7004247643;","A high-latitude convective cloud feedback and equable climates",2008,"10.1002/qj.211","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41949091634&doi=10.1002%2fqj.211&partnerID=40&md5=a2fb8fe86f04cc2aa2baec205619e19c","A convective cloud feedback on extratropical surface temperatures is identified in a zonally averaged two-level atmospheric model. The model contains simplified parametrizations for convection, precipitation, and clouds, and a long-wave radiation scheme that explicitly depends on carbon dioxide, water vapour, and cloud fraction. The convective cloud feedback occurs if the extratropical surface temperature is increased enough to initiate strong atmospheric convection. This results in a change from low to high clouds and from negative to neutral or positive cloud radiative forcing, which further warms the surface and leads to more convection. This positive feedback activates as the CO2 concentration is increased and leads to a climate solution with high boundary-layer temperatures, convection at mid and high latitudes, and an Equator to Pole temperature difference that is reduced by 8-10°C. The reduction in Equator to Pole temperature difference is due to changes in high-latitude local heat balance and occurs despite decreased meridional heat transport. The convective cloud feedback also leads to multiple equilibria and hysteresis with respect to CO2 and other model variables, although these results may be due to the simplicity of the model. The possible connection of the behaviour of the model at high CO2 with equable climates is considered. Copyright © 2008 Royal Meteorological Society."
"7403968239;6602098362;55729083100;15760875400;","On the radiative and dynamical feedbacks over the equatorial Pacific cold tongue",2003,"10.1175/2786.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042890458&doi=10.1175%2f2786.1&partnerID=40&md5=da311c5a46946cbdfc0fc360f8ccf562","An analysis of the climatic feedbacks in the NCAR Community Climate Model, version 3 (CCM3) over the equatorial Pacific cold tongue is presented. Using interannual signals in the underlying SST, the radiative and dynamical feedbacks have been calculated using both observations and outputs from the NCAR CCM3. The results show that the positive feedback from the greenhouse effect of water vapor in the model largely agrees with that from observations. The dynamical feedback from the atmospheric transport in the model is also comparable to that from observations. However, the negative feedback from the solar forcing of clouds in the model is significantly weaker than the observed, while the positive feedback from the greenhouse effect of clouds is significantly larger. Consequently, the net atmospheric feedback in the CCM3 over the equatorial cold tongue region is strongly positive (5.1 W m-2 K-1), while the net atmospheric feedback in the real atmosphere is strongly negative (-6.4 W m-2 K-1). A further analysis with the aid of the International Satellite Cloud Climatology Project (ISCCP) data suggests that cloud cover response to changes in the SST may be a significant error source for the cloud feedbacks. It is also noted that the surface heating over the cold tongue in CCM3 is considerably weaker than in observations. In light of results from a linear feedback system, as well as those from a more sophisticated coupled model, it is suggested that the discrepancy in the net atmospheric feedback may have contributed significantly to the cold bias in the equatorial Pacific in the NCAR Climate System Model (CSM)."
"11939918300;7201504886;","Coupled radiative convective equilibrium simulations with explicit and parameterized convection",2016,"10.1002/2016MS000666","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84990222896&doi=10.1002%2f2016MS000666&partnerID=40&md5=ff4fbe646c4093a5005116e10fe696e2","Radiative convective equilibrium has been applied in past studies to various models given its simplicity and analogy to the tropical climate. At convection-permitting resolution, the focus has been on the organization of convection that appears when using fixed sea surface temperature (SST). Here the SST is allowed to freely respond to the surface energy. The goals are to examine and understand the resulting transient behavior, equilibrium state, and perturbations thereof, as well as to compare these results to a simulation integrated with parameterized cloud and convection. Analysis shows that the coupling between the SST and the net surface energy acts to delay the onset of self-aggregation and may prevent it, in our case, for a slab ocean of less than 1 m. This is so because SST gradients tend to oppose the shallow low-level circulation that is associated with the self-aggregation of convection. Furthermore, the occurrence of self-aggregation is found to be necessary for reaching an equilibrium state and avoiding a greenhouse-like climate. In analogy to the present climate, the self-aggregation generates the dry and clear subtropics that allow the system to efficiently cool. In contrast, strong shortwave cloud radiative effects, much stronger than at convection-permitting resolution, prevent the simulation with parameterized cloud and convection to fall into a greenhouse state. The convection-permitting simulations also suggest that cloud feedbacks, as arising when perturbing the equilibrium state, may be very different, and in our case less negative, than what emerges from general circulation models. © 2016. The Authors."
"7003976079;24329376600;7201485519;","Global-mean radiative feedbacks and forcing in atmosphere-only and coupled atmosphere-ocean climate change experiments",2014,"10.1002/2014GL060347","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902040526&doi=10.1002%2f2014GL060347&partnerID=40&md5=7b62e99cf8de54508f07309b72d4a910","Analysis of the available Coupled Model Intercomparison Project Phase 5 models suggests that sea surface temperature-forced, atmosphere-only global warming experiments (""amip4K,"" ""amipFuture,"" and ""aqua4K"") are a good guide to the global cloud feedbacks determined from coupled atmosphere-ocean CO2-forced simulations, including the intermodel spread. Differences in the total climate feedback parameter between the experiments arise primarily from differences in the clear-sky feedbacks which can largely be anticipated from the nature of the experimental design. The effective CO2 radiative forcing is anticorrelated with the total feedback in the coupled simulations. This anticorrelation strengthens as the experimental design becomes simpler, the number of potential degrees of freedom of the system's response reduces, and the relevant physical processes can be identified. In the aquaplanet simulations the anticorrelation is primarily driven by opposing changes in the rapid cloud adjustment to CO2 and the net cloud response to increased surface warming. Establishing a physical explanation for this behavior is important future work. © 2014. American Geophysical Union. All Rights Reserved."
"55537426400;10241462700;6603196127;","A comparison of climate feedback strength between CO2 doubling and LGM experiments",2009,"10.1175/2009JCLI2801.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67651219260&doi=10.1175%2f2009JCLI2801.1&partnerID=40&md5=6153913f6fded6699de184d0cf55756b","Studies of the climate in the past potentially provide a constraint on the uncertainty of climate sensitivity, but previous studies warn against a simple scaling to the future. Climate sensitivity is determined by a number of feedback processes, and they may vary according to climate states and forcings. In this study, the similarities and differences in feedbacks for CO2 doubling, a Last Glacial Maximum (LGM), and LGM greenhouse gas (GHG) forcing experiments are investigated using an atmospheric general circulation model coupled to a slab ocean model. After computing the radiative forcing, the individual feedback strengths of water vapor, lapse-rate, albedo, and cloud feedbacks are evaluated explicitly. For this particular model, the difference in the climate sensitivity between the experiments is attributed to the shortwave cloud feedback, in which there is a tendency for it to become weaker or even negative in cooling experiments. No significant difference is found in the water vapor feedback between warming and cooling experiments by GHGs. The weaker positive water vapor feedback in the LGM experiment resulting from a relatively weaker tropical forcing is compensated for by the stronger positive lapse-rate feedback resulting from a relatively stronger extratropical forcing. A hypothesis is proposed that explains the asymmetric cloud response between the warming and cooling experiments associated with a displacement of the region of mixed-phase clouds. The difference in the total feedback strength between the experiments is, however, relatively small compared to the current intermodel spread, and does not necessarily preclude the use of LGM climate as a future constraint. © 2009 American Meteorological Society."
"7004390019;57206416522;7402612084;","Constraining climate model parameters from observed 20th century changes",2008,"10.1111/j.1600-0870.2008.00346.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-52949119981&doi=10.1111%2fj.1600-0870.2008.00346.x&partnerID=40&md5=ef605b3953f2dfdf3bd90a63a3a0c663","We present revised probability density functions for climate model parameters (effective climate sensitivity, the rate of deep-ocean heat uptake, and the strength of the net aerosol forcing) that are based on climate change observations from the 20th century. First, we compare observed changes in surface, upper-air, and deep-ocean temperature changes against simulations of 20th century climate in which the climate model parameters were systematically varied. The estimated 90% range of effective climate sensitivity is 2-5 K but no corresponding upper bound can be placed on the equilibrium climate sensitivity. The net aerosol forcing strength for the 1980s has 90% bounds of -0.70 to -0.27 W m-2. The rate of deep-ocean heat uptake corresponds to an effective diffusivity, Kv, with a 90% range of 0.04-4.1 cm2 s-1. Second, we estimate the effective climate sensitivity and rate of deep-ocean heat uptake for 11 of the IPCC AR4 AOGCMs. By comparing against the acceptable combinations inferred from the observations, we conclude that the rates of deep-ocean heat uptake for the majority of AOGCMs lie above the observationally based median value. This implies a bias in the predictions inferred from the IPCC models alone. © 2008 The Authors Journal compilation © 2008 Blackwell Munksgaard."
"55745955800;7004479957;","Mechanisms of low cloud-climate feedback in idealized single-column simulations with the Community Atmospheric Model, version 3 (CAM3)",2008,"10.1175/2008JCLI2237.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56349145252&doi=10.1175%2f2008JCLI2237.1&partnerID=40&md5=7f48126372dea20925585865c5cf393d","This study investigates the physical mechanism of low cloud feedback in the Community Atmospheric Model, version 3 (CAM3) through idealized single-column model (SCM) experiments over the subtropical eastern oceans. Negative cloud feedback is simulated from stratus and stratocumulus that is consistent with previous diagnostics of cloud feedbacks in CAM3 and its predecessor versions. The feedback occurs through the interaction of a suite of parameterized processes rather than from any single process. It is caused by the larger amount of in-cloud liquid water in stratus clouds from convective sources, and longer lifetimes of these clouds in a warmer climate through their interaction with boundary layer turbulence. Thermodynamic effects are found to dominate the negative cloud feedback in the model. The dynamic effect of weaker subsidence in a warmer climate also contributes to the negative cloud feedback, but with about one-quarter of the magnitude of the thermodynamic effect, owing to increased low-level convection in a warmer climate. © 2008 American Meteorological Society."
"8326850700;6602831555;7004194999;","Why radiative forcing might fail as a predictor of climate change",2005,"10.1007/s00382-004-0497-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17544376748&doi=10.1007%2fs00382-004-0497-7&partnerID=40&md5=f520bed708199c4218ea0b06013c98d1","Radiative forcing has been widely used as a metric of climate change, i.e. as a measure by which various contributors to a net surface temperature change can be quantitatively compared. The extent to which this concept is valid for spatially inhomogeneous perturbations to the climate system is tested. A series of climate model simulations involving ozone changes of different spatial structure reveals that the climate sensitivity parameter γ is highly variable: for an ozone increase in the northern hemisphere lower stratosphere, it is more than twice as large as for a homogeneous CO2 perturbation. A global ozone perturbation in the upper troposphere, however, causes a significantly smaller surface temperature response than CO2. The variability of the climate sensitivity parameter is shown to be mostly due to the varying strength of the stratospheric water vapour feedback. The variability of the sea-ice albedo feedback modifies climate sensitivity of perturbations with the same vertical structure but a different horizontal structure. This feedback is also the origin of the comparatively larger climate sensitivity to perturbations restricted to the northern hemisphere extratropics. As cloud feedback does not operate independently from the other feedbacks, quantifying its effect is rather difficult. However, its effect on the variability of γ for horizontally and vertically inhomogeneous perturbations within one model framework seems to be comparatively small. © Springer-Verlag 2005."
"55894937000;7401776640;","Reducing the uncertainty in subtropical cloud feedback",2016,"10.1002/2015GL067416","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959571378&doi=10.1002%2f2015GL067416&partnerID=40&md5=0c98b3ca6d7465e8da98f9bfc58393c7","Large uncertainty remains on how subtropical clouds will respond to anthropogenic climate change and therefore whether they will act as a positive feedback that amplifies global warming or negative feedback that dampens global warming by altering Earth's energy budget. Here we reduce this uncertainty using an observationally constrained formulation of the response of subtropical clouds to greenhouse forcing. The observed interannual sensitivity of cloud solar reflection to varying meteorological conditions suggests that increasing sea surface temperature and atmospheric stability in the future climate will have largely canceling effects on subtropical cloudiness, overall leading to a weak positive shortwave cloud feedback (0.4 ± 0.9 W m-2 K-1). The uncertainty of this observationally based approximation of the cloud feedback is narrower than the intermodel spread of the feedback produced by climate models. Subtropical cloud changes will therefore complement positive cloud feedbacks identified by previous work, suggesting that future global cloud changes will amplify global warming. ©2016. American Geophysical Union. All Rights Reserved."
"55894937000;7401776640;","On the relationships between subtropical clouds and meteorology in observations and CMIP3 and CMIP5 models",2015,"10.1175/JCLI-D-14-00475.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943809416&doi=10.1175%2fJCLI-D-14-00475.1&partnerID=40&md5=bf0e7fa28eac79f16b8bc5c23e0f2ce4","Climate models' simulation of clouds over the eastern subtropical oceans contributes to large uncertainties in projected cloud feedback to global warming. Here, interannual relationships of cloud radiative effect and cloud fraction to meteorological variables are examined in observations and in models participating in phases 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5, respectively). In observations, cooler sea surface temperature, a stronger estimated temperature inversion, and colder horizontal surface temperature advection are each associated with larger low-level cloud fraction and increased reflected shortwave radiation. A moister free troposphere and weaker subsidence are each associated with larger midand high-level cloud fraction and offsetting components of shortwave and longwave cloud radiative effect. It is found that a larger percentage of CMIP5 than CMIP3 models simulate the wrong sign or magnitude of the relationship of shortwave cloud radiative effect to sea surface temperature and estimated inversion strength. Furthermore,most models fail to produce the sign of the relationship between shortwave cloud radiative effect and temperature advection. These deficiencies are mostly, but not exclusively, attributable to errors in the relationship between low-level cloud fraction and meteorology. Poor model performance also arises due to errors in the response of mid- and high-level cloud fraction to variations in meteorology. Models exhibiting relationships closest to observations tend to project less solar reflection by clouds in the late twenty-first century and have higher climate sensitivities than poorer-performing models. Nevertheless, the intermodel spread of climate sensitivity is large even among these realistic models. © 2015 American Meteorological Society."
"7103246957;7102933062;15830822000;","Impact of agriculture, forest and cloud feedback on the surface energy budget in BOREAS",2007,"10.1016/j.agrformet.2006.08.020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846448755&doi=10.1016%2fj.agrformet.2006.08.020&partnerID=40&md5=cc6fe0e40544dcda33d25116e236c0aa","We explore the impact of agriculture, forest and cloud feedback on the surface energy budget using data obtained using a research aircraft, mesonet towers and model data. The forest has an order of magnitude larger roughness length, a lower albedo, a much smaller seasonal cycle in surface Bowen ratio (BR) and a weak mid-summer maximum of CO2 uptake compared to agricultural areas, which have much smaller BR and much higher mid-summer CO2 uptake, but a net CO2 release and much reduced evaporation in spring and fall. Higher surface temperatures and the higher albedo over agricultural land reduce Rnet near local noon in the warm season by about 50 W m-2 in comparison with the adjacent boreal forest. The annual averaged Rnet, derived from 2 years of tower data, is 14 W m-2 less over grass sites than over forest sites. A reanalysis time-series for the BOREAS southern study area shows the coupling on daily timescales between the surface energy partition, the mean boundary layer depth, the cloud field and the long-wave and short-wave radiation fields. The albedo of the cloud field, the cloud short-wave forcing at the surface, varies over the range 0.1-0.8 with decreasing surface BR, and plays a major role in the surface energy budget. We estimate that this cloud feedback may increase albedo by 0.13 and reduce Rnet by 25 W m-2 in summer over agricultural land. © 2006 Elsevier B.V. All rights reserved."
"7201504886;56014511300;35509639400;7201485519;","Prospects for narrowing bounds on Earth's equilibrium climate sensitivity",2016,"10.1002/2016EF000376","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85003451697&doi=10.1002%2f2016EF000376&partnerID=40&md5=3562b3c1702f8891168b217b2e00fb63","The concept of Earth's Equilibrium Climate Sensitivity (ECS) is reviewed. A particular problem in quantifying plausible bounds for ECS has been how to account for all of the diverse lines of relevant scientific evidence. It is argued that developing and refuting physical storylines (hypotheses) for values outside any proposed range has the potential to better constrain these bounds and to help articulate the science needed to narrow the range further. A careful reassessment of all important lines of evidence supporting these storylines, their limitations, and the assumptions required to combine them is therefore required urgently. © 2016 The Authors."
"35098801000;6701455548;23486332900;6602688130;","Climate Feedbacks in CCSM3 under Changing CO2 Forcing. Part II: Variation of Climate Feedbacks and Sensitivity with Forcing",2013,"10.1175/JCLI-D-12-00479.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877642216&doi=10.1175%2fJCLI-D-12-00479.1&partnerID=40&md5=7d6aba9c9f1824297a59c51bb4b029d3","Are equilibrium climate sensitivity and the associated radiative feedbacks a constant property of the climate system, or do they change with forcing magnitude and base climate? Using the radiative kernel technique, feedbacks and climate sensitivity are evaluated in a fully coupled general circulation model (GCM) for three successive doublings of carbon dioxide starting from present-day concentrations. Climate sensitivity increases by 23% between the first and third CO2 doublings. Increases in the positive water vapor and cloud feedbacks are partially balanced by a decrease in the positive surface albedo feedback and an increase in the negative lapse rate feedback. Feedbacks can be decomposed into a radiative flux change and a climate variable response to temperature change. The changes in water vapor and Planck feedbacks are due largely to changes in the radiative response with climate state. Higher concentrations of greenhouse gases and higher temperatures lead to more absorption and emission of longwave radiation. Changes in cloud feedbacks are dominated by the climate response to temperature change, while the lapse rate and albedo feedbacks combine elements of both. Simulations with a slab ocean model (SOM) version of the GCMare used to verify whether an SOM-GCM accurately reproduces the behavior of the fully coupled model. Although feedbacks differ in magnitude between model configurations (with differences as large as those between CO2 doublings for some feedbacks), changes in feedbacks between CO2 doublings are consistent in sign andmagnitude in the SOM-GCM and the fully coupled model. © 2013 American Meteorological Society."
"57212781009;23080010200;6603809220;","Climate feedbacks in a general circulation model incorporating prognostic clouds",2001,"10.1007/s003820100162","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035192861&doi=10.1007%2fs003820100162&partnerID=40&md5=093d858bbeb718df57ef7b1161d354e0","This study performs a comprehensive feedback analysis on the Bureau of Meteorology Research Centre General Circulation Model, quantifying all important feedbacks operating under an increase in atmospheric CO2. The individual feedbacks are analysed in detail, using an offline radiation perturbation method, looking at long- and shortwave components, latitudinal distributions, cloud impacts, non-linearities under 2xCO2 and 4xCO2 warmings and at interannual variability. The water vapour feedback is divided into terms due to moisture height and amount changes. The net cloud feedback is separated into terms due to cloud amount, height, water content, water phase, physical thickness and convective cloud fraction. Globally the most important feedbacks were found to be (from strongest positive to strongest negative) those due to water vapour, clouds, surface albedo, lapse rate and surface temperature. For the longwave (LW) response the most important term of the cloud 'optical property' feedbacks is due to the water content. In the shortwave (SW), both water content and water phase changes are important. Cloud amount and height terms are also important for both LW and SW. Feedbacks due to physical cloud thickness and convective cloud fraction are found to be relatively small. All cloud component feedbacks (other than height) produce conflicting LW/SW feedbacks in the model. Furthermore, the optical property and cloud fraction feedbacks are also of opposite sign. The result is that the net cloud feedback is the (relatively small) product of conflicting physical processes. Non-linearities in the feedbacks are found to be relatively small for all but the surface albedo response and some cloud component contributions. The cloud impact on non-cloud feedbacks is also discussed: greatest impact is on the surface albedo, but impact on water vapour feedback is also significant. The analysis method here proves to be a powerful tool for detailing the contributions from different model processes (and particularly those of the clouds) to the final climate model sensitivity."
"24329376600;7201485519;","The dependence of global cloud and lapse rate feedbacks on the spatial structure of tropical pacific warming",2018,"10.1175/JCLI-D-17-0087.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040608943&doi=10.1175%2fJCLI-D-17-0087.1&partnerID=40&md5=a6c012de5c8979cd4c6cb2b670e6efd1","An atmospheric general circulation model (AGCM) is forced with patterns of observed sea surface temperature (SST) change and those output from atmosphere-ocean GCM (AOGCM) climate change simulations to demonstrate a strong dependence of climate feedback on the spatial structure of surface temperature change. Cloud and lapse rate feedbacks are found to vary the most, depending strongly on the pattern of tropical Pacific SST change. When warming is focused in the southeast tropical Pacific-a region of climatological subsidence and extensive marine low cloud cover-warming reduces the lower-tropospheric stability (LTS) and low cloud cover but is largely trapped under an inversion and hence has little remote effect. The net result is a relatively weak negative lapse rate feedback and a large positive cloud feedback. In contrast, when warming is weak in the southeast tropical Pacific and enhanced in the west tropical Pacific-a strong convective region-warming is efficiently transported throughout the free troposphere. The increased atmospheric stability results in a strong negative lapse rate feedback and increases the LTS in low cloud regions, resulting in a low cloud feedback of weak magnitude. These mechanisms help explain why climate feedback and sensitivity change on multidecadal time scales in AOGCM abrupt4xCO2 simulations and are different from those seen in AGCM experiments forced with observed historical SST changes. From the physical understanding developed here, one should expect unusually negative radiative feedbacks and low effective climate sensitivities to be diagnosed from real-world variations in radiative fluxes and temperature over decades in which the eastern Pacific has lacked warming. © 2018 American Meteorological Society."
"16202694600;7004060399;","Is climate sensitivity related to dynamical sensitivity?",2016,"10.1002/2015JD024687","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029381969&doi=10.1002%2f2015JD024687&partnerID=40&md5=7c4f80844cd8249574125a7d73410bbd","The atmospheric response to increasing CO2 concentrations is often described in terms of the equilibrium climate sensitivity (ECS). Yet the response to CO2 forcing in global climate models is not limited to an increase in global-mean surface temperature: for example, the midlatitude jets shift poleward, the Hadley circulation expands, and the subtropical dry zones are altered. These changes, which are referred to here as “dynamical sensitivity,"" may be more important in practice than the global-mean surface temperature. This study examines to what degree the intermodel spread in the dynamical sensitivity of 23 Coupled Model Intercomparison Project phase 5 (CMIP5) models is captured by ECS. In the Southern Hemisphere, intermodel differences in the value of ECS explain ~60% of the intermodel variance in the annual-mean Hadley cell expansion but just ~20% of the variance in the annual-mean midlatitude jet response. In the Northern Hemisphere, models with larger values of ECS significantly expand the Hadley circulation more during winter months but contract the Hadley circulation more during summer months. Intermodel differences in ECS provide little significant information about the behavior of the Northern Hemisphere subtropical dry zones or midlatitude jets. The components of dynamical sensitivity correlated with ECS appear to be driven largely by increasing sea surface temperatures, whereas the components of dynamical sensitivity independent of ECS are related in part to changes in surface temperature gradients. These results suggest that efforts to narrow the spread in dynamical sensitivity across global climate models must also consider factors that are independent of global-mean surface temperature. © 2016. American Geophysical Union. All Rights Reserved."
"56457851700;7202145115;16444006500;","Observed Southern Ocean cloud properties and shortwave reflection. Part II: Phase changes and low cloud feedback",2014,"10.1175/JCLI-D-14-00288.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919629576&doi=10.1175%2fJCLI-D-14-00288.1&partnerID=40&md5=34081536e75c4dd8659c46a209a561fb","Climate models produce an increase in cloud optical depth in midlatitudes associated with climate warming, but the magnitude of this increase and its impact on reflected solar radiation vary from model to model. Transition from ice to liquid in midlatitude clouds is thought to be one mechanism for producing increased cloud optical depth. Here observations of cloud properties are used from a suite of remote sensing instruments to estimate the effect of conversion of ice to liquid associated with warming on reflected solar radiation in the latitude band from 40° to 60°S. The calculated increase in upwelling shortwave radiation (SW↑) is found to be important and of comparable magnitude to the increase in SW↑ associated with warming-induced increases of optical depth in climate models. The region where the authors' estimate increases SW↑ extends farther equatorward than the region where optical depth increases with warming in models. This difference is likely caused by other mechanisms at work in the models but is also sensitive to the amount of ice present in climate models and its susceptibility to warming. © 2014 American Meteorological Society."
"36097570900;6603809220;7201394533;10039754400;7007107813;7006032064;","The CSIRO Mk3L climate system model version 1.0-Part 2: Response to external forcings",2012,"10.5194/gmd-5-649-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861312442&doi=10.5194%2fgmd-5-649-2012&partnerID=40&md5=093a62fcf24ad31c3d8a7cef3b1c1e3a","The CSIRO Mk3L climate system model is a coupled general circulation model, designed primarily for millennial-scale climate simulation and palaeoclimate research. Mk3L includes components which describe the atmosphere, ocean, sea ice and land surface, and combines computational efficiency with a stable and realistic control climatology. It is freely available to the research community. This paper evaluates the response of the model to external forcings which correspond to past and future changes in the climate system. A simulation of the mid-Holocene climate is performed, in which changes in the seasonal and meridional distribution of incoming solar radiation are imposed. Mk3L correctly simulates increased summer temperatures at northern mid-latitudes and cooling in the tropics. However, it is unable to capture some of the regional-scale features of the mid-Holocene climate, with the precipitation over Northern Africa being deficient. The model simulates a reduction of between 7 and 15% in the amplitude of El Niño-Southern Oscillation, a smaller decrease than that implied by the palaeoclimate record. However, the realism of the simulated ENSO is limited by the model's relatively coarse spatial resolution. Transient simulations of the late Holocene climate are then performed. The evolving distribution of insolation is imposed, and an acceleration technique is applied and assessed. The model successfully captures the temperature changes in each hemisphere and the upward trend in ENSO variability. However, the lack of a dynamic vegetation scheme does not allow it to simulate an abrupt desertification of the Sahara. To assess the response of Mk3L to other forcings, transient simulations of the last millennium are performed. Changes in solar irradiance, atmospheric greenhouse gas concentrations and volcanic emissions are applied to the model. The model is again broadly successful at simulating larger-scale changes in the climate system. Both the magnitude and the spatial pattern of the simulated 20th century warming are consistent with observations. However, the model underestimates the magnitude of the relative warmth associated with the Mediaeval Climate Anomaly. Finally, three transient simulations are performed, in which the atmospheric CO 2 concentration is stabilised at two, three and four times the pre-industrial value. All three simulations exhibit ongoing surface warming, reduced sea ice cover, and a reduction in the rate of North Atlantic Deep Water formation followed by its gradual recovery. Antarctic Bottom Water formation ceases, with the shutdown being permanent for a trebling and quadrupling of the CO 2 concentration. The transient and equilibrium climate sensitivities of the model are determined. The short-term transient response to a doubling of the CO 2 concentration at 1% per year is a warming of 1.59 ± 0.08 K, while the long-term equilibrium response is a warming of at least 3.85 ± 0.02 K. © 2012 Author(s)."
"6507224579;7202671706;55259419600;7402887257;","High-CO2 cloud radiative forcing feedback over both land and ocean in a global climate model",2009,"10.1029/2008GL036703","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65649093701&doi=10.1029%2f2008GL036703&partnerID=40&md5=ae3ad62f3fecc817fd69027d174408ed","A positive feedback on high-latitude winter marine climate change involving convective clouds has recently been proposed using simple models. This feedback could help explain data from equable climates, e.g., the Eocene, and might be relevant for future climate. Here this convective cloud feedback is shown to be active in an atmospheric GCM in modern configuration (CAM) at CO2 = 2240 ppm and in a coupled GCM in Eocene configuration (CCSM) at CO2 = 560 ppm. Changes in boundary conditions that increase surface temperature have a similar effect as increases in CO2 concentration. It is also found that the high-latitude winter cloud radiative forcing over land increases with increases in surface temperature due to either increased CO2 or changes in boundary conditions, which could represent an important part of the explanation for warm continental interior winter surface temperatures during equable climates. This is due to increased low-level layered clouds caused by increased relative humidity. Copyright 2009 by the American Geophysical Union."
"7402064802;7403288995;7401776640;57205867148;","Low-Cloud Feedbacks from Cloud-Controlling Factors: A Review",2017,"10.1007/s10712-017-9433-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032001092&doi=10.1007%2fs10712-017-9433-3&partnerID=40&md5=97e92667b5624d0cff6e37de2b38bf18","The response to warming of tropical low-level clouds including both marine stratocumulus and trade cumulus is a major source of uncertainty in projections of future climate. Climate model simulations of the response vary widely, reflecting the difficulty the models have in simulating these clouds. These inadequacies have led to alternative approaches to predict low-cloud feedbacks. Here, we review an observational approach that relies on the assumption that observed relationships between low clouds and the “cloud-controlling factors” of the large-scale environment are invariant across time-scales. With this assumption, and given predictions of how the cloud-controlling factors change with climate warming, one can predict low-cloud feedbacks without using any model simulation of low clouds. We discuss both fundamental and implementation issues with this approach and suggest steps that could reduce uncertainty in the predicted low-cloud feedback. Recent studies using this approach predict that the tropical low-cloud feedback is positive mainly due to the observation that reflection of solar radiation by low clouds decreases as temperature increases, holding all other cloud-controlling factors fixed. The positive feedback from temperature is partially offset by a negative feedback from the tendency for the inversion strength to increase in a warming world, with other cloud-controlling factors playing a smaller role. A consensus estimate from these studies for the contribution of tropical low clouds to the global mean cloud feedback is 0.25 ± 0.18 W m−2 K−1 (90% confidence interval), suggesting it is very unlikely that tropical low clouds reduce total global cloud feedback. Because the prediction of positive tropical low-cloud feedback with this approach is consistent with independent evidence from low-cloud feedback studies using high-resolution cloud models, progress is being made in reducing this key climate uncertainty. © 2017, The Author(s)."
"54893098900;35509639400;","How may low-cloud radiative properties simulated in the current climate influence low-cloud feedbacks under global warming?",2012,"10.1029/2012GL053265","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868004805&doi=10.1029%2f2012GL053265&partnerID=40&md5=1d51d57a438ff50238be8239091afb9d","The influence of cloud modelling uncertainties on the projection of the tropical low-cloud response to global warming is explored by perturbing model parameters of the IPSL-CM5A climate model in a range of configurations (realistic general circulation model, aqua-planet, single-column model). While the positive sign and the mechanism of the low-cloud response to climate warming predicted by the model are robust, the amplitude of the response can vary considerably depending on the model tuning parameters. Moreover, the strength of the low-cloud response to climate change exhibits a strong correlation with the strength of the low-cloud radiative effects simulated in the current climate. We show that this correlation primarily results from a local positive feedback (referred to as the ""beta feedback"") between boundary-layer cloud radiative cooling, relative humidity and low-cloud cover. Based on this correlation and observational constraints, it is suggested that the strength of the tropical low-cloud feedback predicted by the IPSL-CM5A model in climate projections might be overestimated by about fifty percent. © 2012. American Geophysical Union. All Rights Reserved."
"55339081600;6602600408;","Evaluation of clouds and precipitation in the ECHAM5 general circulation model using CALIPSO and cloudsat satellite data",2012,"10.1175/JCLI-D-11-00347.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864242359&doi=10.1175%2fJCLI-D-11-00347.1&partnerID=40&md5=b20004d4197177ed5327d0610d69d582","Observations from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and CloudSat satellites are used to evaluate clouds and precipitation in the ECHAM5 general circulation model. Active lidar and radar instruments on board CALIPSO and CloudSat allow the vertical distribution of clouds and their optical properties to be studied on a global scale. To evaluate the clouds modeled by ECHAM5with CALIPSO and CloudSat, the lidar and radar satellite simulators of the Cloud Feedback Model Intercomparison Project's Observation Simulator Package are used. Comparison of ECHAM5 with CALIPSO and CloudSat found large-scale features resolved by the model, such as the Hadley circulation, are captured well. The lidar simulator demonstrated ECHAM5 overestimates the amount of high-level clouds, particularly optically thin clouds. High-altitude clouds in ECHAM5 consistently produced greater lidar scattering ratios compared with CALIPSO. Consequently, the lidar signal in ECHAM5 frequently attenuated high in the atmosphere. The large scattering ratios were due to an underestimation of effective ice crystal radii in ECHAM5. Doubling the effective ice crystal radii improved the scattering ratios and frequency of attenuation. Additionally, doubling the effective ice crystal radii improved the detection of ECHAM5's highest-level clouds by the radar simulator, in better agreement with CloudSat. ECHAM5 was also shown to significantly underestimate midlevel clouds and (sub)tropical low-level clouds. The low-level clouds produced were consistently perceived by the lidar simulator as too optically thick. The radar simulator demonstrated ECHAM5 overestimates the frequency of precipitation, yet underestimates its intensity compared with CloudSat observations. These findings imply compensating mechanisms inECHAM5 balance out the radiative imbalance caused by incorrect optical properties of clouds and consistently large hydrometeors in the atmosphere. © 2012 American Meteorological Society."
"6602600408;","Evaluating the ""critical relative humidity"" as a measure of subgrid-scale variability of humidity in general circulation model cloud cover parameterizations using satellite data",2012,"10.1029/2012JD017495","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861168119&doi=10.1029%2f2012JD017495&partnerID=40&md5=02bce8e7c7922fe697e9be65e18d5682","A simple way to diagnose fractional cloud cover in general circulation models is to relate it to the simulated relative humidity, and allowing for fractional cloud cover above a ""critical relative humidity"" of less than 100%. In the formulation chosen here, this is equivalent to assuming a uniform ""top-hat"" distribution of subgrid-scale total water content with a variance related to saturation. Critical relative humidity has frequently been treated as a ""tunable"" constant, yet it is an observable. Here, this parameter, and its spatial distribution, is examined from Atmospheric Infrared Sounder (AIRS) satellite retrievals, and from a combination of relative humidity from the ECMWF Re-Analyses (ERA-Interim) and cloud fraction obtained from CALIPSO lidar satellite data. These observational data are used to evaluate results from different simulations with the ECHAM general circulation model (GCM). In sensitivity studies, a cloud feedback parameter is analyzed from simulations applying the original parameter choice, and applying parameter choices guided by the satellite data. Model sensitivity studies applying parameters adjusted to match the observations show larger positive cloud-climate feedbacks, increasing by up to 30% compared to the standard simulation. Copyright 2012 by the American Geophysical Union."
"23486332900;6701455548;7004169476;","Climate feedbacks determined using radiative kernels in a multi-thousand member ensemble of AOGCMs",2010,"10.1007/s00382-009-0661-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649327281&doi=10.1007%2fs00382-009-0661-1&partnerID=40&md5=12a36881d76f4ddd9e6c5e1a52a7d79c","The use of radiative kernels to diagnose climate feedbacks is a recent development that may be applied to existing climate change simulations. We apply the radiative kernel technique to transient simulations from a multi-thousand member perturbed physics ensemble of coupled atmosphere-ocean general circulation models, comparing distributions of model feedbacks with those taken from the CMIP-3 multi GCM ensemble. Although the range of clear sky longwave feedbacks in the perturbed physics ensemble is similar to that seen in the multi-GCM ensemble, the kernel technique underestimates the net clear-sky feedbacks (or the radiative forcing) in some perturbed models with significantly altered humidity distributions. In addition, the compensating relationship between global mean atmospheric lapse rate feedback and water vapor feedback is found to hold in the perturbed physics ensemble, but large differences in relative humidity distributions in the ensemble prevent the compensation from holding at a regional scale. Both ensembles show a similar range of response of global mean net cloud feedback, but the mean of the perturbed physics ensemble is shifted towards more positive values such that none of the perturbed models exhibit a net negative cloud feedback. The perturbed physics ensemble contains fewer models with strong negative shortwave cloud feedbacks and has stronger compensating positive longwave feedbacks. A principal component analysis used to identify dominant modes of feedback variation reveals that the perturbed physics ensemble produces very different modes of climate response to the multi-model ensemble, suggesting that one may not be used as an analog for the other in estimates of uncertainty in future response. Whereas in the multi-model ensemble, the first order variation in cloud feedbacks shows compensation between longwave and shortwave components, in the perturbed physics ensemble the shortwave feedbacks are uncompensated, possibly explaining the larger range of climate sensitivities observed in the perturbed simulations. Regression analysis suggests that the parameters governing cloud formation, convection strength and ice fall speed are the most significant in altering climate feedbacks. Perturbations of oceanic and sulfur cycle parameters have relatively little effect on the atmospheric feedbacks diagnosed by the kernel technique. © 2009 Springer-Verlag."
"57189755950;7005137442;7202671706;","Global warming, convective threshold and false thermostats",2009,"10.1029/2009GL039849","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049085776&doi=10.1029%2f2009GL039849&partnerID=40&md5=4de9c7e480f160fc7a7bc4e540a01483","We demonstrate a theoretically expected behavior of the tropical sea surface temperature probability density function (PDF) in future and past (Eocene) greenhouse climate simulations. To first order this consists of a shift to warmer temperatures as climate warms, without change of shape of the PDF. The behavior is tied to a shift of the temperature for deep convection onset. Consequently, the threshold for appearance of high clouds and associated radiative forcing shifts along with temperature. An excess entropy coordinate provides a reference to which the onset of deep convection is invariant, and gives a compact description of SST changes and cloud feedbacks suitable for diagnostics and as a basis for simplified climate models. The results underscore that the typically skewed appearance of tropical SST histograms, with a sharp drop-off above some threshold value, should not be taken as evidence for tropical thermostats. Copyright 2009 by the American Geophysical Union."
"57212781009;","On the vertical extent of atmospheric feedbacks",2001,"10.1007/s003820000111","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034835669&doi=10.1007%2fs003820000111&partnerID=40&md5=b618e874dd75e2a27a444164716040cd","This study addresses the question: what vertical regions contribute the most to water vapor, surface temperature, lapse rate and cloud fraction feedback strengths in a general circulation model? Multi-level offline radiation perturbation calculations are used to diagnose the feedback contribution from each model level. As a first step, to locate regions of maximum radiative sensitivity to climate changes, the top of atmosphere radiative impact for each feedback is explored for each process by means of idealized parameter perturbations on top of a control (1 × CO2) model climate. As a second step, the actual feedbacks themselves are calculated using the changes modelled from a 2 × CO2 experiment. The impact of clouds on water vapor and lapse rate feedbacks is also isolated using 'clear sky' calculations. Considering the idealized changes, it is found that the radiative sensitivity to water vapor changes is a maximum in the tropical lower troposphere. The sensitivity to temperature changes has both upper and lower tropospheric maxima. The sensitivity to idealized cloud changes is positive (warming) for upper level cloud increases but negative (cooling) for lower level increases, due to competing long and shortwave effects. Considering the actual feedbacks, it is found that water vapor feedback is a maximum in the tropical upper troposphere, due to the large relative increases in specific humidity which occur there. The actual lapse rate feedback changes sign with latitude and is a maximum (negative) again in the tropical upper troposphere. Cloud feedbacks reflect the general decrease in low- to mid-level low-latitude cloud, with an increase in the very highest cloud. This produces a net positive (negative) shortwave (longwave) cloud feedback. The role of clouds in the strength of the water vapor and lapse rate feedbacks is also discussed."
"55255945700;6603834129;55570248000;36627352900;","The necessity of cloud feedback for a basin-scale Atlantic Multidecadal Oscillation",2016,"10.1002/2016GL068303","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84992302098&doi=10.1002%2f2016GL068303&partnerID=40&md5=af4b56674af3a97fc5002e0d5fad890d","The Atlantic Multidecadal Oscillation (AMO), characterized by basin-scale multidecadal variability in North Atlantic sea surface temperatures (SSTs), has traditionally been interpreted as the surface signature of variability in oceanic heat convergence (OHC) associated with the Atlantic Meridional Overturning Circulation (AMOC). This view has been challenged by recent studies that show that AMOC variability is not simultaneously meridionally coherent over the North Atlantic and that AMOC-induced low-frequency variability of OHC is weak in the tropical North Atlantic. Here we present modeling evidence that the AMO-related SST variability over the extratropical North Atlantic results directly from anomalous OHC associated with the AMOC but that the emergence of the coherent multidecadal SST variability over the tropical North Atlantic requires cloud feedback. Our study identifies atmospheric processes as a necessary component for the existence of a basin-scale AMO, thus amending the canonical view that the AMOC-AMO connection is solely attributable to oceanic processes. ©2016. American Geophysical Union. All Rights Reserved."
"55207447000;","Determination of Earth's Transient and Equilibrium Climate Sensitivities from Observations Over the Twentieth Century: Strong Dependence on Assumed Forcing",2012,"10.1007/s10712-012-9180-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862659055&doi=10.1007%2fs10712-012-9180-4&partnerID=40&md5=4a1c29569b9a6d2b6686fe663e68e331","Relations among observed changes in global mean surface temperature, ocean heat content, ocean heating rate, and calculated radiative forcing, all as a function of time over the twentieth century, that are based on a two-compartment energy balance model, are used to determine key properties of Earth's climate system. The increase in heat content of the world ocean, obtained as the average of several recent compilations, is found to be linearly related to the increase in global temperature over the period 1965-2009; the slope, augmented to account for additional heat sinks, which is an effective heat capacity of the climate system, is 21. 8 ± 2. 1 W year m -2 K -1 (one sigma), equivalent to the heat capacity of 170 m of seawater (for the entire planet) or 240 m for the world ocean. The rate of planetary heat uptake, determined from the time derivative of ocean heat content, is found to be proportional to the increase in global temperature relative to the beginning of the twentieth century with proportionality coefficient 1. 05 ± 0. 06 W m -2 K -1. Transient and equilibrium climate sensitivities were evaluated for six published data sets of forcing mainly by incremental greenhouse gases and aerosols over the twentieth century as calculated by radiation transfer models; these forcings ranged from 1.1 to 2.1 W m -2, spanning much of the range encompassed by the 2007 assessment of the Intergovernmental Panel on Climate Change (IPCC). For five of the six forcing data sets, a rather robust linear proportionality obtains between the observed increase in global temperature and the forcing, allowing transient sensitivity to be determined as the slope. Equilibrium sensitivities determined by two methods that account for the rate of planetary heat uptake range from 0.31 ± 0.02 to 1.32 ± 0.31 K (W m -2) -1 (CO 2 doubling temperature 1.16 ± 0.09-4. 9 ± 1. 2 K), more than spanning the IPCC estimated ""likely"" uncertainty range, and strongly anticorrelated with the forcing used to determine the sensitivities. Transient sensitivities, relevant to climate change on the multidecadal time scale, are considerably lower, 0. 23 ± 0. 01 to 0. 51 ± 0. 04 K (W m -2) -1. The time constant characterizing the response of the upper ocean compartment of the climate system to perturbations is estimated as about 5 years, in broad agreement with other recent estimates, and much shorter than the time constant for thermal equilibration of the deep ocean, about 500 years. © 2012 Springer Science+Business Media B.V. (outside the USA)."
"55537426400;35580303100;7003420726;10241462700;6603196127;","Dependency of feedbacks on forcing and climate state in physics parameter ensembles",2011,"10.1175/2011JCLI3954.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952170856&doi=10.1175%2f2011JCLI3954.1&partnerID=40&md5=ad6495ee801711a15eb2f4dc5d5575a1","Climate sensitivity is one of the most important metrics for future climate projections. In previous studies the climate of the last glacial maximum has been used to constrain the range of climate sensitivity, and similarities and differences of temperature response to the forcing of the last glacial maximum and to idealized future forcing have been investigated. The feedback processes behind the response have not, however, been fully explored in a large model parameter space. In this study, the authors first examine the performance of various feedback analysis methods that identify important feedbacks for a physics parameter ensemble in experiments simulating both past and future climates. The selected methods are then used to reveal the relationship between the different ensemble experiments in terms of individual feedback processes. For the first time, all of the major feedback processes for an ensemble of paleoclimate simulations are evaluated. It is shown that the feedback and climate sensitivity parameters depend on the nature of the forcing and background climate state. The forcing dependency arises through the shortwave cloud feedback while the state dependency arises through the combined water vapor and lapse-rate feedback. The forcing dependency is, however, weakened when the feedback is estimated from the forcing that includes tropospheric adjustments. Despite these dependencies, past climate can still be used to provide a useful constraint on climate sensitivity as long as the limitation is properly taken into account because the strength of each feedback correlates reasonably well between the ensembles. It is, however, shown that the physics parameter ensemble does not cover the range of results simulated by structurally different models, which suggests the need for further study exploring both structural and parameter uncertainties. © 2011 American Meteorological Society."
"6507502433;24468968100;56057294000;7102471083;7006417494;55260519600;56016024700;","Modern and glacial tropical snowlines controlled by sea surface temperature and atmospheric mixing",2014,"10.1038/ngeo2082","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84895425390&doi=10.1038%2fngeo2082&partnerID=40&md5=4b44d4127f6f5220286579ec1ae39c48","During the Last Glacial Maximum, tropical sea surface temperatures were 1 to 3C cooler than present, but the altitude of the snowlines of tropical glaciers was lower than would be expected in light of these sea surface temperatures. Indeed, both glacial and twentieth-century snowlines seem to require lapse rates that are steeper than a moist adiabat. Here we use estimates of Last Glacial Maximum sea surface temperature in the Indo-Pacific warm pool based on the clumped isotope palaeotemperature proxy in planktonic foraminifera and coccoliths, along with radiative-convective calculations of vertical atmospheric thermal structure, to assess the controls on tropical glacier snowlines. Using extensive new data sets for the region, we demonstrate that mean environmental lapse rates are steeper than moist adiabatic during the recent and glacial. We reconstruct glacial sea surface temperatures 4 to 5C cooler than modern. We include modern and glacial sea surface temperatures in calculations of atmospheric convection that account for mixing between rising air and ambient air, and derive tropical glacier snowlines with altitudes consistent with twentieth-century and Last Glacial Maximum reconstructions. Sea surface temperature changes ≤3C are excluded unless glacial relative humidity values were outside the range associated with deep convection in the modern. We conclude that the entrainment of ambient air into rising air masses significantly alters the vertical temperature structure of the troposphere in modern and ancient regions of deep convection. Furthermore, if all glacial tropical temperatures were cooler than previously estimated, it would imply a higher equilibrium climate sensitivity than included in present models. © 2014 Macmillan Publishers Limited."
"8696069500;6506738607;36339753800;8315173500;7201504886;24485834000;","Climate feedback efficiency and synergy",2013,"10.1007/s00382-013-1808-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886721511&doi=10.1007%2fs00382-013-1808-7&partnerID=40&md5=34912af8a22458ed2e7ab2a734322c0c","Earth's climate sensitivity to radiative forcing induced by a doubling of the atmospheric CO2 is determined by feedback mechanisms, including changes in atmospheric water vapor, clouds and surface albedo, that act to either amplify or dampen the response. The climate system is frequently interpreted in terms of a simple energy balance model, in which it is assumed that individual feedback mechanisms are additive and act independently. Here we test these assumptions by systematically controlling, or locking, the radiative feedbacks in a state-of-the-art climate model. The method is shown to yield a near-perfect decomposition of change into partial temperature contributions pertaining to forcing and each of the feedbacks. In the studied model water vapor feedback stands for about half the temperature change, CO2-forcing about one third, while cloud and surface albedo feedback contributions are relatively small. We find a close correspondence between forcing, feedback and partial surface temperature response for the water vapor and surface albedo feedbacks, while the cloud feedback is inefficient in inducing surface temperature change. Analysis suggests that cloud-induced warming in the upper tropical troposphere, consistent with rising convective cloud anvils in a warming climate enhances the negative lapse-rate feedback, thereby offsetting some of the warming that would otherwise be attributable to this positive cloud feedback. By subsequently combining feedback mechanisms we find a positive synergy acting between the water vapor feedback and the cloud feedback; that is, the combined cloud and water vapor feedback is greater than the sum of its parts. Negative synergies surround the surface albedo feedback, as associated cloud and water vapor changes dampen the anticipated climate change induced by retreating snow and ice. Our results highlight the importance of treating the coupling between clouds, water vapor and temperature in a deepening troposphere. © 2013 The Author(s)."
"7102805852;10139397300;7407104838;57203200427;7102953444;7004942632;","The roles of aerosol, water vapor and cloud in future global dimming/brightening",2011,"10.1029/2011JD016000","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80055055695&doi=10.1029%2f2011JD016000&partnerID=40&md5=715be3349a82b9842ef7d644ac0eced6","Observational evidence indicates significant regional trends in solar radiation at the surface in both all-sky and cloud-free conditions. Negative trends in the downwelling solar surface irradiance (SSI) have become known as dimming while positive trends have become known as brightening. We use the Met Office Hadley Centre HadGEM2 climate model to model trends in cloud-free and total SSI from the pre-industrial to the present-day and compare these against observations. Simulations driven by CMIP5 emissions are used to model the future trends in dimming/brightening up to the year 2100. The modeled trends are reasonably consistent with observed regional trends in dimming and brightening which are due to changes in concentrations in anthropogenic aerosols and, potentially, changes in cloud cover owing to the aerosol indirect effects and/or cloud feedback mechanisms. The future dimming/brightening in cloud-free SSI is not only caused by changes in anthropogenic aerosols: aerosol impacts are overwhelmed by a large dimming caused by increases in water vapor. There is little trend in the total SSI as cloud cover decreases in the climate model used here, and compensates the effect of the change in water vapor. In terms of the surface energy balance, these trends in SSI are obviously more than compensated by the increase in the downwelling terrestrial irradiance from increased water vapor concentrations. However, the study shows that while water vapor is widely appreciated as a greenhouse gas, water vapor impacts on the atmospheric transmission of solar radiation and the future of global dimming/brightening should not be overlooked. Copyright © 2011 by the American Geophysical Union."
"7003679645;7006577693;57212781009;","A comparison of present and doubled CO2 climates and feedbacks simulated by three general circulation models",1999,"10.1029/1998JD200049","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033608147&doi=10.1029%2f1998JD200049&partnerID=40&md5=6bbae084d3d39d07733695cb372f7ae7","The present and doubled CO2 equilibrium climates simulated by slab ocean versions of the atmospheric general circulation models from the Commonwealth Scientific and Industrial Research Organisation (CSIRO, Mark 1 and Mark 2) and from the Bureau of Meteorology Research Centre (BMRC) are examined, with the aim of explaining the large variation in mean warming (4.8°C, 4.3°C, and 2.1°C). The present climates are compared firstly with observations. A graphical display of nondimensional measures of local and mean errors is used. For 15 quantities the models produce broadly similar skill, which indicates that such an evaluation is of limited use as a validation of these models for climate change prediction. Comparison of the two climates indicates that for temperature, snow/ice cover, and water column (but not necessarily other fields) the typical magnitudes of local changes are in rough proportion to the mean warming. For tropical precipitation, however, the BMRC model shows a similar sensitivity to CO2 doubling as do the CSIRO models. A standard diagnostic feedback analysis shows that the Mark 1 model has stronger albedo, water vapor, and cloud feedbacks than the BMRC model. A novel regional net feedback analysis is then applied to all three models. Feedbacks for the snow/ice region and clear-sky and cloud forcing components of the snow-free region indicate similar intermodel differences to those from the diagnostic approach. The feedbacks are examined in relation to the simulated climates and model parameterizations. As the application of the regional method requires only standard climatological fields, it is proposed as a convenient analysis tool in further model comparisons. Copyright 1999 by the American Geophysical Union."
"7003696133;6701716171;","Generation and atmospheric heat exchange of coastal polynyas in the Weddell Sea",1992,"10.1007/BF00119376","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027008824&doi=10.1007%2fBF00119376&partnerID=40&md5=eae1ce276f29e221f583638cbb03facc","The forcing mechanisms for Antarctic coastal polynyas and the thermodynamic effects of existing polynyas are studied by means of an air-sea-ice interaction experiment in the Weddell Sea in October and November 1986. Coastal polynyas develop in close relationship to the ice motion and form most rapidly with offshore ice motion. Narrow polynyas occur frequently on the lee side of headlands and with strong curvature of the coastline. From the momentum balance of drifting sea ice, a forcing diagram is constructed, which relates ice motion to the surface-layer wind vector vz and to the geostrophic ocean current vector cg. In agreement with the data, wind forcing dominates when the wind speed at a height of 3 m exceeds the geostrophic current velocity by a factor of at least 33. This condition within the ocean regime of the Antarctic coastal current usually is fulfilled for wind speeds above 5 m/s at a height of 3 m. Based on a nonlinear parameter estimation technique, optimum parameters for free ice drift are calculated. Including a drift dependent geostrophic current in the ice/water drag yields a maximum of explained variance (91%) of ice velocity. The turbulent heat exchange between sea ice and polynya surfaces is derived from surface-layer wind and temperature data, from temperature changes of the air mass along its trajectory and from an application of the resistance laws for the atmospheric PBL. The turbulent heat flux averaged over all randomly distributed observations in coastal polynyas is 143 W/m2. This value is significantly different over pack ice and shelf ice surfaces, where downward fluxes prevail. The large variances of turbulent fluxes can be explained by variable wind speeds and air temperatures. The heat fluxes are also affected by cloud feedback processes and vary in time due to the formation of new ice at the polynya surface. Maximum turbulent fluxes of more than 400 W/m2 result from strong winds and low air temperatures. The heat exchange is similarly intense in a narrow zone close to the ice front, when under weak wind conditions, a local circulation develops and cold air associated with strong surface inversions over the shelf ice is heated above the open water. © 1992 Kluwer Academic Publishers."
"7501757094;7004540083;7403318365;7102425157;","Climate sensitivity of a one-dimensional radiative-convective model with cloud feedback.",1981,"10.1175/1520-0469(1981)038<1167:CSOAOD>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019696331&doi=10.1175%2f1520-0469%281981%29038%3c1167%3aCSOAOD%3e2.0.CO%3b2&partnerID=40&md5=c496d489e74c3f9a63b6f8f9191c41fd","We illustrate the potential complexity of the feedback between global mean cloud amount and global mean surface temperature when variations of the vertical cloud distribution are included by studying the behavior of a one-dimensional radiative-convective model with two types of cloud variation: variable cloud cover with constant optical thickness; and variable optical thickness with constant cloud cover. The model results show that changes in the vertical cloud distribution and mean cloud optical thickness can be as important to climate variations as are changes in the total cloud cover.-from Authors"
"54897465300;56457851700;7202145115;","Observational evidence for a negative shortwave cloud feedback in middle to high latitudes",2016,"10.1002/2015GL067499","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84976240378&doi=10.1002%2f2015GL067499&partnerID=40&md5=798d9ad3419d66db4674a0fbe9ad9399","Exploiting the observed robust relationships between temperature and optical depth in extratropical clouds, we calculate the shortwave cloud feedback from historical data, by regressing observed and modeled cloud property histograms onto local temperature in middle to high southern latitudes. In this region, all CMIP5 models and observational data sets predict a negative cloud feedback, mainly driven by optical thickening. Between 45° and 60°S, the mean observed shortwave feedback (-0.91 ± 0.82 W m-2 K-1, relative to local rather than global mean warming) is very close to the multimodel mean feedback in RCP8.5 (-0.98 W m-2 K-1), despite differences in the meridional structure. In models, historical temperature-cloud property relationships reliably predict the forced RCP8.5 response. Because simple theory predicts this optical thickening with warming, and cloud amount changes are relatively small, we conclude that the shortwave cloud feedback is very likely negative in the real world at middle to high latitudes. © 2016. American Geophysical Union. All Rights Reserved."
"7202660824;7403288995;7402064802;36856321600;","The strength of the tropical inversion and its response to climate change in 18 CMIP5 models",2015,"10.1007/s00382-014-2441-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929703897&doi=10.1007%2fs00382-014-2441-9&partnerID=40&md5=170bc37005cc6490577ff0e9f6190a32","We examine the tropical inversion strength, measured by the estimated inversion strength (EIS), and its response to climate change in 18 models associated with phase 5 of the coupled model intercomparison project (CMIP5). While CMIP5 models generally capture the geographic distribution of observed EIS, they systematically underestimate it off the west coasts of continents, due to a warm bias in sea surface temperature. The negative EIS bias may contribute to the low bias in tropical low-cloud cover in the same models. Idealized perturbation experiments reveal that anthropogenic forcing leads directly to EIS increases, independent of “temperature-mediated” EIS increases associated with long-term oceanic warming. This fast EIS response to anthropogenic forcing is strongly impacted by nearly instantaneous continental warming. The temperature-mediated EIS change has contributions from both uniform and non-uniform oceanic warming. The substantial EIS increases in uniform oceanic warming simulations are due to warming with height exceeding the moist adiabatic lapse rate in tropical warm pools. EIS also increases in fully-coupled ocean–atmosphere simulations where $$\hbox {CO}_{2}$$CO2 concentration is instantaneously quadrupled, due to both fast and temperature-mediated changes. The temperature-mediated EIS change varies with tropical warming in a nonlinear fashion: The EIS change per degree tropical warming is much larger in the early stage of the simulations than in the late stage, due to delayed warming in the eastern parts of the subtropical oceans. Given the importance of EIS in regulating tropical low-cloud cover, this suggests that the tropical low-cloud feedback may also be nonlinear. © 2014, Springer-Verlag Berlin Heidelberg."
"54897465300;7202145115;","Connections Between Clouds, Radiation, and Midlatitude Dynamics: a Review",2015,"10.1007/s40641-015-0010-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84975507874&doi=10.1007%2fs40641-015-0010-x&partnerID=40&md5=7fc19f4aca2a5cb24a53df0493a0b3bd","We review the effects of dynamical variability on clouds and radiation in observations and models and discuss their implications for cloud feedbacks. Jet shifts produce robust meridional dipoles in upper-level clouds and longwave cloud-radiative effect (CRE), but low-level clouds, which do not simply shift with the jet, dominate the shortwave CRE. Because the effect of jet variability on CRE is relatively small, future poleward jet shifts with global warming are only a second-order contribution to the total CRE changes around the midlatitudes, suggesting a dominant role for thermodynamic effects. This implies that constraining the dynamical response is unlikely to reduce the uncertainty in extratropical cloud feedback. However, we argue that uncertainty in the cloud-radiative response does affect the atmospheric circulation response to global warming, by modulating patterns of diabatic forcing. How cloud feedbacks can affect the dynamical response to global warming is an important topic of future research. © 2015, Springer International Publishing AG."
"54408689600;56654815900;22136624400;55293583300;14833720300;24521526600;56165252200;6603497594;","Isolating signatures of major cloud-cloud collisions - II. The lifetimes of broad bridge features",2015,"10.1093/mnras/stv2068","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84960846384&doi=10.1093%2fmnras%2fstv2068&partnerID=40&md5=2b5d2bca6f720c5c1e704123b1cac87a","We investigate the longevity of broad bridge features in position-velocity diagrams that appear as a result of cloud-cloud collisions. Broad bridges will have a finite lifetime due to the action of feedback, conversion of gas into stars and the time-scale of the collision. We make a series of analytic arguments with which to estimate these lifetimes. Our simple analytic arguments suggest that for collisions between clouds larger than R ~ 10 pc the lifetime of the broad bridge is more likely to be determined by the lifetime of the collision rather than the radiative or wind feedback disruption time-scale. However, for smaller clouds feedback becomes much more effective. This is because the radiative feedback time-scale scales with the ionizing flux Nly as R7/4Nly -1/4 so a reduction in cloud size requires a relatively large decrease in ionizing photons to maintain a given time-scale. We find that our analytic arguments are consistent with new synthetic observations of numerical simulations of cloud-cloud collisions (including star formation and radiative feedback).We also argue that if the number of observable broad bridges remains ~ constant, then the disruption time-scale must be roughly equivalent to the collision rate. If this is the case, our analytic arguments also provide collision rate estimates, which we find are readily consistent with previous theoretical models at the scales they consider (clouds larger than about 10 pc) but are much higher for smaller clouds. © 2015 The Authors."
"35509639400;7201504886;16444240700;24723648200;56212055700;6603868770;23017945100;7006184606;55883785100;35551238800;22133985200;57206156792;6603418610;57202531041;23492864500;55940978200;23768540500;6603566335;6602115663;56198145500;35621058500;56567409000;57190209035;7201423091;","EUREC4A: A Field Campaign to Elucidate the Couplings Between Clouds, Convection and Circulation",2017,"10.1007/s10712-017-9428-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030099198&doi=10.1007%2fs10712-017-9428-0&partnerID=40&md5=df9180e49db240179718c7784676b9d6","Trade-wind cumuli constitute the cloud type with the highest frequency of occurrence on Earth, and it has been shown that their sensitivity to changing environmental conditions will critically influence the magnitude and pace of future global warming. Research over the last decade has pointed out the importance of the interplay between clouds, convection and circulation in controling this sensitivity. Numerical models represent this interplay in diverse ways, which translates into different responses of trade-cumuli to climate perturbations. Climate models predict that the area covered by shallow cumuli at cloud base is very sensitive to changes in environmental conditions, while process models suggest the opposite. To understand and resolve this contradiction, we propose to organize a field campaign aimed at quantifying the physical properties of trade-cumuli (e.g., cloud fraction and water content) as a function of the large-scale environment. Beyond a better understanding of clouds-circulation coupling processes, the campaign will provide a reference data set that may be used as a benchmark for advancing the modelling and the satellite remote sensing of clouds and circulation. It will also be an opportunity for complementary investigations such as evaluating model convective parameterizations or studying the role of ocean mesoscale eddies in air–sea interactions and convective organization. © 2017, The Author(s)."
"10241250100;55686667100;55537426400;10241462700;10243650000;7003420726;35580303100;55314995700;36701462300;26667030700;55315186800;8979277400;10240710000;6603196127;7102857642;","Perturbed physics ensemble using the MIROC5 coupled atmosphere-ocean GCM without flux corrections: Experimental design and results: Parametric uncertainty of climate sensitivity",2012,"10.1007/s00382-012-1441-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869509286&doi=10.1007%2fs00382-012-1441-x&partnerID=40&md5=8f677c6ae23c989f3fc4a6dcebb68cd3","In this study, we constructed a perturbed physics ensemble (PPE) for the MIROC5 coupled atmosphere-ocean general circulation model (CGCM) to investigate the parametric uncertainty of climate sensitivity (CS). Previous studies of PPEs have mainly used the atmosphere-slab ocean models. A few PPE studies using a CGCM applied flux corrections, because perturbations in parameters can lead to large radiation imbalances at the top of the atmosphere and climate drifts. We developed a method to prevent climate drifts in PPE experiments using the MIROC5 CGCM without flux corrections. We simultaneously swept 10 parameters in atmosphere and surface schemes. The range of CS (estimated from our 35 ensemble members) was not wide (2. 2-3. 2 °C). The shortwave cloud feedback related to changes in middle-level cloud albedo dominated the variations in the total feedback. We found three performance metrics for the present climate simulations of middle-level cloud albedo, precipitation, and ENSO amplitude that systematically relate to the variations in shortwave cloud feedback in this PPE. © 2012 The Author(s)."
"8718425100;7103060756;7601492669;7101752236;55915206300;","The impact of global warming on marine boundary layer clouds over the eastern Pacific-A regional model study",2010,"10.1175/2010JCLI3666.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649247484&doi=10.1175%2f2010JCLI3666.1&partnerID=40&md5=c439445c47b8e052e4a28163d24bbe24","Cloud simulations and cloud-climate feedbacks in the tropical and subtropical eastern Pacific region in 16 state-of-the-art coupled global climate models (GCMs) and in the International Pacific Research Center (IPRC) Regional Atmospheric Model (iRAM) are examined. The authors find that the simulation of the present-day mean cloud climatology for this region in the GCMs is very poor and that the cloud-climate feedbacks vary widely among the GCMs. By contrast, iRAM simulates mean clouds and interannual cloud variations that are quite similar to those observed in this region. The model also simulates well the observed relationship between lower-tropospheric stability (LTS) and low-level cloud amount. To investigate cloud-climate feedbacks in iRAM, several global warming scenarios were run with boundary conditions appropriate for late twenty-first-century conditions. All the global warming cases simulated with iRAM show a distinct reduction in low-level cloud amount, particularly in the stratocumulus regime, resulting in positive local feedback parameters in these regions in the range of 4-7 W m-2 K-1. Domain-averaged (30°S-30°N, 150°-60°W) feedback parameters from iRAM range between +1.8 and +1.9 W m-2 K-1. At most locations both the LTS and cloud amount are altered in the global warming cases, but the changes in these variables do not follow the empirical relationship found in the present-day experiments. The cloud-climate feedback averaged over the same east Pacific region was also calculated from the Special Report on Emissions Scenarios (SRES) A1B simulations for each of the 16 GCMs with results that varied from -1.0 to +1.3 W m-2 K-1, all less than the values obtained in the comparable iRAM simulations. The iRAM results by themselves cannot be connected definitively to global climate feedbacks; however, among the global GCMs the cloud feedback in the full tropical-subtropical zone is correlated strongly with the east Pacific cloud feedback, and the cloud feedback largely determines the global climate sensitivity. The present iRAM results for cloud feedbacks in the east Pacific provide some support for the high end of current estimates of global climate sensitivity. © 2010 American Meteorological Society."
"7004893330;57193132723;57191598636;","Observational constraints on the cloud thermodynamic phase in midlatitude storms",2006,"10.1175/JCLI3919.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750803493&doi=10.1175%2fJCLI3919.1&partnerID=40&md5=464f7ae57a7226d515ea3f43206b206e","The conditions under which supercooled liquid water gradually gives way to ice in the mixed-phase regions of clouds are still poorly understood and may be an important source of cloud feedback uncertainty in general circulation model projections of long-term climate change. Two winters of cloud phase discrimination, cloud-top temperature, sea surface temperature, and precipitation from several satellite datasets (the NASA Terra and Aqua Moderate Resolution Imaging Spectroradiometer, and the Tropical Rainfall Measuring Mission) for the North Atlantic and Pacific Ocean basins are analyzed to better understand these processes. Reanalysis surface pressures and vertical velocities are used in combination with a synoptic storm-tracking algorithm to define storm tracks, create composite storm dynamical and cloud patterns, and examine changes in storm characteristics over their life cycles. Characteristically different storm cloud patterns exist in the Atlantic and Pacific and on the west and east sides of each ocean basin. This appears to be related to the different spatial patterns of sea surface temperature in the two ocean basins. Glaciation occurs at very warm temperatures in the high, thick, heavily precipitating clouds typical of frontal ascent regions, except where vertical velocities are strongest, similar to previous field experiments. Outside frontal regions, however, where clouds are shallower, supercooled water exists at lower cloud-top temperatures. This analysis is the first large-scale assessment of cloud phase and its relation to dynamics on climatologically representative time scales. It provides a potentially powerful benchmark for the design and evaluation of mixed-phase process parameterizations in general circulation models and suggests that assumptions made in some existing models may negatively bias their cloud feedback estimates."
"7401974644;7402435469;6701464294;6701555556;6602904617;57212416832;56985140700;7102268722;7401936984;","Diagnosis of Community Atmospheric Model 2 (CAM2) in numerical weather forecast configuration at Atmospheric Radiation Measurement sites",2005,"10.1029/2004JD005042","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25844465285&doi=10.1029%2f2004JD005042&partnerID=40&md5=5459d201cb7b07c9f66e5b45502a52dc","The Community Atmospheric Model 2 (CAM2) is run as a short-term (1-5 days) forecast model initialized with reanalysis data. The intent is to reveal model deficiencies before complex interactions obscure the root error sources. Integrations are carried out for three Atmospheric Radiation Measurement (ARM) Program intensive operational periods (IOPs): June/July 1997, April 1997, and March 2000. The ARM data are used to validate the model in detail for the Southern Great Plains (SGP) site for all the periods and in the tropical west Pacific for the March 2000 period. The model errors establish themselves quickly, and within 3 days the model has evolved into a state distinctly different from the ARM observations. The summer forecasts evince a systematic error in convective rainfall. This error manifests itself in the temperature and moisture profiles after a single diurnal cycle. The same error characteristics are seen in the March 2000 tropical west Pacific forecasts. The model performs well in the spring cases at the SGP. Most of the error is manifested during rainy periods. The ARM cloud radar comparison to the model reveals cloud errors which are consistent with the relative humidity profile errors. The cloud errors are similar to those seen in climatological integrations, but the state variable errors are different. Thus there is the possibility that the some basic parameterization errors are obscured in the climatological integrations. The approach described here will facilitate parameterization experimentation, diagnoses, and validation. One way of reducing cloud feedback uncertainty is to make the physical processes behave in the most realistic manner possible. Paradoxically, perhaps the best way to reduce uncertainty in cloud feedback mechanisms is to evaluate the model processes with realistic forcing before such feedbacks have any significant affect. Copyright 2005 by the American Geophysical Union."
"6603925960;55752626400;7003865921;35319507500;7202016984;55805773500;","Comparison of two different cloud climatologies derived from CALIOP-attenuated backscattered measurements (Level 1): The CALIPSO-ST and the CALIPSO-GOCCP",2013,"10.1175/JTECH-D-12-00057.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878390530&doi=10.1175%2fJTECH-D-12-00057.1&partnerID=40&md5=ff395729eb38eb9b8e744dce71d964cc","Two different cloud climatologies have been derived from the same NASA-Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP)-measured attenuated backscattered profile (level 1, version 3 dataset). The first climatology, named Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations-Science Team (CALIPSO-ST), is based on the standard CALIOP cloud mask (level 2 product, version 3), with the aim to document clouds with the highest possible spatiotemporal resolution, taking full advantage of the CALIOP capabilities and sensitivity for a wide range of cloud scientific studies. The second climatology, named GCM-Oriented CALIPSO Cloud Product (CALIPSO-GOCCP), is aimed at a single goal: evaluating GCM prediction of cloudiness. For this specific purpose, it has been designed to be fully consistent with the CALIPSO simulator included in the Cloud Feedback Model Intercomparison Project (CFMIP) Observation Simulator Package (COSP) used within version 2 of the CFMIP (CFMIP-2) experiment and phase 5 of the Coupled Model Intercomparison Project (CMIP5). The differences between the two datasets in the global cloud cover maps-total, low level (P > 680 hPa), midlevel (680 < P < 440 hPa), and high level (P < 440 hPa)-are frequently larger than 10% and vary with region. The two climatologies show significant differences in the zonal cloud fraction profile (which differ by a factor of almost 2 in some regions), which are due to the differences in the horizontal and vertical averaging of the measured attenuated backscattered profile CALIOP profile before the cloud detection and to the threshold used to detect clouds (this threshold depends on the resolution and the signal-to-noise ratio). © 2013 American Meteorological Society."
"57196143493;7006016266;24921297200;6602336407;55605771904;","Separation of longwave climate feedbacks from spectral observations",2010,"10.1029/2009JD012766","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951045672&doi=10.1029%2f2009JD012766&partnerID=40&md5=0aac8c7f0db9deebbc47d5374c6ec2de","We conduct a theoretical investigation into whether changes in the outgoing longwave radiation (OLR) spectrum can be used to constrain longwave greenhousegas forcing and climate feedbacks, with a focus on isolating and quantifying their contributions to the total OLR change in all-sky conditions. First, we numerically compute the spectral signals of CO2 forcing and feedbacks of temperature, water vapor, and cloud. Then, we investigate whether we can separate these signals from the total change in the OLR spectrum through an optimal detection method. Uncertainty in optimal detection arises from the uncertainty in the shape of the spectral fingerprints, the natural variability of the OLR spectrum, and a nonlinearity effect due to the crosscorrelation of different climate responses. We find that the uncertainties in optimally detected greenhousegas forcing, water vapor, and temperature feedbacks are substantially less than their overall magnitudes in a double-CO2 experiment, and thus the detection results are robust. The accuracy in surface temperature and cloud feedbacks, however, is limited by the ambiguity in their fingerprints. Combining ambiguous feedback signals reduces the uncertainty in the combined signal. Auxiliary data are required to fully resolve the difficulty. Copyright 2010 by the American Geophysical Union."
"7102202012;16244029800;","Solar cycle warming at the Earth's surface in NCEP and ERA-40 data: A linear discriminant analysis",2008,"10.1029/2007JD009164","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43449101891&doi=10.1029%2f2007JD009164&partnerID=40&md5=bfad8cbecd4b91ebe4528535df0d22e9","The total solar irradiance (TSI) has been measured by orbiting satellites since 1978 to vary on an 11-year cycle by about 0.08%. Because of previous controversies on the reality of solar cycle response at the surface, in this work we discuss the robustness of the solar response with respect to analysis methods, data sets and periods used. Furthermore we concentrate on the globally coherent signal. Two reanalysis data sets are used: one is from National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP for short) and the other is the European Centre for Medium-Range Weather Forecasts (ECMWF)'s most recent reanalysis denoted by ERA-40. Three analysis methods are considered, with increasing sophistication. Within each data set the analysis results are consistent with each other (i.e., each within the other's error bars), with the method of linear discriminant analysis (LDA) yielding the smallest error bar and the unfiltered global mean data yielding the largest error bar in the temperature amplitude. All three methods and both data sets are able to demonstrate that the 11-year signal is statistically significant and attributable (i.e., related) to the solar cycle. We deduce the spatial surface pattern over the globe which best distinguishes the solar maximum years from the solar minimum years using the LDA method. The resulting warming pattern shows clearly the polar amplification of warming and the preference for continents over oceans. We propose that the magnitude of the surface warming is consistent with direct solar radiative forcing if positive feedback processes such as ice albedo, water vapor/lapse rate and cloud feedbacks, similar to some of those studied for the greenhouse warming problem, are incorporated. It does not appear to be necessary to invoke some previously proposed exotic indirect mechanisms for an explanation of the observed solar signal. Copyright 2008 by the American Geophysical Union."
"7201443624;7004034323;7003976079;","Influence of dynamics on the changes in tropical cloud radiative forcing during the 1998 El Niño",2002,"10.1175/1520-0442(2002)015<1979:IODOTC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037099060&doi=10.1175%2f1520-0442%282002%29015%3c1979%3aIODOTC%3e2.0.CO%3b2&partnerID=40&md5=70117a7329ae74e74082a41a4e83e10d","Satellite measurements of the radiation budget and data from the U.S. National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis are used to investigate the links between anomalous cloud radiative forcing over the tropical west Pacific warm pool and the tropical dynamics and sea surface temperature (SST) distribution during 1998. The ratio, N, of the shortwave cloud forcing (SWCF) to longwave cloud forcing (LWCF) (N = -SWCF/LWCF) is used to infer information on cloud altitude. A higher than average N during 1998 appears to be related to two separate phenomena. First, dynamic regime-dependent changes explain high values of N (associated with low cloud altitude) for small magnitudes of SWCF and LWCF (low cloud fraction), which reflect the unusual occurrence of mean subsiding motion over the tropical west Pacific during 1998, associated with the anomalous SST distribution. Second, Tropics-wide long-term changes in the spatial-mean cloud forcing, independent of dynamic regime, explain the higher values of N during both 1998 and in 1994/95. The changes in dynamic regime and their anomalous structure in 1998 are well simulated by version HadAM3 of the Hadley Centre climate model, forced by the observed SSTs. However, the LWCF and SWCF are poorly simulated, as are the interannual changes in N. It is argued that improved representation of LWCF and SWCF and their dependence on dynamical forcing are required before the cloud feedbacks simulated by climate models can be trusted."
"57202163835;6506101358;57203200427;24511929800;","Sulfate Aerosol Indirect Effect and CO2 Greenhouse Forcing: Equilibrium Response of the LMD GCM and Associated Cloud Feedbacks",1998,"10.1175/1520-0442(1998)011<1673:saieac>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0001733727&doi=10.1175%2f1520-0442%281998%29011%3c1673%3asaieac%3e2.0.co%3b2&partnerID=40&md5=fe5f577fffe3bfe82cc93c068cf4ce19","The climate sensitivity to various forcings, and in particular to changes in CO2 and sulfate aerosol concentrations, imposed separately or in a combined manner, is studied with an atmospheric general circulation model coupled to a simple slab oceanic model. The atmospheric model includes a rather detailed treatment of warm cloud microphysics and takes the aerosol indirect effects into account explicitly, although in a simplified manner. The structure of the model response appears to be organized at a global scale, with a partial independence from the geographical structure of the forcing. Atmospheric and surface feedbacks are likely to explain this feature. In particular the cloud feedbacks play a very similar role in the CO2 and aerosol experiments, but with opposite sign. These results strengthen the idea, already apparent from other studies, that, in spite of their different nature and their different geographical and vertical distributions, aerosol may have substantially counteracted the climate effect of greenhouse gases, at least in the Northern Hemisphere, during the twentieth century. When the effects of the two forcings are added, the model response is not symmetric between the two hemispheres. This feature is also consistent with the findings of other modeling groups and has implications for the detection of future climate changes."
"57213177124;7406372329;","A simple analytical model for understanding the formation of sea surface temperature patterns under global warming",2014,"10.1175/JCLI-D-14-00346.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84909619231&doi=10.1175%2fJCLI-D-14-00346.1&partnerID=40&md5=d269d09976430aa516d4db289b73f6fa","How sea surface temperature (SST) changes under global warming is critical for future climate projection because SST change affects atmospheric circulation and rainfall. Robust features derived from 17 models of phase 5 of the Coupled Model Intercomparison Project (CMIP5) include a much greater warming in high latitudes than in the tropics, an El Niño-like warming over the tropical Pacific and Atlantic, and a dipole pattern in the Indian Ocean. However, the physical mechanism responsible for formation of such warming patterns remains open. A simple theoretical model is constructed to reveal the cause of the future warming patterns. The result shows that a much greater polar, rather than tropical, warming depends primarily on present-day mean SST and surface latent heat flux fields, and atmospheric longwave radiation feedback associated with cloud change further enhances this warming contrast. In the tropics, an El Niño-like warming over the Pacific and Atlantic arises from a similar process, while cloud feedback resulting from different cloud regimes between east and west ocean basins also plays a role. A dipole warming over the equatorial Indian Ocean is a response to weakened Walker circulation in the tropical Pacific. © 2014 American Meteorological Society."
"7201485519;7005056279;","Coupling between subtropical cloud feedback and the local hydrological cycle in a climate model",2013,"10.1007/s00382-012-1608-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884703264&doi=10.1007%2fs00382-012-1608-5&partnerID=40&md5=5f179f1a730f7c8248480832cf35cd81","In HadGEM2-A, AMIP experiments forced with observed sea surface temperatures respond to uniform and patterned +4 K SST perturbations with strong positive cloud feedbacks in the subtropical stratocumulus/trade cumulus transition regions. Over the subtropical Northeast Pacific at 137°W/26°N, the boundary layer cloud fraction reduces considerably in the AMIP +4 K patterned SST experiment. The near-surface wind speed and the air-sea temperature difference reduces, while the near-surface relative humidity increases. These changes limit the local increase in surface evaporation to just 3 W/m2 or 0.6 %/K. Previous studies have suggested that increases in surface evaporation may be required to maintain maritime boundary layer cloud in a warmer climate. This suggests that the supply of water vapour from surface evaporation may not be increasing enough to maintain the low level cloud fraction in the warmer climate in HadGEM2-A. Sensitivity tests which force the surface evaporation to increase substantially in the +4 K patterned SST experiment result in smaller changes in boundary layer cloud and a weaker cloud feedback in HadGEM2-A, supporting this idea. Although global mean surface evaporation in climate models increases robustly with global temperature (and the resulting increase in atmospheric radiative cooling), local values may increase much less, having a significant impact on cloud feedback. These results suggest a coupling between cloud feedback and the hydrological cycle via changes in the patterns of surface evaporation. A better understanding of both the factors controlling local changes in surface evaporation and the sensitivity of clouds to such changes may be required to understand the reasons for inter-model differences in subtropical cloud feedback. © 2012 Crown Copyright."
"7005485117;55716700200;7006508140;6602460564;7202245915;57216559278;","Performance of a High-Resolution Mesoscale Tropical Prediction Model",1990,"10.1016/S0065-2687(08)60428-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0001482647&doi=10.1016%2fS0065-2687%2808%2960428-8&partnerID=40&md5=2ce6f9acbfe7d6bd00a5303fe0974edc","This chapter examines the performance of a high-resolution mesoscale tropical prediction model. There are basically two types of mesoscale models, including quasistatic models and nonhydrostatic mesoscale models. The quasistatic models make use of horizontal resolutions of the order of 50 km or larger and can resolve mesoscale phenomena whose scale is of the order of a few hundred kilometers. The nonhydrostatic mesoscale models use a horizontal resolution of less than 5 km. The physical parametrizations of the model are largely based on the developments from global spectral model. These include shallow and deep moist convection, detailed calculation of radiative processes including cloud feedback processes, and a variable solar zenith angle. The surface fluxes are based on similarity theory and are coupled to the computation of surface hydrology and surface energy balance and they distinguish between the stable and unstable surface layers. The dynamical aspects of the regional model are also elaborated. © 1990 Academic Press Inc."
"25031430500;56014511300;","Processes Responsible for Cloud Feedback",2016,"10.1007/s40641-016-0052-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020637029&doi=10.1007%2fs40641-016-0052-8&partnerID=40&md5=b6b1f7e2b987e7348fc8fe437889d066","Cloud feedback on global climate is determined by the combined action of multiple processes that have different relevance in different cloud regimes. This review lays out the framework for cloud feedback and highlights recent advances and outstanding issues. A consensus is emerging on large-scale controls on cloud feedback. Recent work has made significant progress in the understanding and observationally constraining the local response of shallow clouds. But significant uncertainties remain in microphysical mechanisms for cloud feedback. Important microphysical mechanisms include cloud phase changes, precipitation processes and even aerosol distributions. The treatment of these processes varies across climate models and may contribute to greater spread in feedbacks across models as models advance. Future work will need to try to bound the range of possible cloud microphysical feedback mechanisms and seek observational constraints on them. © 2016, Springer International Publishing AG."
"35300998400;8880094700;23393212200;57218183583;36553486200;","Large-scale ocean circulation-cloud interactions reduce the pace of transient climate change",2016,"10.1002/2016GL067931","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84968725152&doi=10.1002%2f2016GL067931&partnerID=40&md5=bdaf333c1641127e99dcda0ab445c2a5","Changes to the large-scale oceanic circulation are thought to slow the pace of transient climate change due, in part, to their influence on radiative feedbacks. Here we evaluate the interactions between CO2-forced perturbations to the large-scale ocean circulation and the radiative cloud feedback in a climate model. Both the change of the ocean circulation and the radiative cloud feedback strongly influence the magnitude and spatial pattern of surface and ocean warming. Changes in the ocean circulation reduce the amount of transient global warming caused by the radiative cloud feedback by helping to maintain low cloud coverage in the face of global warming. The radiative cloud feedback is key in affecting atmospheric meridional heat transport changes and is the dominant radiative feedback mechanism that responds to ocean circulation change. Uncertainty in the simulated ocean circulation changes due to CO2 forcing may contribute a large share of the spread in the radiative cloud feedback among climate models. ©2016. American Geophysical Union. All Rights Reserved."
"23492864500;8866821900;23768540500;13006055400;","The behavior of trade-wind cloudiness in observations and models: The major cloud components and their variability",2015,"10.1002/2014MS000390","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027925077&doi=10.1002%2f2014MS000390&partnerID=40&md5=6937f1fc0a73bc674d6ce78a5278c96c","Guided by ground-based radar and lidar profiling at the Barbados Cloud Observatory (BCO), this study evaluates trade-wind cloudiness in ECMWF's Integrated Forecast System (IFS) and nine CMIP5 models using their single-timestep output at selected grid points. The observed profile of cloudiness is relatively evenly distributed between two important height levels: the lifting condensation level (LCL) and the tops of the deepest cumuli near the trade-wind inversion (2-3 km). Cloudiness at the LCL dominates the total cloud cover, but is relatively invariant. Variance in cloudiness instead peaks at the inversion. The IFS reproduces the depth of the cloud field and its variability, but underestimates cloudiness at the LCL and the inversion. A few CMIP5 models produce a single stratocumulus-like layer near the LCL, but more than half of the CMIP5 models reproduce the observed cloud layer depth in long-term mean profiles. At single-time steps, however, half of the models do not produce cloudiness near cloud tops along with the (almost ever-present) cloudiness near the LCL. In seven models, cloudiness is zero at both levels 10 to 65% of the time, compared to 3% in the observations. Models therefore tend to overestimate variance in cloudiness near the LCL. This variance is associated with longer time scales than in observations, which suggests that modeled cloudiness is too sensitive to large-scale processes. To conclude, many models do not appear to capture the processes that underlie changes in cloudiness, which is relevant for cloud feedbacks and climate prediction. © 2015. The Authors."
"11940188700;6603749963;6603362421;7102163440;7003777747;","A lower and more constrained estimate of climate sensitivity using updated observations and detailed radiative forcing time series",2014,"10.5194/esd-5-139-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897044238&doi=10.5194%2fesd-5-139-2014&partnerID=40&md5=c52f54c7a132ebe2a0e5176de4f007cf","Equilibrium climate sensitivity (ECS) is constrained based on observed near-surface temperature change, changes in ocean heat content (OHC) and detailed radiative forcing (RF) time series from pre-industrial times to 2010 for all main anthropogenic and natural forcing mechanism. The RF time series are linked to the observations of OHC and temperature change through an energy balance model (EBM) and a stochastic model, using a Bayesian approach to estimate the ECS and other unknown parameters from the data. For the net anthropogenic RF the posterior mean in 2010 is 2.0 Wm-2, with a 90% credible interval (C.I.) of 1.3 to 2.8 Wm-2, excluding present-day total aerosol effects (direct + indirect) stronger than-1.7 Wm2. The posterior mean of the ECS is 1.8° C, with 90% C.I. ranging from 0.9 to 3.2 °C, which is tighter than most previously published estimates. We find that using three OHC data sets simultaneously and data for global mean temperature and OHC up to 2010 substantially narrows the range in ECS compared to using less updated data and only one OHC data set. Using only one OHC set and data up to 2000 can produce comparable results as previously published estimates using observations in the 20th century, including the heavy tail in the probability function. The analyses show a significant contribution of internal variability on a multi-decadal scale to the global mean temperature change. If we do not explicitly account for long-term internal variability, the 90% C.I. is 40% narrower than in the main analysis and the mean ECS becomes slightly lower, which demonstrates that the uncertainty in ECS may be severely underestimated if the method is too simple. In addition to the uncertainties represented through the estimated probability density functions, there may be uncertainties due to limitations in the treatment of the temporal development in RF and structural uncertainties in the EBM. © 2014 Author (s)."
"6506233769;8315173400;7006710430;8308165800;46660947000;24309428500;","The role of ocean gateways on cooling climate on long time scales",2014,"10.1016/j.gloplacha.2014.04.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901228064&doi=10.1016%2fj.gloplacha.2014.04.004&partnerID=40&md5=0dc7e6e6bed7b4a6aa2c756a7ad17abc","We examine ocean changes in response to changes in paleogeography from the Cretaceous to present in an intermediate complexity model and in the fully coupled CCSM3 model. Greenhouse gas concentrations are kept constant to allow a focus on effects arising from changing continental configurations. We find consistent and significant geography-related Cenozoic cooling arising from the opening of Southern Ocean (SO) gateways. Both models show significant deep ocean cooling arising from tectonic evolution alone. Simulations employing continental configurations associated with greenhouse climates, namely the Turonian and the Eocene simulations, systematically exhibit warm deep ocean temperatures at elevated pCO2 close to 10°C. In contrast, continental configurations associated with (later) icehouse climates are associated with cooler deep ocean temperatures at identical pCO2, arising from a progressive strengthening of the Antarctic Circumpolar Current. This suggests that a component of the Cenozoic benthic cooling trend recorded in oxygen isotopes could arise directly from changes in continental configuration, and so be partially decoupled from the Cenozoic greenhouse gas history. In this paper we will present our model results against the background of an extensive review of previous work on ocean gateways and additional modelling results from several other global climate models. © 2014 Elsevier B.V."
"55332348600;26645289600;7003266014;7403931916;","An analysis of the short-term cloud feedback using MODIS data",2013,"10.1175/JCLI-D-12-00547.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880678553&doi=10.1175%2fJCLI-D-12-00547.1&partnerID=40&md5=7b2bf5a7aa9998ea496361a03a5108b6","The cloud feedback in response to short-term climate variations is estimated from cloud measurements combined with offline radiative transfer calculations. The cloud measurements are made by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite and cover the period 2000-10. Low clouds provide a strong negative cloud feedback, mainly because of their impact in the shortwave (SW) portion of the spectrum. Midlevel clouds provide a positive net cloud feedback that is a combination of a positive SW feedback partially canceled by a negative feedback in the longwave (LW). High clouds have only a small impact on the net cloud feedback because of a close cancellation between largeLWandSWcloud feedbacks. Segregating the clouds by optical depth, it is found that the net cloud feedback is set by a positive cloud feedback due to reductions in the thickest clouds (mainly in the SW) and a cancelling negative feedback from increases in clouds with moderate optical depths (also mainly in the SW). The global average SW, LW, and net cloud feedbacks are 10.30 61.10, 20.46 60.74, and 20.16 60.83 W m-2 K-1, respectively. The SW feedback is consistent with previous work; the MODIS LW feedback is lower than previous calculations and there are reasons to suspect it may be biased low. Finally, it is shown that the apparently small control that global mean surface temperature exerts on clouds, which leads to the large uncertainty in the short-term cloud feedback, arises from statistically significant but offsetting relationships between individual cloud types and global mean surface temperature. ©2013 American Meteorological Society."
"6603888947;","Solar and planetary oscillation control on climate change: Hind-cast, forecast and a comparison with the CMIP5 GCMS",2013,"10.1260/0958-305X.24.3-4.455","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880277096&doi=10.1260%2f0958-305X.24.3-4.455&partnerID=40&md5=917b09be62f4ca9f4be915f8afe17957","Global surface temperature records (e.g. HadCRUT4) since 1850 are characterized by climatic oscillations synchronous with specific solar, planetary and lunar harmonics superimposed on a background warming modulation. The latter is related to a long millennial solar oscillation and to changes in the chemical composition of the atmosphere (e.g. aerosol and greenhouse gases). However, current general circulation climate models, e.g. The CMIP5 GCMs, to be used in the AR5 IPCC Report in 2013, fail to reconstruct the observed climatic oscillations. As an alternate, an empirical model is proposed that uses: (1) a specific set of decadal, multidecadal, secular and millennial astronomic harmonics to simulate the observed climatic oscillations; (2) a 0.45 attenuation of the GCM ensemble mean simulations to model the anthropogenic and volcano forcing effects. The proposed empirical model outperforms the GCMs by better hind-casting the observed 1850-2012 climatic patterns. It is found that: (1) about 50-60% of the warming observed since 1850 and since 1970 was induced by natural oscillations likely resulting from harmonic astronomical forcings that are not yet included in the GCMs; (2) a 2000-2040 approximately steady projected temperature; (3) a 2000-2100 projected warming ranging between 0.3°C and 1.6°C, which is significantly lower than the IPCC GCM ensemble mean projected warming of 1.1°C to 4.1°C; (4) an equilibrium climate sensitivity to CO2 doubling centered in 1.35°C and varying between 0.9°C and 2.0°C."
"7004508111;55714712500;55716092000;57196499374;","Atmospheric chemistry-climate feedbacks",2010,"10.1029/2009JD013300","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954486082&doi=10.1029%2f2009JD013300&partnerID=40&md5=54a4706db1a2b3e0d0faf4c7ec6d7d6f","We extend the theory of climate feedbacks to include atmospheric chemistry. A change in temperature caused by a radiative forcing will include, in general, a contribution from the chemical change that is fed back into the climate system; likewise, the change in atmospheric burdens caused by a chemical forcing will include a contribution from the associated climate change that is fed back into the chemical system. The theory includes two feedback gains, G <inf>che</inf> and G<inf>cli</inf>. G<inf>che</inf> is defined as the ratio of the change in equilibrium global mean temperature owing to long-lived greenhouse gas radiative forcing, under full climate-chemistry coupling, to that in the absence of coupling. G<inf>cli</inf> is defined as the ratio of the change in equilibrium mean aerosol or gas-phase burdens owing to chemical forcing under full coupling, to that in the absence of coupling. We employ a climate-atmospheric chemistry model based on the Goddard Institute for Space Studies (GISS) GCM II', including tropospheric gas-phase chemistry, sulfate, nitrate, ammonium, black carbon, and organic carbon. While the model describes many essential couplings between climate and atmospheric chemistry, not all couplings are accounted for, such as indirect aerosol forcing and the role of natural dust and sea salt aerosols. Guided by the feedback theory, we perform perturbation experiments to quantify G<inf>che</inf> and G<inf>cli</inf>. We find that G<inf>che</inf> for surface air temperature is essentially equal to 1.00 on a planetary scale. Regionally, G<inf>che</inf> is estimated to be 0.80-1.30. The gains are small compared to those of the physical feedbacks in the climate system (e.g., water vapor, and cloud feedbacks). These values for G<inf>che</inf> are robust for the specific model used, but may change when using more comprehensive climate-atmospheric chemistry models. Our perturbation experiments do not allow one to obtain robust values for G<inf>cli</inf>. Globally averaged, the values range from 0.99 to 1.28, depending on the chemical species, while, in areas of high pollution, G<inf>cli</inf> can be up to 1.15 for ozone, and as large as 1.40 for total aerosol. These preliminary values indicate a significant role of climate feedbacks in the atmospheric chemistry system. Copyright 2010 by the American Geophysical Union."
"57219951382;7102495313;7004920873;","Cloud radiative forcing of subtropical low level clouds in global models",2008,"10.1007/s00382-007-0322-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42349093515&doi=10.1007%2fs00382-007-0322-1&partnerID=40&md5=9d66d9bd655d1b69a4661e38eb935b5d","Simulations of subtropical marine low clouds and their radiative properties by nine coupled ocean-atmosphere climate models participating in the fourth assesment report (AR4) of the intergovernmental panel on climate change (IPCC) are analyzed. Satellite observations of cloudiness and radiative fluxes at the top of the atmosphere (TOA) are utilized for comparison. The analysis is confined to the marine subtropics in an attempt to isolate low cloudiness from tropical convective systems. All analyzed models have a negative bias in the low cloud fraction (model mean bias of -15%). On the other hand, the models show an excess of cloud radiative cooling in the region (model mean excess of 13 W m-2). The latter bias is shown to mainly originate from too much shortwave reflection by the models clouds rather than biases in the clear-sky fluxes. These results confirm earlier studies, thus no major progress in simulating the marine subtropical clouds is noted. As a consequence of the combination of these two biases, this study suggests that all investigated models are likely to overestimate the radiative response to changes in low level subtropical cloudiness. © Springer-Verlag 2007."
"56023705500;16022263500;23484340400;26659116700;56515771700;7003381311;56942309200;33367455100;57191576880;6507393330;35321650700;57208283518;","Simulating the cloudy atmospheres of HD 209458 b and HD 189733 b with the 3D Met Office Unified Model",2018,"10.1051/0004-6361/201732278","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047192775&doi=10.1051%2f0004-6361%2f201732278&partnerID=40&md5=b63e0383f63c3257d15027fa61f599c7","Aims: To understand and compare the 3D atmospheric structure of HD 209458 b and HD 189733 b, focusing on the formation and distribution of cloud particles, as well as their feedback on the dynamics and thermal profile. Methods: We coupled the 3D Met Office Unified Model (UM), including detailed treatments of atmospheric radiative transfer and dynamics, to a kinetic cloud formation scheme. The resulting model self-consistently solves for the formation of condensation seeds, surface growth and evaporation, gravitational settling and advection, cloud radiative feedback via absorption, and crucially, scattering. We used fluxes directly obtained from the UM to produce synthetic spectral energy distributions and phase curves. Results: Our simulations show extensive cloud formation in both HD 209458 b and HD 189733 b. However, cooler temperatures in the latter result in higher cloud particle number densities. Large particles, reaching 1 µm in diameter, can form due to high particle growth velocities, and sub-µm particles are suspended by vertical flows leading to extensive upper-atmosphere cloud cover. A combination of meridional advection and efficient cloud formation in cooler high latitude regions, results in enhanced cloud coverage for latitudes above 30 ◦ and leads to a zonally banded structure for all our simulations. The cloud bands extend around the entire planet, for HD 209458 b and HD 189733 b, as the temperatures, even on the day side, remain below the condensation temperature of silicates and oxides. Therefore, the simulated optical phase curve for HD 209458 b shows no “offset”, in contrast to observations. Efficient scattering of stellar irradiation by cloud particles results in a local maximum cooling of up to 250 K in the upper atmosphere, and an advection-driven fluctuating cloud opacity causes temporal variability in the thermal emission. The inclusion of this fundamental cloud-atmosphere radiative feedback leads to significant differences with approaches neglecting these physical elements, which have been employed to interpret observations and determine thermal profiles for these planets. This suggests that readers should be cautious of interpretations neglecting such cloud feedback and scattering, and that the subject merits further study. © ESO 2018"
"36856321600;9132948500;7402064802;","CMIP3 subtropical stratocumulus cloud feedback interpreted through a mixed-layer model",2013,"10.1175/JCLI-D-12-00188.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874810144&doi=10.1175%2fJCLI-D-12-00188.1&partnerID=40&md5=db656569dba4aaf794d7c16be6925961","Large-scale conditions over subtropical marine stratocumulus areas are extracted from global climate models (GCMs) participating in phase 3 of the Coupled Model Intercomparison Project (CMIP3) and used to drive an atmospheric mixed-layer model (MLM) for current and future climate scenarios. Cloud fraction is computed as the fraction of days whereGCMforcings produce a cloudy equilibriumMLMstate. This model is a good predictor of cloud fraction and its temporal variations on time scales longer than 1 week but overpredicts liquid water path and entrainment. GCM cloud fraction compares poorly with observations of mean state, variability, and correlation with estimated inversion strength (EIS). MLM cloud fraction driven by these same GCMs, however, agrees well with observations, suggesting that poor GCM low cloud fraction is due to deficiencies in cloud parameterizations rather than large-scale conditions. However, replacing the various GCM cloud parameterizations with a single physics package (the MLM) does not reduce intermodel spread in low-cloud feedback because theMLMismore sensitive than the GCMs to existent intermodel variations in large-scale forcing. This suggests that improving GCM low cloud physics will not by itself reduce intermodel spread in predicted stratocumulus cloud feedback. Differences in EIS and EIS change between GCMs are found to be a good predictor of current-climate MLM cloud amount and future cloud change. CMIP3 GCMs predict a robust increase of 0.5-1 K in EIS over the next century, resulting in a 2.3%-4.5% increase in MLM cloudiness. If EIS increases are real, subtropical stratocumulus may damp global warming in a way not captured by the GCMs studied. © 2013 American Meteorological Society."
"57206546845;7005310521;7005409364;","Paleoclimate data constraints on climate sensitivity: The paleocalibration method",1996,"10.1007/BF00143708","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029667463&doi=10.1007%2fBF00143708&partnerID=40&md5=64346fa139b1d2db969f8d4079e0907e","The relationship between paleoclimates and the future climate, while not as simple as implied in the 'paleoanalog' studies of Budyko and others, nevertheless provides sufficient constraints to broadly confirm the climate sensitivity range of theoretical models and perhaps eventually narrow the model-derived uncertainties. We use a new technique called 'paleocalibration' to calculate the ratio of temperature response to forcing on a global mean scale for three key intervals of Earth history. By examining surface conditions reconstructed from geologic data for the Last Glacial Maximum, the middle Cretaceous and the early Eocene, we can estimate the equilibrium climate sensitivity to radiative forcing changes for different extreme climates. We find that the ratios for these three periods, within error bounds, all lie in the range obtained from general circulation models: 2-5 K global warming for doubled atmospheric carbon dioxide. Paleocalibration thus provides a data-based confirmation of theoretically calculated climate sensitivity. However, when compared with paleodata on regional scales, the models show less agreeement with data. For example, our GCM simulation of the early Eocene fails to obtain the temperature contrasts between the Equator and the Poles (and between land and ocean areas) indicated by the data, even though it agrees with the temperature data in the global average. Similar results have been reported by others for the Cretaceous and for the Last Glacial Maximum. © 1996 Kluwer Academic Publishers."
"57210518852;7003666669;","An analysis of cloud liquid water feedback and global climate sensitivity in a general circulation model",1992,"10.1175/1520-0442(1992)005<0907:AAOCLW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0006832095&doi=10.1175%2f1520-0442%281992%29005%3c0907%3aAAOCLW%3e2.0.CO%3b2&partnerID=40&md5=9f0f7fe1301b592b74f5a6fa10fbb341","A set of general circulation model simulations is analyzed to determine how cloud distribution and cloud radiative properties might change as climate warms and to isolate and quantify the various feedback effects of clouds on climate sensitivity. For this study the NCAR Community Climate Model (CCM1) was modified so that the cloud radiative properties (albedo, emissivity, and absorptivity) are no longer prescribed, but are functions of the cloud liquid water content. Following the Cess and Potter approach for estimating climate sensitivity, we consider results from two sets of simulations. In one set, cloud liquid water is diagnosed from the simulated condensation rate and thus is free to vary with condensation, while in the other set, the cloud liquid water content is a fixed field (dependent only on altitude and latitude) that is obtained by averaging the results of the first set of experiments. The experiments make it possible to isolate the effects of cloud liquid water feedback. We find that changes in cloud amount, cloud liquid water content, and cloud distribution (especially in the vertical) are all of comparable importance, but some of these changes provide a positive feedback while others provide a negative feedback. Separation of cloud feedback into individual components makes it clear that in this model as climate warms the general increase in the liquid water content of each cloud layer is partially offset by an upward shift in cloud altitude. The effects of clouds on longwave radiation also generally tend to cancel the effects on shortwave radiation. Consequently, the net cloud feedback represents a residual of several offsetting effects, which nevertheless is large enough to nearly double the sensitivity of the simulated climate. Another important conclusion is that it is impossible to parameterize cloud albedo in terms of average cloud liquid water content because the average liquid water is dominated by the thicker clouds, whereas the average albedo depends on clouds with relatively little liquid water as well. © 1992 American Meteorological Society."
"57191980050;35547807400;7404105326;57201350004;56572170400;57210303863;55923546200;","FAIR v1.3: A simple emissions-based impulse response and carbon cycle model",2018,"10.5194/gmd-11-2273-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048767428&doi=10.5194%2fgmd-11-2273-2018&partnerID=40&md5=db2587aaf5e3d75db5b1f7fac01661d1","Simple climate models can be valuable if they are able to replicate aspects of complex fully coupled earth system models. Larger ensembles can be produced, enabling a probabilistic view of future climate change. A simple emissions-based climate model, FAIR, is presented, which calculates atmospheric concentrations of greenhouse gases and effective radiative forcing (ERF) from greenhouse gases, aerosols, ozone and other agents. Model runs are constrained to observed temperature change from 1880 to 2016 and produce a range of future projections under the Representative Concentration Pathway (RCP) scenarios. The constrained estimates of equilibrium climate sensitivity (ECS), transient climate response (TCR) and transient climate response to cumulative CO2 emissions (TCRE) are 2.86 (2.01 to 4.22) K, 1.53 (1.05 to 2.41)K and 1.40 (0.96 to 2.23)K (1000GtC)-1 (median and 5-95% credible intervals). These are in good agreement with the likely Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) range, noting that AR5 estimates were derived from a combination of climate models, observations and expert judgement. The ranges of future projections of temperature and ranges of estimates of ECS, TCR and TCRE are somewhat sensitive to the prior distributions of ECSĝ•TCR parameters but less sensitive to the ERF from a doubling of CO2 or the observational temperature dataset used to constrain the ensemble. Taking these sensitivities into account, there is no evidence to suggest that the median and credible range of observationally constrained TCR or ECS differ from climate model-derived estimates. The range of temperature projections under RCP8.5 for 2081-2100 in the constrained FAIR model ensemble is lower than the emissions-based estimate reported in AR5 by half a degree, owing to differences in forcing assumptions and ECS •TCR distributions. © 2018 Copernicus GmbH. All Rights Reserved."
"36856321600;26645289600;7402064802;","Evaluating emergent constraints on equilibrium climate sensitivity",2018,"10.1175/JCLI-D-17-0631.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052929276&doi=10.1175%2fJCLI-D-17-0631.1&partnerID=40&md5=09f7c5d64151389a64eb8f064bc87759","Emergent constraints are quantities that are observable from current measurements and have skill predicting future climate. This study explores 19 previously proposed emergent constraints related to equilibrium climate sensitivity (ECS; the global-average equilibrium surface temperature response to CO2 doubling). Several constraints are shown to be closely related, emphasizing the importance for careful understanding of proposed constraints. A new method is presented for decomposing correlation between an emergent constraint and ECS into terms related to physical processes and geographical regions. Using this decomposition, one can determine whether the processes and regions explaining correlation with ECS correspond to the physical explanation offered for the constraint. Shortwave cloud feedback is generally found to be the dominant contributor to correlations with ECS because it is the largest source of intermodel spread in ECS. In all cases, correlation results from interaction between a variety of terms, reflecting the complex nature of ECS and the fact that feedback terms and forcing are themselves correlated with each other. For 4 of the 19 constraints, the originally proposed explanation for correlation is borne out by our analysis. These four constraints all predict relatively high climate sensitivity. The credibility of six other constraints is called into question owing to correlation with ECS coming mainly from unexpected sources and/or lack of robustness to changes in ensembles. Another six constraints lack a testable explanation and hence cannot be confirmed. The fact that this study casts doubt upon more constraints than it confirms highlights the need for caution when identifying emergent constraints from small ensembles. © 2018 American Meteorological Society."
"7102875574;57203434394;","The Effects of Ocean Heat Uptake on Transient Climate Sensitivity",2016,"10.1007/s40641-016-0048-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84992354993&doi=10.1007%2fs40641-016-0048-4&partnerID=40&md5=9fea482dafc7260c88eef61c19956d7f","Transient climate sensitivity tends to increase on multiple timescales in climate models subject to an abrupt CO2 increase. The interdependence of radiative and ocean heat uptake processes governing this increase are reviewed. Heat uptake tends to be spatially localized to the subpolar oceans, and this pattern emerges rapidly from an initially uniform distribution. Global climatic impact of heat uptake is studied through the lens of the efficacy concept and a linear systems perspective in which responses to individual climate forcing agents are additive. Heat uptake can be treated as a slowly varying forcing on the atmosphere and surface, whose efficacy is strongly determined by its geographical pattern. An illustrative linear model driven by simple prescribed uptake patterns demonstrates the emergence of increasing climate sensitivity as a consequence of the slow decay of high-efficacy subpolar heat uptake. Evidence is reviewed for the key role of shortwave cloud feedbacks in setting the high efficacy of ocean heat uptake and thus in increasing climate sensitivity. A causal physical mechanism is proposed, linking subpolar heat uptake to a global-scale increase in lower-tropospheric stability. It is shown that the rate of increase in estimated inversion strength systematically slows as heat uptake decays. Variations in heat uptake should therefore manifest themselves as differences in low cloud feedbacks. © 2016, Springer International Publishing AG."
"55537426400;7003922138;","On the link between Hadley circulation changes and radiative feedback processes",2009,"10.1029/2009GL040488","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72149087440&doi=10.1029%2f2009GL040488&partnerID=40&md5=69ed2141fddffba8ec06f7ada089404d","Previous studies have demonstrated that meridional displacements of precipitation in the tropics and changes in the Hadley circulation accompany interhemispherically asymmetric surface temperature changes. In this study, an attempt is made to provide a different perspective by linking this dynamical response to radiative feedback processes. An idealized experiment is conducted in which solar irradiance is reduced in the northern hemisphere extratropics. Radiative feedback analysis indicates that the interhemispheric asymmetry of water vapor and lapse rate feedbacks play a key role in maintaining the simulated cross-equatorial heat transport and Hadley circulation change. On the other hand, cloud feedback plays a relatively minor role because of a large cancellation between shortwave and longwave components. While the experiment is idealized, the implications of the results apply widely from paleoclimate to future climate changes. Copyright 2009 by the American Geophysical Union."
"7401559815;7404653593;7201844203;","Water vapor and cloud feedback over the tropical oceans: Can we use ENSO as a surrogate for climate change?",1996,"10.1029/96GL02414","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030265162&doi=10.1029%2f96GL02414&partnerID=40&md5=61cf076a112f64903dd4439c914ea5ce","Based on experiments with the Goddard Earth Observing System (GEOS) global climate model, we find that the basic patterns of anomalous water vapor greenhouse effect and cloud radiative forcing during ENSO are primarily determined by the basin-wide dynamical response to large scale sea surface temperature (SST) forcing. There is no supergreenhouse effect in the sense of unstable interaction due to local thermodynamics and water vapor radiative feedback on interannual time scales. About 80% of the clear sky water vapor greenhouse sensitivity to SST deduced from ENSO anomalies are due to the transport of water vapor by the large scale circulation. The sensitivity of water vapor greenhouse effect to SST due to radiative feedback is found to be about 1.8 Wm-2/°C, much smaller than the values of 6-9 Wn-2/°C previously estimated from satellite observations from ENSO conditions. Our results show that regionally based interannual variability should not be used to infer radiative feedback sensitivity for climate change unless proper corrections are made for the effect of the large scale circulation. Copyright 1996 by the American Geophysical Union."
"57199888745;56962915800;55823994500;57209611475;56410752500;57129528800;57199900499;57214005435;57194552635;55714142500;","The NUIST Earth System Model (NESM) version 3: Description and preliminary evaluation",2018,"10.5194/gmd-11-2975-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050655367&doi=10.5194%2fgmd-11-2975-2018&partnerID=40&md5=6161ae15bae25939af6b26921d4143e0","The Nanjing University of Information Science and Technology Earth System Model version 3 (NESM v3) has been developed, aiming to provide a numerical modeling platform for cross-disciplinary Earth system studies, project future Earth climate and environment changes, and conduct subseasonal-to-seasonal prediction. While the previous model version NESM v1 simulates the internal modes of climate variability well, it has no vegetation dynamics and suffers considerable radiative energy imbalance at the top of the atmosphere and surface, resulting in large biases in the global mean surface air temperature, which limits its utility to simulate past and project future climate changes. The NESM v3 has upgraded atmospheric and land surface model components and improved physical parameterization and conservation of coupling variables. Here we describe the new version's basic features and how the major improvements were made. We demonstrate the v3 model's fidelity and suitability to address global climate variability and change issues. The 500-year preindustrial (PI) experiment shows negligible trends in the net heat flux at the top of atmosphere and the Earth surface. Consistently, the simulated global mean surface air temperature, land surface temperature, and sea surface temperature (SST) are all in a quasi-equilibrium state. The conservation of global water is demonstrated by the stable evolution of the global mean precipitation, sea surface salinity (SSS), and sea water salinity. The sea ice extents (SIEs), as a major indication of high-latitude climate, also maintain a balanced state. The simulated spatial patterns of the energy states, SST, precipitation, and SSS fields are realistic, but the model suffers from a cold bias in the North Atlantic, a warm bias in the Southern Ocean, and associated deficient Antarctic sea ice area, as well as a delicate sign of the double ITCZ syndrome. The estimated radiative forcing of quadrupling carbon dioxide is about 7.24 W m-2, yielding a climate sensitivity feedback parameter of -0.98 W m-2 K-1, and the equilibrium climate sensitivity is 3.69 K. The transient climate response from the 1 % yr-1 CO2 (1pctCO2) increase experiment is 2.16 K. The model's performance on internal modes and responses to external forcing during the historical period will be documented in an accompanying paper. © 2018 Author(s)."
"7007021059;7003976079;7201485519;7404142321;","Quantitative evaluation of the seasonal variations in climate model cloud regimes",2013,"10.1007/s00382-012-1609-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886721481&doi=10.1007%2fs00382-012-1609-4&partnerID=40&md5=feea8c2aebc663a73cde443a1d2d53c4","An extended cloud-clustering method to assess the seasonal variation of clouds is applied to five CMIP5 models. The seasonal variation of the total cloud radiative effect (CRE) is dominated by variations in the relative frequency of occurrence of the different cloud regimes. Seasonal variations of the CRE within the individual regimes contribute much less. This is the case for both observations, models and model errors. The error in the seasonal variation of cloud regimes, and its breakdown into mean amplitude and time varying components, are quantified with a new metric. The seasonal variation of the CRE of the cloud regimes is relatively well simulated by the models in the tropics, but less well in the extra-tropics. The stratocumulus regime has the largest seasonal variation of shortwave CRE in the tropics, despite having a small magnitude in the climatological mean. Most of the models capture the temporal variation of the CRE reasonably well, with the main differences between models coming from the variation in amplitude. In the extra-tropics, most models fail to correctly represent both the amplitude and time variation of the CRE of congestus, frontal and stratocumulus regimes. The annual mean climatology of the CRE and its amplitude in the seasonal variation are both underestimated for the anvil regime in the tropics, the cirrus regime and the congestus regime in the extra-tropics. The models in this study that best capture the seasonal variation of the cloud regimes tend to have higher climate sensitivities. © 2012 Crown Copyright."
"55149724600;9248887100;22941802900;7003975505;","The transient versus the equilibrium response of sea ice to global warming",2013,"10.1175/JCLI-D-12-00492.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880834152&doi=10.1175%2fJCLI-D-12-00492.1&partnerID=40&md5=ad533417b04d935bda276a45ed33e47c","To examine the long-term stability of Arctic and Antarctic sea ice, idealized simulations are carried out with the climate model ECHAM5/Max Planck Institute Ocean Model (MPI-OM). Atmospheric CO2 concentration is increased over 2000 years from preindustrial levels to quadrupling, is then kept constant for 5940 years, is afterward decreased over 2000 years to preindustrial levels, and is finally kept constant for 3940 years. Despite these very slow changes, the sea ice response significantly lags behind the CO2 concentration change. This lag, which is caused by the ocean's thermal inertia, implies that the sea ice equilibrium response to increasing CO2 concentration is substantially underestimated by transient simulations. The sea ice response to CO2 concentration change is not truly hysteretic and is in principle reversible. The authors find no lag in the evolution of Arctic sea ice relative to changes in annual-mean Northern Hemisphere surface temperature. The summer sea ice cover changes linearly with respect to both CO2 concentration and temperature, while the Arctic winter sea ice cover shows a rapid transition to a very low sea ice coverage. This rapid transition of winter sea ice is associated with a sharply enhanced ice-albedo feedback and a sudden onset of convective-cloud feedback in the Arctic. The Antarctic sea ice cover retreats continuously without any rapid transition during the warming. Compared to Arctic sea ice, Antarctic sea ice shows a much more strongly lagged response to changes in CO2 concentration. It even lags behind the surface temperature change, which is caused by a different response of ocean deep convection during the warming and the cooling periods. © 2013 American Meteorological Society."
"57203694321;33867681300;7102953444;6602098362;15071907100;","Constraints on climate sensitivity from radiation patterns in climate models",2011,"10.1175/2010JCLI3403.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955074437&doi=10.1175%2f2010JCLI3403.1&partnerID=40&md5=9558f836f882bb8227aec54ba3a24784","The estimated range of climate sensitivity, the equilibrium warming resulting from a doubling of the atmospheric carbon dioxide concentration, has not decreased substantially in past decades. New statistical methods for estimating the climate sensitivity have been proposed and provide a better quantification of relative probabilities of climate sensitivity within the almost canonical range of 2- 4.5 K; however, large uncertainties remain, in particular for the upper bound. Simple indices of spatial radiation patterns are used here to establish a relationship between an observable radiative quantity and the equilibrium climate sensitivity. The indices are computed for the Coupled Model Intercomparison Project phase 3 (CMIP3) multimodel dataset and offer a possibility to constrain climate sensitivity by considering radiation patterns in the climate system. High correlations between the indices and climate sensitivity are found, for example, in the cloud radiative forcing of the incoming longwave surface radiation and in the clear-sky component of the incoming surface shortwave flux, the net shortwave surface budget, and the atmospheric shortwave attenuation variable b. The climate sensitivity was estimated from the mean of the indices during the years 1990-99 for the CMIP3 models. The surface radiative flux dataset from the Clouds and the Earth's Radiant Energy System (CERES) together with its top-of-atmosphere Energy Balanced and Filled equivalent (CERES EBAF) are used as a reference observational dataset, resulting in a best estimate for climate sensitivity of 3.3 K with a likely range of 2.7-4.0 K. A comparison with other satellite and reanalysis datasets show similar likely ranges and best estimates of 1.7-3.8 (3.3 K) [Earth Radiation Budget Experiment (ERBE)], 2.9-3.7 (3.3 K) [International Satellite Cloud Climatology Project radiative surface flux data (ISCCP-FD)], 2.8-4.1 (3.5 K) [NASA's Modern Era Retrospective-Analysis for Research and Application (MERRA)], 3.0-4.2 (3.6 K) [Japanese 25-yr Reanalysis (JRA-25)], 2.7-3.9 (3.4 K) [European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-Interim)], 3.0-4.0 (3.5 K) [ERA-40], and 3.1-4.7 (3.6 K) for the NCEP reanalysis. For each individual reference dataset, the results suggest that values for the sensitivity below 1.7 K are not likely to be consistent with observed radiation patterns given the structure of current climate models. For the aggregation of the reference datasets, the climate sensitivity is not likely to be below 2.9 K within the framework of this study, whereas values exceeding 4.5 K cannot be excluded from this analysis. While these ranges cannot be interpreted properly in terms of probability, they are consistent with other estimates of climate sensitivity and reaffirm that the current climatology provides a strong constraint on the lower bound of climate sensitivity even in a set of structurally different models. © 2011 American Meteorological Society."
"55332348600;26645289600;7402064802;","Analyzing the dependence of global cloud feedback on the spatial pattern of sea surface temperature change with a Green's function approach",2017,"10.1002/2017MS001096","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029445530&doi=10.1002%2f2017MS001096&partnerID=40&md5=820bc92c099cded22f1a3f1aee63a5e3","The spatial pattern of sea surface temperature (SST) changes has a large impact on the magnitude of cloud feedback. In this study, we seek a basic understanding of the dependence of cloud feedback on the spatial pattern of warming. Idealized experiments are carried out with an AGCM to calculate the change in global mean cloud-induced radiation anomalies (ΔRcloud) in response to imposed surface warming/cooling in 74 individual localized oceanic “patches”. Then the cloud feedback in response to a specific warming pattern can be approximated as the superposition of global cloud feedback in response to a temperature change in each region, weighted by the magnitude of the local temperature changes. When there is a warming in the tropical subsidence or extratropical regions, the local decrease of LCC results in a positive change in Rcloud. Conversely, warming in tropical ascent regions increases the free-tropospheric temperature throughout the tropics, thereby enhancing the inversion strength over remote regions and inducing positive global low-cloud cover (LCC) anomalies and negative Rcloud anomalies. The Green's function approach performs reasonably well in predicting the response of global mean ΔLCC and net ΔRcloud, but poorly for shortwave and longwave components of ΔRcloud due to its ineffectiveness in predicting middle and high cloud cover changes. The approach successfully captures the change of cloud feedback in response to time-evolving CO2-induced warming and captures the interannual variations in ΔRcloud observed by CERES. The results highlight important nonlocal influences of SST changes on cloud feedback. © 2017. The Authors."
"56692405300;57209597073;","Atlantic Multidecadal Variability in a model with an improved North Atlantic Current",2016,"10.1002/2016GL069815","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84982933573&doi=10.1002%2f2016GL069815&partnerID=40&md5=4838b8f1ad0cd0df17ee25cd786b5ad6","We examine the simulated Atlantic Multidecadal Variability (AMV) in a model that includes a correction for a long-standing problem with climate models, namely, the misplacement of the North Atlantic Current. The corrected model shows that in the warm AMV phase, heat is lost by the ocean in the northwestern part of the basin and gained by the ocean to the east, suggesting an advective transfer of heat by the midlatitude westerlies. The basin-wide response is consistent with a role for cloud feedback and is in broad agreement with estimates from observations but is poorly represented in the uncorrected model. The corrected model is then used to show that the ocean/atmosphere heat transfer is influenced by low-frequency variability in the overlying atmosphere. We also argue that changing ocean heat transport is an essential feature of our results. ©2016. American Geophysical Union. All Rights Reserved."
"55232897900;7402064802;26645289600;","Constraining the low-cloud optical depth feedback at middle and high latitudes using satellite observations",2016,"10.1002/2016JD025233","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983394793&doi=10.1002%2f2016JD025233&partnerID=40&md5=dadbdcf3c758432cfd3313bafec26409","The increase in cloud optical depth with warming at middle and high latitudes is a robust cloud feedback response found across all climate models. This study builds on results that suggest the optical depth response to temperature is timescale invariant for low-level clouds. The timescale invariance allows one to use satellite observations to constrain the models’ optical depth feedbacks. Three passive-sensor satellite retrievals are compared against simulations from eight models from the Atmosphere Model Intercomparison Project (AMIP) of the 5th Coupled Model Intercomparison Project (CMIP5). This study confirms that the low-cloud optical depth response is timescale invariant in the AMIP simulations, generally at latitudes higher than 40°. Compared to satellite estimates, most models overestimate the increase in optical depth with warming at the monthly and interannual timescales. Many models also do not capture the increase in optical depth with estimated inversion strength that is found in all three satellite observations and in previous studies. The discrepancy between models and satellites exists in both hemispheres and in most months of the year. A simple replacement of the models’ optical depth sensitivities with the satellites’ sensitivities reduces the negative shortwave cloud feedback by at least 50% in the 40°-70°S latitude band and by at least 65% in the 40°-70°N latitude band. Based on this analysis of satellite observations, we conclude that the low-cloud optical depth feedback at middle and high latitudes is likely too negative in climate models. © 2016. American Geophysical Union. All Rights Reserved."
"8631239200;6701562113;56188688000;7005751636;","Increasing the credibility of regional climate simulations by introducing subgrid-scale cloud-radiation interactions",2014,"10.1002/2014JD021504","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901725235&doi=10.1002%2f2014JD021504&partnerID=40&md5=97854ffe4b40325f3c5745d07fc6f0e9","The radiation schemes in the Weather Research and Forecasting (WRF) model have previously not accounted for the presence of subgrid-scale cumulus clouds, thereby resulting in unattenuated shortwave radiation, which can lead to overly energetic convection and overpredicted surface precipitation. This deficiency can become problematic when applying WRF as a regional climate model (RCM). Therefore, modifications were made to the WRF model to allow the Kain-Fritsch (KF) convective parameterization to provide subgrid-scale cloud fraction and condensate feedback to the rapid radiative transfer model-global (RRTMG) shortwave and longwave radiation schemes. The effects of these changes are analyzed via 3 year simulations using the standard and modified versions of WRF, comparing the modeled results with the North American Regional Reanalysis (NARR) and Climate Forecast System Reanalysis data, as well as with available data from the Surface Radiation Network and Clouds and Earth’s Radiant Energy System. During the summer period, including subgrid cloudiness estimated by KF in the RRTMG reduces the surface shortwave radiation, leading to less buoyant energy, which is reflected in a smaller diabatic convective available potential energy, thereby alleviating the overly energetic convection. Overall, these changes have reduced the overprediction of monthly, regionally averaged precipitation during summer for this RCM application, e.g., by as much as 49mm for the southeastern U.S., to within 0.7% of the NARR value of 221mm. These code modifications have been incorporated as an option available in the latest version of WRF (v3.6). © 2014. American Geophysical Union. All Rights Reserved."
"22959252400;7404829395;56537463000;","Long-term cloud change imprinted in seasonal cloud variation: More evidence of high climate sensitivity",2015,"10.1002/2015GL065911","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946549097&doi=10.1002%2f2015GL065911&partnerID=40&md5=31e6ebf841ccbbb28a0da29b35c496f3","The large spread of model equilibrium climate sensitivity (ECS) is mainly caused by the differences in the simulated marine boundary layer cloud (MBLC) radiative feedback. We examine the variations of MBLC fraction in response to the changes of sea surface temperature (SST) at seasonal and centennial time scales for 27 climate models that participated in the Coupled Model Intercomparison Project phase 3 and phase 5. We find that the intermodel spread in the seasonal variation of MBLC fraction with SST is strongly correlated with the intermodel spread in the centennial MBLC fraction change per degree of SST warming and that both are well correlated with ECS. Seven models that are consistent with the observed seasonal variation of MBLC fraction with SST at a rate -1.28 ± 0.56%/K all have ECS higher than the multimodel mean of 3.3 K yielding an ensemble-mean ECS of 3.9 K and a standard deviation of 0.45 K. Key Points Boundary cloud variations at seasonal and centennial scales are correlated Boundary cloud seasonal response is correlated with sensitivity Observations suggest a higher climate sensitivity than multimodel mean © 2015. American Geophysical Union. All Rights Reserved."
"8315173500;6506738607;8696069500;","Separation of contributions from radiative feedbacks to polar amplification on an aquaplanet",2012,"10.1175/JCLI-D-11-00246.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859950145&doi=10.1175%2fJCLI-D-11-00246.1&partnerID=40&md5=306f2dd1fdd32699a3ba07aded0c35fc","When climate is forced by a doubling of CO 2, a number of feedback processes are induced, such as changes of water vapor, clouds, and surface albedo. Here the CO 2 forcing and concomitant feedbacks are studied individually using a general circulation model coupled to an aquaplanet mixed layer ocean. A technique for fixing the radiative effects of moisture and clouds by reusing these variables from 1 × CO 2 and 2 × CO 2 equilibriumclimates in the model's radiation code allows for a detailed decomposition of forcings, feedbacks, and responses. The cloud feedback in this model is found to have a weak global average effect and surface albedo feedbacks have been eliminated. As in previous studies, the water vapor feedback is found to approximately double climate sensitivity, but while its radiative effect is strongly amplified at low latitudes, the resulting response displays about the same degree of polar amplification as the full all-feedbacks experiment. In fact, atmospheric energy transports are found to change in a way that yields the same meridional pattern of response as when the water vapor feedback is turned off. The authors conclude that while the water vapor feedback does not in itself lead to polar amplification by increasing the ratio of high- to low-latitude warming, it does double climate sensitivity both at low and high latitudes. A polar amplification induced by other feedbacks in the system, such as the Planck and lapse rate feedbacks here, is thus strengthened in the sense of increasing the difference in high- and low-latitude warming. © 2012 American Meteorological Society."
"57197802873;","Compensation between model feedbacks and curtailment of climate sensitivity",2010,"10.1175/2010JCLI3380.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954367350&doi=10.1175%2f2010JCLI3380.1&partnerID=40&md5=3ae9269477a8bded77f546d0c460a9c3","The spread in climate sensitivity obtained from 12 general circulation model runs used in the Fourth Assessment of the Intergovernmental Panel on Climate Change indicates a 95% confidence interval of 2.1°-5.5°C, but this reflects compensation between model feedbacks. In particular, cloud feedback strength negatively covaries with the albedo feedback as well as with the combined water vapor plus lapse rate feedback. If the compensation between feedbacks is removed, the 95% confidence interval for climate sensitivity expands to 1.9°-8.0°C. Neither of the quoted 95% intervals adequately reflects the understanding of climate sensitivity, but their differences illustrate that model interdependencies must be understood before model spread can be correctly interpreted. The degree of negative covariance between feedbacks is unlikely to result from chance alone. It may, however, result from the method by which the feedbacks were estimated, physical relationships represented in the models, or from conditioning the models upon some combination of observations and expectations. This compensation between model feedbacks-when taken together with indications that variations in radiative forcing and the rate of ocean heat uptake play a similar compensatory role in models-suggests that conditioning of the models acts to curtail the intermodel spread in climate sensitivity. Observations used to condition the models ought to be explicitly stated, or there is the risk of doubly calling on data for purposes of both calibration and evaluation. Conditioning the models upon individual expectation (e.g., anchoring to the Charney range of 3° ± 1.5°C), to the extent that it exists, greatly complicates statistical interpretation of the intermodel spread. © 2010 American Meteorological Society."
"35201039100;25943390200;","Long run surface temperature dynamics of an A-OGCM: The HadCM3 4×CO2 forcing experiment revisited",2009,"10.1007/s00382-009-0581-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957815304&doi=10.1007%2fs00382-009-0581-0&partnerID=40&md5=f10230aa3424cd2ab616eed1525ed699","The global mean surface temperature (GMST) response of HadCM3 to a 1,000 year 4×CO2 forcing is analysed using a transfer function methodology. We identify a third order transfer function as being an appropriate characterisation of the dynamic relationship between the radiative forcing input and GMST output of this Atmosphere-Ocean General Circulation Model (A-OGCM). From this transfer function the equilibrium climate sensitivity is estimated as 4.62 (3.92-11.88) K which is significantly higher than previously estimated for HadCM3. The response is also characterised by time constants of 4.5 (3.2-6.4),140 (78-191) and 1,476 (564-11,737) years. The fact that the longest time constant element is significantly longer than the 1,000 year simulation run makes estimation of this element of the response problematic, highlighting the need for significantly longer model runs to express A-OGCM behaviour fully. The transfer function is interpreted in relation to a three box global energy balance model. It was found that this interpretation gave rise to three fractions of ocean heat capacity with effective depths of 63.0 (46.7-85.4), 1291.7 (787.3-2,955.3) and 2,358.0 (661.3-17,283.8) meters of seawater, associated with three discrete time constants of 4.6 (3.2-6.5), 107.7 (68.9-144.3) and 537.1 (196.2-1,243.1) years. Given this accounts for approximately 94% of the ocean heat capacity in HadCM3, it appears HadCM3 could be significantly more well mixed than previously thought when viewed on the millennial timescale. © Springer-Verlag 2009."
"57193017893;7402480218;7202048112;7003495982;7005877775;7103373860;7003666669;56228672600;","Evaluating regional cloud-permitting simulations of the WRF model for the Tropical Warm Pool International Cloud Experiment (TWP-ICE), Darwin, 2006",2009,"10.1029/2009JD012729","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049125308&doi=10.1029%2f2009JD012729&partnerID=40&md5=5eb4e12717f706dd5dccaecccb332851","Data from the Tropical Warm Pool International Cloud Experiment (TWP-ICE) were used to evaluate Weather Research and Forecasting (WRF) model simulations with foci on the performance of three six-class bulk microphysical parameterizations (BMPs). Before the comparison with data from TWP-ICE, a suite of WRF simulations were carried out under an idealized condition, in which the other physical parameterizations were turned off. The idealized simulations were intended to examine the interaction of BMP at a ""cloud-resolving"" scale (250 m) with the nonhydrostatic dynamic core of the WRF model. The other suite of nested WRF simulations was targeted on the objective analysis of TWP-ICE at a ""cloud-permitting"" scale (quasi-convective resolving, 4 km). Wide ranges of discrepancies exist among the three BMPs when compared with ground-based and satellite remote sensing retrievals for TWP-ICE. Although many processes and associated parameters may influence clouds, it is strongly believed that atmospheric processes fundamentally govern the cloud feedbacks through the interactions between the atmospheric circulations, cloudiness, and the radiative and latent heating of the atmosphere. Based on the idealized experiments, we suggest that the discrepancy is a result of the different treatment of ice-phase microphysical processes (e.g., cloud ice, snow, and graupel). Because of the turn-off of the radiation and other physical parameterizations, the cloud radiation feedback is not studied in idealized experiments. On the other hand, the ""cloud-permitting"" experiments engage all physical parameterizations in the WRF model so that the radiative heating processes are considered together with other physical processes. Common features between these two experiment suites indicate that the major discrepancies among the three BMPs are similar. This strongly suggests the importance of ice-phase microphysics. To isolate the influence of cloud radiation feedback, we further carried out an additional suite of simulations, which turns off the interactions between cloud and radiation schemes. It is found that the cloud radiation feedback plays a secondary, but nonnegligible role in contributing to the wide range of discrepancies among the three BMPs. 2009 by the American Geophysical Union."
"55317190600;55720018700;55688930000;57193073844;55802246600;7006705919;","Black Carbon Amplifies Haze Over the North China Plain by Weakening the East Asian Winter Monsoon",2019,"10.1029/2018GL080941","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059870641&doi=10.1029%2f2018GL080941&partnerID=40&md5=c5389cda0a3f9cb3b3d22b05f589136d","Black carbon (BC) has previously been found to intensify haze in China by stabilizing the planetary boundary layer. With ocean, sea ice, and cloud feedbacks included in a global aerosol-climate model, we show that BC emitted from the North China Plain can be transported to the oceans, which in turn changes cloud structure and land-sea thermal contrast. As a result, East Asian winter monsoon wind speeds decrease over the North China Plain. This decrease causes air stagnation that can further intensify haze. Our results suggest that in addition to the local BC-induced interactions between aerosol and the planetary boundary layer, BC can also amplify haze in the North China Plain by weakening East Asian winter monsoon through ocean, sea ice, and cloud feedbacks. It implies that reducing BC emissions could have significant indirect benefits for air quality in the North China Plain. ©2018. American Geophysical Union. All Rights Reserved."
"34979885900;16678944000;55897579400;6701751765;6701316538;","A warm or a cold early Earth? New insights from a 3-D climate-carbon model",2017,"10.1016/j.epsl.2017.06.029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030544767&doi=10.1016%2fj.epsl.2017.06.029&partnerID=40&md5=6e4798c1e3594aa384a83cd4e3a690fd","Oxygen isotopes in marine cherts have been used to infer hot oceans during the Archean with temperatures between 60 °C (333 K) and 80 °C (353 K). Such climates are challenging for the early Earth warmed by the faint young Sun. The interpretation of the data has therefore been controversial. 1D climate modeling inferred that such hot climates would require very high levels of CO2 (2–6 bars). Previous carbon cycle modeling concluded that such stable hot climates were impossible and that the carbon cycle should lead to cold climates during the Hadean and the Archean. Here, we revisit the climate and carbon cycle of the early Earth at 3.8 Ga using a 3D climate-carbon model. We find that CO2 partial pressures of around 1 bar could have produced hot climates given a low land fraction and cloud feedback effects. However, such high CO2 partial pressures should not have been stable because of the weathering of terrestrial and oceanic basalts, producing an efficient stabilizing feedback. Moreover, the weathering of impact ejecta during the Late Heavy Bombardment (LHB) would have strongly reduced the CO2 partial pressure leading to cold climates and potentially snowball Earth events after large impacts. Our results therefore favor cold or temperate climates with global mean temperatures between around 8 °C (281 K) and 30 °C (303 K) and with 0.1–0.36 bar of CO2 for the late Hadean and early Archean. Finally, our model suggests that the carbon cycle was efficient for preserving clement conditions on the early Earth without necessarily requiring any other greenhouse gas or warming process. © 2017 Elsevier B.V."
"56567409000;23492864500;7201504886;","The role of precipitation and spatial organization in the response of trade-wind clouds to warming",2016,"10.1002/2015MS000568","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84973596894&doi=10.1002%2f2015MS000568&partnerID=40&md5=303428d89742eb71514ba2b52edd4300","Using highly resolved large-eddy simulations on two different domain sizes, we investigate the influence of precipitation and spatial organization on the thermodynamic structure of the trade-wind layer, under a uniform 4 K warming at constant relative humidity. In nonprecipitating simulations, the increased surface latent heat flux in the warmer climate produces a deeper and drier cloud layer with reduced cloud fractions between 1.5 and 4 km. Precipitation prevents the deepening and drying of the cloud layer in response to warming. Cloud fractions still decrease in the upper cloud layer, because stratiform outflow layers near cloud tops are less pronounced and because the larger liquid water contents are confined to narrower updrafts. Simulations on a 16-fold larger domain lead to the spatial organization of clouds into larger and deeper cloud clusters. The presence of deeper clouds results in a shallower, warmer, and drier trade-wind layer, with strongly reduced cloud cover. The warming response in the precipitating large-domain simulation nevertheless remains similar to the small-domain precipitating simulation. On the large domain, deeper clouds can also develop without precipitation, because moisture-convection feedbacks strengthen in the absence of cold-pool dynamics. Overall, total cloud cover and albedo decrease only slightly with warming in all cases. This demonstrates the robustness of shallow cumuli—in particular of cloud fraction near the lifting condensation level—to changes in the large-scale environment. © 2016. The Authors."
"7003521825;35234249500;57206487279;7003875226;","Equilibrium climate sensitivity in light of observations over the warming hiatus",2015,"10.1038/nclimate2573","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928572974&doi=10.1038%2fnclimate2573&partnerID=40&md5=e63eee4443ae96a2c4a4c8180fbd8eeb","A key uncertainty in projecting future climate change is the magnitude of equilibrium climate sensitivity (ECS), that is, the eventual increase in global annual average surface temperature in response to a doubling of atmospheric CO 2 concentration. The lower bound of the likely range for ECS given in the IPCC Fifth Assessment Report (AR5; refs,) was revised downwards to 1.5 °C, from 2 °C in its previous report, mainly as an effect of considering observations over the warming hiatus - the period of slowdown of global average temperature increase since the early 2000s. Here we analyse how estimates of ECS change as observations accumulate over time and estimate the contribution of potential causes to the hiatus. We find that including observations over the hiatus reduces the most likely value for ECS from 2.8 °C to 2.5 °C, but that the lower bound of the 90% range remains stable around 2 °C. We also find that the hiatus is primarily attributable to El Niño/Southern Oscillation-related variability and reduced solar forcing. © 2015 Macmillan Publishers Limited. All rights reserved."
"56278161100;26324818700;7202699757;7006518289;7005965757;12769875100;","Individual feedback contributions to the seasonality of surface warming",2014,"10.1175/JCLI-D-13-00658.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904479647&doi=10.1175%2fJCLI-D-13-00658.1&partnerID=40&md5=f3a0a6b4223ad37e68b95874ef69a7bb","Using the climate feedback response analysis method, the authors examine the individual contributions of the CO2 radiative forcing and climate feedbacks to the magnitude, spatial pattern, and seasonality of the transient surface warming response in a 1%yr-1 CO2 increase simulation of the NCAR Community Climate System Model, version 4 (CCSM4). The CO2 forcing and water vapor feedback warm the surface everywhere throughout the year. The tropical warming is predominantly caused by the CO2 forcing and water vapor feedback, while the evaporation feedback reduces the warming. Most feedbacks exhibit noticeable seasonal variations; however, their net effect has little seasonal variation due to compensating effects, which keeps the tropical warming relatively invariant all year long. The polar warming has a pronounced seasonal cycle, with maximum warming in fall/winter and minimum warming in summer. In summer, the large cancelations between the shortwave and longwave cloud feedbacks and between the surface albedo feedback warming and the cooling from the ocean heat storage/dynamics feedback lead to a warming minimum. In polar winter, surface albedo and shortwave cloud feedbacks are nearly absent due to a lack of insolation. However, the ocean heat storage feedback relays the polar warming due to the surface albedo feedback from summer to winter, and the longwave cloud feedback warms the polar surface. Therefore, the seasonal variations in the cloud feedback, surface albedo feedback, and ocean heat storage/dynamics feedback, directly caused by the strong annual cycle of insolation, contribute primarily to the large seasonal variation of polar warming. Furthermore, the CO2 forcing and water vapor and atmospheric dynamics feedbacks add to the maximum polar warming in fall/winter. © 2014 American Meteorological Society."
"36458535100;7202671706;7006328089;","Does Antarctic glaciation cool the world?",2013,"10.5194/cp-9-173-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873862548&doi=10.5194%2fcp-9-173-2013&partnerID=40&md5=317829901f6ad87c55beafeca1276f87","In this study, we compare the simulated climatic impact of adding an Antarctic ice sheet (AIS) to the ""greenhouse world"" of the Eocene and removing the AIS from the modern world. The modern global mean surface temperature anomaly (&Delta;T) induced by Antarctic Glaciation depends on the background CO2 levels and ranges from -1.22 to -0.18 K. The Eocene &Delta;T is nearly constant at ∼-0.25 K. We calculate an climate sensitivity parameter S[Antarctica] which we define as &Delta;T divided by the change in effective radiative forcing (&Delta;QAntarctica) which includes some fast feedbacks imposed by prescribing the glacial properties of Antarctica. <br><br> The main difference between the modern and Eocene responses is that a negative cloud feedback warms much of the Earth's surface as a large AIS is introduced in the Eocene, whereas this cloud feedback is weakly positive and acts in combination with positive sea-ice feedbacks to enhance cooling introduced by adding an ice sheet in the modern. Because of the importance of cloud feedbacks in determining the final temperature sensitivity of the AIS, our results are likely to be model dependent. Nevertheless, these model results suggest that the effective radiative forcing and feedbacks induced by the AIS did not significantly decrease global mean surface temperature across the Eocene-Oligocene transition (EOT -34.1 to 33.6 Ma) and that other factors like declining atmospheric CO2 are more important for cooling across the EOT. The results illustrate that the efficacy of AIS forcing in the Eocene is not necessarily close to one and is likely to be model and state dependent. This implies that using EOT paleoclimate proxy data by itself to estimate climate sensitivity for future climate prediction requires climate models and consequently these estimates will have large uncertainty, largely due to uncertainties in modelling low clouds. © Author(s) 2013."
"8877858700;7404240633;7006744538;7006577693;55806795100;13402835300;","Evaluation of clouds in access using the satellite simulator package cosp: Global, seasonal, and regional cloud properties",2013,"10.1029/2012JD018469","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880915814&doi=10.1029%2f2012JD018469&partnerID=40&md5=0e2cb59849a148154d7a7b3162e60491","Cloud properties from the Australian Community Climate and Earth System Simulator (ACCESS1.3) are evaluated using the Cloud Feedback Model Intercomparison Project (CFMIP) Observational Simulator Package (COSP). CloudSat, CALIPSO, and International Satellite Cloud Climatology Project (ISCCP) observations are used to evaluate the modeled cloud cover, condensate properties, and cloud optical depths for two seasons. The global distribution of cloud in the model is generally well represented with maximum high cloud in the tropics and low cloud over the eastern edges of the ocean basins. The model captures the observed position of the midlatitude storm track clouds and the modeled cloud top heights compare well with the observations in the upper troposphere. However, there is a lack of modeled midlevel cloud in the tropics and midlatitudes. The average high cloud cover in the Tropical Warm Pool region shows good agreement with CALIPSO. However, the modeled radar reflectivities and lidar scattering ratios are biased toward lower values, suggesting that the ice water contents and particles sizes of these clouds in the model are too small. Over the Southern Ocean the modeled cloud cover is underestimated due to a lack of mid- And low-level cloud. The low clouds over the Southern Ocean and the California stratocumulus clouds in the model have too little condensate and optical thickness and too much rain and drizzle. A sensitivity experiment showed that reducing the ice fall speeds improves aspects of the modeled cloud properties by increasing the frequency of occurrence of high clouds with large scattering ratios and optically thick low clouds. ACCESS1.3 has a reasonable representation of cloud. However, the underestimate of ice water content and particles sizes in high clouds and the too frequent occurrence of drizzle may impact the modeled cloud feedbacks and regional precipitation associated with current and perturbed climates. © 2012. American Geophysical Union."
"56218203200;7401945370;9838847000;25647939800;7003601758;","Comparison of high-level clouds represented in a global cloud system-resolving model with CALIPSO/CloudSat and geostationary satellite observations",2010,"10.1029/2009JD012371","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953170577&doi=10.1029%2f2009JD012371&partnerID=40&md5=02b73e97c5cbffc175ba267908c8414d","Vertical and horizontal distributions of high-level clouds (ice and snow) simulated in high-resolution global cloud system-resolving simulations by the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) are compared with satellite observations. Ice and snow data in a 1 week experiment by the NICAM 3.5 km grid mesh global simulation initiated at 0000 UTC 25 December 2006 are used in this study. The vertical structure of ice and snow represented by NICAM was compared with Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat observations. High-level clouds (cumulonimbus and cirrus type clouds) classified by the split window (11 and 12 μm) data on board geostationary meteorological satellites (GMSs) were used for comparison of the horizontal distributions of ice and snow in NICAM. The vertical distributions of ice and snow simulated by NICAM qualitatively agree well with those of cloud signals observed by CALIPSO and CloudSat. We computed corresponding cloud lidar backscatter coefficients and cloud radar reflectivity signals from ice and snow data of NICAM using Cloud Feedback Model Intercomparison Project (CFMIP) observational simulator packages. The contoured frequency by altitude diagram for the cloud lidar backscatter coefficients shows lower frequency at higher altitude of 8-14 km by NICAM than CALIOP observations. This suggests that the amount of ice is not well represented in NICAM. The simulated cloud radar reflectivity signals by NICAM indicated higher frequency at 8-10 km altitude than CloudSat observations, although there were some differences between over oceans and continents. This implies that the amount of snow is larger in NICAM simulations. The horizontal pattern of ice clouds (column-integrated ice and snow of greater than 0.01 kg/m2) in NICAM shows good agreement with that of high-level clouds identified by the split window analysis. During this 1 week simulation, 48-59% of ice clouds in NICAM matches with observed high-level clouds. The cross correlation between the spatial distributions of simulated ice clouds and satellite-observed high-level clouds is 0.40-0.51, and the equitable threat score is 0.31-0.45. Furthermore, temporal variations of column-integrated ice clouds in NICAM are compared with high-level clouds classified by the split window at the decaying stage of deep convection over the tropics. The results indicate that themean decaying speed of ice clouds of NICAM and high-level clouds by satellite observations agrees well for this analysis area and period, although the variances are larger in NICAM. This implies that the fall speed of snow in this NICAM experiment is appropriate to depict the decay of anvil clouds by compensating for the excess of snow in NICAMsimulations, when we assume that the decay of anvil clouds is largely controlled by the evaporation of ice and snow. Copyright 2010 by the American Geophysical Union."
"57158739200;6506970350;7202122235;","The relationship between radiative forcing and temperature: What do statistical analyses of the instrumental temperature record measure?",2006,"10.1007/s10584-006-9063-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33748916251&doi=10.1007%2fs10584-006-9063-0&partnerID=40&md5=c2a5770d99f2d8707a248f3f736fb1d2","Comparing statistical estimates for the long-run temperature effect of doubled CO2 with those generated by climate models begs the question, is the long-run temperature effect of doubled CO2 that is estimated from the instrumental temperature record using statistical techniques consistent with the transient climate response, the equilibrium climate sensitivity, or the effective climate sensitivity. Here, we attempt to answer the question, what do statistical analyses of the observational record measure, by using these same statistical techniques to estimate the temperature effect of a doubling in the atmospheric concentration of carbon dioxide from seventeen simulations run for the Coupled Model Intercomparison Project 2 (CMIP2). The results indicate that the temperature effect estimated by the statistical methodology is consistent with the transient climate response and that this consistency is relatively unaffected by sample size or the increase in radiative forcing in the sample. © Springer 2006."
"6603875926;10143232600;6603906450;","Adjustment and feedbacks in a global coupled ocean-atmosphere model",1997,"10.1007/s003820050179","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031396246&doi=10.1007%2fs003820050179&partnerID=40&md5=ab2fb73f21fdc293da5fcb0e91fab473","We report the analysis of two 20-year simulations performed with the low resolution version of the IPSL coupled ocean-atmosphere model, with no flux correction at the air-sea interface. The simulated climate is characterized by a global sea surface temperature warming of about 4°C in 20 years, driven by a net heat gain at the top of the atmosphere. Despite this drift, the circulation is quite realistic both in the ocean and the atmosphere. Several distinct periods are analyzed. The first corresponds to an adjustment during which the heat gain weakens both at the top of the atmosphere and at the ocean surface, and the tropical circulation is slightly modified. Then, the surface warming is enhanced by an increase of the greenhouse feedback. We show that the mechanisms involved in the model share common features with sensitivity experiments to greenhouse gases or to SST warming. At the top of the atmosphere, most of the longwave trapping in the atmosphere is driven by the tropical circulation. At the surface, the reduction of longwave cooling is a direct response to increased temperature and moisture content at low levels in the atmospheric model. During the last part of the simulation, a regulation occurs from evaporation at the surface and longwave cooling at TOA. Most of the model drift is attributed to a too large heating by solar radiation in middle and high latitudes. The reduction of the north-south temperature gradient, and the related changes in the meridional equator-to-pole ocean heat transport lead to a warming of equatorial and subtropical regions. This is also well demonstrated by the difference between the two simulations which differ only in the parametrization of sea-ice. When the sea-ice cover is not restored to climatology the model does not maintain sea-ice at high latitudes. The climate warms more rapidly and the water vapor and clouds feedback occurs earlier."
"57188924386;57203030873;6603925960;57193321831;56297151300;","Isolating the Liquid Cloud Response to Recent Arctic Sea Ice Variability Using Spaceborne Lidar Observations",2018,"10.1002/2017JD027248","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040225886&doi=10.1002%2f2017JD027248&partnerID=40&md5=7d92617f3abc5770dbe5024dfbea5b5f","While the radiative influence of clouds on Arctic sea ice is known, the influence of sea ice cover on Arctic clouds is challenging to detect, separate from atmospheric circulation, and attribute to human activities. Providing observational constraints on the two-way relationship between sea ice cover and Arctic clouds is important for predicting the rate of future sea ice loss. Here we use 8 years of CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) spaceborne lidar observations from 2008 to 2015 to analyze Arctic cloud profiles over sea ice and over open water. Using a novel surface mask to restrict our analysis to where sea ice concentration varies, we isolate the influence of sea ice cover on Arctic Ocean clouds. The study focuses on clouds containing liquid water because liquid-containing clouds are the most important cloud type for radiative fluxes and therefore for sea ice melt and growth. Summer is the only season with no observed cloud response to sea ice cover variability: liquid cloud profiles are nearly identical over sea ice and over open water. These results suggest that shortwave summer cloud feedbacks do not slow long-term summer sea ice loss. In contrast, more liquid clouds are observed over open water than over sea ice in the winter, spring, and fall in the 8 year mean and in each individual year. Observed fall sea ice loss cannot be explained by natural variability alone, which suggests that observed increases in fall Arctic cloud cover over newly open water are linked to human activities. ©2018. American Geophysical Union. All Rights Reserved."
"57196143493;36553486200;57188745140;","On the pattern of CO2 radiative forcing and poleward energy transport",2017,"10.1002/2017JD027221","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85031682698&doi=10.1002%2f2017JD027221&partnerID=40&md5=9de9743ff6726deef9dc6d9375efbb49","A set of general circulation model experiments are conducted to analyze how the poleward energy transport (PET) is related to the spatial pattern of CO2 radiative forcing. The effects of forcing pattern are affirmed by comparing the conventional doubling CO2 experiment, in which the forcing pattern is inhomogeneous, to a set of forcing homogenization experiments, in which the top of atmosphere (TOA), surface, or atmospheric forcing distribution is homogenized respectively. In addition, we separate and compare the effects of CO2 forcing to various feedbacks on atmospheric and oceanic PETs, by using a set of radiative kernels that we have developed for both TOA and surface radiation fluxes. The results here show that both the enhancement of atmospheric PET and weakening of oceanic PET during global warming are directly driven by the meridional gradients of the CO2 forcing. Interestingly, the overall feedback effect is to reinforce the forcing effect, mainly through the cloud feedback in the case of atmospheric PET and the albedo feedback in the case of the oceanic PET. Contrary to previous studies, we find that the water vapor feedback only has a weak effect on atmospheric PET. The Arctic warming amplification, which strongly affects atmospheric PET, is sensitive to the CO2 forcing pattern. ©2017. American Geophysical Union. All Rights Reserved."
"49664027700;35509639400;7004714030;36187387300;","Coupling between lower-tropospheric convective mixing and low-level clouds: Physical mechanisms and dependence on convection scheme",2016,"10.1002/2016MS000740","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85006810877&doi=10.1002%2f2016MS000740&partnerID=40&md5=a20be38c148f3d09842c4df9633d7141","Several studies have pointed out the dependence of low-cloud feedbacks on the strength of the lower-tropospheric convective mixing. By analyzing a series of single-column model experiments run by a climate model using two different convective parametrizations, this study elucidates the physical mechanisms through which marine boundary-layer clouds depend on this mixing in the present-day climate and under surface warming. An increased lower-tropospheric convective mixing leads to a reduction of low-cloud fraction. However, the rate of decrease strongly depends on how the surface latent heat flux couples to the convective mixing and to boundary-layer cloud radiative effects: (i) on the one hand, the latent heat flux is enhanced by the lower-tropospheric drying induced by the convective mixing, which damps the reduction of the low-cloud fraction, (ii) on the other hand, the latent heat flux is reduced as the lower troposphere stabilizes under the effect of reduced low-cloud radiative cooling, which enhances the reduction of the low-cloud fraction. The relative importance of these two different processes depends on the closure of the convective parameterization. The convective scheme that favors the coupling between latent heat flux and low-cloud radiative cooling exhibits a stronger sensitivity of low-clouds to convective mixing in the present-day climate, and a stronger low-cloud feedback in response to surface warming. In this model, the low-cloud feedback is stronger when the present-day convective mixing is weaker and when present-day clouds are shallower and more radiatively active. The implications of these insights for constraining the strength of low-cloud feedbacks observationally is discussed. © 2016. The Authors."
"7103180783;7402401574;57087451200;56228672600;7402969850;55737749900;","Abrupt summer warming and changes in temperature extremes over Northeast Asia since the mid-1990s: Drivers and physical processes",2016,"10.1007/s00376-016-5247-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84979079606&doi=10.1007%2fs00376-016-5247-3&partnerID=40&md5=41dbd80727b36a5c9e8aba401f5b2123","This study investigated the drivers and physical processes for the abrupt decadal summer surface warming and increases in hot temperature extremes that occurred over Northeast Asia in the mid-1990s. Observations indicate an abrupt increase in summer mean surface air temperature (SAT) over Northeast Asia since the mid-1990s. Accompanying this abrupt surface warming, significant changes in some temperature extremes, characterized by increases in summer mean daily maximum temperature (Tmax), daily minimum temperature (Tmin), annual hottest day temperature (TXx), and annual warmest night temperature (TNx) were observed. There were also increases in the frequency of summer days (SU) and tropical nights (TR). Atmospheric general circulation model experiments forced by changes in sea surface temperature (SST)/sea ice extent (SIE), anthropogenic greenhouse gas (GHG) concentrations, and anthropogenic aerosol (AA) forcing, relative to the period 1964–93, reproduced the general patterns of observed summer mean SAT changes and associated changes in temperature extremes, although the abrupt decrease in precipitation since the mid-1990s was not simulated. Additional model experiments with different forcings indicated that changes in SST/SIE explained 76% of the area-averaged summer mean surface warming signal over Northeast Asia, while the direct impact of changes in GHG and AA explained the remaining 24% of the surface warming signal. Analysis of physical processes indicated that the direct impact of the changes in AA (through aerosol–radiation and aerosol–cloud interactions), mainly related to the reduction of AA precursor emissions over Europe, played a dominant role in the increase in TXx and a similarly important role as SST/SIE changes in the increase in the frequency of SU over Northeast Asia via AA-induced coupled atmosphere–land surface and cloud feedbacks, rather than through a direct impact of AA changes on cloud condensation nuclei. The modelling results also imply that the abrupt summer surface warming and increases in hot temperature extremes over Northeast Asia since the mid-1990s will probably sustain in the next few decades as GHG concentrations continue to increase and AA precursor emissions over both North America and Europe continue to decrease. © 2016, Science Press."
"23492864500;8866821900;23768540500;13006055400;","Observed and modeled patterns of covariability between low-level cloudiness and the structure of the trade-wind layer",2015,"10.1002/2015MS000483","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959546807&doi=10.1002%2f2015MS000483&partnerID=40&md5=d9685e9d91ca5ace5783cfc9e940ff03","We present patterns of covariability between low-level cloudiness and the trade-wind boundary layer structure using long-term measurements at a site representative of dynamical regimes with moderate subsidence or weak ascent. We compare these with ECMWF's Integrated Forecast System and 10 CMIP5 models. By using single-time step output at a single location, we find that models can produce a fairly realistic trade-wind layer structure in long-term means, but with unrealistic variability at shorter-time scales. The unrealistic variability in modeled cloudiness near the lifting condensation level (LCL) is due to stronger than observed relationships with mixed-layer relative humidity (RH) and temperature stratification at the mixed-layer top. Those relationships are weak in observations, or even of opposite sign, which can be explained by a negative feedback of convection on cloudiness. Cloudiness near cumulus tops at the trade-wind inversion instead varies more pronouncedly in observations on monthly time scales, whereby larger cloudiness relates to larger surface winds and stronger trade-wind inversions. However, these parameters appear to be a prerequisite, rather than strong controlling factors on cloudiness, because they do not explain submonthly variations in cloudiness. Models underestimate the strength of these relationships and diverge in particular in their responses to large-scale vertical motion. No model stands out by reproducing the observed behavior in all respects. These findings suggest that climate models do not realistically represent the physical processes that underlie the coupling between trade-wind clouds and their environments in present-day climate, which is relevant for how we interpret modeled cloud feedbacks. © 2015. The Authors."
"23009736100;7004270629;","Long-memory effects in linear response models of Earth's temperature and implications for future global warming",2014,"10.1175/JCLI-D-13-00296.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904489103&doi=10.1175%2fJCLI-D-13-00296.1&partnerID=40&md5=5ba77d5250d6c3a6584ef6570d26dacd","A linearized energy-balance model for global temperature is formulated, featuring a scale-invariant longrange memory (LRM) response and stochastic forcing representing the influence on the ocean heat reservoir from atmospheric weather systems. The model is parameterized by an effective response strength, the stochastic forcing strength, and the memory exponent. The instrumental global surface temperature record and the deterministic component of the forcing are used to estimate these parameters by means of the maximumlikelihood method. The residual obtained by subtracting the deterministic solution from the observed record is analyzed as a noise process and shown to be consistent with a long-memory time series model and inconsistent with a short-memory model. By decomposing the forcing record in contributions from solar, volcanic, and anthropogenic activity one can estimate the contribution of each to twentieth-century global warming. The LRM model is applied with a reconstruction of the forcing for the last millenniumto predict the large-scale features of Northern Hemisphere temperature reconstructions, and the analysis of the residual also clearly favors the LRM model on millennium time scale. The decomposition of the forcing shows that volcanic aerosols give a considerably greater contribution to the cooling during the Little Ice Age than the reduction in solar irradiance associated with the Maunder Minimum in solar activity. TheLRMmodel implies a transient climate response in agreement with IPCC projections, but the stronger response on longer time scales suggests replacing the notion of equilibrium climate sensitivity by a time scale-dependent sensitivity. © 2014 American Meteorological Society."
"16029674800;57199907553;","Climate simulations and projections with a super-parameterized climate model",2014,"10.1016/j.envsoft.2014.06.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903700780&doi=10.1016%2fj.envsoft.2014.06.013&partnerID=40&md5=450e8664ca9416d95a4ba2c4e4236d3b","The mean climate and its variability are analyzed in a suite of numerical experiments with a fully coupled general circulation model in which subgrid-scale moist convection is explicitly represented through embedded 2D cloud-system resolving models. Control simulations forced by the present day, fixed atmospheric carbon dioxide concentration are conducted using two horizontal resolutions and validated against observations and reanalyses. The mean state simulated by the higher resolution configuration has smaller biases. Climate variability also shows some sensitivity to resolution but not as uniform as in the case of mean state. The interannual and seasonal variability are better represented in the simulation at lower resolution whereas the subseasonal variability is more accurate in the higher resolution simulation. The equilibrium climate sensitivity of the model is estimated from a simulation forced by an abrupt quadrupling of the atmospheric carbon dioxide concentration. The equilibrium climate sensitivity temperature of the model is 2.77. °C, and this value is slightly smaller than the mean value (3.37. °C) of contemporary models using conventional representation of cloud processes. The climate change simulation forced by the representative concentration pathway 8.5 scenario projects an increase in the frequency of severe droughts over most of the North America. © 2014 The Authors."
"55686667100;10241250100;10241462700;36701462300;55537426400;10243650000;7003420726;35580303100;8979277400;7102857642;","Using a multiphysics ensemble for exploring diversity in cloud-shortwave feedback in GCMs",2012,"10.1175/JCLI-D-11-00564.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865091777&doi=10.1175%2fJCLI-D-11-00564.1&partnerID=40&md5=20ba26eede1f7482db11d517d0091f30","This study proposes a systematic approach to investigate cloud-radiative feedbacks to climate change induced by an increase of CO2 concentrations in global climatemodels (GCMs). Based on two versions of theModel for Interdisciplinary Research on Climate (MIROC), which have opposite signs for cloud-shortwave feedback (DSWcld) and hence different equilibrium climate sensitivities (ECSs), hybrid models are constructed by replacing one or more parameterization schemes for cumulus convection, cloud, and turbulence between them. An ensemble of climate change simulations using a suite of eightmodels, called amultiphysics ensemble(MPE), is generated. TheMPE provides a range of ECS as wide as the CoupledModel Intercomparison Project phase 3 (CMIP3) multimodel ensemble and reveals a different magnitude and sign of DSWcld over the tropics, which is crucial for determining ECS. It is found that no single process controls DSWcld, but that the coupling of two processes does. Namely, changing the cloud and turbulence schemes greatly alters the mean and the response of low clouds, whereas replacing the convection and cloud schemes affects low and middle clouds over the convective region. For each of the circulation regimes, DSWcld and cloud changes in theMPE have a nonlinear, but systematic, relationship with the mean cloud amount, which can be constrained from satellite estimates. The analysis suggests a positive feedback over the subsidence regime and a near-neutral or weak negative DSWcld over the convective regime in these model configurations, which, however, may not be carried into other models. © 2012 American Meteorological Society."
"6603079840;7006452341;","Another look at climate sensitivity",2010,"10.5194/npg-17-113-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951861610&doi=10.5194%2fnpg-17-113-2010&partnerID=40&md5=8a16da9654b1044d833e575c0367edfe","We revisit a recent claim that the Earth's climate system is characterized by sensitive dependence to parameters; in particular, that the system exhibits an asymmetric, large-amplitude response to normally distributed feedback forcing. Such a response would imply irreducible uncertainty in climate change predictions and thus have notable implications for climate science and climate-related policy making. We show that equilibrium climate sensitivity in all generality does not support such an intrinsic indeterminacy; the latter appears only in essentially linear systems. The main flaw in the analysis that led to this claim is inappropriate linearization of an intrinsically nonlinear model; there is no room for physical interpretations or policy conclusions based on this mathematical error. Sensitive dependence nonetheless does exist in the climate system, as well as in climate models ĝ€"" albeit in a very different sense from the one claimed in the linear work under scrutiny ĝ€"" and we illustrate it using a classical energy balance model (EBM) with nonlinear feedbacks. EBMs exhibit two saddle-node bifurcations, more recently called ""tipping points,"" which give rise to three distinct steady-state climates, two of which are stable. Such bistable behavior is, furthermore, supported by results from more realistic, nonequilibrium climate models. In a truly nonlinear setting, indeterminacy in the size of the response is observed only in the vicinity of tipping points. We show, in fact, that small disturbances cannot result in a large-amplitude response, unless the system is at or near such a point. We discuss briefly how the distance to the bifurcation may be related to the strength of Earth's ice-albedo feedback. © 2010 Author(s)."
"36862677400;7202145115;","Interactions among cloud, water vapor, radiation, and large-scale circulation in the tropical climate. Part I: Sensitivity to uniform sea surface temperature changes",2003,"10.1175/1520-0442-16.10.1425","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038128200&doi=10.1175%2f1520-0442-16.10.1425&partnerID=40&md5=4fd899fd3cb01714efe20d919927dcf8","The responses of tropical clouds and water vapor to SST variations are investigated with simple numerical experiments. The fifth-generation Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) Mesoscale Model is used with doubly periodic boundary conditions and a uniform constant sea surface temperature (SST). The SST is varied and the equilibrium statistics of cloud properties, water vapor, and circulation at different temperatures are compared. The top of the atmosphere (TOA) radiative fluxes have the same sensitivities to SST as in observations averaged from 20°N to 20°S over the Pacific, suggesting that the model sensitivities are realistic. As the SST increases, the temperature profile approximately follows a moist-adiabatic lapse rate. The rain rate and cloud ice amounts increase with SST. The average relative humidity profile stays approximately constant, but the upper-tropospheric relative humidity increases slightly with SST. The clear-sky mean temperature and water vapor feedbacks have similar magnitudes to each other and opposite signs. The net clear-sky feedback is thus about equal to the lapse rate feedback, which is about -2 W m-2 K-1. The clear-sky outgoing longwave radiation (OLR) thus increases with SST, but the high cloud-top temperature is almost constant with SST, and the high cloud amount increases with SST. The result of these three effects is an increase of cloud longwave forcing with SST and a mean OLR that is almost independent of SST. The high cloud albedo remains almost constant with increasing SST, but the increase in high cloud area causes a negative shortwave cloud radiative forcing feedback, which partly cancels the longwave cloud feedback. The net radiation decreases slightly with SST, giving a small net negative feedback, implying a stable, but very sensitive climate."
"7004390019;7404105326;7402612084;57206416522;","Constraining climate model properties using optimal fingerprint detection methods",2001,"10.1007/s003820100175","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035669674&doi=10.1007%2fs003820100175&partnerID=40&md5=c513b6edbd2e27a4519beadadac1327f","We present a method for constraining key properties of the climate system that are important for climate prediction (climate sensitivity and rate of heat penetration into the deep ocean) by comparing a model's response to known forcings over the twentieth century against climate observations for that period. We use the MIT 2D climate model in conjunction with results from the Hadley Centre's coupled atmosphere-ocean general circulation model (AOGCM) to determine these constraints. The MIT 2D model, which is a zonally averaged version of a 3D GCM, can accurately reproduce the global-mean transient response of coupled AOGCMs through appropriate choices of the climate sensitivity and the effective rate of diffusion of heat anomalies into the deep ocean. Vertical patterns of zonal mean temperature change through the troposphere and lower stratosphere also compare favorably with those generated by 3-D GCMs. We compare the height-latitude pattern of temperature changes as simulated by the MIT 2D model with observed changes, using optimal finger-print detection statistics. Using a linear regression model as in Allen and Tett this approach yields an objective measure of model-observation goodness-of-fit (via the residual sum of squares weighted by differences expected due to internal variability). The MIT model permits one to systematically vary the model's climate sensitivity (by varying the strength of the cloud feedback) and rate of mixing of heat into the deep ocean and determine how the goodness-of-fit with observations depends on these factors. This provides an efficient framework for interpreting detection and attribution results in physical terms. With aerosol forcing set in the middle of the IPCC range, two sets of model parameters are rejected as being implausible when the model response is compared with observations. The first set corresponds to high climate sensitivity and slow heat uptake by the deep ocean. The second set corresponds to low sensitivities for all magnitudes of heat uptake. These results demonstrate that fingerprint patterns must be carefully chosen, if their detection is to reduce the uncertainty of physically important model parameters which affect projections of climate change."
"7004828383;6507797248;56283400100;6506101358;6603906450;","Cloud processes associated with past and future climate changes",1998,"10.1007/s003820050220","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031817432&doi=10.1007%2fs003820050220&partnerID=40&md5=93670addf01c072721373a3127fbe066","To investigate the cloud response during cold and warm periods, we have performed simulations of the Last Glacial Maximum (LGM-21ky BP) and of double CO2 concentration using the LMD AGCM model. We observe that the thermal characteristics of these two climates are opposite, but the cloud response is more complex and does not display the same symmetry When doubling the CO2, the warming of the troposphere and the cooling of the stratosphere are clearly linked with a reduction in low-level clouds and an increase of high-level clouds associated with relative humidity changes. For the LGM, the cloud response is more complex. In the inter tropical region, we show that the Hadley cell is reinforced during LGM (+20%) whereas it is reduced (-10%) for the double CO2 experiments. The most important feature is that we observe an enlarged Hadley cell for LGM climate which strongly modifies the atmospheric dynamics and water transport. For LGM conditions, the cloud response is then mostly driven by these dynamical changes at low latitudes though at high latitudes the thermal changes explain a large part of the cloud response. Two different versions of the model, using different parametrizations for the precipitation show that cloud feedbacks may act differently for cold and warm climates; and that the cloud response may be more complex that previously expected, but also indicate that the details of these effects are model dependent."
"36018467800;9248887100;8696069500;57201945714;7003823107;","On the potential for abrupt Arctic winter sea ice loss",2016,"10.1175/JCLI-D-15-0466.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85013696787&doi=10.1175%2fJCLI-D-15-0466.1&partnerID=40&md5=d6a2bd9d2369534082335f696dd009b3","The authors examine the transition from a seasonally ice-covered Arctic to an Arctic Ocean that is sea ice free all year round under increasing atmospheric CO2 levels. It is shown that in comprehensive climate models, such loss of Arctic winter sea ice area is faster than the preceding loss of summer sea ice area for the same rate of warming. In two of the models, several million square kilometers of winter sea ice are lost within only one decade. It is shown that neither surface albedo nor cloud feedbacks can explain the rapid winter ice loss in the climate model MPI-ESM by suppressing both feedbacks in the model. The authors argue that the large sensitivity of winter sea ice area in the models is caused by the asymmetry between melting and freezing: an ice-free summer requires the complete melt of even the thickest sea ice, which is why the perennial ice coverage decreases only gradually as more and more of the thinner ice melts away. In winter, however, sea ice areal coverage remains high as long as sea ice still forms, and then drops to zero wherever the ocean warms sufficiently to no longer form ice during winter. The loss of basinwide Arctic winter sea ice area, however, is still gradual in most models since the threshold mechanism proposed here is reversible and not associated with the existence of multiple steady states. As this occurs in every model analyzed here and is independent of any specific parameterization, it is likely to be relevant in the real world. © 2016 American Meteorological Society."
"56572170400;55758131600;35547807400;25030776200;7004169476;7404105326;","Model structure in observational constraints on transient climate response",2015,"10.1007/s10584-015-1384-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84933675195&doi=10.1007%2fs10584-015-1384-4&partnerID=40&md5=31c384bd2a59df25d5ba060bb2edaf25","The transient climate response (TCR) is a highly policy-relevant quantity in climate science. We show that recent revisions to TCR in the IPCC 5th Assessment Report have more impact on projections over the next century than revisions to the equilibrium climate sensitivity (ECS). While it is well known that upper bounds on ECS are dependent on model structure, here we show that the same applies to TCR. Our results use observations of the planetary energy budget, updated radiative forcing estimates and a number of simple climate models. We also investigate the ratio TCR:ECS, or realised warming fraction (RWF), a highly policy-relevant quantity. We show that global climate models (GCMs) don’t sample a region of low TCR and high RWF consistent with observed climate change under all simple models considered. Whether the additional constraints from GCMs are sufficient to rule out these low climate responses is a matter for further research. © 2015, Springer Science+Business Media Dordrecht."
"55332348600;7003266014;26645289600;7403931916;55802031900;","Cirrus feedback on interannual climate fluctuations",2014,"10.1002/2014GL062095","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921831180&doi=10.1002%2f2014GL062095&partnerID=40&md5=1b90534c8808c33d4f6918e6cd314eca","Cirrus clouds are not only important in determining the current climate but also play an important role in climate change and variability. Analysis of satellite observations shows that the amount and altitude of cirrus clouds (cloud optical depth &lt; 3.6, cloud top pressure &lt; 440 hPa) increase in response to interannual surface warming. Using cirrus cloud radiative kernels, the magnitude of the interannual cirrus feedback is estimated to be 0.20 ± 0.21 W/m2/°C, which represents an important component of the cloud feedback. Thus, cirrus clouds are likely to act as a positive feedback on interannual climate fluctuations, by reducing the Earth's ability to radiate longwave radiation to space in response to planetary surface warming. Most of the cirrus feedback comes from increasing cloud amount in the tropical tropopause layer (TTL) and subtropical upper troposphere. Key Points Cirrus clouds likely contribute a positive feedback on climate fluctuationsCirrus cloud amount and altitude increase in response to surface warmingCirrus clouds represent an important component of the cloud feedback ©2014. American Geophysical Union. All Rights Reserved."
"57196143493;57195636034;","The implication of radiative forcing and feedback for meridional energy transport",2014,"10.1002/2013GL059079","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84894752824&doi=10.1002%2f2013GL059079&partnerID=40&md5=c15eedfc76e2907f847e0e8fa2cc34ad","The distributions of radiative forcing and feedback in the Coupled Model Intercomparison Project phase 5 abrupt4xCO2 and Historical experiments are diagnosed, with a focus on their effects on the zonal mean structure of the top-of-the-atmosphere radiation anomalies and implications for the meridional energy transport. It is found that because the greenhouse gas longwave forcing peaks in the low latitudes, it reinforces the equator-to-pole net radiation gradient and accounts for the increase in the poleward energy transport in both hemispheres under global warming. The shortwave forcing by aerosol, ozone, etc. peaks in the Northern Hemisphere and instead implies an interhemispheric energy transport. Although the water vapor feedback also reinforces the equator-to-pole gradient of the net radiation, the temperature and albedo feedback act against it. The feedback tend to offset the zonal mean radiation anomaly caused by the forcing, although the overall feedback effect on the energy transport is rather uncertain, mainly due to the uncertainty in the cloud feedback. Key Points CO2 forcing increases meridional gradient in net radiation Forcing, rather than feedback, accounts for enhanced poleward energy transport Aerosol forcing accounts for an inter-hemispheric transport anomaly ©2014. American Geophysical Union. All Rights Reserved."
"56005080300;23082420800;8696069500;57197233116;7201504886;","Simulating the role of subtropical stratocumulus clouds in driving Pacific climate variability",2014,"10.1175/JCLI-D-13-00548.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903398794&doi=10.1175%2fJCLI-D-13-00548.1&partnerID=40&md5=1e6ff096dc77f31888a28513f9f059d4","This study examines the influence of the northeast and southeast Pacific subtropical stratocumulus cloud regions on the modes of Pacific climate variability simulated by an atmospheric general circulation model (ECHAM6) coupled to a slab ocean. The sensitivity of cloud liquid water to underlying SST is changed in the radiation module of the atmospheric model to increase the strength of positive low-cloud feedback in the two regions. Enhanced low-cloud feedback increases the persistence and variance of the leading modes of climate variability at decadal and longer time scales. Additional integrations show that the southeast Pacific influences climate variability in the equatorial ENSO region, whereas the effects of the northeast Pacific remain confined to the North Pacific. The results herein suggest that a positive feedback among SST, cloud cover, and large-scale atmospheric circulation can explain decadal climate variability in the Pacific Ocean. In particular, cloud feedbacks over the subtropical stratocumulus regions set the time scale of climate variability. A proper representation of low-level cloud feedbacks in the subtropical stratocumulus regions could therefore improve the simulation of Pacific climate variability. © 2014 American Meteorological Society."
"6507224579;7402887257;7004247643;","Can a convective cloud feedback help to eliminate winter sea ice at high CO2 concentrations?",2009,"10.1175/2009JCLI2854.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77649296808&doi=10.1175%2f2009JCLI2854.1&partnerID=40&md5=2e6fe3d69c71a35e53a890be986bb2f8","Winter sea ice dramatically cools the Arctic climate during the coldest months of the year and may have remote effects on global climate as well. Accurate forecasting of winter sea ice has significant social and economic benefits. Such forecasting requires the identification and understanding of all of the feedbacks that can affect sea ice. A convective cloud feedback has recently been proposed in the context of explaining equable climates, for example, the climate of the Eocene, which might be important for determining future winter sea ice. In this feedback, CO2-initiated warming leads to sea ice reduction, which allows increased heat and moisture fluxes from the ocean surface, which in turn destabilizes the atmosphere and leads to atmospheric convection. This atmospheric convection produces optically thick convective clouds and increases high-altitude moisture levels, both of which trap outgoing longwave radiation and therefore result in further warming and sea ice loss. Here it is shown that this convective cloud feedback is active at high CO2 during polar night in the coupled ocean-sea ice-land-atmosphere global climate models used for the 1% yr-1 CO2 increase to the quadrupling (1120 ppm) scenario of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. At quadrupledCO2, model forecasts of maximum seasonal (March) sea ice volume are found to be correlated with polar winter cloud radiative forcing, which the convective cloud feedback increases. In contrast, sea ice volume is entirely uncorrelated with model global climate sensitivity. It is then shown that the convective cloud feedback plays an essential role in the elimination of March sea ice at quadrupled CO2 in NCAR's Community Climate System Model (CCSM), one of the IPCC models that loses sea ice year-round at thisCO2 concentration. A new method is developed to disable the convective cloud feedback in the Community Atmosphere Model (CAM), the atmospheric component of CCSM, and to show that March sea ice cannot be eliminated in CCSM at CO2 = 1120 ppm without the aide of the convective cloud feedback. © 2009 American Meteorological Society."
"15032788000;8502218100;7103119050;57196263581;","Acceleration by aerosol of a radiative-thermodynamic cloud feedback influencing Arctic surface warming",2009,"10.1029/2009GL040195","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049106104&doi=10.1029%2f2009GL040195&partnerID=40&md5=117a84ea88a68d206e92e8e63342bc10","Recent work suggests that short-lived pollutants with mid-latitude origins are contributing to observed warming of the Arctic surface. Candidate mechanisms include an ""aerosol indirect effect"" associated with increases in cloud longwave emissivity: small cloud droplets associated with polluted conditions are efficient absorbers and emitters of longwave radiation. Here, we argue that the associated surface warming can be temporarily amplified: particulate pollution, by increasing cloud emissivity, additionally accelerates a preexisting positive feedback loop between cloud top radiative cooling and new droplet condensation. Copyright 2009 by the American Geophysical Union."
"7007021059;6603196127;7102875645;","Radiative damping of annual variation in global mean surface temperature: Comparison between observed and simulated feedback",2005,"10.1007/s00382-005-0002-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23844490151&doi=10.1007%2fs00382-005-0002-y&partnerID=40&md5=d7423dc65fc81ed5af22d46a26c18e2c","The sensitivity of the global climate is essentially determined by the radiative damping of the global mean surface temperature anomaly through the outgoing radiation from the top of the atmosphere (TOA). Using the TOA fluxes of terrestrial and reflected solar radiation obtained from the Earth radiation budget experiment (ERBE), this study estimates the magnitude of the overall feedback, which modifies the radiative damping of the annual variation of the global mean surface temperature, and compare it with model simulations. Although the pattern of the annually varying anomaly is quite different from that of the global warming, the analysis conducted here may be used for assessing the systematic bias of the feedback that operates on the CO2-induced warming of the surface temperature. In the absence of feedback effect, the outgoing terrestrial radiation at the TOA is approximately follows the Stefan-Boltzmann's fourth power of the planetary emission temperature. However, it deviates significantly from the blackbody radiation due to various feedbacks involving water vapor and cloud cover. In addition, the reflected solar radiation is altered by the feedbacks involving sea ice, snow and cloud, thereby affecting the radiative damping of surface temperature. The analysis of ERBE reveals that the radiative damping is weakened by as much as 70% due to the overall effect of feedbacks, and is only 30% of what is expected for the blackbody with the planetary emission temperature. Similar feedback analysis is conducted for three general circulation models of the atmosphere, which was used for the study of cloud feedback in the preceding study. The sign and magnitude of the overall feedback in the three models are similar to those of the observed. However, when it is subdivided into solar and terrestrial components, they are quite different from the observation mainly due to the failure of the models to simulate individually the solar and terrestrial components of the cloud feedback. It is therefore desirable to make the similar comparison not only for the overall feedback but also for its individual components such as albedo- and cloud-feedbacks. Although the pattern of the annually-varying anomaly is quite different from that of global warming, the methodology of the comparative analysis presented here may be used for the identification of the systematic bias of the overall feedback in a model. A proposal is made for the estimation of the best guess value of climate sensitivity using the outputs from many climate models submitted to the Intergovernmental panel on Climate Change. © Springer-Verlag 2005."
"57205868741;","Scaling fluctuation analysis and statistical hypothesis testing of anthropogenic warming",2014,"10.1007/s00382-014-2128-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899987393&doi=10.1007%2fs00382-014-2128-2&partnerID=40&md5=c28040f2bfe63b906650ca99bc12a168","Although current global warming may have a large anthropogenic component, its quantification relies primarily on complex General Circulation Models (GCM's) assumptions and codes; it is desirable to complement this with empirically based methodologies. Previous attempts to use the recent climate record have concentrated on ""fingerprinting"" or otherwise comparing the record with GCM outputs. By using CO2 radiative forcings as a linear surrogate for all anthropogenic effects we estimate the total anthropogenic warming and (effective) climate sensitivity finding: ΔT anth = 0.87 ± 0.11 K, λ2xCO2,eff= 3.08 ± 0.58 K. These are close the IPPC AR5 values ΔT anth = 0.85 ± 0.20 K and λ2xCO2= 1.5 - 4.5 K (equilibrium) climate sensitivity and are independent of GCM models, radiative transfer calculations and emission histories. We statistically formulate the hypothesis of warming through natural variability by using centennial scale probabilities of natural fluctuations estimated using scaling, fluctuation analysis on multiproxy data. We take into account two nonclassical statistical features-long range statistical dependencies and ""fat tailed"" probability distributions (both of which greatly amplify the probability of extremes). Even in the most unfavourable cases, we may reject the natural variability hypothesis at confidence levels &gt;99 %. © 2014 Springer-Verlag Berlin Heidelberg."
"56048942300;7201425334;35232873900;16025402200;","Atmospheric teleconnection mechanisms of extratropical North Atlantic SST influence on Sahel rainfall",2014,"10.1007/s00382-014-2094-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84894543687&doi=10.1007%2fs00382-014-2094-8&partnerID=40&md5=9897135f526e90927c4fe568e23bacd1","Extratropical North Atlantic cooling has been tied to droughts over the Sahel in both paleoclimate observations and modeling studies. This study, which uses an atmospheric general circulation model (GCM) coupled to a slab ocean model that simulates this connection, explores the hypothesis that the extratropical North Atlantic cooling causes the Sahel droughts via an atmospheric teleconnection mediated by tropospheric cooling. The drying is also produced in a regional climate model simulation of the Sahel when reductions in air temperature (and associated geopotential height and humidity changes) from the GCM simulation are imposed as the lateral boundary conditions. This latter simulation explicitly demonstrates the central role of tropospheric cooling in mediating the atmospheric teleconnection from extratropical North Atlantic cooling. Diagnostic analyses are applied to the GCM simulation to infer teleconnection mechanisms. An analysis of top of atmosphere radiative flux changes diagnosed with a radiative kernel technique shows that extratropical North Atlantic cooling is augmented by a positive low cloud feedback and advected downstream, cooling Europe and North Africa. The cooling over North Africa is further amplified by a reduced greenhouse effect from decreased atmospheric specific humidity. A moisture budget analysis shows that the direct moisture effect and monsoon weakening, both tied to the ambient cooling and resulting circulation changes, and feedbacks by vertical circulation and evaporation augment the rainfall reduction. Cooling over the Tropical North Atlantic in response to the prescribed extratropical cooling also augments the Sahel drying. Taken together, they suggest a thermodynamic pathway for the teleconnection. The teleconnection may also be applicable to understanding the North Atlantic influence on Sahel rainfall over the twentieth century. © 2014, Springer-Verlag Berlin Heidelberg."
"6507224579;7004247643;","Controls on the activation and strength of a high-latitude convective cloud feedback",2009,"10.1175/2008JAS2840.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549114592&doi=10.1175%2f2008JAS2840.1&partnerID=40&md5=ab7770d549d55d421f03dec41e7bb1a6","Previous work has shown that a convective cloud feedback can greatly increase high-latitude surface temperature upon the removal of sea ice and can keep sea ice from forming throughout polar night. This feedback activates at increased greenhouse gas concentrations. It may help to explain the warm ""equable climates"" of the late Cretaceous and early Paleogene eras (∼100 to ∼35 million years ago) and may be relevant for future climate under global warming. Here, the factors that determine the critical threshold CO2 concentration at which this feedback is active and the magnitude of the warming caused by the feedback are analyzed using both a highly idealized model and NCAR's single-column atmospheric model (SCAM) run under Arctic-like conditions. The critical CO2 is particularly important because it helps to establish the relevance of the feedback for past and future climates. Both models agree that increased heat flux into the high latitudes at low altitudes generally decreases the critical CO2. Increases in oceanic heat transport and in solar radiation absorbed during the summer should cause a sharp decrease in the critical CO2, but the effect of increases in atmospheric heat transport depends on its vertical distribution. It is furthermore found (i) that if the onset of convection produces more clouds and moisture, the critical CO2 should decrease, and the maximum temperature increase caused by the convective cloud feedback should increase and (ii) that reducing the depth of convection reduces the critical CO2 but has little effect on the maximum temperature increase caused by the convective cloud feedback. These results should help with interpretation of the strength and onset of the convective cloud feedback as found, for example, in Intergovernmental Panel on Climate Change (IPCC) coupled ocean - atmosphere models with different cloud and convection schemes. © 2009 American Meteorological Society."
"56676874900;6602230939;","Potential biases in feedback diagnosis from observational data: A simple model demonstration",2008,"10.1175/2008JCLI2253.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56349107460&doi=10.1175%2f2008JCLI2253.1&partnerID=40&md5=4a3d095f97f1c21edebdab0a976064c3","Feedbacks are widely considered to be the largest source of uncertainty in determining the sensitivity of the climate system to increasing anthropogenic greenhouse gas concentrations, yet the ability to diagnose them from observations has remained controversial. Here a simple model is used to demonstrate that any nonfeedback source of top-of-atmosphere radiative flux variations can cause temperature variability, which then results in a positive bias in diagnosed feedbacks. This effect is demonstrated with daily random flux variations, as might be caused by stochastic fluctuations in low cloud cover. The daily noise in radiative flux then causes interannual and decadal temperature variations in the model's 50-m-deep swamp ocean. The amount of bias in the feedbacks diagnosed from time-averaged model output depends upon the size of the nonfeedback flux variability relative to the surface temperature variability, as well as the sign and magnitude of the specified (true) feedback. For model runs producing monthly shortwave flux anomaly and temperature anomaly statistics similar to those measured by satellites, the diagnosed feedbacks have positive biases generally in the range -0.3 to 0.8 W m2 K-61. These results suggest that current observational diagnoses of cloud feedback - and possibly other feedbacks - could be significantly biased in the positive direction. © 2008 American Meteorological Society."
"36127012800;7005449794;","Modeling the biosphere-atmosphere system: The impact of the subgrid variability in rainfall interception",2000,"10.1175/1520-0442(2000)013<2887:MTBAST>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034253121&doi=10.1175%2f1520-0442%282000%29013%3c2887%3aMTBAST%3e2.0.CO%3b2&partnerID=40&md5=85b49b404e09175b5c3d08e800643d9b","Subgrid variability in rainfall distribution has been widely recognized as an important factor to include in the representation of land surface hydrology within climate models. In this paper, using West Africa as a case study, the impact of the subgrid variability in rainfall interception on the modeling of the biosphere-atmosphere system is investigated. According to the authors' results, when neglecting the rainfall spatial variability, even if the impact on the total evapotranspiration is negligible, significant errors may result in the representation of surface hydrological processes and surface energy balance. These findings are consistent with the results of previous studies. However, in this paper, this issue is further explored and it is demonstrated that the extent of the resulting errors is not limited to the land surface processes. They extend to the atmosphere via the low-level cloud feedback to impact solar radiation, boundary layer energy, atmospheric circulation, and the distribution of precipitation. The same errors also propagate into the biosphere through vegetation dynamics and can eventually lead to a significantly different biosphere-atmosphere equilibrium state. This study provides a good example for the need to have physical realism in modeling the subgrid variability and most other details of the complex biosphere-atmosphere-ocean system.Subgrid variability in rainfall distribution has been widely recognized as an important factor to include in the representation of land surface hydrology within climate models. In this paper, using West Africa as a case study, the impact of the subgrid variability in rainfall interception on the modeling of the biosphere-atmosphere system is investigated. According to the authors' results, when neglecting the rainfall spatial variability, even if the impact on the total evapotranspiration is negligible, significant errors may result in the representation of surface hydrological processes and surface energy balance. These findings are consistent with the results of previous studies. However, in this paper, this issue is further explored and it is demonstrated that the extent of the resulting errors is not limited to the land surface processes. They extend to the atmosphere via the low-level cloud feedback to impact solar radiation, boundary layer energy, atmospheric circulation, and the distribution of precipitation. The same errors also propagate into the biosphere through vegetation dynamics and can eventually lead to a significantly different biosphere-atmosphere equilibrium state. This study provides a good example for the need to have physical realism in modeling the subgrid variability and most other details of the complex biosphere-atmosphere-ocean system."
"7401513228;","A dynamical stabilizer in the climate system: A mechanism suggested by a simple model",1999,"10.3402/tellusa.v51i3.13458","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032883258&doi=10.3402%2ftellusa.v51i3.13458&partnerID=40&md5=705ae4d7e1cf0e74fe0e025d37e4ac31","A simple zonally averaged hemispheric model of the climate system is constructed, based on energy equations for two ocean basins separated at 30°latitude with the surface fluxes calculated explicitly. A combination of empirical input and theoretical calculation is used to determine an annual mean equilibrium climate for the model and to study its stability with respect to small perturbations. The insolation, the mean albedos and the equilibrium temperatures for the two model zones are prescribed from observation. The principal agent of interaction between the zones is the vertically integrated poleward transport of atmospheric angular momentum across their common boundary. This is parameterized using an empirical formula derived from a multiyear atmospheric data set. The surface winds are derived from the angular momentum transport assuming the atmosphere to be in a state of dynamic balance on the climatic timescales of interest. A further assumption that the air-sea temperature difference and low level relative humidity remain fixed at their mean observed values then allows the surface fluxes of latent and sensible heat to be calculated. Results from a radiative model, which show a positive lower tropospheric water vapour/infrared radiative feedback on SST perturbations in both zones, are used to calculate the net upward infrared radiative fluxes at the surface. In the model's equilibrium climate, the principal processes balancing the solar radiation absorbed at the surface are evaporation in the tropical zone and net infrared radiation in the extratropical zone. The stability of small perturbations about the equilibrium is studied using a linearized form of the ocean energy equations. Ice-albedo and cloud feedbacks are omitted and attention is focussed on the competing effects of the water vapour/infrared radiative feedback and the turbulent surface flux and oceanic heat transport feedbacks associated with the angular momentum cycle. The perturbation equations involve inter-zone coupling and have coefficients dependent on the values of the equilibrium fluxes and the sensitivity of the angular momentum transport. Analytical solutions for the perturbations are obtained. These provide criteria for the stability of the equilibrium climate. If the evaporative feedback on SST perturbations is omitted, the equilibrium climate is unstable due to the influence of the water vapour/infrared radiative feedback, which dominates over the effects of the sensible heat and ocean heat transport feedbacks. The inclusion of evaporation gives a negative feedback which is of sufficient strength to stabilize the system. The stabilizing mechanism involves wind and humidity factors in the evaporative fluxes that are of comparable magnitude. Both factors involve the angular momentum transport. In including angular momentum and calculating the surface fluxes explicitly, the model presented here differs from the many simple climate models based on the Budyko-Sellers formulation. In that formulation, an atmospheric energy balance equation is used to eliminate surface fluxes in favour of top-of-the-atmosphere radiative fluxes and meridional atmospheric energy transports. In the resulting models, infrared radiation appears as a stabilizing influence on SST perturbations and the dynamical stabilizing mechanism found here cannot be identified."
"57203200427;37099000200;57218280315;55903834200;6701597468;36150424300;56259852000;57197744260;35509639400;6603699075;6603875926;35271071300;9536987500;35271389900;6602504047;6507671561;24766067800;36464907600;7005246023;55325436900;56088313600;10243911900;22134074500;57200852217;6603433697;7004714030;57218282336;6507151484;6602886421;57218280800;55599515600;35271846300;57218283332;24512349100;55318190700;6602080773;36026605700;36961905100;57203142176;54412307700;7003977187;6701735773;6505465237;6603906450;7007181954;6506341850;56134359300;56880134300;54896136700;7202219277;24511929800;56186932200;24734166800;6602635049;57194045072;28568039300;12239764200;7102059695;10143232600;8349315600;57193170776;8651824700;8937991200;7003355588;55907220900;57194027154;7004910963;23981063100;54881950900;16305266000;8709662700;15726663700;13610836500;53985573100;7004452524;8925509300;49664027700;7003539477;57192414605;16403683500;","Presentation and Evaluation of the IPSL-CM6A-LR Climate Model",2020,"10.1029/2019MS002010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086872610&doi=10.1029%2f2019MS002010&partnerID=40&md5=2c2c3187ddbe9f3eab8eb2cca203b2c8","This study presents the global climate model IPSL-CM6A-LR developed at Institut Pierre-Simon Laplace (IPSL) to study natural climate variability and climate response to natural and anthropogenic forcings as part of the sixth phase of the Coupled Model Intercomparison Project (CMIP6). This article describes the different model components, their coupling, and the simulated climate in comparison to previous model versions. We focus here on the representation of the physical climate along with the main characteristics of the global carbon cycle. The model's climatology, as assessed from a range of metrics (related in particular to radiation, temperature, precipitation, and wind), is strongly improved in comparison to previous model versions. Although they are reduced, a number of known biases and shortcomings (e.g., double Intertropical Convergence Zone [ITCZ], frequency of midlatitude wintertime blockings, and El Niño–Southern Oscillation [ENSO] dynamics) persist. The equilibrium climate sensitivity and transient climate response have both increased from the previous climate model IPSL-CM5A-LR used in CMIP5. A large ensemble of more than 30 members for the historical period (1850–2018) and a smaller ensemble for a range of emissions scenarios (until 2100 and 2300) are also presented and discussed. ©2020. The Authors."
"55758496500;7202162685;","The impact of recent forcing and ocean heat uptake data on estimates of climate sensitivity",2018,"10.1175/JCLI-D-17-0667.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85049748532&doi=10.1175%2fJCLI-D-17-0667.1&partnerID=40&md5=d53de9638a0a616ceba059462fa9b9b3","Energy budget estimates of equilibrium climate sensitivity (ECS) and transient climate response (TCR) are derived based on the best estimates and uncertainty ranges for forcing provided in the IPCC Fifth Assessment Report (AR5). Recent revisions to greenhouse gas forcing and post-1990 ozone and aerosol forcing estimates are incorporated and the forcing data extended from 2011 to 2016. Reflecting recent evidence against strong aerosol forcing, its AR5 uncertainty lower bound is increased slightly. Using an 1869-82 base period and a 2007-16 final period, which are well matched for volcanic activity and influence from internal variability, medians are derived for ECS of 1.50 K (5%-95% range: 1.05-2.45 K) and for TCR of 1.20 K (5%-95% range: 0.9-1.7 K). These estimates both have much lower upper bounds than those from a predecessor study using AR5 data ending in 2011. Using infilled, globally complete temperature data give slightly higher estimates: a median of 1.66 K for ECS (5%-95% range: 1.15-2.7 K) and 1.33 K for TCR (5%-95% range: 1.0-1.9 K). These ECS estimates reflect climate feedbacks over the historical period, assumed to be time invariant. Allowing for possible time-varying climate feedbacks increases the median ECS estimate to 1.76 K (5%-95% range: 1.2-3.1 K), using infilled temperature data. Possible biases from non-unit forcing efficacy, temperature estimation issues, and variability in sea surface temperature change patterns are examined and found to be minor when using globally complete temperature data. These results imply that high ECS and TCR values derived from a majority of CMIP5 climate models are inconsistent with observed warming during the historical period. © 2018 American Meteorological Society."
"57194876603;57203030873;","The influence of extratropical cloud phase and amount feedbacks on climate sensitivity",2018,"10.1007/s00382-017-3796-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85023776541&doi=10.1007%2fs00382-017-3796-5&partnerID=40&md5=62340bc0a1e82da635ab262c9f4de75a","Global coupled climate models have large long-standing cloud and radiation biases, calling into question their ability to simulate climate and climate change. This study assesses the impact of reducing shortwave radiation biases on climate sensitivity within the Community Earth System Model (CESM). The model is modified by increasing supercooled cloud liquid to better match absorbed shortwave radiation observations over the Southern Ocean while tuning to reduce a compensating tropical shortwave bias. With a thermodynamic mixed-layer ocean, equilibrium warming in response to doubled CO2 increases from 4.1 K in the control to 5.6 K in the modified model. This 1.5 K increase in equilibrium climate sensitivity is caused by changes in two extratropical shortwave cloud feedbacks. First, reduced conversion of cloud ice to liquid at high southern latitudes decreases the magnitude of a negative cloud phase feedback. Second, warming is amplified in the mid-latitudes by a larger positive shortwave cloud feedback. The positive cloud feedback, usually associated with the subtropics, arises when sea surface warming increases the moisture gradient between the boundary layer and free troposphere. The increased moisture gradient enhances the effectiveness of mixing to dry the boundary layer, which decreases cloud amount and optical depth. When a full-depth ocean with dynamics and thermodynamics is included, ocean heat uptake preferentially cools the mid-latitude Southern Ocean, partially inhibiting the positive cloud feedback and slowing warming. Overall, the results highlight strong connections between Southern Ocean mixed-phase cloud partitioning, cloud feedbacks, and ocean heat uptake in a climate forced by greenhouse gas changes. © 2017, Springer-Verlag GmbH Germany."
"56005080300;23082420800;7201572530;7004060399;7006248174;","New observational evidence for a positive cloud feedback that amplifies the Atlantic Multidecadal Oscillation",2016,"10.1002/2016GL069961","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84987936751&doi=10.1002%2f2016GL069961&partnerID=40&md5=689e78ff63b505fc42927354244fd847","The Atlantic Multidecadal Oscillation (AMO) affects climate variability in the North Atlantic basin and adjacent continents with potential societal impacts. Previous studies based on model simulations and short-term satellite retrievals hypothesized an important role for cloud radiative forcing in modulating the persistence of the AMO in the tropics, but this mechanism remains to be tested with long-term observational records. Here we analyze data sets that span multiple decades and present new observational evidence for a positive feedback between total cloud amount, sea surface temperature (SST), and atmospheric circulation that can strengthen the persistence and amplitude of the tropical branch of the AMO. In addition, we estimate cloud amount feedback from observations and quantify its impact on SST with idealized modeling experiments. From these experiments we conclude that cloud feedbacks can account for 10% to 31% of the observed SST anomalies associated with the AMO over the tropics. ©2016. American Geophysical Union. All Rights Reserved."
"7007021059;7003976079;8918407000;13405561000;36187387300;8397494800;55686667100;10241462700;13402835300;7404142321;7201485519;","Robustness, uncertainties, and emergent constraints in the radiative responses of stratocumulus cloud regimes to future warming",2016,"10.1007/s00382-015-2750-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940180949&doi=10.1007%2fs00382-015-2750-7&partnerID=40&md5=18ff867579d09f7d2d4e23e1040ee89d","Future responses of cloud regimes are analyzed for five CMIP5 models forced with observed SSTs and subject to a patterned SST perturbation. Correlations between cloud properties in the control climate and changes in the warmer climate are investigated for each of a set of cloud regimes defined using a clustering methodology. The only significant (negative) correlation found is in the in-regime net cloud radiative effect for the stratocumulus regime. All models overestimate the in-regime albedo of the stratocumulus regime. Reasons for this bias and its relevance to the future response are investigated. A detailed evaluation of the models’ daily-mean contributions to the albedo from stratocumulus clouds with different cloud cover fractions reveals that all models systematically underestimate the relative occurrence of overcast cases but overestimate those of broken clouds. In the warmer climate the relative occurrence of overcast cases tends to decrease while that of broken clouds increases. This suggests a decrease in the climatological in-regime albedo with increasing temperature (a positive feedback); this is opposite to the feedback suggested by the analysis of the bulk in-regime albedo. Furthermore we find that the inter-model difference in the sign of the in-cloud albedo feedback is consistent with the difference in sign of the in-cloud liquid water path response, and there is a strong positive correlation between the in-regime liquid water path in the control climate and its response to warming. We therefore conclude that further breakdown of the in-regime properties into cloud cover and in-cloud properties is necessary to better understand the behavior of the stratocumulus regime. Since cloud water is a physical property and is independent of a model’s radiative assumptions, it could potentially provide a useful emergent constraint on cloud feedback. © 2015, © Crown Copyright as represented by the Met Office 2015."
"23016793700;7004423053;","Transient Earth system responses to cumulative carbon dioxide emissions: Linearities, uncertainties, and probabilities in an observation-constrained model ensemble",2016,"10.5194/bg-13-1071-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959191855&doi=10.5194%2fbg-13-1071-2016&partnerID=40&md5=bb8d62d00839bc48e833f9e4d6e036b7","Information on the relationship between cumulative fossil CO2 emissions and multiple climate targets is essential to design emission mitigation and climate adaptation strategies. In this study, the transient response of a climate or environmental variable per trillion tonnes of CO2 emissions, termed TRE, is quantified for a set of impact-relevant climate variables and from a large set of multi-forcing scenarios extended to year 2300 towards stabilization. An ∼ 1000-member ensemble of the Bern3D-LPJ carbon-climate model is applied and model outcomes are constrained by 26 physical and biogeochemical observational data sets in a Bayesian, Monte Carlo-type framework. Uncertainties in TRE estimates include both scenario uncertainty and model response uncertainty. Cumulative fossil emissions of 1000 Gt C result in a global mean surface air temperature change of 1.9 °C (68 % confidence interval (c.i.): 1.3 to 2.7 °C), a decrease in surface ocean pH of 0.19 (0.18 to 0.22), and a steric sea level rise of 20 cm (13 to 27 cm until 2300). Linearity between cumulative emissions and transient response is high for pH and reasonably high for surface air and sea surface temperatures, but less pronounced for changes in Atlantic meridional overturning, Southern Ocean and tropical surface water saturation with respect to biogenic structures of calcium carbonate, and carbon stocks in soils. The constrained model ensemble is also applied to determine the response to a pulse-like emission and in idealized CO2-only simulations. The transient climate response is constrained, primarily by long-term ocean heat observations, to 1.7 °C (68 % c.i.: 1.3 to 2.2 °C) and the equilibrium climate sensitivity to 2.9 °C (2.0 to 4.2 °C). This is consistent with results by CMIP5 models but inconsistent with recent studies that relied on short-term air temperature data affected by natural climate variability. © Author(s) 2016."
"7102284923;36772864900;8315173400;26656246100;7004326742;","On the state dependency of the equilibrium climate sensitivity during the last 5 million years",2015,"10.5194/cp-11-1801-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84952022342&doi=10.5194%2fcp-11-1801-2015&partnerID=40&md5=ddd9d6fd441cd34eed1c8e840026b671","It is still an open question how equilibrium warming in response to increasing radiative forcing - the specific equilibrium climate sensitivity S - depends on background climate. We here present palaeodata-based evidence on the state dependency of S, by using CO2 proxy data together with a 3-D ice-sheet-model-based reconstruction of land ice albedo over the last 5 million years (Myr). We find that the land ice albedo forcing depends non-linearly on the background climate, while any non-linearity of CO2 radiative forcing depends on the CO2 data set used. This non-linearity has not, so far, been accounted for in similar approaches due to previously more simplistic approximations, in which land ice albedo radiative forcing was a linear function of sea level change. The latitudinal dependency of ice-sheet area changes is important for the non-linearity between land ice albedo and sea level. In our set-up, in which the radiative forcing of CO2 and of the land ice albedo (LI) is combined, we find a state dependence in the calculated specific equilibrium climate sensitivity, S[CO2,LI], for most of the Pleistocene (last 2.1 Myr). During Pleistocene intermediate glaciated climates and interglacial periods, S[CO2,LI] is on average ∼ 45 % larger than during Pleistocene full glacial conditions. In the Pliocene part of our analysis (2.6-5 Myr BP) the CO2 data uncertainties prevent a well-supported calculation for S[CO2,LI], but our analysis suggests that during times without a large land ice area in the Northern Hemisphere (e.g. before 2.82 Myr BP), the specific equilibrium climate sensitivity, S[CO2,LI], was smaller than during interglacials of the Pleistocene. We thus find support for a previously proposed state change in the climate system with the widespread appearance of northern hemispheric ice sheets. This study points for the first time to a so far overlooked non-linearity in the land ice albedo radiative forcing, which is important for similar palaeodata-based approaches to calculate climate sensitivity. However, the implications of this study for a suggested warming under CO2 doubling are not yet entirely clear since the details of necessary corrections for other slow feedbacks are not fully known and the uncertainties that exist in the ice-sheet simulations and global temperature reconstructions are large. © Author(s) 2015."
"23486734100;16645242800;","Sensitivity of radiative forcing, ocean heat uptake, and climate feedback to changes in anthropogenic greenhouse gases and aerosols",2015,"10.1002/2015JD023364","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945445981&doi=10.1002%2f2015JD023364&partnerID=40&md5=72296241078d3c47d0f251fa9e51dbc0","We use both prescribed sea surface temperature and fully coupled versions of the Geophysical Fluid Dynamics Laboratory coupled climate model (CM3) to analyze the sensitivity of radiative forcing, ocean heat uptake, and climate feedback to changes in anthropogenic greenhouse gases and aerosols considered separately over the 1870 to 2005 period. The global anthropogenic aerosol climate feedback parameter (-α) of -1.13 ± 0.33 Wm-2 K-1 is indistinguishable from the greenhouse gas -α of 1.28 ± 0.23 Wm-2 K-1. However, this greenhouse gas climate feedback parameter is about 50% larger than that obtained for CM3 from a widely used linear extrapolation method of regressing Earth’s top of atmosphere imbalance against surface air temperature change in idealized CO2 radiative forcing experiments. This implies that the global mean surface temperature change due to forcing over the 1870–2005 period is 50% smaller than that predicted using the climate feedback parameter obtained from idealized experiments. This difference results from time dependence in α, which makes the radiative forcing obtained by the fixed sea surface temperature method incompatible with that obtained by the linear extrapolation method fitted over the first 150 years after CO2 is quadrupled. On a regional scale, α varies greatly between the greenhouse gas and aerosol case. This suggests that the relationship between transient and equilibrium climate sensitivities obtained from idealized CO2 simulations, using techniques such as regional feedback analysis and heat uptake efficacy, may not hold for other forcing scenarios. © 2015. American Geophysical Union. All rights reserved."
"24485834000;28367935500;7201504886;","On the connection between tropical circulation, convective mixing, and climate sensitivity",2015,"10.1002/qj.2450","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84932108727&doi=10.1002%2fqj.2450&partnerID=40&md5=d9554a51e8ac5c33d11f7c050f8a270e","The connection between the large-scale tropical circulation of the atmosphere, convective mixing, and climate sensitivity is explored in a wide range of climates through a perturbed-parameter ensemble of a comprehensive Earth System Model. Four parameters related to the representation of atmospheric moist convection are found to dominate the response of the model. Their values govern the strength of the tropical circulation, the surface temperature, atmospheric humidity, and the strength of the tropical overturning circulation, largely through their influence on the atmospheric stability. The same convective parameters, albeit in different combinations, also have a strong influence on the equilibrium climate sensitivity of the model, which ranges from a little over 3 °C to more than 10 °C. The importance of the most poorly represented processes in determining important aspects of the behaviour of the model argues for the need to move beyond statistical approaches to estimating climate sensitivity and to focus on the development of a better understanding and representation of convective mixing, particularly in the Tropics. © 2014 Royal Meteorological Society."
"56202403600;7003266014;","The impact of forcing efficacy on the equilibrium climate sensitivity",2014,"10.1002/2014GL060046","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902246210&doi=10.1002%2f2014GL060046&partnerID=40&md5=34f72b7a95a3f1fa372e5cc9fb0cbbad","Estimates of the Earth's equilibrium climate sensitivity (ECS) from twentieth century observations predict a lower ECS than estimates from climate models, paleoclimate data, and interannual variability. Here we show that estimates of ECS from the twentieth century observations are sensitive to the assumed efficacy of aerosol and ozone forcing (efficacy for a forcer is the amount of warming per unit global average forcing divided by the warming per unit forcing from CO2). Previous estimates of ECS based on the twentieth century observations have assumed that the efficacy is unity, which in our study yields an ECS of 2.3 K (5%-95% confidence range of 1.6-4.1 K), near the bottom of the Intergovernmental Panel on Climate Change's likely range of 1.5-4.5 K. Increasing the aerosol and ozone efficacy to 1.33 increases the ECS to 3.0 K (1.9-6.8 K), a value in excellent agreement with other estimates. Forcing efficacy therefore provides a way to bridge the gap between the different estimates of ECS. © 2014. American Geophysical Union. All Rights Reserved."
"7501720647;36934610300;55220976100;","Stratocumulus clouds in Southeastern pacific simulated by eight CMIP5-CFMIP global climate models",2014,"10.1175/JCLI-D-13-00376.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898020225&doi=10.1175%2fJCLI-D-13-00376.1&partnerID=40&md5=1ad15a4c5095cfbc6b70e22dfb33955c","This study examines the stratocumulus clouds and associated cloud feedback in the southeast Pacific (SEP) simulated by eight global climate models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5) and Cloud Feedback Model Intercomparison Project (CFMIP) using long-term observations of clouds, radiative fluxes, cloud radiative forcing (CRF), sea surface temperature (SST), and large-scale atmosphere environment. The results show that the state-of-the-art global climate models still have significant difficulty in simulating the SEP stratocumulus clouds and associated cloud feedback. Comparing with observations, the models tend to simulate significantly less cloud cover, higher cloud top, and a variety of unrealistic cloud albedo. The insufficient cloud cover leads to overly weak shortwave CRF and net CRF. Only two of the eight models capture the observed positive cloud feedback at subannual to decadal time scales. The cloud and radiation biases in the models are associated with 1) model biases in large-scale temperature structure including the lack of temperature inversion, insufficient lower troposphere stability (LTS), and insufficient reduction of LTS with local SST warming, and 2) improper model physics, especially insufficient increase of low cloud cover associated with larger LTS. The two models that arguably do best at simulating the stratocumulus clouds and associated cloud feedback are the only ones using cloud-top radiative cooling to drive boundary layer turbulence. © 2014 American Meteorological Society."
"7403282069;8977001000;55745955800;","Cloud-Resolving Simulation of Low-Cloud Feedback to an Increase in Sea Surface Temperature",2010,"10.1175/2009JAS3239.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953347773&doi=10.1175%2f2009JAS3239.1&partnerID=40&md5=5e3a24729f0c7c4072326e89f5614f69","This study investigates the physical mechanisms of the low cloud feedback through cloud-resolving simulations of cloud-radiative equilibrium response to an increase in sea surface temperature (SST). Six pairs of perturbed and control simulations are performed to represent different regimes of low clouds in the subtropical region by specifying SST differences (ΔSST) in the range of 4 and 14 K between the warm tropical and cool subtropical regions. The SST is uniformly increased by 2 Kin the perturbed set of simulations.Equilibriumstates are characterized by cumulus and stratocumulus cloud regimes with variable thicknesses and vertical extents for the range of specied ΔSSTs, with the perturbed set of simulations having higher cloud bases and tops and larger geometric thicknesses. The cloud feedback effect is negative for this ΔSST range (-0.68 to -5.22 W m-2 K-1) while the clear-sky feedback effect is mostly negative (-1.45 to 0.35 W m-2 K-1). The clear-sky feedback effect contributes greatly to the climate sensitivity parameter for the cumulus cloud regime whereas the cloud feedback effect dominates for the stratocumulus regime. The increase of liquid water path (LWP) and cloud optical depth is related to the increase of cloud thickness and liquid water content with SST. The rates of change in surface latent heat flux are much higher than those of saturation water vapor pressure in the cumulus simulations. The increase in surface latent heat flux is the pri marymechanism for the large change of cloud physical properties with +2 K SST, which leads to the negative cloud feedback effects. The changes in cloud fraction also contribute to the negative cloud feedback effects in the cumulus regime. Comparison of these results with prior modeling studies is also discussed. © 2010 American Meteorological Society."
"13402835300;25652188900;24329376600;7404142321;7003976079;7103016965;25924878400;","Strong Dependence of Atmospheric Feedbacks on Mixed-Phase Microphysics and Aerosol-Cloud Interactions in HadGEM3",2019,"10.1029/2019MS001688","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067486765&doi=10.1029%2f2019MS001688&partnerID=40&md5=f3c8706352832e655af6185f7246ce99","We analyze the atmospheric processes that explain the large changes in radiative feedbacks between the two latest climate configurations of the Hadley Centre Global Environmental model. We use a large set of atmosphere-only climate change simulations (amip and amip-p4K) to separate the contributions to the differences in feedback parameter from all the atmospheric model developments between the two latest model configurations. We show that the differences are mostly driven by changes in the shortwave cloud radiative feedback in the midlatitudes, mainly over the Southern Ocean. Two new schemes explain most of the differences: the introduction of a new aerosol scheme and the development of a new mixed-phase cloud scheme. Both schemes reduce the strength of the preexisting shortwave negative cloud feedback in the midlatitudes. The new aerosol scheme dampens a strong aerosol-cloud interaction, and it also suppresses a negative clear-sky shortwave feedback. The mixed-phase scheme increases the amount of cloud liquid water path (LWP) in the present day and reduces the increase in LWP with warming. Both changes contribute to reducing the negative radiative feedback of the increase of LWP in the warmer climate. The mixed-phase scheme also enhances a strong, preexisting, positive cloud fraction feedback. We assess the realism of the changes by comparing present-day simulations against observations and discuss avenues that could help constrain the relevant processes. ©2019 Crown copyright. This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland."
"35069282600;57044397100;7202899330;","Aerosol indirect effect dictated by liquid clouds",2016,"10.1002/2016JD025245","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007404014&doi=10.1002%2f2016JD025245&partnerID=40&md5=e5d71edc085f9384458f17811d9db18e","Anthropogenic aerosols have been shown to enhance the solar reflection from warm liquid clouds and mask part of the warming due to the buildup of greenhouse gases. However, very little is known about the effects of aerosol on mixed-phase stratiform clouds as well as other cloud regimes including cumulus, altocumulus, nimbostratus, deep convection, and anvil cirrus. These additional cloud categories are ubiquitous and typically overlooked in satellite-based assessments of the global aerosol indirect forcing. Here we provide their contribution to the aerosol indirect forcing estimate using satellite data collected from several colocated sensors in the A-train for the period 2006-2010. Cloud type is determined according to the 2B-CLDCLASS-LIDAR CloudSat product, and the observations are matched to the radiative flux measurements from CERES (Clouds and the Earth’s Radiant Energy System) and aerosol retrievals from MODIS (MODerate resolution Imaging Spectroradiometer). The oceanic mean aerosol indirect forcing is estimated to be -0.20 ± 0.31Wm-2 with warm low-level cloud largely dictating the strength of the response (-0.36 ± 0.21Wm-2) due to their abundance and strong cloud albedo effect. Contributions from mixed-phase low-level cloud (0.01 ± 0.06Wm-2) and convective cloud (0.15 ± 0.23Wm-2) are positive and buffer the system due to strong aerosol-cloud feedbacks that reduce the cloud albedo effect and/or lead to convective invigoration causing a countering positive longwave warming response. By combining all major cloud categories together, aerosol indirect forcing decreases and now contains positive values in the uncertainty estimate. © 2016. American Geophysical Union. All Rights Reserved."
"7007021059;8962699100;7202954964;7401945370;57212988186;7201485519;","High cloud increase in a perturbed SST experiment with a global nonhydrostatic model including explicit convective processes",2015,"10.1002/2013MS000301","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907823728&doi=10.1002%2f2013MS000301&partnerID=40&md5=b23519623440f028e884b4e71759387d","Results are presented from a series of sensitivity tests in idealized global warming experiments using the global nonhydrostatic model, NICAM, in which convection at scales of 7-14 km is explicitly resolved. All have a strong positive longwave cloud feedback larger than that seen in conventional GCMs with parameterized convection. Consequently, the global mean net outgoing radiation decreases in response to increased sea surface temperatures. Large increases in high clouds with tops between 180 and 50 hPa are found, and these changes contribute the most to this longwave cloud feedback. Relative humidity and upper tropospheric temperature also increases strongly, again more so than typically seen in conventional GCMs. The magnitude of the response varies considerably between different versions of NICAM. Most of the NICAM control simulations show large overestimates in cloud fraction between 180 and 50 hPa compared to observations. The changes in cloud fraction in the upper troposphere are strongly correlated with their control values. Versions of NICAM with stronger cloud feedbacks have large positive biases in high-top cloud amount and temperature in the free troposphere in their control simulations. The version which has the best agreement with the observations in this regard has the weakest longwave cloud feedback; however, this is still more strongly positive than that typically seen in conventional GCMs. These results demonstrate the potential for stronger high cloud fraction feedbacks in climate warming scenarios than currently predicted by conventional GCMs and highlight the potential relevance of deep convective processes. Key Points Larger positive longwave feedback in NICAM than in conventional GCMs High cloud fraction increases in NICAM in increased SST experiments Possibility of larger high cloud fraction feedback in future models © 2014. The Authors."
"23767277800;7401776640;55894937000;","How has subtropical stratocumulus and associated meteorology changed since the 1980s?",2015,"10.1175/JCLI-D-15-0120.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946227883&doi=10.1175%2fJCLI-D-15-0120.1&partnerID=40&md5=6810ad765e64a79db853bf40697e9470","The importance of low-level cloud feedbacks to climate sensitivity motivates an investigation of how low-level cloud amount and related meteorological conditions have changed in recent decades in subtropical stratocumulus regions. Using satellite cloud datasets corrected for inhomogeneities, it is found that during 1984-2009 low-level cloud amount substantially increased over the northeastern Pacific, southeastern Pacific, and southeastern Atlantic; decreased over the northeastern Atlantic; and weakly increased over the southeastern Indian Ocean subtropical stratocumulus regions. Examination of meteorological parameters from four reanalyses indicates that positive trends in low-level cloud amount are associated with cooler sea surface temperature, greater inversion strength, and enhanced cold-air advection. The converse holds for negative trends in low-level cloud amount. A multilinear regression model based on these three meteorological variables reproduces the sign and magnitude of observed cloud amount trends in all stratocumulus regions within the range of observational uncertainty. Changes in inversion strength have the largest independent effect on cloud trends, followed by changes in advection strength. Changes in sea surface temperature have the smallest independent effect on cloud trends. Differing signs of cloud trends and differing contributions from meteorological parameters suggest that observed changes in subtropical stratocumulus since the 1980s may be due to natural variability rather than a systematic response to climate change. © 2015 American Meteorological Society."
"57131609600;7402989545;55913183200;","Climate sensitivities of two versions of FGOALS model to idealized radiative forcing",2014,"10.1007/s11430-013-4692-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901255008&doi=10.1007%2fs11430-013-4692-4&partnerID=40&md5=7ff3fc0177e4d21c9ee310a014a27118","Projections of future climate change by climate system models depend on the sensitivities of models to specified greenhouse gases. To reveal and understand the different climate sensitivities of two versions of LASG/IAP climate system model FGOALS-g2 and FGOALS-s2, we investigate the global mean surface air temperature responses to idealized CO2 forcing by using the output of abruptly quadrupling CO2 experiments. The Gregory-style regression method is used to estimate the ""radiative forcing"" of quadrupled CO2 and equilibrium sensitivity. The model response is separated into a fast-response stage associated with the CO2 forcing during the first 20 years, and a slow-response stage post the first 20 years. The results show that the radiative forcing of CO2 is overestimated due to the positive water-vapor feedback and underestimated due to the fast cloud processes. The rapid response of water vapor in FGOALS-s2 is responsible for the stronger radiative forcing of CO2. The climate sensitivity, defined as the equilibrium temperature change under doubled CO2 forcing, is about 3.7 K in FGOALS-g2 and 4.5 K in FGOALS-s2. The larger sensitivity of FGOALS-s2 is due mainly to the weaker negative longwave clear-sky feedback and stronger positive shortwave clear-sky feedback at the fast-response stage, because of the more rapid response of water vapor increase and sea-ice decrease in FGOALS-s2 than in FGOALS-g2. At the slow-response stage, similar to the fast-response stage, net negative clear-sky feedback is weaker in FGOALS-s2. Nevertheless, the total negative feedback is larger in FGOALS-s2 due to a larger negative shortwave cloud feedback that involves a larger response of total cloud fraction and condensed water path increase. The uncertainties of estimated forcing and net feedback mainly come from the shortwave cloud processes. © 2013 Science China Press and Springer-Verlag Berlin Heidelberg."
"57196143493;","On the longwave climate feedbacks",2013,"10.1175/JCLI-D-13-00025.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884952414&doi=10.1175%2fJCLI-D-13-00025.1&partnerID=40&md5=782f8cdbe2c1b7e37801953795f63c94","This paper mainly addresses two issues that concern the longwave climate feedbacks. First, it is recognized that the radiative forcing of greenhouse gases, as measured by their impact on the outgoing longwave radiation (OLR), may vary across different climate models even when the concentrations of these gases are identically prescribed. This forcing variation contributes to the discrepancy in these models' projections of surface warming.Amethod is proposed to account for this effect in diagnosing the sensitivity and feedbacks in the models. Second, it is shown that the stratosphere is an important factor that affects the OLR in transient climate change. Stratospheric water vapor and temperature changes may both act as a positive feedback mechanism during global warming and cannot be fully accounted as a ""stratospheric adjustment"" of radiative forcing. Neglecting these two issues may cause a bias in the longwave cloud feedback diagnosed as a residual term in the decomposition of OLR variations. There is no consensus among the climate models on the sign of the longwave cloud feedback after accounting for both issues. © 2013 American Meteorological Society."
"55745955800;7004479957;8882641700;35509639400;54893098900;6701752471;","The CGILS experimental design to investigate low cloud feedbacks in general circulation models by using single-column and large-eddy simulation models",2012,"10.1029/2012MS000182","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871665708&doi=10.1029%2f2012MS000182&partnerID=40&md5=048f3b6d83de4403a0d83ddd6aada9eb","A surrogate climate change is designed to investigate low cloud feedbacks in the northeastern Pacific by using Single Column Models (SCMs), Cloud Resolving Models (CRMs), and Large Eddy Simulation models (LES), as part of the CGILS study (CFMIP-GASS Intercomparison of LES and SCM models). The constructed large-scale forcing fields, including subsidence and advective tendencies, and their perturbations in the warmer climate are shown to compare well with conditions in General Circulation Models (GCMs), but they are free from the impact of any GCM parameterizations. The forcing fields in the control climate are also shown to resemble the mean conditions in the ECMWF-Interim Reanalysis. Applications of the forcing fields in SCMs are presented. It is shown that the idealized design can offer considerable insight into the mechanisms of cloud feedbacks in the models. Caveats and advantages of the design are also discussed. © 2012. American Geophysical Union. All Rights Reserved."
"6602705884;","Bias correction and post-processing under climate change",2011,"10.5194/npg-18-911-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84984410003&doi=10.5194%2fnpg-18-911-2011&partnerID=40&md5=75e77a7f132805601e75a7c6fec5a2be","The statistical and dynamical properties of bias correction and linear post-processing are investigated when the system under interest is affected by model errors and is experiencing parameter modifications, mimicking the potential impact of climate change. The analysis is first performed for simple typical scalar systems, an Ornstein-Uhlenbeck process (O-U) and a limit point bifurcation. It reveals system's specific (linear or non-linear) dependences of biases and post-processing corrections as a function of parameter modifications. A more realistic system is then investigated, a low-order model of moist general circulation, incorporating several processes of high relevance in the climate dynamics (radiative effects, cloud feedbacks…), but still sufficiently simple to allow for an extensive exploration of its dynamics. In this context, bias or post-processing corrections also display complicate variations when the system experiences temperature climate changes up to a few degrees. This precludes a straightforward application of these corrections from one system's state to another (as usually adopted for climate projections), and increases further the uncertainty in evaluating the amplitudes of climate changes. © Author(s) 2011."
"10241462700;8979277400;10240710000;10243650000;6603378233;7007021059;55619301899;6603412788;6603196127;7003967390;56284545500;7102857642;","Comparison of equilibrium and transient responses to CO2 increase in eight state-of-the-art climate models",2008,"10.1111/j.1600-0870.2008.00345.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-52949139119&doi=10.1111%2fj.1600-0870.2008.00345.x&partnerID=40&md5=a64070947623a535416827397b002c0f","We compared the climate response of doubled CO2 equilibrium experiments (2 × CO2) by atmosphere-slab ocean coupled general circulation models (ASGCMs) and that of 1% per year CO2 increase experiments (1%CO2 by atmosphere-ocean coupled general circulation models (AOGCMs) using eight state-of-the-art climate models. Climate feedback processes in 2 × CO2 are different from those in 1%CO2, and the equilibrium climate sensitivity (T2×) in 2 × CO2 is different from the effective climate sensitivity (T2×,eff) in 1%CO2. The difference between T2× and T2×,eff is from -1.3 to 1.6 K, a large part of which can be explained by the difference in the ice-albedo and cloud feedback. The largest contribution is cloud SW feedback, and the difference in cloud SW feedback for 2 × CO2 and 1%CO2 could be determined by the distribution of the SAT anomaly which causes differences in the atmospheric thermal structure. An important factor which determines the difference in ice-albedo feedback is the initial sea ice distribution at the Southern Ocean, which is generally overestimated in 2 ×CO2 as compared to 1%CO2 and observation. Through the comparison of climate feedback processes in 2 × CO2 and 1%CO2, the possible behaviour of the time evolution of T2×,eff is discussed. © 2008 The Authors Journal compilation © 2008 Blackwell Munksgaard."
"10243650000;8979277400;7201485519;7007021059;10241462700;6603196127;7102857642;","Towards understanding cloud response in atmospheric GCMs: The use of tendency diagnostics",2008,"10.2151/jmsj.86.69","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42449148943&doi=10.2151%2fjmsj.86.69&partnerID=40&md5=5b41d215e42dcb11618e14d01d98552a","In climate change projections, inter-model differences in cloud feedback have been identified as the largest source of uncertainty. The source terms of the cloud condensate tendency equation (CCTD) are expected to be useful diagnostics to better understand the different cloud responses to a CO2 increase in GCMs. To demonstrate the idea, analysis of the CCTD response to CO2 doubling is presented using two versions of a climate model with different climate sensitivities of 6.2°C ('HS' version) and 4.1°C ('LS' version). The model's response to CO2 doubling is characterized with a marked difference in the cloud feedback between the two versions, which is consistent with the cloud response in the southern middle latitudes: cloud decreases in the HS version and increases in the LS version. Analysis of the source terms reveals that the difference in cloud response is attributable to the ice sedimentation process. The results also suggest the importance of the vertical cloud ice profile which controls the ice sedimentation response to a CO2 increase, indicating the potential for providing constraints on the aspect of cloud feedback. © 2008, Meteorological Society of Japan."
"49664027700;35509639400;7201504886;56567409000;","Mechanisms and Model Diversity of Trade-Wind Shallow Cumulus Cloud Feedbacks: A Review",2017,"10.1007/s10712-017-9418-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85023747214&doi=10.1007%2fs10712-017-9418-2&partnerID=40&md5=7e050b54327abd8ddd9399b2213abd03","Shallow cumulus clouds in the trade-wind regions are at the heart of the long standing uncertainty in climate sensitivity estimates. In current climate models, cloud feedbacks are strongly influenced by cloud-base cloud amount in the trades. Therefore, understanding the key factors controlling cloudiness near cloud-base in shallow convective regimes has emerged as an important topic of investigation. We review physical understanding of these key controlling factors and discuss the value of the different approaches that have been developed so far, based on global and high-resolution model experimentations and process-oriented analyses across a range of models and for observations. The trade-wind cloud feedbacks appear to depend on two important aspects: (1) how cloudiness near cloud-base is controlled by the local interplay between turbulent, convective and radiative processes; (2) how these processes interact with their surrounding environment and are influenced by mesoscale organization. Our synthesis of studies that have explored these aspects suggests that the large diversity of model responses is related to fundamental differences in how the processes controlling trade cumulus operate in models, notably, whether they are parameterized or resolved. In models with parameterized convection, cloudiness near cloud-base is very sensitive to the vigor of convective mixing in response to changes in environmental conditions. This is in contrast with results from high-resolution models, which suggest that cloudiness near cloud-base is nearly invariant with warming and independent of large-scale environmental changes. Uncertainties are difficult to narrow using current observations, as the trade cumulus variability and its relation to large-scale environmental factors strongly depend on the time and/or spatial scales at which the mechanisms are evaluated. New opportunities for testing physical understanding of the factors controlling shallow cumulus cloud responses using observations and high-resolution modeling on large domains are discussed. © 2017, The Author(s)."
"13402835300;24329376600;24597575200;7003976079;","Cloud liquid water path and radiative feedbacks over the Southern Ocean",2016,"10.1002/2016GL070770","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84995701641&doi=10.1002%2f2016GL070770&partnerID=40&md5=4c608db4ad4fb93c5f2c3207937df4b4","Climate models show a robust shortwave negative feedback in the midlatitude oceans in climate change simulations. This feedback is commonly attributed to an increase in cloud optical depth due to ice to liquid phase change as the climate warms. Here we use a cyclone compositing technique to show that the models' cloud liquid water path (LWP) response is strongly dependent on cloud regime. The radiative and LWP responses are not as tightly coupled as a zonal-mean analysis would suggest, implying that the physical mechanisms that control the overall LWP response are not necessarily responsible for the radiative response. The area of the cyclone dominated by low-level stratiform and shallow convective clouds plays a dominant role in the radiative response. Since these are mostly supercooled liquid clouds, the strength of a negative cloud phase feedback in the real world should be smaller than the one predicted by current models. ©2016 Crown copyright. This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland."
"6603546080;7403180902;57208727319;8723505700;55916098100;8555710700;8669714200;","Advances in geostationary-derived longwave fluxes for the CERES synoptic (SYN1deg) product",2016,"10.1175/JTECH-D-15-0147.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84962850134&doi=10.1175%2fJTECH-D-15-0147.1&partnerID=40&md5=240b7716c2466df13d19d30893ef1d28","The Clouds and the Earth's Radiant Energy System (CERES) project has provided the climate community 15 years of globally observed top-of-the-atmosphere fluxes critical for climate and cloud feedback studies. To accurately monitor the earth's radiation budget, the CERES instrument footprint fluxes must be spatially and temporally averaged properly. The CERES synoptic 1° (SYN1deg) product incorporates derived fluxes from the geostationary satellites (GEOs) to account for the regional diurnal flux variations in between Terra and Aqua CERES measurements. The Edition 4 CERES reprocessing effort has provided the opportunity to reevaluate the derivation of longwave (LW) fluxes from GEO narrowband radiances by examining the improvements from incorporating 1-hourly versus 3-hourly GEO data, additional GEO infrared (IR) channels, and multichannel GEO cloud properties. The resultant GEO LW fluxes need to be consistent across the 16-satellite climate data record. To that end, the addition of the water vapor channel, available on all GEOs, was more effective than using a reanalysis dataset's column-weighted relative humidity combined with the window channel radiance. The benefit of the CERES LW angular directional model to derive fluxes was limited by the inconsistency of the GEO cloud retrievals. Greater success was found in the direct conversion of window and water vapor channel radiances into fluxes. Incorporating 1-hourly GEO fluxes had the greatest impact on improving the accuracy of high-temporal-resolution fluxes, and normalizing the GEO LW fluxes with CERES greatly reduced the monthly regional LW flux bias. © 2016 American Meteorological Society."
"13403622000;55683910600;35572096100;","Cloud Phase Changes Induced by CO2 Warming—a Powerful yet Poorly Constrained Cloud-Climate Feedback",2015,"10.1007/s40641-015-0026-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981762625&doi=10.1007%2fs40641-015-0026-2&partnerID=40&md5=f5188554a4fc98a978bd864c2ebe1bae","We review a cloud feedback mechanism that has so far been considered of secondary importance, despite a body of research suggesting that it represents a powerful climate feedback that can control the sign of the overall cloud feedback simulated in global climate models (GCMs). The feedback mechanism is associated with phase changes in clouds triggered by a warming atmosphere, which in turn yields optically thicker clouds. Output from the latest generation of GCMs suggest that this is the dominant cloud feedback at high latitudes, with obvious implications for climatically sensitive regions such as the Arctic and the Southern Ocean. Here, we present an overview of the relatively few modeling studies that have investigated this particular feedback mechanism to date, along with new results suggesting that the cloud-climate feedback simulated by a GCM can change dramatically depending on its cloud phase partitioning. © 2015, Springer International Publishing AG."
"56005080300;23082420800;8696069500;57197233116;7201504886;","The influence of cloud feedbacks on equatorial atlantic variability",2015,"10.1175/JCLI-D-14-00495.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944073510&doi=10.1175%2fJCLI-D-14-00495.1&partnerID=40&md5=25086a96ab8f046b4f017b004e7ccea1","Observations show that cloud feedback over the Namibian stratocumulus region is positive because cloud cover is anticorrelated with local sea surface temperature (SST) anomalies. Moreover, regressions of observed atmospheric fields on equatorial Atlantic SST anomalies indicate that cloud feedbacks over the Namibian stratocumulus region covary with Atlantic Niño. However, from observations alone, it is not possible to quantify the influence of regional cloud feedbacks on equatorial climate variability. To address this question, a set of sensitivity experiments are conducted using an atmospheric general circulation model (ECHAM6) coupled to a slab ocean in which the strength of positive cloud feedback is enhanced over several regions in the South Atlantic basin. Enhanced positive cloud feedback over the Namibian stratocumulus region increases local as well as equatorial SST variability, whereas enhanced cloud feedback over other regions in the South Atlantic increases local SST variability but exhibits negligible responses at the equator. The authors' results indicate that the Namibian region plays a central role in enhancing equatorial SST variability because it is located where the SST anomalies associated with the simulated Atlantic Niño in the slab-ocean model develop. These results highlight the important role of the regional coupling of cloud cover over the Namibian region with local SSTs and its effects on equatorial Atlantic climate variability. © 2015 American Meteorological Society."
"55716092000;9244954000;9249239700;7003278104;7101801476;7202772927;7404829395;7003406400;","Partitioning CloudSat ice water content for comparison with upper tropospheric ice in global atmospheric models",2011,"10.1029/2010JD015179","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054827157&doi=10.1029%2f2010JD015179&partnerID=40&md5=1d1abe0cd95b8acf2a4148985895bfeb","The ice cloud estimates in current global models exhibit significant inconsistency, resulting in a significant amount of uncertainties in climate forecasting. Vertically resolved ice water content (IWC) is recently available from new satellite products, such as CloudSat, providing important observational constraints for evaluating the global models. To account for the varied nature of the model parameterization schemes, it is valuable to develop methods to distinguish the cloud versus precipitating ice components from the remotely sensed estimates in order to carry out meaningful model-data comparisons. The present study develops a new technique that partitions CloudSat total IWC into small and large ice hydrometeors, using the ice particle size distribution (PSD) parameters provided by the retrieval algorithm. The global statistics of CloudSat-retrieved PSD are analyzed for the filtered subsets on the basis of convection and precipitation flags to identify appropriate particle size separation. Results are compared with previous partitioning estimates and suggest that the small particles contribute to ∼25-45% of the global mean total IWC in the upper to middle troposphere. Sensitivity measures with respect to the PSD parameters and the retrieval algorithm are presented. The current estimates are applied to evaluate the IWC estimates from the European Centre for Medium-Range Weather Forecasts model and the finite-volume multiscale modeling framework model, pointing to specific areas of potential model improvements. These results are discussed in terms of applications to model diagnostics, providing implications for reducing the uncertainty in the model representation of cloud feedback and precipitation. Copyright 2011 by the American Geophysical Union."
"23094149200;7003278104;9249239700;","Boundary layer and cloud structure controls on tropical low cloud cover using A-Train satellite data and ECMWF analyses",2011,"10.1175/2010JCLI3702.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79251578013&doi=10.1175%2f2010JCLI3702.1&partnerID=40&md5=00a77cb1c247abaab5c0c9e0dec6829b","The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), CloudSat radar, and the Moderate Resolution Imaging Spectroradiometer (MODIS) cloud data on the A-Train constellation complemented with the European Centre for Medium-Range Forecasts (ECMWF) analyses are used to investigate the cloud and boundary layer structure across a 10° wide cross section starting at 5°S near the international date line and extending to 35°N near the California coast from March 2008 to February 2009. The mean large-scale inversion height and low-level cloud tops, which correspond very closely to each other, are very shallow (~500 m) over cold SSTs and high static stability near California and deepen southwestward (to a maximum of ~1.5-2.0 km) along the cross section as SSTs rise. Deep convection near the ITCZ occurs at a surface temperature close to 298 K. While the boundary layer relative humidity (RH) is nearly constant where a boundary layer is well defined, it drops sharply near cloud top in stratocumulus regions, corresponding with strong thermal inversions and water vapor decrease, such that the maximum (-∂RH/∂z) marks the boundary layer cloud top very well. The magnitude correlates well with low cloud frequency during March-May (MAM), June-August (JJA), and September-November (SON) (r2 = 0.85, 0.88, and 0.86, respectively). Also, CALIPSO and MODIS isolated low cloud frequency generally agree quite well, but CloudSat senses only slightly more than one-third of the low clouds as observed by the other sensors, as many clouds are shallower than 1 km and thus cannot be discerned with CloudSat due to contamination from the strong signal from surface clutter. Mean tropospheric ω between 300 and 700 hPa is examined from the ECMWF Year of Tropical Convection (YOTC) analysis data set, and during JJA and SON, strong rising motion in the middle troposphereis confined to a range of 2-m surface temperatures between 297 and 300 K, consistent with previous studies that show a narrow range of SSTs over which deep ascent occurs. During December-February (DJF), large-scale ascending motion extends to colder SSTs and high boundary layer stability. A slightly different boundary layer stability metric is derived, the difference of moist static energy (MSE) at the middle point of the inversion (or at 700 hPa if no inversion exists) and the surface, referred to as ΔMSE. The utility of ΔMSE is its prediction of isolated uniform low cloud frequency, with very high r2 values of 0.93 and 0.88, respectively, for the MODIS and joint lidar plus radar product during JJA but significantly lower values during DJF (0.46 and 0.40), with much scatter. To quantify the importance of free tropospheric dynamics in modulating the ΔMSE-low cloud relationships, the frequency as a function of ΔMSE of rising motion profiles (ω &lt; -0.05 Pa s-1) is added to the observed low cloud frequency for a maximum hypothetical low cloud frequency. Doing this greatly reduces the interseasonal differences and holds promise for using ΔMSE for parameterization schemes and examining low cloud feedbacks. © 2011 American Meteorological Society."
"56085869400;","A kriging approach to the analysis of climate model experiments",2009,"10.1198/jabes.2009.0006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78249273375&doi=10.1198%2fjabes.2009.0006&partnerID=40&md5=74204a2ff47125f4d69546bb115fed81","A climate model is a computer implementation of a mathematical model for the physical, chemical and biological processes underlying the climate. An immediate use of a climate model is in performing climate model experiments, where uncertain input quantities, such as greenhouse gas and aerosol concentrations, are systematically varied to gain insight into their effects on the climate system. Climate models are computationally intensive, allowing only small experiments.We present a multidimensional kriging method to predict climate model variables at new inputs, based on the experimental data available. The method is particularly suitable for situations in which the climate model data sets share a common pattern across the input space, such as surface temperatures that are lower at the Poles, higher at the Equator, and increasing over time. The results demonstrate the potential of our kriging method as an exploratory tool in climate science. © 2009 American Statistical Association and the International Biometric Society."
"55636322183;24067647600;35234249500;35264959100;","Insufficient forcing uncertainty underestimates the risk of high climate sensitivity",2009,"10.1029/2009GL039642","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71949118435&doi=10.1029%2f2009GL039642&partnerID=40&md5=0c387668c4491cc22dabbf369333de3c","Uncertainty in climate sensitivity is a fundamental problem for projections of die future climate. Equilibrium climate sensitivity is defined as the asymptotic response of global-mean surface air temperature to a doubling of the atmospheric CO<inf>2</inf> concentration from die preindustrial level (»280 ppm). In spite of various efforts to estimate its value, climate sensitivity is still not well constrained. Here we show mat die probability of high climate sensitivity is higher than previously thought because uncertainty in historical radiative forcing has not been sufficiently considered. The greater the uncertainty that is considered for radiative forcing, the more difficult it is to rule out high climate sensitivity, although low climate sensitivity (<2°C) remains unlikely. We call for further research on how best to represent forcing uncertainty. Copyright 2009 by the American Geophysical Union."
"7004325649;6603546080;7404150761;7004364155;36973693100;22958155300;","Climate quality broadband and narrowband solar reflected radiance calibration between sensors in orbit",2008,"10.1109/IGARSS.2008.4778842","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649763928&doi=10.1109%2fIGARSS.2008.4778842&partnerID=40&md5=2c48a72b5ad7653f3dc1320950927023","As the potential impacts of global climate change become more clear [1], the need to determine the accuracy of climate prediction over decade-to-century time scales has become an urgent and critical challenge. The most critical tests of climate model predictions will occur using observations of decadal changes in climate forcing, response, and feedback variables. Many of these key climate variables are observed by remotely sensing the global distribution of reflected solar spectral and broadband radiance. These ""reflected solar"" variables include aerosols, clouds, radiative fluxes, snow, ice, vegetation, ocean color, and land cover. Achieving sufficient satellite instrument accuracy, stability, and overlap to rigorously observe decadal change signals has proven very difficult in most cases and has not yet been achieved in others [2]. One of the earliest efforts to make climate quality observations was for Earth Radiation Budget: Nimbus 6/7 in the late 1970s, ERBE in the 1980s/90s, and CERES in 2000s are examples of the most complete global records. The recent CERES data products have carried out the most extensive intercomparisons because if the need to merge data from up to 11 instruments (CERES, MODIS, geostationary imagers) on 7 spacecraft (Terra, Aqua, and 5 geostationary) for any given month. In order to achieve climate calibration for cloud feedbacks, the radiative effect of clear-sky, all-sky, and cloud radiative effect must all be made with very high stability and accuracy. For shortwave solar reflected flux, even the 1% CERES broadband absolute accuracy (1-σ confidence bound) is not sufficient to allow gaps in the radiation record for decadal climate change. Typical absolute accuracy for the best narrowband sensors like SeaWiFS, MISR, and MODIS range from 2 to 4% (1-σ). IPCC greenhouse gas radiative forcing is ̃ 0.6 Wm -2 per decade or 0.6% of the global mean shortwave reflected flux, so that a 50% cloud feedback would change the global reflected flux by ̃ 0.3 Wm -2 or 0.3% per decade in broadband SW calibration change. Recent results comparing CERES reflected flux changes with MODIS, MISR, and SeaWiFS narrowband changes concluded that only SeaWiFS and CERES were approaching sufficient stability in calibration for decadal climate change [3]. Results using deep convective clouds in the optically thick limit as a stability target may prove very effective for improving past data sets like ISCCP. Results for intercalibration of geostationary imagers to CERES using an entire month of regional nearly coincident data demonstrates new approaches to constraining the calibration of current geostationary imagers. The new Decadal Survey Mission CLARREO is examining future approaches to a ""NIST-in- Orbit"" approach of very high absolute accuracy reference radiometers that cover the full solar and infrared spectrum at high spectral resolution but at low spatial resolution. Sampling studies have shown that a precessing CLARREO mission could calibrate other geo and leo reflected solar radiation and thermal infrared sensors. © 2008 IEEE."
"7005890514;7005495256;7103060756;","Inferring climate sensitivity from volcanic events",2007,"10.1007/s00382-006-0193-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847153042&doi=10.1007%2fs00382-006-0193-x&partnerID=40&md5=f20570532d4a324a20145e8e1b08db97","The possibility of estimating the equilibrium climate sensitivity of the earth-system from observations following explosive volcanic eruptions is assessed in the context of a perfect model study. Two modern climate models (the CCCma CGCM3 and the NCAR CCSM2) with different equilibrium climate sensitivities are employed in the investigation. The models are perturbed with the same transient volcano-like forcing and the responses analysed to infer climate sensitivities. For volcano-like forcing the global mean surface temperature responses of the two models are very similar, despite their differing equilibrium climate sensitivities, indicating that climate sensitivity cannot be inferred from the temperature record alone even if the forcing is known. Equilibrium climate sensitivities can be reasonably determined only if both the forcing and the change in heat storage in the system are known very accurately. The geographic patterns of clear-sky atmosphere/surface and cloud feedbacks are similar for both the transient volcano-like and near-equilibrium constant forcing simulations showing that, to a considerable extent, the same feedback processes are invoked, and determine the climate sensitivity, in both cases. © Springer-Verlag 2006."
"7004764167;","Comparison of mechanisms of cloud-climate feedbacks in GCMs",1999,"10.1175/1520-0442(1999)012<1480:comocc>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032883626&doi=10.1175%2f1520-0442%281999%29012%3c1480%3acomocc%3e2.0.co%3b2&partnerID=40&md5=d79ecfbd9ee23ef20e01ace019f2fdd2","International model comparisons of cloud-climate feedbacks have typically been restricted to assessing only the radiative effect of changes in clouds and have not attempted to explain the mechanisms for differences in cloud feedbacks. This paper uses different versions of the U.K. Meteorological Office GCM run at the Hadley Centre to illustrate the usefulness of a detailed comparison of microphysical cloud properties in understanding cloud feedback mechanisms and their effect on the regional distribution of the predicted warming in simulations of climate change. The inclusion of interactive cloud radiative properties explains much of the difference in the spatial patterns of cloud feedback and leads to a marked difference in the response of the large-scale circulation and in the resulting meridional gradient of surface temperature changes. In the model versions that include interactive radiative properties, the strength of the related feedback is determined by the water path of the cloud in the control experiment. Difficulties in performing such a detailed comparison on a wider range of models may arise from the lack of diagnostics in a common format being available from different models and because of the range of assumptions about how clouds are treated by different radiation schemes. A suggestion is put forward for a possible common format that would enable comparison of such diagnostics."
"57210687618;16644246500;","Clouds, Circulation, and Climate Sensitivity in a Radiative-Convective Equilibrium Channel Model",2017,"10.1002/2017MS001111","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040726266&doi=10.1002%2f2017MS001111&partnerID=40&md5=3a49224d3d1b31f31cb6d8de66870849","Tropical cloud and circulation changes are large sources of uncertainty in future climate change. This problem owes partly to the scale separation between large-scale tropical dynamics (~104 km) and convective dynamics (~7 km), which generally requires parameterizing convection in models that resolve large-scale dynamics, or parameterizing (or omitting) large-scale dynamics in models that permit convection. Here we discuss simulations of radiative-convective equilibrium (RCE) across a wide range of surface temperatures in long-channel geometry—where the domain size and resolution marginally resolve both large-scale dynamics and convection. Self-aggregation of convection in these simulations spontaneously produces realistic dynamical regimes of large-scale vertical motion. The circulation weakens with surface warming but changes in the degree of self-aggregation depend on the metric that is used; there is no obvious trend in aggregation with warming. Surface warming causes an upward shift and decrease in area of high clouds, and a sharp decline in midlevel clouds, but no systematic trend in low cloud cover. We introduce a method for approximate radiative kernel feedback analysis in RCE, and apply it to both simulations in long-channel geometry and in a smaller square domain. The kernel-corrected cloud feedback is positive but its magnitude varies across temperatures. Compared to simulations that do not have aggregation, there is a more negative net feedback due to the effects of aggregation on relative humidity and cloud cover. These results are consistent with the hypothesis that self-aggregation moderately reduces climate sensitivity. © 2017. The Authors."
"55537426400;6603196127;16480666100;","The role of atmospheric heat transport and regional feedbacks in the Arctic warming at equilibrium",2017,"10.1007/s00382-017-3523-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85009727215&doi=10.1007%2fs00382-017-3523-2&partnerID=40&md5=44ee4f98ed27710e759291f73bd08ca0","It is well known that the Arctic warms much more than the rest of the world even under spatially quasi-uniform radiative forcing such as that due to an increase in atmospheric CO2 concentration. While the surface albedo feedback is often referred to as the explanation of the enhanced Arctic warming, the importance of atmospheric heat transport from the lower latitudes has also been reported in previous studies. In the current study, an attempt is made to understand how the regional feedbacks in the Arctic are induced by the change in atmospheric heat transport and vice versa. Equilibrium sensitivity experiments that enable us to separate the contributions of the Northern Hemisphere mid-high latitude response to the CO2 increase and the remote influence of surface warming in other regions are carried out. The result shows that the effect of remote forcing is predominant in the Arctic warming. The dry-static energy transport to the Arctic is reduced once the Arctic surface warms in response to the local or remote forcing. The feedback analysis based on the energy budget reveals that the increased moisture transport from lower latitudes, on the other hand, warms the Arctic in winter more effectively not only via latent heat release but also via greenhouse effect of water vapor and clouds. The change in total atmospheric heat transport determined as a result of counteracting dry-static and latent heat components, therefore, is not a reliable measure for the net effect of atmospheric dynamics on the Arctic warming. The current numerical experiments support a recent interpretation based on the regression analysis: the concurrent reduction in the atmospheric poleward heat transport and future Arctic warming predicted in some models does not imply a minor role of the atmospheric dynamics. Despite the similar magnitude of poleward heat transport change, the Arctic warms more than the Southern Ocean even in the equilibrium response without ocean dynamics. It is shown that a large negative shortwave cloud feedback over the Southern Ocean, greatly influenced by low-latitude surface warming, is responsible for this asymmetric polar warming. © 2017, Springer-Verlag Berlin Heidelberg."
"55714908600;7003802133;7006354215;53979793000;55569698000;","Transient climate sensitivity depends on base climate ocean circulation",2017,"10.1175/JCLI-D-16-0581.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85012273227&doi=10.1175%2fJCLI-D-16-0581.1&partnerID=40&md5=bf6cb150373257436f7ce6511cd1a553","There is large uncertainty in the simulation of transient climate sensitivity. This study aims to understand how such uncertainty is related to the simulation of the base climate by comparing two simulations with the same model but in which CO2 is increased from either a preindustrial (1860) or a present-day (1990) control simulation. This allows different base climate ocean circulations that are representative of those in current climate models to be imposed upon a single model. As a result, the model projects different transient climate sensitivities that are comparable to the multimodel spread. The greater warming in the 1990-start run occurs primarily at high latitudes and particularly over regions of oceanic convection. In the 1990-start run, ocean overturning circulations are initially weaker and weaken less from CO2 forcing. As a consequence, there are smaller reductions in the poleward ocean heat transport, leading to less tropical ocean heat storage and less moderated high-latitude surface warming. This process is evident in both hemispheres, with changes in the Atlantic meridional overturning circulation and the Antarctic Bottom Water formation dominating the warming differences in each hemisphere. The high-latitude warming in the 1990-start run is enhanced through albedo and cloud feedbacks, resulting in a smaller ocean heat uptake efficacy. The results highlight the importance of improving the base climate ocean circulation in order to provide a reasonable starting point for assessments of past climate change and the projection of future climate change. © 2017 American Meteorological Society."
"25227529700;15071907100;","Projecting the release of carbon from permafrost soils using a perturbed parameter ensemble modelling approach",2016,"10.5194/bg-13-2123-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84964319117&doi=10.5194%2fbg-13-2123-2016&partnerID=40&md5=0ec8ffc84a942035800e1fd2e279af87","The soils of the northern hemispheric permafrost region are estimated to contain 1100 to 1500 Pg of carbon. A substantial fraction of this carbon has been frozen and therefore protected from microbial decay for millennia. As anthropogenic climate warming progresses much of this permafrost is expected to thaw. Here we conduct perturbed model experiments on a climate model of intermediate complexity, with an improved permafrost carbon module, to estimate with formal uncertainty bounds the release of carbon from permafrost soils by the year 2100 and 2300 CE. We estimate that by year 2100 the permafrost region may release between 56 (13 to 118) Pg C under Representative Concentration Pathway (RCP) 2.6 and 102 (27 to 199) PgC under RCP 8.5, with substantially more to be released under each scenario by the year 2300. Our analysis suggests that the two parameters that contribute most to the uncertainty in the release of carbon from permafrost soils are the size of the non-passive fraction of the permafrost carbon pool and the equilibrium climate sensitivity. A subset of 25 model variants are integrated 8000 years into the future under continued RCP forcing. Under the moderate RCP 4.5 forcing a remnant near-surface permafrost region persists in the high Arctic, eventually developing a new permafrost carbon pool. Overall our simulations suggest that the permafrost carbon cycle feedback to climate change will make a significant contribution to climate change over the next centuries and millennia, releasing a quantity of carbon 3 to 54 % of the cumulative anthropogenic total. © Author(s) 2016."
"56230988400;56033466400;6603566335;6603606681;23484340400;36701462300;36187387300;49664027700;","A single-column model intercomparison on the stratocumulus representation in present-day and future climate",2015,"10.1002/2014MS000377","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027919200&doi=10.1002%2f2014MS000377&partnerID=40&md5=a6deccded1850060a65b829f6ecb8648","Six Single-Column Model (SCM) versions of climate models are evaluated on the basis of their representation of the dependence of the stratocumulus-topped boundary layer regime on the free tropospheric thermodynamic conditions. The study includes two idealized experiments corresponding to the present-day and future climate conditions in order to estimate the low-cloud feedback. Large-Eddy Simulation (LES) results are used as a benchmark and GCM outputs are included to assess whether the SCM results are representative of their 3-D counterparts. The SCMs present a variety of dependencies of the cloud regime on the free tropospheric conditions but, at the same time, several common biases. For all the SCMs the stratocumulus-topped boundary layer is too shallow, too cool, and too moist as compared to the LES results. Moreover, they present a lack of clouds and liquid water and an excess of precipitation. The disagreement among SCMs is even more distinct for the response to a climate perturbation. Even though the overall feedback is positive for all the models, in line with the LES results, the SCMs show a rather noisy behavior, which depends irregularly on the free tropospheric conditions. Finally, the comparison with the host GCM outputs demonstrates that the considered approach is promising but needs to be further generalized for the SCMs to fully capture the behavior of their 3-D counterparts. Key Points: The article presents a hierarchy of models: six SCMs, the corresponding GCMs, one LES SCM biases: too shallow, cool, moist, and precipitating ABL, lack of clouds Positive overall cloud feedback in line with LES but SCMs show a noisy behavior © 2015. The Authors."
"7402989545;57131609600;","Uncertainty in the 2℃C warming threshold related to climate sensitivity and climate feedback",2015,"10.1007/s13351-015-5036-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007189790&doi=10.1007%2fs13351-015-5036-4&partnerID=40&md5=b9fc6e194db317dfd007ff3f6fe41739","Climate sensitivity is an important index that measures the relationship between the increase in greenhouse gases and the magnitude of global warming. Uncertainties in climate change projection and climate modeling are mostly related to the climate sensitivity. The climate sensitivities of coupled climate models determine the magnitudes of the projected global warming. In this paper, the authors thoroughly review the literature on climate sensitivity, and discuss issues related to climate feedback processes and the methods used in estimating the equilibrium climate sensitivity and transient climate response (TCR), including the TCR to cumulative CO2emissions. After presenting a summary of the sources that affect the uncertainty of climate sensitivity, the impact of climate sensitivity on climate change projection is discussed by addressing the uncertainties in 2℃ warming. Challenges that call for further investigation in the research community, in particular the Chinese community, are discussed. © The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2015."
"9635016300;7006622255;24490844700;14051038900;57194275819;","Historical and future learning about climate sensitivity",2014,"10.1002/2014GL059484","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899036813&doi=10.1002%2f2014GL059484&partnerID=40&md5=cbf96ead12e0691cbeb25097ce05b4a5","Equilibrium climate sensitivity measures the long-term response of surface temperature to changes in atmospheric CO2 the range of climate sensitivities in the Intergovernmental Panel on Climate Change Fifth Assessment Report is unchanged from that published almost 30-years earlier in the Charney Report. We conduct perfect model experiments using an energy balance model to study the rate at which uncertainties might be reduced by observation of global temperature and ocean heat uptake. We find that a climate sensitivity of 1.5°C can be statistically distinguished from 3°C by 2030, 3°C from 4.5°C by 2040, and 4.5°C from 6°C by 2065. Learning rates are slowest in the scenarios of greatest concern (high sensitivities), due to a longer ocean response time, which may have bearing on wait-and-see versus precautionary mitigation policies. Learning rates are optimistic in presuming the availability of whole ocean heat data but pessimistic by using simple aggregated metrics and model physics. Key Points Climate sensitivity uncertainty not greatly reduced over decades of research Continued observations may substantially reduce uncertainty over the next decades Rate of learning may affect wait-and-see versus precautionary mitigation policies © 2014. American Geophysical Union. All Rights Reserved."
"56450100300;7201504886;","Climate and climate sensitivity to changing CO2 on an idealized land planet",2014,"10.1002/2014MS000369","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027939481&doi=10.1002%2f2014MS000369&partnerID=40&md5=47d46b7709de128768f2c825bdb3b92d","The comprehensive general circulation model ECHAM6 is used in a radiative-convective equilibrium configuration. It is coupled to a perfectly conducting slab. To understand the local impact of thermodynamic surface properties on the land-ocean warming contrast, the surface latent heat flux and surface heat capacity are reduced stepwise, aiming for a land-like climate. Both ocean-like and land-like RCE simulation reproduce the tropical atmosphere over ocean and land in a satisfactory manner and lead to reasonable land-ocean warming ratios. A small surface heat capacity induces a high diurnal surface temperature range which triggers precipitation during the day and decouples the free troposphere from the diurnal mean temperature. With increasing evaporation resistance, the net atmospheric cooling rate decreases because cloud base height rises, causing a reduction of precipitation. Climate sensitivity depends more on changes in evaporation resistance than on changes in surface heat capacity. A feedback analysis with the partial radiation perturbation method shows that amplified warming over idealized land can be associated with disproportional changes in the lapse rate versus the water vapor feedback. Cloud feedbacks, convective aggregation, and changes in global mean surface temperature confuse the picture. © 2014. The Authors."
"6602845217;56020871100;55330583500;36537081500;","Analysis of the Slab Ocean El Nino atmospheric feedbacks in observed and simulated ENSO dynamics",2014,"10.1007/s00382-014-2057-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901987382&doi=10.1007%2fs00382-014-2057-0&partnerID=40&md5=be9d6462c9b94b33b25ddd835f2f846e","In a recent study it was illustrated that the El Nino Southern Oscillation (ENSO) mode can exist in the absence of any ocean dynamics. This oscillating mode exists just due to the interaction between atmospheric heat fluxes and ocean heat capacity. The primary purpose of this study is to further explore these atmospheric Slab Ocean ENSO dynamics and therefore the role of positive atmospheric feedbacks in model simulations and observations. The positive solar radiation feedback to sea surface temperature (SST), due to reduced cloud cover for anomalous warm SSTs, is the main positive feedback in the Slab Ocean El Nino dynamics. The strength of this positive cloud feedback is strongly related to the strength of the equatorial cold tongue. The combination of positive latent and sensible heat fluxes to the west and negative ones to the east of positive anomalies leads to the westward propagation of the SST anomalies, which allows for oscillating behavior with a preferred period of 6-7 years. Several indications are found that parts of these dynamics are indeed observed and simulated in other atmospheric or coupled general circulation models (AGCMs or CGCMs). The CMIP3 AGCM-slab ensemble of 13 different AGCM simulations shows unstable ocean-atmosphere interactions along the equatorial Pacific related to stronger cold tongues. In observations and in the CMIP3 and CMIP5 CGCM model ensemble the strength and sign of the cloud feedback is a function of the strength of the cold tongue. In summary, this indicates that the Slab Ocean El Nino dynamics are indeed a characteristic of the equatorial Pacific climate that is only dominant or significantly contributing to the ENSO dynamics if the SST cold tongue is sufficiently strong. In the observations this is only the case during strong La Nina conditions. The presence of the Slab Ocean ENSO atmospheric feedbacks in observations and CGCM model simulations implies that the family of physical ENSO modes does have another member, which is entirely driven by atmospheric processes and does not need to have the same spatial pattern nor the same time scales as the main ENSO dynamics. © 2014 Springer-Verlag Berlin Heidelberg."
"57196752024;","Observational estimate of climate sensitivity from changes in the rate of ocean heat uptake and comparison to CMIP5 models",2014,"10.1007/s00382-013-1770-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897578132&doi=10.1007%2fs00382-013-1770-4&partnerID=40&md5=c0763455458c8051282625bb04ddb7f1","Climate sensitivity is estimated based on 0-2,000 m ocean heat content and surface temperature observations from the second half of the 20th century and first decade of the 21st century, using a simple energy balance model and the change in the rate of ocean heat uptake to determine the radiative restoration strength over this time period. The relationship between this 30-50 year radiative restoration strength and longer term effective sensitivity is investigated using an ensemble of 32 model configurations from the Coupled Model Intercomparison Project phase 5 (CMIP5), suggesting a strong correlation between the two. The mean radiative restoration strength over this period for the CMIP5 members examined is 1.16 Wm-2K-1, compared to 2.05 Wm-2K-1 from the observations. This suggests that temperature in these CMIP5 models may be too sensitive to perturbations in radiative forcing, although this depends on the actual magnitude of the anthropogenic aerosol forcing in the modern period. The potential change in the radiative restoration strength over longer timescales is also considered, resulting in a likely (67 %) range of 1.5-2.9 K for equilibrium climate sensitivity, and a 90 % confidence interval of 1.2-5.1 K. © 2013 Springer-Verlag Berlin Heidelberg."
"56005080300;23082420800;7401776640;7003543851;","Observational and model estimates of cloud amount feedback over the Indian and Pacific oceans",2014,"10.1175/JCLI-D-13-00165.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892526467&doi=10.1175%2fJCLI-D-13-00165.1&partnerID=40&md5=d715a20a07be32eb4530bf7c6509a6a6","Constraining intermodel spread in cloud feedback with observations is problematic because available cloud datasets are affected by spurious behavior in long-term variability. This problem is addressed by examining cloud amount in three independent ship-based [Extended Edited Cloud Reports Archive (EECRA)] and satellite-based [International SatelliteCloudClimatology Project (ISCCP) andAdvancedVeryHighResolution Radiometer Pathfinder Atmosphere-Extended (PATMOS-X)] observational datasets, and models from phase 5 of the Coupled Model Intercomparison Project (CMIP5). The three observational datasets show consistent cloud variability in the overlapping years of coverage (1984-2007). The long-term cloud amount change from 1954 to 2005 in ship-based observations shares many of the same features with the multimodel mean cloud amount change of 42 CMIP5 historical simulations, although the magnitude of the multimodel mean is smaller. The radiative impact of cloud changes is estimated by computing an observationally derived estimate of cloud amount feedback. The observational estimates of cloud amount feedback are statistically significant over four regions: the northeast Pacific subtropical stratocumulus region and equatorial western Pacific, where cloud amount feedback is found to be positive, and the southern central Pacific and western Indian Ocean, where cloud amount feedback is found to be negative. Multimodel mean cloud amount feedback is consistent in sign but smaller in magnitude than in observations over these four regions because models simulate weaker cloud changes. Individual models, however, can simulate cloud amount feedback of the same magnitude if not larger than observed. Focusing on the regions where models and observations agree can lead to improved understanding of the mechanisms of cloud amount changes and associated radiative impact. © 2014 American Meteorological Society."
"7003851161;36991619500;57202891769;7003406456;","The dependence of equilibrium climate sensitivity on climate state: Applications to studies of climates colder than present",2013,"10.1002/grl.50724","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880603628&doi=10.1002%2fgrl.50724&partnerID=40&md5=229f3618c6dd1354e8eeecb02d4f62be","We investigate the sensitivity of climate to a broad range of greenhouse gas forcing with coupled atmosphere-ocean general circulation models using atmospheric CO2 concentrations ranging from ~1400 to ~200 ppm. We show that climate sensitivity is greater when the base state climate is colder, a result noted previously but with models of much lower resolution and different parameterizations. The enhanced cold state sensitivity is more apparent in models coupled to dynamical versus slab oceans. The disproportionately large sensitivity for cold climates has applications to studies of climates colder than present. © 2013. American Geophysical Union. All Rights Reserved."
"7801693068;7403282069;7403531523;","An estimate of low-cloud feedbacks from variations of cloud radiative and physical properties with sea surface temperature on interannual time scales",2011,"10.1175/2010JCLI3670.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955037981&doi=10.1175%2f2010JCLI3670.1&partnerID=40&md5=def656fdf744c4e29fd3c0e0d52b68ae","Simulations of climate change have yet to reach a consensus on the sign and magnitude of the changes in physical properties of marine boundary layer clouds. In this study, the authors analyze how cloud and radiative properties vary with SST anomaly in low-cloud regions, based on five years (March 2000-February 2005) of Clouds and the Earth's Radiant Energy System (CERES)-Terra monthly gridded data and matched European Centre for Medium-Range Weather Forecasts (ECMWF) meteorological reanalaysis data. In particular, this study focuses on the changes in cloud radiative effect, cloud fraction, and cloud optical depth with SST anomaly. The major findings are as follows. First, the low-cloud amount (-1.9% to 3.4% K-1) and the logarithm of low-cloud optical depth (-0.085 to 0.100 K-1) tend to decrease while the net cloud radiative effect (3.86 W m-2 K-1) becomes less negative as SST anomalies increase. These results are broadly consistent with previous observational studies. Second, after the changes in cloud and radiative properties with SST anomaly are separated into dynamic, thermodynamic, and residual components, changes in the dynamic component (taken as the vertical velocity at 700 hPa) have relatively little effect on cloud and radiative properties. However, the estimated inversion strength decreases with increasing SST, accounting for a large portion of the measured decreases in cloud fraction and cloud optical depth. The residual positive change in net cloud radiative effect (1.48 W m-2 K-1) and small changes in low-cloud amount (-0.81% to 0.22% K-1) and decrease in the logarithm of optical depth (-0.035 to -0.046 K-1) with SST are interpreted as a positive cloud feedback, with cloud optical depth feedback being the dominant contributor. Last, the magnitudes of the residual changes differ greatly among the six low-cloud regions examined in this study, with the largest positive feedbacks (~4 W m-2 K-1) in the southeast and northeast Atlantic regions and a slightly negative feedback (-0.2 W m-2 K-1) in the south-central Pacific region. Because the retrievals of cloud optical depth and/or cloud fraction are difficult in the presence of aerosols, the transport of heavy African continental aerosols may contribute to the large magnitudes of estimated cloud feedback in the two Atlantic regions. © 2011 American Meteorological Society."
"57212781009;7101785401;","Atmospheric radiative feedbacks associated with transient climate change and climate variability",2010,"10.1007/s00382-009-0541-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952876531&doi=10.1007%2fs00382-009-0541-8&partnerID=40&md5=106edc392bbad1a1b53845613d64d67f","This study examines in detail the 'atmospheric' radiative feedbacks operating in a coupled General Circulation Model (GCM). These feedbacks (defined as the change in top of atmosphere radiation per degree of global surface temperature change) are due to responses in water vapour, lapse rate, clouds and surface albedo. Two types of radiative feedback in particular are considered: those arising from century scale 'transient' warming (from a 1% per annum compounded CO2 increase), and those operating under the model's own unforced 'natural' variability. The time evolution of the transient (or 'secular') feedbacks is first examined. It is found that both the global strength and the latitudinal distributions of these feedbacks are established within the first two or three decades of warming, and thereafter change relatively little out to 100 years. They also closely approximate those found under equilibrium warming from a 'mixed layer' ocean version of the same model forced by a doubling of CO2. These secular feedbacks are then compared with those operating under unforced (interannual) variability. For water vapour, the interannual feedback is only around two-thirds the strength of the secular feedback. The pattern reveals widespread regions of negative feedback in the interannual case, in turn resulting from patterns of circulation change and regions of decreasing as well as increasing surface temperature. Considering the vertical structure of the two, it is found that although positive net mid to upper tropospheric contributions dominate both, they are weaker (and occur lower) under interannual variability than under secular change and are more narrowly confined to the tropics. Lapse rate feedback from variability shows weak negative feedback over low latitudes combined with strong positive feedback in mid-to-high latitudes resulting in no net global feedback-in contrast to the dominant negative low to mid-latitude response seen under secular climate change. Surface albedo feedback is, however, slightly stronger under interannual variability-partly due to regions of extremely weak, or even negative, feedback over Antarctic sea ice in the transient experiment. Both long and shortwave global cloud feedbacks are essentially zero on interannual timescales, with the shortwave term also being very weak under climate change, although cloud fraction and optical property components show correlation with global temperature both under interannual variability and transient climate change. The results of this modelling study, although for a single model only, suggest that the analogues provided by interannual variability may provide some useful pointers to some aspects of climate change feedback strength, particularly for water vapour and surface albedo, but that structural differences will need to be heeded in such an analysis. © 2009 Springer-Verlag."
"14623355800;6701359648;","Impact of atmospheric small-scale fluctuations on climate sensitivity",2008,"10.1029/2008GL033483","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57149131010&doi=10.1029%2f2008GL033483&partnerID=40&md5=42ea66e7363366bc08bfbae7041dc0a5","Climate change scenarios are based on numerical models with finite spatial and temporal resolutions. The impact of unresolved processes is parameterized without taking the variability induced by subscale processes into account. this drawback could lead to an over-/ underestimation of the climate sensitivity. The aim of this study is to investigate the impact of small-scale atmospheric fluctuations on the modeled climate sensitivity to increased CO2 concentration. Using a complex coupled atmosphere-ocean general Circulation model (ECHAM5/MPI-OM) climate response experiments with enhanced small-scale fluctuations are performed. Our results show that the strength of the global warming due to a CO2 doubling depends on the representation of small-scale fluctuations. Reducing the horizontal diffusion by a factor of 3 leads to an increase of the equilibrium climate sensitivity by 13%. If white noise is added to the small scales, the climate sensitivity tends to weaken. The largest changes in responses occur in the upper troposphere. Copyright 2008 by the American Geophysical Union."
"6603809220;","Climate sensitivity of the CSIRO GCM: Effect of cloud modeling assumptions",1999,"10.1175/1520-0442(1999)012<0334:CSOTCG>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033079618&doi=10.1175%2f1520-0442%281999%29012%3c0334%3aCSOTCG%3e2.0.CO%3b2&partnerID=40&md5=b3c00b150115bb78a20d3c19dcb4e398","The climate sensitivity of the CSIRO Global Climate Model is investigated using uniform sea surface temperature perturbation experiments. One experiment (denoted DIAG) uses a diagnostic treatment of clouds, with fixed cloud radiative properties that vary with height. The other experiment (denoted CTRL) uses a recently introduced prognostic treatment of stratiform clouds, with interactive calculation of cloud radiative properties. The DIAG experiment has a positive shortwave (SW) cloud feedback and a negative longwave (LW) feedback, due to an overall reduction of midlevel and high cloudiness in the warmer climate. The signs of both the SW and LW feedbacks are opposite in the CTRL experiment due to an overall increase of cloud water content in the warmer climate. Because of cancellation between the SW and LW components, there is not a large difference in the net cloud feedback between the two experiments, with both having a modest negative cloud feedback, as measured by the change in cloud radiative forcing. The CTRL experiment has a larger clear-sky climate sensitivity than the DIAG experiment. Off-line radiative calculations are used to show that this is primarily because of a stronger water vapor feedback. This is caused by differences in upper-tropospheric cloud radiative forcing that give a stronger upward shift of the tropopause on warming when the prognostic scheme is used. A sensitivity test shows that an artificial restriction on the maximum height of high clouds that exists in the diagnostic scheme is the reason for the different behavior. The robustness of the result obtained in the CTRL experiment is investigated via 18 perturbation experiments, in which key parameters in the prognostic cloud scheme are varied, while retaining the overall approach used in the CTRL experiment. As far as possible, theory and observations are used to constrain the ranges within which these parameters are varied. It is found that the behavior of the scheme under climate change is generally robust, with no statistically significant changes in LW cloud feedback and only modest changes in SW cloud feedback. Overall, larger differences (both in control climate and in climate sensitivity) result from parameter changes that effect cloud formation than from changes that affect precipitation processes or cloud radiative properties.The climate sensitivity of the CSIRO Global Climate Model is investigated using uniform sea surface temperature perturbation experiments. One experiment (denoted DIAG) uses a diagnostic treatment of clouds, with fixed cloud radiative properties that vary with height. The other experiment (denoted CTRL) uses a recently introduced prognostic treatment of stratiform clouds, with interactive calculation of cloud radiative properties. The DIAG experiment has a positive shortwave (SW) cloud feedback and a negative longwave (LW) feedback, due to an overall reduction of midlevel and high cloudiness in the warmer climate. The signs of both the SW and LW feedbacks are opposite in the CTRL experiment due to an overall increase of cloud water content in the warmer climate. Because of cancellation between the SW and LW components, there is not a large difference in the net cloud feedback between the two experiments, with both having a modest negative cloud feedback, as measured by the change in cloud radiative forcing. The CTRL experiment has a larger clear-sky climate sensitivity than the DIAG experiment. Off-line radiative calculations are used to show that this is primarily because of a stronger water vapor feedback. This is caused by differences in upper-tropospheric cloud radiative forcing that give a stronger upward shift of the tropopause on warming when the prognostic scheme is used. A sensitivity test shows that an artificial restriction on the maximum height of high clouds that exists in the diagnostic scheme is the reason for the different behavior. The robustness of the result obtained in the CTRL experiment is investigated via 18 perturbation experiments, in which key parameters in the prognostic cloud scheme are varied, while retaining the overall approach used in the CTRL experiment. As far as possible, theory and observations are used to constrain the ranges within which these parameters are varied. It is found that the behavior of the scheme under climate change is generally robust, with no statistically significant changes in LW cloud feedback and only modest changes in SW cloud feedback. Overall, larger differences (both in control climate and in climate sensitivity) result from parameter changes that affect cloud formation than from changes that affect precipitation processes or cloud radiative properties."
"24329376600;56059501400;13402835300;55715917500;6602893477;26659116700;49663766700;7006766881;7003976079;36161386500;7004764167;56063791400;","Forcings, Feedbacks, and Climate Sensitivity in HadGEM3-GC3.1 and UKESM1",2019,"10.1029/2019MS001866","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076773201&doi=10.1029%2f2019MS001866&partnerID=40&md5=d4bb48290965dc2b1acdce2f5aa9cf88","Climate forcing, sensitivity, and feedback metrics are evaluated in both the United Kingdom's physical climate model HadGEM3-GC3.1 at low (-LL) and medium (-MM) resolution and the United Kingdom's Earth System Model UKESM1. The effective climate sensitivity (EffCS) to a doubling of CO2 is 5.5 K for HadGEM3.1-GC3.1-LL and 5.4 K for UKESM1. The transient climate response is 2.5 and 2.8 K, respectively. While the EffCS is larger than that seen in the previous generation of models, none of the model's forcing or feedback processes are found to be atypical of models, though the cloud feedback is at the high end. The relatively large EffCS results from an unusual combination of a typical CO2 forcing with a relatively small feedback parameter. Compared to the previous U.K. climate model, HadGEM3-GC2.0, the EffCS has increased from 3.2 to 5.5 K due to an increase in CO2 forcing, surface albedo feedback, and midlatitude cloud feedback. All changes are well understood and due to physical improvements in the model. At higher atmospheric and ocean resolution (HadGEM3-GC3.1-MM), there is a compensation between increased marine stratocumulus cloud feedback and reduced Antarctic sea-ice feedback. In UKESM1, a CO2 fertilization effect induces a land surface vegetation change and albedo radiative effect. Historical aerosol forcing in HadGEM3-GC3.1-LL is −1.1 W m−2. In HadGEM3-GC3.1-LL historical simulations, cloud feedback is found to be less positive than in abrupt-4xCO2, in agreement with atmosphere-only experiments forced with observed historical sea surface temperature and sea-ice variations. However, variability in the coupled model's historical sea-ice trends hampers accurate diagnosis of the model's total historical feedback. ©2019. The Authors."
"55575258400;57205867148;35561911800;36705143500;","Internal Variability and Disequilibrium Confound Estimates of Climate Sensitivity From Observations",2018,"10.1002/2017GL076468","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042496642&doi=10.1002%2f2017GL076468&partnerID=40&md5=a77312046ff01d830948365be98a0e4d","An emerging literature suggests that estimates of equilibrium climate sensitivity (ECS) derived from recent observations and energy balance models are biased low because models project more positive climate feedback in the far future. Here we use simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to show that across models, ECS inferred from the recent historical period (1979–2005) is indeed almost uniformly lower than that inferred from simulations subject to abrupt increases in CO2 radiative forcing. However, ECS inferred from simulations in which sea surface temperatures are prescribed according to observations is lower still. ECS inferred from simulations with prescribed sea surface temperatures is strongly linked to changes to tropical marine low clouds. However, feedbacks from these clouds are a weak constraint on long-term model ECS. One interpretation is that observations of recent climate changes constitute a poor direct proxy for long-term sensitivity. ©2018. American Geophysical Union. All Rights Reserved."
"36598281300;55667384900;36627288300;35769583500;55883034700;6603618077;24921885300;16403388800;","Assessing the habitability of planets with Earth-like atmospheres with 1D and 3D climate modeling",2016,"10.1051/0004-6361/201628413","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84978880079&doi=10.1051%2f0004-6361%2f201628413&partnerID=40&md5=d00b669281617e009749fbb8499c13cb","Context. The habitable zone (HZ) describes the range of orbital distances around a star where the existence of liquid water on the surface of an Earth-like planet is in principle possible. The applicability of one-dimensional (1D) climate models for the estimation of the HZ boundaries has been questioned by recent three-dimensional (3D) climate studies. While 3D studies can calculate the water vapor, ice albedo, and cloud feedback self-consistently and therefore allow for a deeper understanding and the identification of relevant climate processes, 1D model studies rely on fewer model assumptions and can be more easily applied to the large parameter space possible for extrasolar planets. Aims. We evaluate the applicability of 1D climate models to estimate the potential habitability of Earth-like extrasolar planets by comparing our 1D model results to those of 3D climate studies in the literature. We vary the two important planetary properties, surface albedo and relative humidity, in the 1D model. These depend on climate feedbacks that are not treated self-consistently in most 1D models. Methods. We applied a cloud-free 1D radiative-convective climate model to calculate the climate of Earth-like planets around different types of main-sequence stars with varying surface albedo and relative humidity profile. We compared the results to those of 3D model calculations available in the literature and investigated to what extent the 1D model can approximate the surface temperatures calculated by the 3D models. Results. The 1D parameter study results in a large range of climates possible for an Earth-sized planet with an Earth-like atmosphere and water reservoir at a certain stellar insolation. At some stellar insolations the full spectrum of climate states could be realized, i.e., uninhabitable conditions due to surface temperatures that are too high or too low as well as habitable surface conditions, depending only on the relative humidity and surface albedo assumed. When treating the surface albedo and the relative humidity profile as parameters in 1D model studies and using the habitability constraints found by recent 3D modeling studies, the same conclusions about the potential habitability of a planet can be drawn as from 3D model calculations. © 2016 ESO."
"7004764167;24329376600;36842027200;35742922300;16177522400;55318394800;6603153821;37019252000;36106706200;7006766881;7003976079;7007021059;","Idealized climate change simulations with a high-resolution physical model: HadGEM3-GC2",2016,"10.1002/2015MS000614","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84971432659&doi=10.1002%2f2015MS000614&partnerID=40&md5=9df517c0257d72bcb976eb2292a66874","Idealized climate change simulations with a new physical climate model, HadGEM3-GC2 from The Met Office Hadley Centre are presented and contrasted with the earlier MOHC model, HadGEM2-ES. The role of atmospheric resolution is also investigated. The Transient Climate Response (TCR) is 1.9 K/2.1 K at N216/N96 and Effective Climate Sensitivity (ECS) is 3.1 K/3.2 K at N216/N96. These are substantially lower than HadGEM2-ES (TCR: 2.5 K; ECS: 4.6 K) arising from a combination of changes in the size of climate feedbacks. While the change in the net cloud feedback between HadGEM3 and HadGEM2 is relatively small, there is a change in sign of its longwave and a strengthening of its shortwave components. At a global scale, there is little impact of the increase in atmospheric resolution on the future climate change signal and even at a broad regional scale, many features are robust including tropical rainfall changes, however, there are some significant exceptions. For the North Atlantic and western Europe, the tripolar pattern of winter storm changes found in most CMIP5 models is little impacted by resolution but for the most intense storms, there is a larger percentage increase in number at higher resolution than at lower resolution. Arctic sea-ice sensitivity shows a larger dependence on resolution than on atmospheric physics. © 2016. The Authors."
"57214989533;8315173500;6602142887;6603854453;","Southward intertropical convergence zone shifts and implications for an atmospheric bipolar seesaw",2013,"10.1175/JCLI-D-12-00279.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880283425&doi=10.1175%2fJCLI-D-12-00279.1&partnerID=40&md5=f680f72e5c8f3e6e6891d84ffe010f4a","In this study, southward intertropical convergence zone (ITCZ) shifts are investigated in three different scenarios: Northern Hemispheric cooling, Southern Hemispheric warming, and a bipolar seesaw-like forcing that combines the latter two. The experiments demonstrate the mutual effects that northern- and southernhigh- latitude forcings exert on tropical precipitation, suggesting a time-scale-dependent dominance of northern versus southern forcings. In accordance with this, two-phase tropical precipitation shifts are suggested, involving a fast component dominated by the high-northern-latitude forcing and a slower component due to the southern-high-latitude forcing. The results may thus be useful for the future understanding and interpretation of high-resolution tropical paleoprecipitation proxies and their relation to high-latitude records (e.g., ice core data). The experiments also show that Southern Ocean warming has a global impact, affecting both the tropics and northern extratropics, as seen in a southward ITCZ shift and mid- and high-latitude North Atlantic surface temperature and wind changes. In terms of dynamical considerations, the tropical circulation response to high-latitude forcing is found to be nonlinear: the atmospheric heat transport and Hadley cell anomalies differ significantly (in magnitude) when comparing the warming and cooling experiments. These are related to different interhemispheric temperature gradients that are altered mainly by nonlinearities in water vapor response. Decomposition of the top-of-the-atmosphere flux response into atmospheric feedback effects shows the dominance of water vapor and cloud feedbacks in the tropics, with the longwave cloud feedback effect governing the overall cloud response. © 2013 American Meteorological Society."
"7201606127;7401776640;","Cluster analysis of midlatitude oceanic cloud regimes: Mean properties and temperature sensitivity",2010,"10.5194/acp-10-6435-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955678558&doi=10.5194%2facp-10-6435-2010&partnerID=40&md5=6a60ea515bd0a99134c4137c77a8efd1","Clouds play an important role in the climate system by reducing the amount of shortwave radiation reaching the surface and the amount of longwave radiation escaping to space. Accurate simulation of clouds in computer models remains elusive, however, pointing to a lack of understanding of the connection between large-scale dynamics and cloud properties. This study uses a k-means clustering algorithm to group 21 years of satellite cloud data over midlatitude oceans into seven clusters, and demonstrates that the cloud clusters are associated with distinct large-scale dynamical conditions. Three clusters correspond to low-level cloud regimes with different cloud fraction and cumuliform or stratiform characteristics, but all occur under large-scale descent and a relatively dry free troposphere. Three clusters correspond to vertically extensive cloud regimes with tops in the middle or upper troposphere, and they differ according to the strength of large-scale ascent and enhancement of tropospheric temperature and humidity. The final cluster is associated with a lower troposphere that is dry and an upper troposphere that is moist and experiencing weak ascent and horizontal moist advection. Since the present balance of reflection of shortwave and absorption of longwave radiation by clouds could change as the atmosphere warms from increasing anthropogenic greenhouse gases, we must also better understand how increasing temperature modifies cloud and radiative properties. We therefore undertake an observational analysis of how midlatitude oceanic clouds change with temperature when dynamical processes are held constant (i.e., partial derivative with respect to temperature). For each of the seven cloud regimes, we examine the difference in cloud and radiative properties between warm and cold subsets. To avoid misinterpreting a cloud response to large-scale dynamical forcing as a cloud response to temperature, we require horizontal and vertical temperature advection in the warm and cold subsets to have near-median values in three layers of the troposphere. Across all of the seven clusters, we find that cloud fraction is smaller and cloud optical thickness is mostly larger for the warm subset. Cloud-top pressure is higher for the three low-level cloud regimes and lower for the cirrus regime. The net upwelling radiation flux at the top of the atmosphere is larger for the warm subset in every cluster except cirrus, and larger when averaged over all clusters. This implies that the direct response of midlatitude oceanic clouds to increasing temperature acts as a negative feedback on the climate system. Note that the cloud response to atmospheric dynamical changes produced by global warming, which we do not consider in this study, may differ, and the total cloud feedback may be positive. © Author(s) 2010."
"56574013600;","Assessing the value of price caps and floors",2009,"10.3763/cpol.2008.0586","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73649090067&doi=10.3763%2fcpol.2008.0586&partnerID=40&md5=7563a6d5ffe479decc7a85d2fca7f1b2","This article assesses the long-term economic and climatic effects of introducing price caps and price floors in hypothetical global climate change mitigation policy. Based on emission trends, abatement costs and equilibrium climate sensitivity from IPCC and IEA reports, this quantitative analysis confirms that price caps could significantly reduce economic uncertainty. This uncertainty stems primarily from unpredictable economic growth and energy prices, and ultimately unabated emission trends. In addition, the development of abatement technologies is uncertain. Furthermore, this analysis shows that rigid targets may entail greater economic risks with little or no comparative advantage for the climate. More ambitious emission objectives, combined with price caps and price floors, could still entail significantly lower expected costs while driving similar, or even slightly better, climatic outcomes in probabilistic terms. © 2009 OECD/IEA."
"57203053317;23095483400;","The importance of mixed-phase and ice clouds for climate sensitivity in the global aerosol-climate model ECHAM6-HAM2",2018,"10.5194/acp-18-8807-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85049192092&doi=10.5194%2facp-18-8807-2018&partnerID=40&md5=f5973568cb16dc80fe6a99bc62f440e2","How clouds change in a warmer climate remains one of the largest uncertainties for the equilibrium climate sensitivity (ECS). While a large spread in the cloud feedback arises from low-level clouds, it was recently shown that mixed-phase clouds are also important for ECS. If mixed-phase clouds in the current climate contain too few supercooled cloud droplets, too much ice will change to liquid water in a warmer climate. As shown by Tan et al. (2016), this overestimates the negative cloud-phase feedback and underestimates ECS in the CAM global climate model (GCM). Here we use the newest version of the ECHAM6-HAM2 GCM to investigate the importance of mixed-phase and ice clouds for ECS. Although we also considerably underestimate the fraction of supercooled liquid water globally in the reference version of the ECHAM6-HAM2 GCM, we do not obtain increases in ECS in simulations with more supercooled liquid water in the present-day climate, different from the findings by Tan et al. (2016). We hypothesize that it is not the global supercooled liquid water fraction that matters, but only how well low-and mid-level mixed-phase clouds with cloud-top temperatures in the mixed-phase temperature range between 0 and-35 °C that are not shielded by higher-lying ice clouds are simulated. These occur most frequently in midlatitudes, in particular over the Southern Ocean where they determine the amount of absorbed shortwave radiation. In ECHAM6-HAM2 the amount of absorbed shortwave radiation over the Southern Ocean is only significantly overestimated if all clouds below 0 °C consist exclusively of ice. Only in this simulation is ECS significantly smaller than in all other simulations and the cloud optical depth feedback is the dominant cloud feedback. In all other simulations, the cloud optical depth feedback is weak and changes in cloud feedbacks associated with cloud amount and cloud-top pressure dominate the overall cloud feedback. However, apart from the simulation with only ice below 0 °C, differences in the overall cloud feedback are not translated into differences in ECS in our model. This insensitivity to the cloud feedback in our model is explained with compensating effects in the clear sky. © 2018 Author(s)."
"55437450100;7201504886;8696069500;6603247427;","Radiative convective equilibrium as a framework for studying the interaction between convection and its large-scale environment",2016,"10.1002/2016MS000629","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983485991&doi=10.1002%2f2016MS000629&partnerID=40&md5=44ee641ec13077ca2401ea4e533a94d7","An uncertain representation of convective clouds has emerged as one of the key barriers to our understanding of climate sensitivity. The large gap in resolved spatial scales between General Circulation Models (GCMs) and high resolution models has made a systematic study of convective clouds across model configurations difficult. It is shown here that the simulated atmosphere of a GCM in Radiative Convective Equilibrium (RCE) is sufficiently similar across a range of domain sizes to justify the use of RCE to study both a GCM and a high resolution model on the same domain with the goal of improved constraints on the parameterized clouds. Simulations of RCE with parameterized convection have been analyzed on domains with areas spanning more than two orders of magnitude (0.80-204X106km2), all having the same grid spacing of 13km. The simulated climates on different domains are qualitatively similar in their degree of convective organization, the precipitation rates, and the vertical structure of the clouds and water vapor, with the similarity increasing as the domain size increases. Sea surface temperature perturbation experiments are used to estimate the climate feedback parameter for the differently configured experiments, and the cloud radiative effect is computed to examine the role which clouds play in the response. Despite the similar climate states between the domains the feedback parameter varies by more than a factor of two; the hydrological sensitivity parameter is better behaved, varying by a factor of 1.4. The sensitivity of the climate feedback parameter to domain size is related foremost to a nonsystematic response of low-level clouds as well as an increasingly negative longwave feedback on larger domains. © 2016. The Authors."
"7402332362;7102976560;15724543600;7004060399;","Stratospheric ozone chemistry feedbacks are not critical for the determination of climate sensitivity in CESM1(WACCM)",2016,"10.1002/2016GL068344","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84992292114&doi=10.1002%2f2016GL068344&partnerID=40&md5=1d1a6f5eb47d1b8a4bc479f895a874e4","The Community Earth System Model-Whole Atmosphere Community Climate Model (CESM1-WACCM) is used to assess the importance of including chemistry feedbacks in determining the equilibrium climate sensitivity (ECS). Two 4×CO2 model experiments were conducted: one with interactive chemistry and one with chemical constituents other than CO2 held fixed at their preindustrial values. The ECS determined from these two experiments agrees to within 0.01 K. Similarly, the net feedback parameter agrees to within 0.01 W m-2 K-1. This agreement occurs in spite of large changes in stratospheric ozone found in the simulation with interactive chemistry: a 30% decrease in the tropical lower stratosphere and a 40% increase in the upper stratosphere, broadly consistent with other published estimates. Off-line radiative transfer calculations show that ozone changes alone account for the difference in radiative forcing. We conclude that at least for determining global climate sensitivity metrics, the exclusion of chemistry feedbacks is not a critical source of error in CESM. ©2016. American Geophysical Union. All Rights Reserved."
"16202694600;8866821900;","Understanding the varied influence of midlatitude jet position on clouds and cloud radiative effects in observations and global climate models",2016,"10.1175/JCLI-D-16-0295.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85001129201&doi=10.1175%2fJCLI-D-16-0295.1&partnerID=40&md5=643798e509e718599a55450a539d5633","This study examines the dynamical mechanisms responsible for changes in midlatitude clouds and cloud radiative effects (CRE) that occur in conjunction with meridional shifts in the jet streams over the North Atlantic, North Pacific, and Southern Oceans. When the midlatitude jet shifts poleward, extratropical cyclones and their associated upward vertical velocity anomalies closely follow. As a result, a poleward jet shift contributes to a poleward shift in high-topped storm-track clouds and their associated longwave CRE. However, when the jet shifts poleward, downward vertical velocity anomalies increase equatorward of the jet, contributing to an enhancement of the boundary layer estimated inversion strength (EIS) and an increase in low cloud amount there. Because shortwave CRE depends on the reflection of solar radiation by clouds in all layers, the shortwave cooling effects of midlatitude clouds increase with both upward vertical velocity anomalies and positive EIS anomalies. Over midlatitude oceans where a poleward jet shift contributes to positive EIS anomalies but downward vertical velocity anomalies, the two effects cancel, and net observed changes in shortwave CRE are small. Global climate models generally capture the observed anomalies associated with midlatitude jet shifts. However, there is large intermodel spread in the shortwave CRE anomalies, with a subset of models showing a large shortwave cloud radiative warming over midlatitude oceans with a poleward jet shift. In these models, midlatitude shortwave CRE is sensitive to vertical velocity perturbations, but the observed sensitivity to EIS perturbations is underestimated. Consequently, these models might incorrectly estimate future midlatitude cloud feedbacks in regions where appreciable changes in both vertical velocity and EIS are projected. © 2016 American Meteorological Society."
"12769875100;7006738324;26324818700;","Seasonal variations of climate feedbacks in the NCAR CCSM3",2011,"10.1175/2011JCLI3862.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960333163&doi=10.1175%2f2011JCLI3862.1&partnerID=40&md5=341b1fbf54ef07b166280e031081118f","This study investigates the annual cycle of radiative contributions to global climate feedbacks. A partial radiative perturbation (PRP) technique is used to diagnose monthly radiative perturbations at the top of atmosphere (TOA) due to CO2 forcing; surface temperature response; and water vapor, cloud, lapse rate, and surface albedo feedbacks using NCAR Community Climate System Model, version 3 (CCSM3) output from a Special Report on Emissions Scenarios (SRES) A1B emissions-scenario-forced climate simulation. The seasonal global mean longwave TOA radiative feedback was found to be minimal. However, the global mean shortwave (SW) TOA cloud and surface albedo radiative perturbations exhibit large seasonality. The largest contributions to the negative SW cloud feedback occur during summer in each hemisphere, marking the largest differences with previous results. Results suggest that intermodel spread in climate sensitivity may occur, partially from cloud and surface albedo feedback seasonality differences. Further, links between the climate feedback and surface temperature response seasonality are investigated, showing a strong relationship between the seasonal climate feedback distribution and the seasonal surface temperature response. © 2011 American Meteorological Society."
"12801992200;7005304841;7004920873;","Response to the eruption of Mount Pinatubo in relation to climate sensitivity in the CMIP3 models",2010,"10.1007/s00382-010-0777-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957021690&doi=10.1007%2fs00382-010-0777-3&partnerID=40&md5=df0535c678a00bbc08e49275803eb2e2","The radiative flux perturbations and subsequent temperature responses in relation to the eruption of Mount Pinatubo in 1991 are studied in the ten general circulation models incorporated in the Coupled Model Intercomparison Project, phase 3 (CMIP3), that include a parameterization of volcanic aerosol. Models and observations show decreases in global mean temperature of up to 0.5 K, in response to radiative perturbations of up to 10 W m-2, averaged over the tropics. The time scale representing the delay between radiative perturbation and temperature response is determined by the slow ocean response, and is estimated to be centered around 4 months in the models. Although the magniude of the temperature response to a volcanic eruption has previously been used as an indicator of equilibrium climate sensitivity in models, we find these two quantities to be only weakly correlated. This may partly be due to the fact that the size of the volcano-induced radiative perturbation varies among the models. It is found that the magnitude of the modelled radiative perturbation increases with decreasing climate sensitivity, with the exception of one outlying model. Therefore, we scale the temperature perturbation by the radiative perturbation in each model, and use the ratio between the integrated temperature perturbation and the integrated radiative perturbation as a measure of sensitivity to volcanic forcing. This ratio is found to be well correlated with the model climate sensitivity, more sensitive models having a larger ratio. Further, if this correspondence between ""volcanic sensitivity"" and sensitivity to CO2 forcing is a feature not only among the models, but also of the real climate system, the alleged linear relation can be used to estimate the real climate sensitivity. The observational value of the ratio signifying volcanic sensitivity is hereby estimated to correspond to an equilibrium climate sensitivity, i.e. equilibrium temperature increase due to a doubling of the CO2 concentration, between 1.7 and 4.1 K. Several sources of uncertainty reside in the method applied, and it is pointed out that additional model output, related to ocean heat storage and radiative forcing, could refine the analysis, as could reduced uncertainty in the observational record, of temperature as well as forcing. © 2010 Springer-Verlag."
"15135280400;15122248200;7004723203;","Impact of extreme CO2 levels on tropical climate: A CGCM study",2008,"10.1007/s00382-008-0414-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-54949096958&doi=10.1007%2fs00382-008-0414-6&partnerID=40&md5=2abf47087133dabda11f7e93c51545cb","A coupled general circulation model has been used to perform a set of experiments with high CO2 concentration (2, 4, 16 times the present day mean value). The experiments have been analyzed to study the response of the climate system to strong radiative forcing in terms of the processes involved in the adjustment at the ocean-atmosphere interface. The analysis of the experiments revealed a non-linear response of the mean state of the atmosphere and ocean to the increase in the carbon dioxide concentration. In the 16 × CO2 experiment the equilibrium at the ocean-atmosphere interface is characterized by an atmosphere with a shut off of the convective precipitation in the tropical Pacific sector, associated with air warmer than the ocean below. A cloud feedback mechanism is found to be involved in the increased stability of the troposphere. In this more stable condition the mean total precipitation is mainly due to large-scale moisture flux even in the tropics. In the equatorial Pacific Ocean the zonal temperature gradient of both surface and sub-surface waters is significantly smaller in the 16 × CO2 experiment than in the control experiment. The thermocline slope and the zonal wind stress decrease as well. When the CO2 concentration increases by about two and four times with respect to the control experiment there is an intensification of El Niño. On the other hand, in the experiment with 16 times the present-day value of CO2, the Tropical Pacific variability weakens, suggesting the possibility of the establishment of permanent warm conditions that look like the peak of El Niño. © Springer-Verlag Berlin Heidelberg 2008."
"6603839217;7005853435;7003299599;","Maximum entropy production, cloud feedback, and climate change",2007,"10.1029/2007GL029925","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548597135&doi=10.1029%2f2007GL029925&partnerID=40&md5=26a68228513ef7d642af1b192efb1769","A steady-state energy-balance climate model based on a global constraint of maximum entropy production is used to examine cloud feedback and the response of surface temperature T to doubled atmospheric CO2. The constraint ensures that change in zonal cloud amount øo necessarily involves change in the convergence KX of meridional energy flow. Without other feedbacks, the changes in øo, KX and T range from about 2%, 2 Wm-2 and 1.5 K respectively at the equator to -2%, -2 WM-2 and 0.5 K at the poles. Global-average cloud effectively remains unchanged with increasing CO2 and has little effect on global-average temperature. Global-average cloud decreases with increasing water vapour and amplifies the positive feedback of water vapour and lapse rate. The net result is less cloud at all latitudes and a rise in T of the order of 3 K at the equator and 1 K at the poles Ice-albedo and solar absorption feedbacks are not considered. Copynght 2007 by the American Geophysical Union."
"7007021059;7102875645;","Influence of cloud feedback on annual variation of global mean surface temperature",2001,"10.1029/2000JD000235","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034754465&doi=10.1029%2f2000JD000235&partnerID=40&md5=a0cd49850ab885ec133a1bca0274ecf5","The goal of this study is to estimate the cloud radiative feedback effect on the annual variation of the global mean surface temperature using radiative flux data from the Earth Radiation Budget Experiment. We found that the influence of the cloud feedback upon the change of the global mean surface temperature is quite small, though the increase of the temperature is as much as 3.3 K from January to July. On a global scale, we found no significant relationship between either solar reflectivity of clouds or effective cloud top height and the annual cycle of surface temperature. The same analysis was repeated using the output from three general circulation models, which explicitly predict microphysical properties of cloud cover. On a global scale, both solar cloud reflectivity and cloud top height increase significantly with the increase of surface temperature, in contrast to the observation. The comparative analysis conducted here could be used as an effective test for evaluating the cloud feedback process of a model. Copyright 2001 by the American Geophysical Union."
"55715079700;7006095466;","Effects of sea surface temperature and large-scale dynamics on the thermodynamic equilibrium state and convection over the tropical western Pacific",1999,"10.1029/1998JD200116","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033608688&doi=10.1029%2f1998JD200116&partnerID=40&md5=f0f7a3aa38652947c320042db0bf82dd","The effects of sea surface temperature (SST) variations and large-scale dynamics on the cloud feedback and water vapor feedback are quantified using a fine-scale numerical model, or cloud-resolving model, in which the cloud-scale dynamics is explicitly treated instead of being parameterized as is necessary in a general circulation model. The SST variation has large impacts on the water vapor feedback and small impacts on the cloud feedback, radiation budget, and surface energy budget under a given large-scale dynamic state. As the SST gets warmer (increasing 2°), the warm and moist equilibrium state of temperature and water vapor mixing ratio is obtained; the upper tropospheric relative humidity is enhanced; and the cloud amount and convective intensity are slightly reduced. The cooling (about 10 W m-2) at the surface due to the increase of surface evaporation is almost compensated by the warming at the surface due to the increase of surface shortwave flux, which results in a small increase of net surface heat flux. However, the change of large-scale dynamics has large effects on the cloud feedback, radiation budget, and surface energy budget and small effects on the water vapor feedback under a constant SST. An increased large-scale forcing slightly affects the equilibrium states of temperature and water vapor mixing ratio; the relative humidity is decreased above 10 km and increased below; and the cloud amount and convective intensity are enhanced. Both the variations of SST and large-scale dynamics are positively correlated with the surface precipitation. Copyright 1999 by the American Geophysical Union."
"55569698000;56695227400;57203049177;24329376600;8696069500;55149724600;16645242800;23486734100;6602688130;7408519438;7004714030;35301550500;35561911800;6603196127;57112070700;15071907100;","Equilibrium Climate Sensitivity Estimated by Equilibrating Climate Models",2020,"10.1029/2019GL083898","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078273521&doi=10.1029%2f2019GL083898&partnerID=40&md5=6e0022ee76dbe58b5b0a650f488945ad","The methods to quantify equilibrium climate sensitivity are still debated. We collect millennial-length simulations of coupled climate models and show that the global mean equilibrium warming is higher than those obtained using extrapolation methods from shorter simulations. Specifically, 27 simulations with 15 climate models forced with a range of CO2 concentrations show a median 17% larger equilibrium warming than estimated from the first 150 years of the simulations. The spatial patterns of radiative feedbacks change continuously, in most regions reducing their tendency to stabilizing the climate. In the equatorial Pacific, however, feedbacks become more stabilizing with time. The global feedback evolution is initially dominated by the tropics, with eventual substantial contributions from the mid-latitudes. Time-dependent feedbacks underscore the need of a measure of climate sensitivity that accounts for the degree of equilibration, so that models, observations, and paleo proxies can be adequately compared and aggregated to estimate future warming. © 2019. American Geophysical Union. All Rights Reserved."
"23486734100;16645242800;7103206141;55437450100;","Equilibrium Climate Sensitivity Obtained From Multimillennial Runs of Two GFDL Climate Models",2018,"10.1002/2017JD027885","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042084409&doi=10.1002%2f2017JD027885&partnerID=40&md5=61710ed0ec260d1293c64b76c1281b8e","Equilibrium climate sensitivity (ECS), defined as the long-term change in global mean surface air temperature in response to doubling atmospheric CO2, is usually computed from short atmospheric simulations over a mixed layer ocean, or inferred using a linear regression over a short-time period of adjustment. We report the actual ECS from multimillenial simulations of two Geophysical Fluid Dynamics Laboratory (GFDL) general circulation models (GCMs), ESM2M, and CM3 of 3.3 K and 4.8 K, respectively. Both values are ~1 K higher than estimates for the same models reported in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change obtained by regressing the Earth's energy imbalance against temperature. This underestimate is mainly due to changes in the climate feedback parameter (−α) within the first century after atmospheric CO2 has stabilized. For both GCMs it is possible to estimate ECS with linear regression to within 0.3 K by increasing CO2 at 1% per year to doubling and using years 51–350 after CO2 is constant. We show that changes in −α differ between the two GCMs and are strongly tied to the changes in both vertical velocity at 500 hPa (ω500) and estimated inversion strength that the GCMs experience during the progression toward the equilibrium. This suggests that while cloud physics parametrizations are important for determining the strength of −α, the substantially different atmospheric state resulting from a changed sea surface temperature pattern may be of equal importance. ©2018. American Geophysical Union. All Rights Reserved."
"7003420726;35580303100;","On the meaning of independence in climate science",2017,"10.5194/esd-8-211-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85015857746&doi=10.5194%2fesd-8-211-2017&partnerID=40&md5=a6ac4b690fd224499f5ec3513b713e12","The concept of independence has been frequently mentioned in climate science research, but has rarely been defined and discussed in a theoretically robust and quantifiable manner. In this paper we argue that any discussion must start from a clear and unambiguous definition of what independence means and how it can be determined. We introduce an approach based on the statistical definition of independence, and illustrate with simple examples how it can be applied to practical questions. Firstly, we apply these ideas to climate models, which are frequently argued to not be independent of each other, raising questions as to the robustness of results from multi-model ensembles. We explore the dependence between models in a multi-model ensemble, and suggest a possible way forward for future weighting strategies. Secondly, we discuss the issue of independence in relation to the synthesis of multiple observationally based constraints on the climate system, using equilibrium climate sensitivity as an example. We show that the same statistical theory applies to this problem, and illustrate this with a test case, indicating how researchers may estimate dependence between multiple constraints. © Author(s) 2017."
"36822103700;7201463831;8643993200;6506458269;57203776263;26643054400;7004242319;6701378450;6603372665;6602356428;6506424404;18134565600;","Aircraft-measured indirect cloud effects from biomass burning smoke in the Arctic and subarctic",2016,"10.5194/acp-16-715-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957311125&doi=10.5194%2facp-16-715-2016&partnerID=40&md5=3ec7c09c07ef3916bb0849befaef46e8","The incidence of wildfires in the Arctic and subarctic is increasing; in boreal North America, for example, the burned area is expected to increase by 200-300g% over the next 50-100 years, which previous studies suggest could have a large effect on cloud microphysics, lifetime, albedo, and precipitation. However, the interactions between smoke particles and clouds remain poorly quantified due to confounding meteorological influences and remote sensing limitations. Here, we use data from several aircraft campaigns in the Arctic and subarctic to explore cloud microphysics in liquid-phase clouds influenced by biomass burning. Median cloud droplet radii in smoky clouds were g1/4 g40-60g% smaller than in background clouds. Based on the relationship between cloud droplet number (Nliq) and various biomass burning tracers (BBt) across the multi-campaign data set, we calculated the magnitude of subarctic and Arctic smoke aerosol-cloud interactions (ACIs, where ACI Combining double low line (1g•3) × dln(Nliq)g•dln(BBt)) to be g1/4 g0.16 out of a maximum possible value of 0.33 that would be obtained if all aerosols were to nucleate cloud droplets. Interestingly, in a separate subarctic case study with low liquid water content ( g1/4 g0.02gggmg'3) and very high aerosol concentrations (2000-3000gcmg'3) in the most polluted clouds, the estimated ACI value was only 0.05. In this case, competition for water vapor by the high concentration of cloud condensation nuclei (CCN) strongly limited the formation of droplets and reduced the cloud albedo effect, which highlights the importance of cloud feedbacks across scales. Using our calculated ACI values, we estimate that the smoke-driven cloud albedo effect may decrease local summertime short-wave radiative flux by between 2 and 4gWgmg'2 or more under some low and homogeneous cloud cover conditions in the subarctic, although the changes should be smaller in high surface albedo regions of the Arctic. We lastly explore evidence suggesting that numerous northern-latitude background Aitken particles can interact with combustion particles, perhaps impacting their properties as cloud condensation and ice nuclei. © Author(s) 2016."
"7801340314;7201520140;8559604100;","Transition into a Hothouse World at the Permian-Triassic boundary-A model study",2015,"10.1016/j.palaeo.2015.09.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943327743&doi=10.1016%2fj.palaeo.2015.09.008&partnerID=40&md5=074224dcb642ac8e9ce9c9cc99796787","The Permian-Triassic boundary (PTB, ~252.3Ma) marks the largest mass extinction of the Phanerozoic, with a loss of more than 90% of marine organisms, and is characterized by lethally hot surface temperatures. The PTB global warming has been linked to greenhouse gas emissions from the Siberian Traps and associated coal-bed intrusions and likely led to severe environmental consequences, such as ocean acidification, a decline in the marine productivity, and extensive hypoxia. In order to understand these changes, feedbacks in the climate system have been explored with sensitivity climate simulations and compared to temperature proxies from the sedimentary record. The response of the PTB ocean circulation to an atmospheric perturbation of ~5000PgC, comparable to Earth's total fossil fuel inventory, leads to a global temperature increase by 3-4°C and an increase in ocean stratification. The pole-to-equator temperature gradient decreases by 2°C with an increase in CO2-radiative forcing, predominately due to snow albedo feedbacks over Gondwana. The greenhouse-induced warming would have led to a weakening of the Hadley cell and an associated decrease in the trade winds and equatorial primary productivity. These climatic changes might have been amplified by cloud-feedback processes. A reduced concentration of cloud condensation nuclei due to a biologic decline of dimethylsulfide caused by the temperature stress or changes in airborne mineral particles could have reduced the cloud albedo, particularly in high latitudes. Results from a climate simulation with reduced cloud albedo suggest a polar warming of up to 7°C and a reduction of the pole-to-equator temperature gradient by ~4°C in addition to the reduction caused by the increase in greenhouse-induced radiative forcing. The scenario with reduced cloud albedo further leads to an increase in ocean stratification and widespread low-oxygen concentrations in the Panthalassa during the Early Triassic. © 2015 Elsevier B.V."
"55026747900;14051038900;55813857400;12240995900;9635016300;57194275819;","What is the effect of unresolved internal climate variability on climate sensitivity estimates?",2013,"10.1002/jgrd.50390","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881149555&doi=10.1002%2fjgrd.50390&partnerID=40&md5=8cf40b3eca97172d747f324c25df0760","Many studies have attempted to estimate the equilibrium climate sensitivity (CS) to the doubling of CO<inf>2</inf>concentrations. One common methodology is to compare versions of Earth models of intermediate complexity (EMICs) to spatially and/or temporally averaged historical observations. Despite the persistent efforts, CS remains uncertain. It is, thus far, unclear what is driving this uncertainty. Moreover, the effects of the internal climate variability on the CS estimates obtained using this method have not received thorough attention in the literature. Using a statistical approximator (""emulator"") of an EMIC, we show in an observation system simulation study that unresolved internal climate variability appears to be a key driver of CS uncertainty (as measured by the 68% credible interval). We first simulate many realizations of pseudo-observations from an emulator at a ""true"" prescribed CS, and then reestimate the CS using the pseudo-observations and an inverse parameter estimation method. We demonstrate that a single realization of the internal variability can result in a sizable discrepancy between the best CS estimate and the truth. Specifically, the average discrepancy is 0.84°C, with the feasible range up to several °C. The results open the possibility that recent climate sensitivity estimates from global observations and EMICs are systematically considerably lower or higher than the truth, since they are typically based on the same realization of climate variability. This possibility should be investigated in future work. We also find that estimation uncertainties increase at higher climate sensitivities, suggesting that a high CS might be difficult to detect. Key pointsInternal climate variability is a key driver of climate sensitivity uncertaintyHigh climate sensitivities are especially difficult to estimate ©2013. American Geophysical Union. All Rights Reserved."
"55716995500;35209683700;26324818700;","Feedback attribution of the El Nio-Southern Oscillation-related atmospheric and surface temperature anomalies",2012,"10.1029/2012JD018468","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870612607&doi=10.1029%2f2012JD018468&partnerID=40&md5=7665f92c1416ec1792fa8fdf6282525a","A feedback attribution analysis is conducted for the ENSO-related atmospheric and surface temperature anomalies in boreal winter. Local temperature anomalies are decomposed into partial temperature changes due to changes in oceanic dynamics/heat storage, water vapor, clouds, atmospheric dynamics, ozone, and surface albedo. It is shown that atmospheric dynamics plays distinctly different roles in establishing the tropical and extratropical temperature response to El Nio. The atmospheric dynamics serves as a primary negative feedback to the tropical (tropospheric) warming by transporting out of the tropics excessive energy production associated with oceanic dynamical forcing. In the northern extratropics, it is the main forcing of atmospheric temperature changes and also modulates surface temperatures via longwave radiative heating and cooling. This provides an alternative view of the ""atmospheric bridge"" mechanism from the perspective of local energetics and temperature feedback attribution. Substantial tropospheric cooling over the eastern North Pacific is found to be collectively contributed by water vapor, cloud, and atmospheric dynamical feedbacks, driven at least partly by the equatorward shift of the Pacific storm track during El Nio. Polar stratospheric warming (cooling), largely due to atmospheric dynamics, is seen over the Eurasian-Pacific (Atlantic) sector, with ozone feedback contributing significantly to the midstratospheric cooling over the Atlantic sector. Water vapor (atmospheric dynamical) feedback has an overall warming (cooling) effect throughout the tropical troposphere, and cloud feedback cools (warms) the tropical lower to middle (upper) troposphere. Atmospheric dynamics induces stratospheric warming over the entire northern extratropics and drives over northern midlatitudes (high latitudes) a tropospheric cooling (warming) that generally intensifies with altitude. © 2012. American Geophysical Union. All Rights Reserved."
"57193132723;7403174207;7403318365;","Evaluation of regional cloud feedbacks using single-column models",2005,"10.1029/2004JD005011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25844433386&doi=10.1029%2f2004JD005011&partnerID=40&md5=2c641f31fe41b1ddd649da7bd4bc93e0","Cloud feedbacks in a warmer climate have not yet been constrained by models or observations. We present an approach that combines a general circulation model (GCM), single-column model (SCM), satellite and surface remote sensing data, and analysis product to infer regional cloud feedbacks and evaluate model simulations of them. The Atmospheric Radiation Measurement (ARM) Program Southern Great Plains (SGP) continuous forcing product, derived from a mesoscale analysis constrained by top-of-atmosphere and surface data, provides long-term advective forcing that links the models to the data. We drive an SCM with the continuous forcing for 10 cold season months in which synoptic forcing dominates the meteorology. Cloud feedbacks in midlatitude winter are primarily responses to changes in dynamical forcing. Thus we select times when observed advective forcing anomalies resemble doubled CO2 advective forcing changes in the parent GCM. For these times we construct cloud type anomaly histograms in the International Satellite Cloud Climatology Project and Active Remotely Sensed Cloud Locations data sets and simulated versions of these histograms in the SCM. Comparison of the SCM subset to GCM doubled CO2 cloud type changes tells us how relevant the selected times are to the GCM's cloud feedbacks, while comparisons of the SCM to the data tell us how well the model performs in these situations. The data suggest that in midlatitude winter, high thick clouds should increase while cirrus and low clouds decrease in upwelling regimes in a climate warming. Downwelling regime cloud feedbacks are dominated by changes in low clouds but are not as well constrained by the data. Copyright 2005 by the American Geophysical Union."
"7203054240;16197778800;7202155374;","Response of tropical clouds to the interannual variation of sea surface temperature",1996,"10.1175/1520-0442(1996)009<0616:ROTCTT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029730933&doi=10.1175%2f1520-0442%281996%29009%3c0616%3aROTCTT%3e2.0.CO%3b2&partnerID=40&md5=b78e315451e984c25ae613be9e78759e","Connections between the large-scale interannual variations of clouds, deep convection, atmospheric winds, vertical thermodynamic structure, and SSTs over global tropical oceans are examined over the period July 1983-December 1990. The SST warming associated with El Niño had a significant impact on the global tropical cloud field, although the warming itself was confined to the equatorial central and eastern Pacific. Extensive variations of the total cloud field occurred in the northeastern Indian, western and central Pacific, and western Atlantic Oceans. The changes of high and middle clouds dominated the total cloud variation in these regions. Total cloud variation was relatively weak in the eastern Pacific and the Atlantic because of the cancellation between the changes of high and low clouds. The variation of low clouds dominated the total cloud change in those areas. The destabilization of the lapse rate between 900 and 750 mb was more important for enhancing convective instability than was the change of local SSTs in the equatorial central Pacific during the 1987 El Niño. This destabilization is associated with anomalous rising motion in that region. As a result, convection and high and middle clouds increased in the equatorial central Pacific. In the subtropical Pacific, both the change of lapse rate between 900 and 750 mb associated with anomalous subsidence and the decrease of boundary-layer buoyancy due to a decrease of temperature and moisture played an important role in enhancing convective stability. Consequently, convection, as well as high and middle clouds, decreased in these areas. The change of low clouds in the equatoral and southeastern Atlantic was correlated to both local SSTs and the SST changes in the equatorial eastern Pacific. In this area, the increase of low clouds was consistent with the sharper inversion during the 1987 El Niño. The strengthening of the inversion was not caused by a local SST change, although the local SST change appeared to be correlated to the change of low clouds. The coherence between clouds and SST tendency shows that SST tendency leads cloud variation in the equatorial Pacific. Thus, the change of clouds does not dominate the sign of SST tendency even though the cloud change was maximum during the 1987 El Niño. In some areas of the Indian, subtropical Pacific, and North Atlantic Oceans, cloud change leads SST tendency. Cloud change might affect SST tendency in these regions."
"55894937000;7004544454;30667558200;55796430300;7003278104;","Cloud Feedback Key to Marine Heatwave off Baja California",2018,"10.1029/2018GL078242","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046628414&doi=10.1029%2f2018GL078242&partnerID=40&md5=8000fce89101e928fe584e7310247250","Between 2013 and 2015, the northeast Pacific Ocean experienced the warmest surface temperature anomalies in the modern observational record. This “marine heatwave” marked a shift of Pacific decadal variability to its warm phase and was linked to significant impacts on marine species as well as exceptionally arid conditions in western North America. Here we show that the subtropical signature of this warming, off Baja California, was associated with a record deficit in the spatial coverage of co-located marine boundary layer clouds. This deficit coincided with a large increase in downwelling solar radiation that dominated the anomalous energy budget of the upper ocean, resulting in record-breaking warm sea surface temperature anomalies. Our observation-based analysis suggests that a positive cloud-surface temperature feedback was key to the extreme intensity of the heatwave. The results demonstrate the extent to which boundary layer clouds can contribute to regional variations in climate. ©2018. American Geophysical Union. All Rights Reserved."
"16645237600;57203049177;57212781009;24329376600;","What Climate Sensitivity Index Is Most Useful for Projections?",2018,"10.1002/2017GL075742","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041726980&doi=10.1002%2f2017GL075742&partnerID=40&md5=b0e2624d91a387fad97781a173d2455e","Transient climate response (TCR), transient response at 140 years (T140), and equilibrium climate sensitivity (ECS) indices are intended as benchmarks for comparing the magnitude of climate response projected by climate models. It is generally assumed that TCR or T140 would explain more variability between models than ECS for temperature change over the 21st century, since this timescale is the realm of transient climate change. Here we find that TCR explains more variability across Coupled Model Intercomparison Project phase 5 than ECS for global temperature change since preindustrial, for 50 or 100 year global trends up to the present, and for projected change under representative concentration pathways in regions of delayed warming such as the Southern Ocean. However, unexpectedly, we find that ECS correlates higher than TCR for projected change from the present in the global mean and in most regions. This higher correlation does not relate to aerosol forcing, and the physical cause requires further investigation. ©2018. American Geophysical Union. All Rights Reserved."
"55332129600;57205867148;13402835300;","The Cloud Feedback Model Intercomparison Project Observational Simulator Package: Version 2",2018,"10.5194/gmd-11-77-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041338893&doi=10.5194%2fgmd-11-77-2018&partnerID=40&md5=e3ee705cf1a904bebc7de02cd5656f42","The Cloud Feedback Model Intercomparison Project Observational Simulator Package (COSP) gathers together a collection of observation proxies or <q>satellite simulators</q> that translate model-simulated cloud properties to synthetic observations as would be obtained by a range of satellite observing systems. This paper introduces COSP2, an evolution focusing on more explicit and consistent separation between host model, coupling infrastructure, and individual observing proxies. Revisions also enhance flexibility by allowing for model-specific representation of sub-grid-scale cloudiness, provide greater clarity by clearly separating tasks, support greater use of shared code and data including shared inputs across simulators, and follow more uniform software standards to simplify implementation across a wide range of platforms. The complete package including a testing suite is freely available. © Author(s) 2018."
"7003444634;57126848900;22635999400;7203034123;56767841200;35547214900;8627503500;6602407753;57208765879;7202727242;","Polarized view of supercooled liquid water clouds",2016,"10.1016/j.rse.2016.04.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84963877334&doi=10.1016%2fj.rse.2016.04.002&partnerID=40&md5=27fc97e8b17c867d5703b314b2499ae5","Supercooled liquid water (SLW) clouds, where liquid droplets exist at temperatures below 0°C present a well-known aviation hazard through aircraft icing, in which SLW accretes on the airframe. SLW clouds are common over the Southern Ocean, and climate-induced changes in their occurrence is thought to constitute a strong cloud feedback on global climate. The two recent NASA field campaigns POlarimeter Definition EXperiment (PODEX, based in Palmdale, California, January-February 2013) and Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS, based in Houston, Texas in August-September 2013) provided a unique opportunity to observe SLW clouds from the high-altitude airborne platform of NASA's ER-2 aircraft. We present an analysis of measurements made by the Research Scanning Polarimeter (RSP) during these experiments accompanied by correlative retrievals from other sensors. The RSP measures both polarized and total reflectance in 9 spectral channels with wavelengths ranging from 410 to 2250 nm. It is a scanning sensor taking samples at 0.8° intervals within 60° from nadir in both forward and backward directions. This unique angular resolution allows for characterization of liquid water droplet size using the rainbow structure observed in the polarized reflectances in the scattering angle range between 135° and 165°. Simple parametric fitting algorithms applied to the polarized reflectance provide retrievals of the droplet effective radius and variance assuming a prescribed size distribution shape (gamma distribution). In addition to this, we use a non-parametric method, Rainbow Fourier Transform (RFT), which allows retrieval of the droplet size distribution without assuming a size distribution shape. We present an overview of the RSP campaign datasets available from the NASA GISS website, as well as two detailed examples of the retrievals. In these case studies we focus on cloud fields with spatial features varying between glaciated and liquid phases at altitudes as high as 10 km, which correspond to temperatures close to the homogeneous freezing temperature of pure water drops (about -35°C or colder). The multimodal droplet size distributions retrieved from RSP data in these cases are consistent with the multi-layer cloud structure observed by correlative Cloud Physics Lidar (CPL) measurements. © 2016 Elsevier Inc."
"7005528388;7102171439;6603126554;56219284300;15726427000;16645127300;8953038700;","Observation-based longwave cloud radiative kernels derived from the A-Train",2016,"10.1175/JCLI-D-15-0257.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84962278687&doi=10.1175%2fJCLI-D-15-0257.1&partnerID=40&md5=f1f5d35e33e7e45e44ac84bc6445fc4b","The authors present a new method to derive both the broadband and spectral longwave observation-based cloud radiative kernels (CRKs) using cloud radiative forcing (CRF) and cloud fraction (CF) for different cloud types using multisensor A-Train observations and MERRA data collocated on the pixel scale. Both observation-based CRKs and model-based CRKs derived from the Fu-Liou radiative transfer model are shown. Good agreement between observation- and model-derived CRKs is found for optically thick clouds. For optically thin clouds, the observation-based CRKs show a larger radiative sensitivity at TOA to cloud-cover change than model-derived CRKs. Four types of possible uncertainties in the observed CRKs are investigated: 1) uncertainties in Moderate Resolution Imaging Spectroradiometer cloud properties, 2) the contributions of clear-sky changes to the CRF, 3) the assumptions regarding clear-sky thresholds in the observations, and 4) the assumption of a single-layer cloud. The observation-based CRKs show the TOA radiative sensitivity of cloud types to unit cloud fraction change as observed by the A-Train. Therefore, a combination of observation-based CRKs with cloud changes observed by these instruments over time will provide an estimate of the short-term cloud feedback by maintaining consistency between CRKs and cloud responses to climate variability. © 2016 American Meteorological Society."
"57197840302;14036628000;","Progressive midlatitude afforestation: Impacts on clouds, global energy transport, and precipitation",2016,"10.1175/jcli-d-15-0748.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85016333409&doi=10.1175%2fjcli-d-15-0748.1&partnerID=40&md5=b0275e8c2a2e514fee4a7bb1e15945f5","Vegetation influences the atmosphere in complex and nonlinear ways, such that large-scale changes in vegetation cover can drive changes in climate on both local and global scales. Large-scale land surface changes have been shown to introduce excess energy to one hemisphere, causing a shift in atmospheric circulation on a global scale. However, past work has not quantified how the climate response scales with the area of vegetation. Here, the response of climate to linearly increasing the area of forest cover in the northern midlatitudes is systematically evaluated. This study shows that the magnitude of afforestation of the northern midlatitudes determines the local climate response in a nonlinear fashion, and the authors identify a threshold in vegetation-induced cloud feedbacks-a concept not previously addressed by large-scale vegetation manipulation experiments. Small increases in tree cover drive compensating cloud feedbacks, while latent heat fluxes reach a threshold after sufficiently large increases in tree cover, causing the troposphere to warm and dry, subsequently reducing cloud cover. Increased absorption of solar radiation at the surface is driven by both surface albedo changes and cloud feedbacks. This study shows how atmospheric cross-equatorial energy transport changes as the area of afforestation is incrementally increased. The results highlight the importance of considering both local and remote climate effects of large-scale vegetation change and explore the scaling relationship between changes in vegetation cover and resulting climate impacts. © 2016 American Meteorological Society."
"16202694600;7004060399;6602098362;","Reexamining the relationship between climate sensitivity and the Southern Hemisphere radiation budget in CMIP models",2015,"10.1175/JCLI-D-15-0031.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950138463&doi=10.1175%2fJCLI-D-15-0031.1&partnerID=40&md5=b3b7a71d4eb235bc632670a60dddd5e0","Recent efforts to narrow the spread in equilibrium climate sensitivity (ECS) across global climate models have focused on identifying observationally based constraints, which are rooted in empirical correlations between ECS and biases in the models' present-day climate. This study reexamines one such constraint identified from CMIP3 models: the linkage between ECS and net top-of-the-atmosphere radiation biases in the Southern Hemisphere (SH). As previously documented, the intermodel spread in the ECS of CMIP3 models is linked to present-day cloud and net radiation biases over the midlatitude Southern Ocean, where higher cloud fraction in the present-day climate is associated with larger values of ECS. However, in this study, no physical explanation is found to support this relationship. Furthermore, it is shown here that this relationship disappears in CMIP5 models and is unique to a subset of CMIP models characterized by unrealistically bright present-day clouds in the SH subtropics. In view of this evidence, Southern Ocean cloud and net radiation biases appear inappropriate for providing observationally based constraints on ECS. Instead of the Southern Ocean, this study points to the stratocumulus-to-cumulus transition regions of the SH subtropical oceans as key to explaining the intermodel spread in the ECS of both CMIP3 and CMIP5 models. In these regions, ECS is linked to present-day cloud and net radiation biases with a plausible physical mechanism: models with brighter subtropical clouds in the present-day climate show greater ECS because 1) subtropical clouds dissipate with increasing CO2 concentrations in many models and 2) the dissipation of brighter clouds contributes to greater solar warming of the surface. © 2015 American Meteorological Society."
"8315173400;7102284923;7004326742;7006710430;","On the state dependency of fast feedback processes in (paleo) climate sensitivity",2014,"10.1002/2014GL061121","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911191675&doi=10.1002%2f2014GL061121&partnerID=40&md5=a661d047088a5af1d11695a38fc7e1e0","Paleo data have been frequently used to determine the equilibrium (Charney) climate sensitivity Sa, and - if slow feedback processes (e.g., land-ice albedo) are adequately taken into account - they indicate a similar range as estimates based on instrumental data and climate model results. Many studies assume the (fast) feedback processes to be independent of the background climate state, e.g., equally strong during warm and cold periods. Here we assess the dependency of the fast feedback processes on the background climate state using data of the last 800 kyr and a box model of the climate system for interpretation. Applying a new method to account for background state dependency, we find Sa=0.61±0.07 K (W m-2)-1(±1σ) using a reconstruction of Last Glacial Maximum (LGM) cooling of -4.0 K and significantly lower climate sensitivity during glacial climates. Due to uncertainties in reconstructing the LGM temperature anomaly, Sa is estimated in the range Sa = 0.54-0.95 K (W m-2)-1. Key PointsWe analyzed data of radiative forcing and temperature from the last 800,000 yearsThe equilibrium climate sensitivity depends on the background climate stateEquilibrium climate sensitivity is higher in warmer than in colder climates ©2014. American Geophysical Union. All Rights Reserved."
"7202641466;7005986663;25925401000;7006280684;7201832531;","Discrepancies between the modeled and proxy-reconstructed response to volcanic forcing over the past millennium: Implications and possible mechanisms",2013,"10.1002/jgrd.50609","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882754867&doi=10.1002%2fjgrd.50609&partnerID=40&md5=d6f2b478ccc5e7cce48aee7a6709b437","We show that a systematic discrepancy between model simulations and proxy reconstructions of hemispheric temperature changes over the past millennium appears to arise from a small number of radiatively large volcanic eruptions. Past work has shown that accounting for this mismatch alone appears to reconcile inconsistencies between the overall amplitude of simulated and proxy-reconstructed temperature changes. We provide empirical support for the previously posited hypothesis that this discrepancy may arise from threshold growth effects in tree line-proximal trees that limit their response to large volcanic cooling events. Such threshold responses could lead to an absence of growth rings (as many as six accumulated years over the past eight centuries) for some fraction of tree line-proximal trees, leading to a potential misalignment of volcanic cooling events in trees from climatically distinct regions, and a further attenuation and smearing of the volcanic cooling signal. Since the high-frequency component of nearly all proxy reconstructions of past hemispheric temperature change is derived from tree ring data, this bias would likely impact nearly all such reconstructions. We show here that the discrepancy may have led to an underestimation bias in past studies attempting to infer equilibrium climate sensitivity from proxy temperature reconstructions of the past millennium. Key Points mismatch between modeled and proxy-reconstructed volcanic cooling models and reconstructions can be reconciled if threshold effects accounted for empirical evidence supports biases in tree-ring volcanic cooling estimates ©2013. American Geophysical Union. All Rights Reserved."
"7101632204;7404210007;6701631872;","Importance of oceanic heat uptake in transient climate change",2006,"10.1029/2006GL027242","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845644592&doi=10.1029%2f2006GL027242&partnerID=40&md5=fb20d9a6bc2b504cf51022757b48e67b","The impact of the differences in the oceanic heat uptake and storage on the transient response to changes in radiative forcing is investigated using two newly developed coupled atmosphere-ocean models. In spite of its larger equilibrium climate sensitivity, one model (CM2.1) has smaller transient globally averaged surface air temperature (SAT) response than is found in the second model (CM2.0). The differences in the SAT response become larger as radiative forcing increases and the time scales become longer. The smaller transient SAT response in CM2.1 is due to its larger oceanic heat uptake. The heat storage differences between the two models also increase with time and larger rates of radiative forcing. The larger oceanic heat uptake in CM2.1 can be traced to differences in the Southern Ocean heat uptake and is related to a more realistic Southern Ocean simulation in the control integration. Copyright 2006 by the American Geophysical Union."
"55547130379;7004942632;","A one-dimensional study of possible cirrus cloud feedbacks",1994,"10.1175/1520-0442(1994)007<0158:AODSOP>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028323775&doi=10.1175%2f1520-0442%281994%29007%3c0158%3aAODSOP%3e2.0.CO%3b2&partnerID=40&md5=e729275847e3fd79a86723dc30fe7792","A standard radiative-convective model with high vertical resolution (10-mb grid spacing in the upper troposphere) is used to investigate some of these feedbacks in response to changes in atmospheric carbon dioxide concentration. It is shown that such a high resolution (or, indeed, an even higher resolution) may be necessary to resolve the change in tropopause height following a doubling of carbon dioxide. The cirrus cloud is allowed to adjust its height and ice water content in response to the warming, and experiments are repeated: 1) for fixed and moist adiabatic lapse rates, 2) with and without a prescribed relative humidity feedback, 3) at low as well as high vertical resolution, and 4) with the inclusion of a simple correction to account for the uncertain number of small ice crystals in cirrus clouds. The results imply that models with a coarse vertical resolution may be unable to capture small changes in cloud position that could substantially affect the overall strength of cirrus cloud feedbacks. -from Authors"
"57203049177;24329376600;54897465300;8696069500;7201485519;","How accurately can the climate sensitivity to CO 2 be estimated from historical climate change?",2020,"10.1007/s00382-019-04991-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074525690&doi=10.1007%2fs00382-019-04991-y&partnerID=40&md5=11a2abbf538b74a020e9403e120749d1","The equilibrium climate sensitivity (ECS, in K) to CO 2 doubling is a large source of uncertainty in projections of future anthropogenic climate change. Estimates of ECS made from non-equilibrium states or in response to radiative forcings other than 2 × CO 2 are called “effective climate sensitivity” (EffCS, in K). Taking a “perfect-model” approach, using coupled atmosphere–ocean general circulation model (AOGCM) experiments, we evaluate the accuracy with which CO 2 EffCS can be estimated from climate change in the “historical” period (since about 1860). We find that (1) for statistical reasons, unforced variability makes the estimate of historical EffCS both uncertain and biased; it is overestimated by about 10% if the energy balance is applied to the entire historical period, 20% for 30-year periods, and larger factors for interannual variability, (2) systematic uncertainty in historical radiative forcing translates into an uncertainty of ±30to45% (standard deviation) in historical EffCS, (3) the response to the changing relative importance of the forcing agents, principally CO 2 and volcanic aerosol, causes historical EffCS to vary over multidecadal timescales by a factor of two. In recent decades it reached its maximum in the AOGCM historical experiment (similar to the multimodel-mean CO 2 EffCS of 3.6 K from idealised experiments), but its minimum in the real world (1.6 K for an observational estimate for 1985–2011, similar to the multimodel-mean value for volcanic forcing). The real-world variations mean that historical EffCS underestimates CO 2 EffCS by 30% when considering the entire historical period. The difference for recent decades implies that either unforced variability or the response to volcanic forcing causes a much stronger regional pattern of sea surface temperature change in the real world than in AOGCMs. We speculate that this could be explained by a deficiency in simulated coupled atmosphere–ocean feedbacks which reinforce the pattern (resembling the Interdecadal Pacific Oscillation in some respects) that causes the low EffCS. We conclude that energy-balance estimates of CO 2 EffCS are most accurate from periods unaffected by volcanic forcing. Atmosphere GCMs provided with observed sea surface temperature for the 1920s to the 1950s, which was such a period, give a range of about 2.0–4.5 K, agreeing with idealised CO 2 AOGCM experiments; the consistency is a reason for confidence in this range as an estimate of CO 2 EffCS. Unless another explosive volcanic eruption occurs, the first 30 years of the present century may give a more accurate energy-balance historical estimate of this quantity. © 2019, The Author(s)."
"7201798916;6506257601;57208225926;7004174939;7006790175;","The harp hyperangular imaging polarimeter and the need for small satellite payloads with high science payoff for earth science remote sensing",2018,"10.1109/IGARSS.2018.8518823","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058141206&doi=10.1109%2fIGARSS.2018.8518823&partnerID=40&md5=d64f1e1412dca1b4e091b356c7a6160e","The largest uncertainties on estimating climate change revolve around the lack of quantitative information on aerosol and cloud microphysical properties, which limits our understanding of cloud-aerosol interaction processes and cloud feedbacks in the climate system. Part of this limitation comes from the small number of global satellite sensors which in turn only measures a restricted subset of aerosol and cloud microphysical properties. Enabling small satellites to perform high quality cloud and aerosol microphysical measurements is an important pathway to resolve this puzzle. The reduced cost of small satellites can enable the use of multiple platforms or even constellations to increase spatial and temporal coverage for the required measurements. The HARP (HyperAngular Rainbow Polarimeter) is a 3U CubeSat sensor designed for the measurement of aerosol, clouds and surface properties with a wide FOV that enables nearly global coverage from multiple wavelengths and tens of different along track viewing angles. The technology developed for HARP allows for all these characteristics to be packaged within the envelope of a CubeSat sensor while preserving strict science requirements. © 2018 IEEE."
"7006237834;","Climate Sensitivity in the Geologic Past",2016,"10.1146/annurev-earth-100815-024150","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977147327&doi=10.1146%2fannurev-earth-100815-024150&partnerID=40&md5=f888570aabfc908dd8d95633892434e4","The response of temperature to CO2 change (climate sensitivity) in the geologic past may help inform future climate predictions. Proxies for CO2 and temperature generally imply high climate sensitivities: ≥3 K per CO2 doubling during ice-free times (fast-feedback sensitivity) and ≥6 K during times with land ice (Earth-system sensitivity). Climate models commonly underpredict the magnitude of climate change and have fast-feedback sensitivities close to 3 K. A better characterization of feedbacks in warm worlds raises climate sensitivity to values more in line with proxies and produces climate simulations that better fit geologic evidence. As CO2 builds in our atmosphere, we should expect both slow (e.g., land ice) and fast (e.g., vegetation, clouds) feedbacks to elevate the long-term temperature response over that predicted from the canonical fast-feedback value of 3 K. Because temperatures will not decline for centuries to millennia, climate sensitivities that integrate slower processes have relevance for current climate policy. Copyright © 2016 by Annual Reviews. All rights reserved."
"36623311400;6603268269;7006270084;6603156461;57193213111;","A three-dimensional sectional representation of aerosol mixing state for simulating optical properties and cloud condensation nuclei",2016,"10.1002/2015JD024323","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021156278&doi=10.1002%2f2015JD024323&partnerID=40&md5=1305ff5b9fb8dd4ff62bce39d0a52321","Light absorption by black carbon (BC) particles emitted from fossil fuel combustion depends on their size and how thickly they are coated with nonrefractory species such as ammonium, sulfate, nitrate, organics, and water. The cloud condensation nuclei (CCN) activation behavior of a particle depends on its dry size and the hygroscopicities of all the individual species mixed together. It is therefore necessary to represent both size and mixing state of aerosols to reliably predict their climate-relevant properties in atmospheric models. Here we describe and evaluate a novel sectional framework in the Model for Simulating Aerosol Interactions and Chemistry (box model), referred to as MOSAIC-mix, that represents the mixing state by resolving aerosol dry size (Ddry), BC dry mass fraction (WBC), and hygroscopicity (k). Using 10 idealized urban plume scenarios in which different types of aerosols evolve over 24 h under a range of atmospherically relevant conditions, we examine errors in CCN concentrations and optical properties with respect to the level of detail of the aerosol mixing state representation. We find that a small number of WBC and k bins can achieve significant reductions in the errors and propose a configuration with 24 Ddry bins, 2 WBC bins, and 2 k bins that give average errors of about 5% or less in CCN concentrations and optical properties, 3-4 times lower than those from size-only resolved (i.e., internally mixed) simulations. These results suggest that MOSAIC-mix is suitable for use in regional and global models to examine the effects of mixing state on aerosol-radiation-cloud feedbacks. © 2016. American Geophysical Union. All Rights Reserved."
"36701462300;10241250100;55686667100;10243650000;10241462700;7102857642;","Lower-tropospheric mixing as a constraint on cloud feedback in a multiparameter multiphysics ensemble",2016,"10.1175/JCLI-D-16-0042.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983490086&doi=10.1175%2fJCLI-D-16-0042.1&partnerID=40&md5=6280a8dcc3db8d96cab2c1ade2403b6c","Factors and possible constraints to extremely large spread of effective climate sensitivity (ECS) ranging about 2.1-10.4K are examined by using a large-member ensemble of quadrupling CO2 experiments with an atmospheric general circulation model (AGCM). The ensemble, called the multiparameter multiphysics ensemble (MPMPE), consists of both parametric and structural uncertainties in parameterizations of cloud, cumulus convection, and turbulence based on two different versions of AGCM. The sum of the low- and middle-cloud shortwave feedback explains most of the ECS spread among the MPMPE members. For about half of the perturbed physics ensembles (PPEs) in the MPMPE, variation in lower-tropospheric mixing intensity (LTMI) corresponds well with the ECS variation, whereas it does not for the other half. In the latter PPEs, large spread in optically thick middle-cloud feedback over the equatorial ocean substantially affects the ECS, disrupting the LTMI-ECS relationship. Although observed LTMI can constrain uncertainty in the lowcloud feedback, total uncertainty of the ECS among the MPMPE cannot solely be explained by the LTMI, suggesting a limitation of single emergent constraint for the ECS."
"16177084000;57203200427;36600036800;8397494800;7101672097;37037519900;7407104838;35096299800;7005955015;57207008570;53878006900;6506373162;7006705919;7004299063;55544607500;7404732357;57205638870;55893823700;9249627300;55317177900;","Forcings and feedbacks in the geomip ensemble for a reduction in solar irradiance and increase in CO2",2014,"10.1002/2013JD021110","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901723947&doi=10.1002%2f2013JD021110&partnerID=40&md5=f98cb7a2b2a4be357da362528f091d4f","The effective radiative forcings (including rapid adjustments) and feedbacks associated with an instantaneous quadrupling of the preindustrial CO2 concentration and a counterbalancing reduction of the solar constant are investigated in the context of the Geoengineering Model Intercomparison Project (GeoMIP). The forcing and feedback parameters of the net energy flux, as well as its different components at the top-of-atmosphere (TOA) and surface, were examined in 10 Earth System Models to better understand the impact of solar radiation management on the energy budget. In spite of their very different nature, the feedback parameter and its components at the TOA and surface are almost identical for the two forcing mechanisms, not only in the global mean but also in their geographical distributions. This conclusion holds for each of the individual models despite intermodel differences in how feedbacks affect the energy budget. This indicates that the climate sensitivity parameter is independent of the forcing (when measured as an effective radiative forcing). We also show the existence of a large contribution of the cloudy-sky component to the shortwave effective radiative forcing at the TOA suggesting rapid cloud adjustments to a change in solar irradiance. In addition, the models present significant diversity in the spatial distribution of the shortwave feedback parameter in cloudy regions, indicating persistent uncertainties in cloud feedback mechanisms. © 2014. American Geophysical Union. All Rights Reserved."
"16246205000;55738957800;","Role of climate feedback in El Niño-like SST response to global warming",2014,"10.1175/JCLI-D-14-00072.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907572369&doi=10.1175%2fJCLI-D-14-00072.1&partnerID=40&md5=1575d9a7cf62f897e0a8f45b09c4de3f","Under global warming from the doubling of CO2, the equatorial Pacific experiences an El Niño-like warming, as simulated by most global climate models. A new climate feedback and response analysis method (CFRAM) is applied to 10 years of hourly output of the slab ocean model (SOM) version of the NCAR Community Climate System Model, version 3.0, (CCSM3-SOM) to determine the processes responsible for this warming. Unlike the traditional surface heat budget analysis, the CFRAM can explicitly quantify the contributions of each radiative climate feedback and of each physical and dynamical process of a GCM to temperature changes. The mean bias in the sum of partial SST changes due to each feedback derived with CFRAMin the tropical Pacific is negligible (0.5%) compared to the mean SST change from the CCSM3-SOM simulations, with a spatial pattern correlation of 0.97 between the two. The analysis shows that the factors contributing to the El Niño-like SST warming in the central Pacific are different from those in the eastern Pacific. In the central Pacific, the largest contributor to El Niño-like SST warming is dynamical advection, followed by PBL diffusion, water vapor feedback, and surface evaporation. In contrast, in the eastern Pacific the dominant contributor to El Niño-like SST warming is cloud feedback, with water vapor feedback further amplifying the warming. © 2014 American Meteorological Society."
"55471474500;7401945370;","Response of ice and liquid water paths of tropical cyclones to global warming simulated by a global nonhydrostatic model with explicit cloud microphysics",2013,"10.1175/JCLI-D-13-00182.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890216284&doi=10.1175%2fJCLI-D-13-00182.1&partnerID=40&md5=06cb31a4fac213b13a1a173c8c94f3c2","Cloud feedback plays a key role in the future climate projection. Using global nonhydrostatic model (GNHM) simulation data for a present-day [control (CTL)] and a warmer [global warming (GW)] experiment, the authors estimate the contribution of tropical cyclones (TCs) to ice water paths (IWP) and liquid water paths (LWP) associated with TCs and their changes between CTL and GW experiments. They use GNHM with a 14-km horizontal mesh for explicitly calculating cloud microphysics without cumulus parameterization. This dataset shows that the cyclogenesis underGWconditions reduces to approximately 70% of that under CTL conditions, as shown in a previous study, and the tropical averaged IWP (LWP) is reduced by approximately 2.76% (0.86%). Horizontal distributions of IWP and LWP changes seem to be closely related to TC track changes. To isolate the contributions of IWP/LWP associated with TCs, the authors first examine the radial distributions of IWP/LWP from the TC center at their mature stages and find that they generally increase for more intense TCs. As the intense TC in GW increases, the IWP and LWP around the TC center in GW becomes larger than that in CTL. The authors next define the TC area as the region within 500km from the TC center at its mature stages. They find that the TC's contribution to the total tropical IWP (LWP) is 4.93% (3.00%) in CTL and 5.84% (3.69%) in GW. Although this indicates that the TC's contributions to the tropical IWP/LWP are small, IWP/LWP changes in each basin behave in a manner similar to those of the cyclogenesis and track changes under GW. © 2013 Park-media, Ltd."
"24485834000;57112070700;7004714030;6505465237;13607567200;55581675600;8696069500;6603247427;6602600408;","The respective roles of surface temperature driven feedbacks and tropospheric adjustment to CO2 in CMIP5 transient climate simulations",2013,"10.1007/s00382-013-1682-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888029321&doi=10.1007%2fs00382-013-1682-3&partnerID=40&md5=c9a7ff64419303cf21e46a093c5e3074","An overview of radiative climate feedbacks and ocean heat uptake efficiency diagnosed from idealized transient climate change experiments of 14 CMIP5 models is presented. Feedbacks explain about two times more variance in transient climate response across the models than ocean heat uptake efficiency. Cloud feedbacks can clearly be identified as the main source of inter-model spread. Models with strong longwave feedbacks in the tropics feature substantial increases in cloud ice around the tropopause suggestive of changes in cloud-top heights. The lifting of the tropical tropopause goes together with a general weakening of the tropical circulation. Distinctive inter-model differences in cloud shortwave feedbacks occur in the subtropics including the equatorward flanks of the storm-tracks. Related cloud fraction changes are not confined to low clouds but comprise middle level clouds as well. A reduction in relative humidity through the lower and mid troposphere can be identified as being the main associated large-scale feature. Experiments with prescribed sea surface temperatures are analyzed in order to investigate whether the diagnosed feedbacks from the transient climate simulations contain a tropospheric adjustment component that is not conveyed through the surface temperature response. The strengths of the climate feedbacks computed from atmosphere-only experiments with prescribed increases in sea surface temperatures, but fixed CO2 concentrations, are close to the ones derived from the transient experiment. Only the cloud shortwave feedback exhibits discernible differences which, however, can not unequivocally be attributed to tropospheric adjustment to CO2. Although for some models a tropospheric adjustment component is present in the global mean shortwave cloud feedback, an analysis of spatial patterns does not lend support to the view that cloud feedbacks are dominated by their tropospheric adjustment part. Nevertheless, there is positive correlation between the strength of tropospheric adjustment processes and cloud feedbacks across different climate models. © 2013 Springer-Verlag Berlin Heidelberg."
"36339753800;6602600408;7201504886;","Assessment of different metrics for physical climate feedbacks",2013,"10.1007/s00382-013-1757-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884704176&doi=10.1007%2fs00382-013-1757-1&partnerID=40&md5=ecc4436a64d5cd5eb339af60d1352e96","We quantify the feedbacks from the physical climate system on the radiative forcing for idealized climate simulations using four different methods. The results differ between the methods and differences are largest for the cloud feedback. The spatial and temporal variability of each feedback is used to estimate the averaging scale necessary to satisfy the feedback concept of one constant global mean value. We find that the year-to-year variability, combined with the methodological differences, in estimates of the feedback strength from a single model is comparable to the model-to-model spread in feedback strength of the CMIP3 ensemble. The strongest spatial and temporal variability is in the short-wave component of the cloud feedback. In our simulations, where many sources of natural variability are neglected, long-term averages are necessary to get reliable feedback estimates. Considering the large natural variability and relatively small forcing present in the real world, as compared to the forcing imposed by doubling CO2 concentrations in the simulations, implies that using observations to constrain feedbacks is a challenging task and requires reliable long-term measurements. © 2013 The Author(s)."
"7102403008;55207447000;","Determination of a lower bound on Earth's climate sensitivity",2013,"10.3402/tellusb.v65i0.21533","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904394234&doi=10.3402%2ftellusb.v65i0.21533&partnerID=40&md5=cadd47cce5a26d44115d9b05af6facaf","Transient and equilibrium sensitivity of Earth's climate has been calculated using global temperature, forcing and heating rate data for the period 1970-2010. We have assumed increased long-wave radiative forcing in the period due to the increase of the long-lived greenhouse gases. By assuming the change in aerosol forcing in the period to be zero, we calculate what we consider to be lower bounds to these sensitivities, as the magnitude of the negative aerosol forcing is unlikely to have diminished in this period. The radiation imbalance necessary to calculate equilibrium sensitivity is estimated from the rate of ocean heat accumulation as 0.37±0.03W m-2 (all uncertainty estimates are 1- σ). With these data, we obtain best estimates for transient climate sensitivity 0.39±0.07K (W m-2)-1 and equilibrium climate sensitivity 0.54±0.14K (W m-2)-1, equivalent to 1.5±0.3 and 2.0±0.5K (3.7W m-2)-1, respectively. The latter quantity is equal to the lower bound of the 'likely' range for this quantity given by the 2007 IPCC Assessment Report. The uncertainty attached to the lower- bound equilibrium sensitivity permits us to state, within the assumptions of this analysis, that the equilibrium sensitivity is greater than 0.31K (W m-2)-1, equivalent to 1.16K (3.7W m-2)-1, at the 95% confidence level. © 2013 L. Bengtsson and S. E. Schwartz."
"13406647100;7403288995;7202660824;","On the relationship between low cloud variability and lower tropospheric stability in the Southeast Pacific",2011,"10.5194/acp-11-9053-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052512541&doi=10.5194%2facp-11-9053-2011&partnerID=40&md5=8d10896e61b9f670f867e7e3c8ef0fa7","In this study, we examine marine low cloud cover variability in the Southeast Pacific and its association with lower-tropospheric stability (LTS) across a spectrum of timescales. On both daily and interannual timescales, LTS and low cloud amount are very well correlated in austral summer (DJF). Meanwhile in winter (JJA), when ambient LTS increases, the LTS-low cloud relationship substantially weakens. The DJF LTS-low cloud relationship also weakens in years with unusually large ambient LTS values. These are generally strong El Niño years, in which DJF LTS values are comparable to those typically found in JJA. Thus the LTS-low cloud relationship is strongly modulated by the seasonal cycle and the ENSO phenomenon. We also investigate the origin of LTS anomalies closely associated with low cloud variability during austral summer. We find that the ocean and atmosphere are independently involved in generating anomalies in LTS and hence variability in the Southeast Pacific low cloud deck. This highlights the importance of the physical (as opposed to chemical) component of the climate system in generating internal variability in low cloud cover. It also illustrates the coupled nature of the climate system in this region, and raises the possibility of cloud feedbacks related to LTS. We conclude by addressing the implications of the LTS-low cloud relationship in the Southeast Pacific for low cloud feedbacks in anthropogenic climate change. © 2011 Author(s)."
"23980042500;7003371432;","Aerosol-cloud interactions in a mesoscale model. Part I: Sensitivity to activation and collision-coalescence",2008,"10.1175/2007JAS2207.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40949114685&doi=10.1175%2f2007JAS2207.1&partnerID=40&md5=e165ab84f2b9111e0f1f664b27b590f4","High-resolution numerical simulations of the aerosol-cloud feedbacks are performed with a mesoscale model. The multimodal aerosol species, added to the model, and the cloud species were represented by two spectral moments. The aerosol sources include particle activation, solute transfer between drops due to collision, and coalescence of drops, and particle regeneration. A summertime case was simulated consisting of a cold frontal cloud system and a postfrontal stratus. Experiments with both simple and mechanistic activation parameterization of aerosol and with one and two aerosol modes were performed. Verification was made of the stratus properties against measurements taken during the Radiation Aerosol and Cloud Experiment (RACE). The results demonstrate a significant sensitivity of the stratus and of the frontal system to the aerosol and a moderate impact on the particle spectrum of drop collision-coalescence. The stratus simulation with mechanistic activation and unimodal aerosol showed the best agreement of droplet concentration with the observations, and the simulations with mechanistic activation and a bimodal aerosol and with simple activation underestimated the droplet concentration. A similar high sensitivity was found for the frontal precipitation intensity. Drop collision-coalescence in the frontal system was found to have an impact on the particle mean radius whose magnitude amounted to 10% and 15% for one and multiple cloud cycles, respectively. This impact was also found to be highly variable in space. The modified particle spectrum, following activation in clouds, was found to increase droplet concentration. © 2008 American Meteorological Society."
"7402612084;","Does model sensitivity to changes in CO2 provide a measure of sensitivity to other forcings?",2006,"10.1175/JCLI3791.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746848476&doi=10.1175%2fJCLI3791.1&partnerID=40&md5=f9c0e68be552238d72174dfffe4c0ca6","Simulation of both the climate of the twentieth century and a future climate change requires taking into account numerous forcings, while climate sensitivities of general circulation models are defined as the equilibrium surface warming due to a doubling of atmospheric CO2 concentration. A number of simulations with the Massachusetts Institute of Technology (MIT) climate model of intermediate complexity with different forcings have been carried out to study to what extent sensitivity to changes in CO2 concentration (SCO2) represent sensitivities to other forcings. The MIT model, similar to other models, shows a strong dependency of the simulated surface warming on the vertical structure of the imposed forcing. This dependency is a result of ""semidirect"" effects in the simulations with localized tropospheric heating. A method for estimating semidirect effects associated with different feedback mechanisms is presented. It is shown that forcing that includes these effects is a better measure of expected surface warming than a forcing that accounts for stratospheric adjustment only. Simulations with the versions of the MIT model with different strengths of cloud feedback show that, for the range of sensitivities produced by existing GCMs, SCO2 provides a good measure of the model sensitivity to other forcings. In the case of strong cloud feedback, sensitivity to the increase in CO2 concentration overestimates model sensitivity to both negative forcings, leading to the cooling of the surface and ""black carbon""-like forcings with elevated heating. This is explained by the cloud feedback being less efficient in the case of increasing sea ice extent and snow cover or by the above-mentioned semidirect effects, which are absent in the CO2 simulations, respectively. © 2006 American Meteorological Society."
"7201844203;7005548544;7006957668;","Comments on ""the Iris hypothesis: A negative or positive cloud feedback?""",2002,"10.1175/1520-0442(2002)015<2713:COTIHA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037106827&doi=10.1175%2f1520-0442%282002%29015%3c2713%3aCOTIHA%3e2.0.CO%3b2&partnerID=40&md5=f0cdbde18a47a0b8b5ee5f8721c4800b",[No abstract available]
"57212781009;","Geographical contributions to global climate sensitivity in a General Circulation Model",2002,"10.1016/S0921-8181(01)00142-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037091307&doi=10.1016%2fS0921-8181%2801%2900142-4&partnerID=40&md5=17375e88819dfd2ca9a1ecb2bb2f380d","This paper addresses two questions: how do radiative contributions to global climate model feedbacks vary geographically, and hence which regions and physical processes are most important in determining final climate sensitivity in a General Circulation Model (GCM)? Offline radiation calculations were used to evaluate in detail the strength and spatial distribution of top of atmosphere (TOA) radiative perturbations for the BMRC GCM under a doubling of CO2. The long wave and short wave radiative perturbations were considered separately. The net global effect of these radiative perturbations determines the strength of the global model feedbacks, and hence the climate sensitivity. The geographical distribution of the radiative perturbations on the other hand helps to identify the model processes that are most important for determining the strength of model feedbacks. This study found that globally, the dominant positive feedbacks were for (a) water vapour amount and height, and cloud height for long wave radiation and (b) albedo and cloud amount for short wave radiation. The dominant negative feedback (apart from the surface temperature term itself) occurred for cloud amount changes in the long wave. Geographically, the contributions to the water vapour feedback strength varied markedly by location, with subtropical, and upper tropospheric regions contributing relatively strongly to the net global feedback. The water vapour height component correlated quite strongly with convective changes while the amount term was correlated with fractional precipitable water changes. The contribution of different precipitable water regimes in the tropics to global water vapour feedback was assessed - relatively dry areas contributed disproportionately, but did not dominate the overall feedback because of their small areas. Contributions to cloud amount and height feedbacks in the long wave were found to be uncorrelated in space, indicating their different controlling processes. The long wave amount component correlated strongly with upper cloud, and convective changes. The short wave component of the cloud feedback depended on cloud changes at all levels, producing its strongest contribution to feedbacks in mid latitudes, where the sign of cloud changes agreed at different heights. The effect of cloud cover on non-cloud feedbacks was also investigated. This study found that clouds weaken all feedbacks, except that of lapse rate, with the greatest impact being on the surface albedo and water vapour amount. The radiative perturbation analysis method presented here proves to be a powerful tool for identifying important physical processes that determine final climate model sensitivity. Crown © 2002 Published by Elsevier Science B.V. All rights reserved."
"6601982043;25953950400;","Mesoscale numerical simulation of cirrus clouds - FIRE case study and sensitivity analysis",1993,"10.1175/1520-0493(1993)121<2264:MNSOCC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027802827&doi=10.1175%2f1520-0493%281993%29121%3c2264%3aMNSOCC%3e2.0.CO%3b2&partnerID=40&md5=bce803304ae1f6dbbc24cc03331e3e79","The three-dimensional mesoscale model was applied in nonhydrostatic and nested-grid mode using explicit, bulk microphysics and radiation. The simulation resulted in very good agreement between observed and model-predicted dynamic and cloud fields. Cloud height, thickness, areal extent, and microphysical composition were verified against GOES satellite imagery, lidar, and aircraft measurements taken during the FIRE cirrus intensive field observation. Cloud-top generation zones and layering were simulated. Sensitivity simulations were run to determine long- and shortwave radiative forcing. Also a simulation was run with no condensate to examine cloud feedbacks on the environment. Longwave radiation appeared to be instrumental in developing weak convective-like activity, thereby increasing the cloud's optical depth. -from Authors"
"7201472576;57190384098;","Characterization of AVHRR global cloud detection sensitivity based on CALIPSO-CALIOP cloud optical thickness information: Demonstration of results based on the CM SAF CLARA-A2 climate data record",2018,"10.5194/amt-11-633-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041909609&doi=10.5194%2famt-11-633-2018&partnerID=40&md5=7442b855b4fc52d1660d2fe165efd115","The sensitivity in detecting thin clouds of the cloud screening method being used in the CM SAF cloud, albedo and surface radiation data set from AVHRR data (CLARA-A2) cloud climate data record (CDR) has been evaluated using cloud information from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard the CALIPSO satellite. The sensitivity, including its global variation, has been studied based on collocations of Advanced Very High Resolution Radiometer (AVHRR) and CALIOP measurements over a 10-year period (2006-2015). The cloud detection sensitivity has been defined as the minimum cloud optical thickness for which 50ĝ€% of clouds could be detected, with the global average sensitivity estimated to be 0.225. After using this value to reduce the CALIOP cloud mask (i.e. clouds with optical thickness below this threshold were interpreted as cloud-free cases), cloudiness results were found to be basically unbiased over most of the globe except over the polar regions where a considerable underestimation of cloudiness could be seen during the polar winter. The overall probability of detecting clouds in the polar winter could be as low as 50ĝ€% over the highest and coldest parts of Greenland and Antarctica, showing that a large fraction of optically thick clouds also remains undetected here. The study included an in-depth analysis of the probability of detecting a cloud as a function of the vertically integrated cloud optical thickness as well as of the cloud's geographical position. Best results were achieved over oceanic surfaces at mid- to high latitudes where at least 50ĝ€% of all clouds with an optical thickness down to a value of 0.075 were detected. Corresponding cloud detection sensitivities over land surfaces outside of the polar regions were generally larger than 0.2 with maximum values of approximately 0.5 over the Sahara and the Arabian Peninsula. For polar land surfaces the values were close to 1 or higher with maximum values of 4.5 for the parts with the highest altitudes over Greenland and Antarctica. It is suggested to quantify the detection performance of other CDRs in terms of a sensitivity threshold of cloud optical thickness, which can be estimated using active lidar observations. Validation results are proposed to be used in Cloud Feedback Model Intercomparison Project (CFMIP) Observation Simulation Package (COSP) simulators for cloud detection characterization of various cloud CDRs from passive imagery."
"56203249800;7006550762;6507308842;57193132723;9242540400;55408944000;","Interactive nature of climate change and aerosol forcing",2017,"10.1002/2016JD025809","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85017335882&doi=10.1002%2f2016JD025809&partnerID=40&md5=b9230d19d8ff7f74a312b4fdabf47689","The effect of changing cloud cover on climate, based on cloud-aerosol interactions, is one of the major unknowns for climate forcing and climate sensitivity. It has two components: (1) the impact of aerosols on clouds and climate due to in situ interactions (i.e., rapid response) and (2) the effect of aerosols on the cloud feedback that arises as climate changes-climate feedback response. We examine both effects utilizing the NASA Goddard Institute for Space Studies ModelE2 to assess the indirect effect, with both mass-based and microphysical aerosol schemes, in transient twentieth century simulations. We separate the rapid response and climate feedback effects by making simulations with a coupled version of the model as well as one with no sea surface temperature or sea ice response (“atmosphere-only” simulations). We show that the indirect effect of aerosols on temperature is altered by the climate feedbacks following the ocean response, and this change differs depending upon which aerosol model is employed. Overall, the effective radiative forcing (ERF) for the “direct effect” of aerosol-radiation interaction (ERFari) ranges between 0.2 and 0.6Wm-2 for atmosphere-only experiments, while the total effective radiative forcing, including the indirect effect (ERFari+aci) varies between about -0.4 and 1.1Wm-2for atmosphere-only simulations; both ranges are in agreement with those given in Intergovernmental Panel on Climate Change (2013). Including the full feedback of the climate system lowers these ranges to -0.2 to 0.5Wm-2 for ERFari and -0.3 to 0.74Wm-2 for ERFari+aci. With both aerosol schemes, the climate change feedbacks have reduced the global average indirect radiative effect of atmospheric aerosols relative to what the emission changes would have produced, at least partially due to its effect on tropical upper tropospheric clouds. © 2017. American Geophysical Union. All Rights Reserved."
"6602845217;35423159000;","The seasonally changing cloud feedbacks contribution to the ENSO seasonal phase-locking",2016,"10.1007/s00382-016-3034-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84958817486&doi=10.1007%2fs00382-016-3034-6&partnerID=40&md5=d2a36ee131ebe9009a7314797d68fc1b","ENSO variability has a seasonal phase-locking, with SST anomalies on average decreasing during the beginning of the year and SST anomalies increasing during the second half of the year. As a result of this, the ENSO SST variability is smallest in April and the so call ‘spring barrier’ exists in the predictability of ENSO. In this study we analysis how the seasonal phase-locking of surface short wave radiation associated with cloud cover feedbacks contribute to this phenomenon. We base our analysis on observations and simplified climate model simulations. At the beginning of the year, the warmer mean SST in the eastern equatorial Pacific leads to deeper clouds whose anomalous variability are positively correlated with the underlying SST anomalies. These observations highlight a strong negative surface short wave radiation feedback at the beginning of the year in the eastern Pacific (NINO3 region). This supports the observed seasonal phase-locking of ENSO SST variability. This relation also exists in model simulations of the linear recharge oscillator and in the slab ocean model coupled to a fully complex atmospheric GCM. The Slab ocean simulation has seasonal phase-locking similar to observed mostly caused by similar seasonal changing cloud feedbacks as observed. In the linear recharge oscillator simulations seasonal phase-locking is also similar to observed, but is not just related to seasonal changing cloud feedbacks, but is also related to changes in the sensitivity of the zonal wind stress and to a lesser extent to seasonally change sensitivities to the thermocline depth. In summary this study has shown that the seasonal phase-locking, as observed and simulated, is linked to seasonally changing cloud feedbacks. © 2016, Springer-Verlag Berlin Heidelberg."
"55596887300;7003406400;7102006474;12042092500;7006592026;","Numerical framework and performance of the new multiple-phase cloud microphysics scheme in RegCM4.5: Precipitation, cloud microphysics, and cloud radiative effects",2016,"10.5194/gmd-9-2533-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84979929571&doi=10.5194%2fgmd-9-2533-2016&partnerID=40&md5=ade2a44f87a163830cd95e7ad583a26d","We implement and evaluate a new parameterization scheme for stratiform cloud microphysics and precipitation within regional climate model RegCM4. This new parameterization is based on a multiple-phase one-moment cloud microphysics scheme built upon the implicit numerical framework recently developed and implemented in the ECMWF operational forecasting model. The parameterization solves five prognostic equations for water vapour, cloud liquid water, rain, cloud ice, and snow mixing ratios. Compared to the pre-existing scheme, it allows a proper treatment of mixed-phase clouds and a more physically realistic representation of cloud microphysics and precipitation. Various fields from a 10-year long integration of RegCM4 run in tropical band mode with the new scheme are compared with their counterparts using the previous cloud scheme and are evaluated against satellite observations. In addition, an assessment using the Cloud Feedback Model Intercomparison Project (CFMIP) Observational Simulator Package (COSP) for a 1-year sub-period provides additional information for evaluating the cloud optical properties against satellite data. The new microphysics parameterization yields an improved simulation of cloud fields, and in particular it removes the overestimation of upper level cloud characteristics of the previous scheme, increasing the agreement with observations and leading to an amelioration of a long-standing problem in the RegCM system. The vertical cloud profile produced by the new scheme leads to a considerably improvement of the representation of the longwave and shortwave components of the cloud radiative forcing. © Author(s) 2016."
"16480666100;55537426400;6603196127;","Surface arctic amplification factors in CMIP5 models: Land and oceanic surfaces and seasonality",2016,"10.1175/JCLI-D-15-0497.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84966312444&doi=10.1175%2fJCLI-D-15-0497.1&partnerID=40&md5=0026892260ec1f2e327ecfe72bfe0e5a","Arctic amplification (AA) is a major characteristic of observed global warming, yet the different mechanisms responsible for it and their quantification are still under investigation. In this study, the roles of different factors contributing to local surface warming are quantified using the radiative kernel method applied at the surface after 100 years of global warming under a representative concentration pathway 4.5 (RCP4.5) scenario simulated by 32 climate models from phase 5 of the Coupled Model Intercomparison Project. The warming factors and their seasonality for land and oceanic surfaces were investigated separately and for different domains within each surface type where mechanisms differ. Common factors contribute to both land and oceanic surface warming: Tropospheric-mean atmospheric warming and greenhouse gas increases (mostly through water vapor feedback) for both tropical and Arctic regions, nonbarotropic warming and surface warming sensitivity effects (negative in the tropics, positive in the Arctic), and warming cloud feedback in the Arctic in winter. Some mechanisms differ between land and oceanic surfaces: Sensible and latent heat flux in the tropics, albedo feedback peaking at different times of the year in the Arctic due to different mean latitudes, a very large summer energy uptake and winter release by the Arctic Ocean, and a large evaporation enhancement in winter over the Arctic Ocean, whereas the peak occurs in summer over the ice-free Arctic land. The oceanic anomalous energy uptake and release is further studied, suggesting the primary role of seasonal variation of oceanic mixed layer temperature changes. © 2016 American Meteorological Society."
"57033686900;7202145115;","On the influence of poleward jet shift on shortwave cloud feedback in global climate models",2015,"10.1002/2015MS000520","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959563799&doi=10.1002%2f2015MS000520&partnerID=40&md5=e47fa124f7dcfb637edef3940788bacd","Experiments designed to separate the effect of atmospheric warming from the effect of shifts of the eddy-driven jet on shortwave (SW) cloud feedback are performed with three global climate models (GCMs). In each model a warming simulation produces a robust SW cloud feedback dipole, with a negative (positive) feedback in the high-latitudes (subtropics). The cloud brightening in high-latitudes that characterizes warming simulations is not produced by jet shifts alone in any of the models, but is highly sensitive to perturbations of freezing temperature seen by the cloud microphysics scheme, indicating that thermodynamic mechanisms involving the phase of cloud condensate dominate the SW feedback at high-latitudes. In one of the models a poleward jet shift causes significant cloud dimming throughout the midlatitudes, but in two models it does not. Differences in cloud response to jet shifts in two of the models are attributed to differences in the shallow convection parameterizations. © 2015. The Authors."
"56989640500;21935606200;36915461700;7102913661;","Aerosol-cloud associations over gangetic basin during a typical monsoon depression event using WRF-Chem simulation",2015,"10.1002/2015JD023634","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84954379322&doi=10.1002%2f2015JD023634&partnerID=40&md5=c7543a39936b98bff00cc24c24fc2ce7","To study aerosol-cloud interactions over the Gangetic Basin of India, the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) has been applied to a typical monsoon depression event prevalent between the 23 and 29 August 2009. This event was sampled during the Cloud Aerosol Interaction and Precipitation Enhancement EXperiment (CAIPEEX) aircraft campaign, providing measurements of aerosol and cloud microphysical properties from two sorties. Comparison of the simulated meteorological, thermodynamical, and aerosol fields against satellite and in situ aircraft measurements illustrated that the westward propagation of the monsoon depression and the cloud, aerosol, and rainfall spatial distribution was simulated reasonably well using anthropogenic emission rates from Monitoring Atmospheric Composition and Climate project along with cityZEN projects (MACCity)+Intercontinental Chemical Transport Experiment Phase B anthropogenic emission rates. However,the magnitude of aerosol optical depth was underestimated by up to 50%. A simulation with aerosol emissions increased by a factor of 6 over the CAIPEEX campaign domain increased the simulated aerosol concentrations to values close to the observations, mainly within boundary layer. Comparison of the low-aerosol simulation and high-aerosol simulation for the two sorties illustrated that more anthropogenic aerosols increased the cloud condensing nuclei (CCN) and cloud droplet mass concentrations. The number of simulated cloud droplets increased while the cloud droplet effective radii decreased, highlighting the importance of CCN-cloud feedbacks over this region. The increase in simulated anthropogenic aerosols (including absorbing aerosols) also increased the temperature of air parcels below clouds and thus the convective available potential energy (CAPE). The increase in CAPE intensified the updraft and invigorated the cloud, inducing formation of deeper clouds with more ice-phase hydrometeors for both cases. These case studies provide evidence of aerosol-induced cloud invigoration over the Gangetic Basin. © 2015. American Geophysical Union. All Rights Reserved."
"56577620100;7003355879;6603054569;7006019301;","Observed anomalous atmospheric patterns in summers of unusual Arctic sea icemelt",2015,"10.1002/2014JD022608","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928642075&doi=10.1002%2f2014JD022608&partnerID=40&md5=24e2bc4419b57e0477143cadb57ce39c","The Arctic sea ice retreat has accelerated over the last decade. The negative trend is largest in summer, but substantial interannual variability still remains. Here we explore observed atmospheric conditions and feedback mechanisms during summer months of anomalous sea ice melt in the Arctic. Compositing months of anomalous low and high sea ice melt over 1979-2013, we find distinct patterns in atmospheric circulation, precipitation, radiation, and temperature. Compared to summer months of anomalous low sea ice melt, high melt months are characterized by anomalous high sea level pressure in the Arctic (up to 7 hPa), with a corresponding tendency of storms to track on a more zonal path. As a result, the Arctic receives less precipitation overall and 39% less snowfall. This lowers the albedo of the region and reduces the negative feedback the snowfall provides for the sea ice. With an anticyclonic tendency, 12 W/m2 more incoming shortwave radiation reaches the surface in the start of the season. The melting sea ice in turn promotes cloud development in the marginal ice zones and enhances downwelling longwave radiation at the surface toward the end of the season. A positive cloud feedback emerges. In midlatitudes, the more zonally tracking cyclones give stormier, cloudier, wetter, and cooler summers in most of northern Europe and around the Sea of Okhotsk. Farther south, the region from the Mediterranean Sea to East Asia experiences significant surface warming (up to 2.4°C), possibly linked to changes in the jet stream. © 2015. American Geophysical Union. All Rights Reserved."
"24329376600;7003976079;","Cloud feedbacks, rapid adjustments, and the forcing-response relationship in a transient CO2 reversibility scenario",2014,"10.1175/JCLI-D-13-00421.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893829965&doi=10.1175%2fJCLI-D-13-00421.1&partnerID=40&md5=b6d40fd0aae4b5d842401acd14f81e0b","The Hadley Centre Global Environment Model, version 2-Earth System (HadGEM2-ES) climate model is forced by a 1%yr-1 compound increase in atmospheric CO2 for 140 years, followed by a 1%yr-1 CO2 decrease back to the starting level. Analogous atmosphere-only simulations are performed to diagnose the component of change associated with the effective radiative forcing and rapid adjustments. The residual change is associated with radiative feedbacks that are shown to be linearly related to changes in global-mean surface air temperature and are found to be reversible under this experimental design, even for regional cloud feedback changes. The cloud adjustment is related to changes in cloud amount, with little indication of any large-scale changes in cloud optical depth. Plant physiological forcing plays a significant role in determining the cloud adjustment in this model and is the dominant contribution to the low-level cloud changes over land. Low-level cloud adjustments are associated with changes in surface turbulent fluxes and lower tropospheric stability, with significant adjustments in boundary layer cloud types and in the depth of the boundary layer itself. The linearity of simple forcing-response frameworks are examined and found to be generally applicable. Small regional departures from linearity occur during the early part of the ramp-down phase, where the Southern Ocean and eastern tropical Pacific continue to warm for a few decades, despite the reversal in radiative forcing and global temperatures. The importance of considering time-varying patterns of warming and regional phenomena when diagnosing and understanding feedbacks in a coupled atmosphere-ocean framework is highlighted."
"37861539400;6507224579;","Why tropical sea surface temperature is insensitive to ocean heat transport changes",2013,"10.1175/JCLI-D-13-00192.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884221915&doi=10.1175%2fJCLI-D-13-00192.1&partnerID=40&md5=b07e5c3136f745311f3319aecce78291","Previous studies have shown that increases in poleward ocean heat transport (OHT) do not strongly affect tropical SST. The goal of this paper is to explain this observation. To do so, the authors force two atmospheric global climate models (GCMs) in aquaplanet configuration with a variety of prescribed OHTs. It is found that increased OHT weakens the Hadley circulation, which decreases equatorial cloud cover and shortwave reflection, as well as reduces surface winds and evaporation, which both limit changes in tropical SST. The authors also modify one of the GCMs by alternatively setting the radiative effect of clouds to zero and disabling wind-driven evaporation changes to show that the cloud feedback is more important than the wind-evaporation feedback for maintaining constant equatorial SST as OHT changes. This work highlights the fact that OHT can reduce the meridional SST gradient without affecting tropical SST and could therefore serve as an additional degree of freedom for explaining past warm climates. © 2013 American Meteorological Society."
"42661269900;7003922138;23082420800;","The contribution of radiative feedbacks to orbitally driven climate change",2013,"10.1175/JCLI-D-12-00419.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881635656&doi=10.1175%2fJCLI-D-12-00419.1&partnerID=40&md5=7a7cef489860b5ee9d7eaffc78964296","Radiative feedbacks influence Earth's climate response to orbital forcing, amplifying some aspects of the response while damping others. To better understand this relationship, the GFDL Climate Model, version 2.1 (CM2.1), is used to perform idealized simulations in which only orbital parameters are altered while ice sheets, atmospheric composition, and other climate forcings are prescribed at preindustrial levels. These idealized simulations isolate the climate response and radiative feedbacks to changes in obliquity and longitude of the perihelion alone. Analysis shows that, despite being forced only by a redistribution of insolation with no global annual-mean component, feedbacks induce significant global-mean climate change, resulting in mean temperature changes of 20.5K in a lowered obliquity experiment and 10.6K in a NH winter solstice perihelion minus NH summer solstice perihelion experiment. In the obliquity experiment, some global-mean temperature response may be attributable to vertical variations in the transport of moist static energy anomalies, which can affect radiative feedbacks in remote regions by altering atmospheric stability. In the precession experiment, cloud feedbacks alter the Arctic radiation balance with possible implications for glaciation. At times when the orbital configuration favors glaciation, reductions in cloud water content and low-cloud fraction partially counteract changes in summer insolation, posing an additional challenge to understanding glacial inception.Additionally, several systems, such as the Hadley circulation and monsoons, influence climate feedbacks in ways that would not be anticipated from analysis of feedbacks in the more familiar case of anthropogenic forcing, emphasizing the complexity of feedback responses. © 2013 American Meteorological Society."
"55171972400;55170561300;6603415703;13406764900;53876838300;14421382400;7501592612;55183842400;7006280684;55233965300;7402478173;7404105326;","Obtaining diverse behaviors in a climate model without the use of flux adjustments",2013,"10.1002/jgrd.50304","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882320373&doi=10.1002%2fjgrd.50304&partnerID=40&md5=ce07e4b1324d84323cb4437278fc868d","A number of studies have set out to obtain a range of atmosphere and ocean model behavior by perturbing parameters in a single climate model (perturbed physics ensemble: PPE). Early studies used shallow layer slab ocean or flux-adjusted coupled oceanatmosphere models to obtain a broad range of behavior as characterized by climate sensitivity. A recent study reports a relatively narrow range of sensitivities (2.2-3.2°C) in a PPE of 35 coupled models without flux adjustment, raising the question whether previous broad ranges were an artifact of the use of models that were not in top-of-atmosphere (TOA) energy balance. Moreover, no PPE experiment has reported a large spread of behavior of the ocean compared to that exhibited in a multi-model ensemble (MME) such as Coupled Model Intercomparison Project phase 3 (CMIP3). In this work, we randomly perturb model parameters of a coupled ocean-atmosphere general circulation model using a space-filling design containing 10,000 combinations. The ensemble is run over the distributed computing platform of climateprediction.net under fixed pre-industrial forcing without flux adjustment. We resample a second, 20,000-member, ensemble with perturbations conditioned on the TOA fluxes from the first ensemble to not drift significantly from a realistic base state while targeting a range of behavior. Models within the targeted ensemble show realistic regional control climates when compared to the CMIP3 ensemble, although there is a bias in global mean surface temperature. The range of predicted equilibrium climate sensitivities of the targeted ensemble is substantially smaller than that obtained with flux adjustment, but larger than the range in the CMIP3 ensemble or in the 35-model un-flux-adjusted PPE in a recent study mentioned above. The Atlantic meridional overturning circulation in the targeted ensemble exhibits a spread in strength as wide as that found in the CMIP3 ensemble. We conclude that flux adjustment is not a prerequisite for obtaining a broad spread of behavior in a perturbed physics ensemble. © 2013. American Geophysical Union. All Rights Reserved."
"7003266014;7004364155;","Impact of dataset choice on calculations of the short-term cloud feedback",2013,"10.1002/jgrd.50199","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880672717&doi=10.1002%2fjgrd.50199&partnerID=40&md5=a55c29c9af3ec0df8370ee75163eebd5","Dessler [2010, hereafter D10] estimated the magnitude of the cloud feedback in response to short-term climate variations and concluded that it was likely positive, with an average magnitude of +0.50±0.75 W/m2/K. This paper investigates the sensitivity of D10's results to the choice of clear-sky top-of-atmosphere flux (ΔR<inf>clear-sky</inf>), surface temperature (ΔT<inf>s</inf>), and reanalysis data sets. Most of the alternative ΔR<inf>clear-sky</inf> data sets produce cloud feedbacks that are close to D10, differing by 0.2-0.3 W/m2/K. An exception is the Terra SSF1deg ΔR<inf>clear-sky</inf> product, which produces an overall negative cloud feedback. However, a critical examination of those data leads us to conclude that that result is due to problems in the Terra ΔR<inf>clear-sky</inf> arising from issues with cloud clearing prior to July 2001. Eliminating the problematic early portion yields a cloud feedback in good agreement with D10. We also present an alternative calculation of the cloud feedback that does not require an estimate of ΔR<inf>clear-sky</inf>, and this calculation also produces a positive cloud feedback in agreement with D10. The various ΔT<inf>s</inf> data sets produce cloud feedbacks that differ by as much as 0.8 W/m2/K. The choice of reanalysis, used as a source of ΔR<inf>clear-sky</inf> or as adjustments for the cloud radiative forcing, has a small impact on the inferred cloud feedback. Overall, these results confirm the robustness of D10's estimate of a likely positive feedback. © 2013. American Geophysical Union. All Rights Reserved."
"23486332900;6701455548;","Model-specific radiative kernels for calculating cloud and noncloud climate feedbacks",2012,"10.1175/JCLI-D-11-00726.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870014753&doi=10.1175%2fJCLI-D-11-00726.1&partnerID=40&md5=685c0b5d99dabeae83d03c29138f5f45","Radiative kernels have become a common tool for evaluating and comparing radiative feedbacks to climate change in different general circulation models. However, kernel feedback calculations are inaccurate for simulations where the atmosphere is significantly perturbed from its base state, such as for very large forcing or perturbed physics simulations. In addition, past analyses have not produced kernels relating to prognostic cloud variables because of strong nonlinearities in their relationship to radiative forcing. A new methodology is presented that allows for fast statistical optimizing of existing kernels such that accuracy is increased for significantly altered climatologies. International Satellite Cloud Climatology Project (ISCCP) simulator output is used to relate changes in cloud-type histograms to radiative fluxes. With minimal additional computation, an individual set of kernels is created for each climate experiment such that climate feedbacks can be reliably estimated even in significantly perturbed climates. This methodology is applied to successive generations of the Community Atmosphere Model (CAM).Increased climate sensitivity in CAM5 is shown to be due to reduced negative stratus and stratocumulus feedbacks in the tropics and midlatitudes, strong positive stratus feedbacks in the southern oceans, and a strengthened positive longwave cirrus feedback. Results also suggest that CAM5 exhibits a stronger surface albedo feedback than its predecessors, a feature not apparent when using a single kernel. Optimized kernels for CAM5 suggest weaker global-mean shortwave cloud feedback than one would infer from using the original kernels and an adjusted cloud radiative forcing methodology. © 2012 American Meteorological Society."
"12645767500;7004114883;7202899330;","An observed tropical oceanic radiative-convective cloud feedback",2010,"10.1175/2009JCLI3091.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953702221&doi=10.1175%2f2009JCLI3091.1&partnerID=40&md5=991af70dd979fea8d2c8c2efb315fb52","Anomalies of precipitation, cloud, thermodynamic, and radiation variables are analyzed on the large spatial scale defined by the tropical oceans. In particular, relationships between the mean tropical oceanic precipitation anomaly and radiative anomalies are examined. It is found that tropical mean precipitation is well correlated with cloud properties and radiative fields. In particular, the tropical mean precipitation anomaly is positively correlated with the top of the atmosphere reflected shortwave anomaly and negatively correlated with the emitted longwave anomaly. The tropical mean relationships are found to primarily result from a coherent oscillation of precipitation and the area of high-level cloudiness. The correlations manifest themselves radiatively as a modest decrease in net downwelling radiation at the top of the atmosphere, and a redistribution of energy from the surface to the atmosphere through reduced solar radiation to the surface and decreased longwave emission to space. Integrated over the tropical oceanic domain, the anomalous atmospheric column radiative heating is found to be about 10% of the magnitude of the anomalous latent heating. The temporal signature of the radiative heating is observed in the column mean temperature that indicates a coherent phase-lagged oscillation between atmospheric stability and convection. These relationships are identified as a radiative-convective cloud feedback that is observed on intraseasonal time scales in the tropical atmosphere. © 2010 American Meteorological Society."
"36148316400;15045669300;23072989400;56726831200;","Past, present and future vegetation-cloud feedbacks in the Amazon Basin",2009,"10.1007/s00382-009-0536-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62549132029&doi=10.1007%2fs00382-009-0536-5&partnerID=40&md5=fb77e2d5c7d0ab9c35b849575eac7646","To begin exploring the underlying mechanisms that couple vegetation to cloud formation processes, we derive the lifting condensation level (LCL) to estimate cumulus cloud base height. Using a fully coupled land - ocean - atmosphere general circulation model (HadCM3LC), we investigate Amazonian forest feedbacks on cloud formation over three geological periods; modern-day (a.d. 1970-1990), the last glacial maximum (LGM; 21 kya), and under a future climate scenario (IS92a; a.d. 2070-2090). Results indicate that for both past and future climate scenarios, LCL is higher relative to modern-day. Statistical analyses indicate that the 800 m increase in LCL during the LGM is related primarily to the drier atmosphere promoted by lower tropical sea surface temperatures. In contrast, the predicted 1,000 m increase in LCL in the future scenario is the result of a large increase in surface temperature and reduced vegetation cover. © Springer-Verlag 2009."
"12139043600;56250250300;7005955015;12139310900;6506436908;","On the additivity of climate response to anthropogenic aerosols and CO2, and the enhancement of future global warming by carbonaceous aerosols",2008,"10.1111/j.1600-0870.2008.00308.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42549165534&doi=10.1111%2fj.1600-0870.2008.00308.x&partnerID=40&md5=5e1884e25dd71ee8b62c5b21cd6f33a4","Climate responses to aerosol forcing at present-day and doubled CO2-levels are studied based on equilibrium simulations with the CCM-Oslo atmospheric GCM coupled to a slab ocean. Aerosols interact on-line with meteorology through life-cycling of sulphate and black carbon (BC), and tables for aerosol optics and CCN activation. Anthropogenic aerosols counteract the warming by CO2 through a negative radiative forcing dominated by the indirect effect. Anthropogenic aerosols reduce precipitation by 4%, while CO2 doubling gives a 5% increase, mainly through enhanced convective activity, including a narrower ITCZ. Globally, the aerosol cooling is insensitive to CO2, and the effects of CO2 doubling are insensitive to aerosols. Hence, global climate responses to these sources of forcing are almost additive, although sulphate and BC burdens are slightly increased due to reduced stratiform precipitation over major anthropogenic source regions and a modified ITCZ. Regionally, positive cloud feedbacks give up to 5 K stronger aerosol cooling at present-day CO2 than after CO2 doubling. Aerosol emissions projected for year-2100 (SRES A2) strongly increase BC and change the sign of the direct effect. This results in a 0.3 K warming and 0.1% increase in precipitation compared to the year 2000, thus enhancing the global warming by greenhouse gases. © 2008 The Authors Journal compilation © 2008 Blackwell Munksgaard."
"12801992200;","A note on the effect of GCM tuning on climate sensitivity",2008,"10.1088/1748-9326/3/1/014001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43149094019&doi=10.1088%2f1748-9326%2f3%2f1%2f014001&partnerID=40&md5=7d795bf07d24bf95b14fac921b0c9347","A tuning experiment is carried out with the Community Atmosphere Model version 3, where the top-of-the-atmosphere radiative balance is tuned to agree with global satellite estimates from ERBE and CERES, respectively, to investigate if the climate sensitivity of the model is dependent upon which of the datasets is used. The tuning is done through alterations of cloud parameters that affect, for instance, the model cloud water content, but the difference in cloud water content between the two model configurations is found to be negligible compared to the wide spread of the same quantity in a number of state-of-the-art GCMs. The equilibrium climate sensitivities of the two model configurations differ by ca.0.24K, and both lie well within the range of present estimates of climate sensitivity in different GCMs. This indicates that it is possible to tune the model to either of the two satellite datasets without drastically changing the climate sensitivity. However, the study illustrates that the climate sensitivity is a product of choices of parameter values that are not well restricted by observations, which allows for a certain degree of arbitrariness in the estimates of climate sensitivity. © 2008 IOP Publishing Ltd."
"7005485117;7403295159;7407043017;6603173671;57191117406;57191116942;","Numerical weather prediction for GATE",1979,"10.1002/qj.49710544617","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84987081386&doi=10.1002%2fqj.49710544617&partnerID=40&md5=7616c7f5f5af0684dc4e7ae8bbcb0968","The results of a few numerical weather prediction experiments that utilize GATE data are presented. Aside from some simple forecasts based on single‐level models, experiments with a multilevel model examine the roles of some of the physical processes. They include the influences of diurnally varying radiative effects, effects of cloud feedback on shortwave and longwave radiation, the heat balance of land surfaces, and the influence of West African orography in the 3‐ to 4‐day range of numerical weather prediction. Data sources for these experiments include surface and upper air observations from the World Weather Watch, GATE ships, upper winds from commercial aircraft, low‐ and high‐level cloud winds from geostationary satellites, winds from GATE research aircraft, and special surface observations from a ship data collection. The data analysis is based on a successive correction method where a subjective interface is also incorporated. The initial data are further subjected to a static as well as a dynamic initialization process. The major results are that single‐level forecasts are very promising with this data set if they are carried out at 700 mb. The multilevel adiabatic experiment produces very poor predictions due to lack of adequate vertical coupling between the lower and the upper troposphere and due to its inability to describe the broad‐scale monsoons. The diurnally varying heat balance of the earth's surface and cloudiness in radiative calculations appear to be important in the 3‐ to 4‐day range of prediction of African disturbances. In this paper we show some interesting vertical structure diagrams of African waves based on the results of numerical weather prediction, which exhibit a close similarity to the structures of composite GATE disturbances constructed by Professor R. J. Reed and his associates. Copyright © 1979 Royal Meteorological Society"
"57197840302;7005557215;14036628000;","Separating the impact of individual land surface properties on the terrestrial surface energy budget in both the coupled and uncoupled land–atmosphere system",2019,"10.1175/JCLI-D-18-0812.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074786282&doi=10.1175%2fJCLI-D-18-0812.1&partnerID=40&md5=adda6d77936bf1d7d11046e81b3e521a","Changes in the land surface can drive large responses in the atmosphere on local, regional, and global scales. Surface properties control the partitioning of energy within the surface energy budget to fluxes of shortwave and longwave radiation, sensible and latent heat, and ground heat storage. Changes in surface energy fluxes can impact the atmosphere across scales through changes in temperature, cloud cover, and large-scale atmospheric circulation. We test the sensitivity of the atmosphere to global changes in three land surface properties: albedo, evaporative resistance, and surface roughness. We show the impact of changing these surface properties differs drastically between simulations run with an offline land model, compared to coupled land–atmosphere simulations that allow for atmospheric feedbacks associated with land–atmosphere coupling. Atmospheric feedbacks play a critical role in defining the temperature response to changes in albedo and evaporative resistance, particularly in the extratropics. More than 50% of the surface temperature response to changing albedo comes from atmospheric feedbacks in over 80% of land areas. In some regions, cloud feedbacks in response to increased evaporative resistance result in nearly 1 K of additional surface warming. In contrast, the magnitude of surface temperature responses to changes in vegetation height are comparable between offline and coupled simulations. We improve our fundamental understanding of how and why changes in vegetation cover drive responses in the atmosphere, and develop understanding of the role of individual land surface properties in controlling climate across spatial scales—critical to understanding the effects of land-use change on Earth’s climate. © 2019 American Meteorological Society."
"7003266014;35547807400;","An Estimate of Equilibrium Climate Sensitivity From Interannual Variability",2018,"10.1029/2018JD028481","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052814027&doi=10.1029%2f2018JD028481&partnerID=40&md5=898e9146382da7d0e61d61427f19569a","Estimating the equilibrium climate sensitivity (ECS; the equilibrium warming in response to a doubling of CO2) from observations is one of the big problems in climate science. Using observations of interannual climate variations covering the period 2000 to 2017 and a model-derived relationship between interannual variations and forced climate change, we estimate that ECS is likely 2.4–4.6 K (17–83% confidence interval), with a mode and median value of 2.9 and 3.3 K, respectively. This analysis provides no support for low values of ECS (below 2 K) suggested by other analyses. The main uncertainty in our estimate is not observational uncertainty but rather uncertainty in converting observations of short term, mainly unforced climate variability to an estimate of the response of the climate system to long-term forced warming. ©2018. American Geophysical Union. All Rights Reserved."
"7003266014;8696069500;7201504886;","The influence of internal variability on Earth's energy balance framework and implications for estimating climate sensitivity",2018,"10.5194/acp-18-5147-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045505891&doi=10.5194%2facp-18-5147-2018&partnerID=40&md5=e52575a1617a30ceac403c3c815bdd5d","Our climate is constrained by the balance between solar energy absorbed by the Earth and terrestrial energy radiated to space. This energy balance has been widely used to infer equilibrium climate sensitivity (ECS) from observations of 20th-century warming. Such estimates yield lower values than other methods, and these have been influential in pushing down the consensus ECS range in recent assessments. Here we test the method using a 100-member ensemble of the Max Planck Institute Earth System Model (MPI-ESM1.1) simulations of the period 1850-2005 with known forcing. We calculate ECS in each ensemble member using energy balance, yielding values ranging from 2.1 to 3.9K. The spread in the ensemble is related to the central assumption in the energy budget framework: That global average surface temperature anomalies are indicative of anomalies in outgoing energy (either of terrestrial origin or reflected solar energy). We find that this assumption is not well supported over the historical temperature record in the model ensemble or more recent satellite observations. We find that framing energy balance in terms of 500hPa tropical temperature better describes the planet's energy balance. © 2018 Author(s)."
"56246453200;24722339600;25640569400;","Identifying Meteorological Controls on Open and Closed Mesoscale Cellular Convection Associated with Marine Cold Air Outbreaks",2017,"10.1002/2017JD027031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032882868&doi=10.1002%2f2017JD027031&partnerID=40&md5=631fa8486c2b50b8d8929767bcdb374a","Mesoscale cellular convective (MCC) clouds occur in large-scale patterns over the ocean and have important radiative effects on the climate system. An examination of time-varying meteorological conditions associated with satellite-observed open and closed MCC clouds is conducted to illustrate the influence of large-scale meteorological conditions. Marine cold air outbreaks (MCAO) influence the development of open MCC clouds and the transition from closed to open MCC clouds. MCC neural network classifications on Moderate Resolution Imaging Spectroradiometer (MODIS) data for 2008 are collocated with Clouds and the Earth's Radiant Energy System (CERES) data and ERA-Interim reanalysis to determine the radiative effects of MCC clouds and their thermodynamic environments. Closed MCC clouds are found to have much higher albedo on average than open MCC clouds for the same cloud fraction. Three meteorological control metrics are tested: sea-air temperature difference (ΔT), estimated inversion strength (EIS), and a MCAO index (M). These predictive metrics illustrate the importance of atmospheric surface forcing and static stability for open and closed MCC cloud formation. Predictive sigmoidal relations are found between M and MCC cloud frequency globally and regionally: negative for closed MCC cloud and positive for open MCC cloud. The open MCC cloud seasonal cycle is well correlated with M, while the seasonality of closed MCC clouds is well correlated with M in the midlatitudes and EIS in the tropics and subtropics. M is found to best distinguish open and closed MCC clouds on average over shorter time scales. The possibility of a MCC cloud feedback is discussed. ©2017. American Geophysical Union. All Rights Reserved."
"55249801100;6701385171;7102167757;55268454800;","Transient response of the Southern Ocean to changing ozone: Regional responses and physical mechanisms",2017,"10.1175/JCLI-D-16-0474.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85015856267&doi=10.1175%2fJCLI-D-16-0474.1&partnerID=40&md5=86de0f8e48fae574c032ce0069fef1e4","The impact of changing ozone on the climate of the Southern Ocean is evaluated using an ensemble of coupled climate model simulations. By imposing a step change from 1860 to 2000 conditions, response functions associated with this change are estimated. The physical processes that drive this response are different across time periods and locations, as is the sign of the response itself. Initial cooling in the Pacific sector is driven not only by the increased winds pushing cold water northward, but also by the southward shift of storms associated with the jet stream. This shift drives both an increase in cloudiness (resulting in less absorption of solar radiation) and an increase in net freshwater flux to the ocean (resulting in a decrease in surface salinity that cuts off mixing of warm water from below). A subsurface increase in temperature associated with this reduction in mixing then upwells along the Antarctic coast, producing a subsequent warming. Similar changes in convective activity occur in the Weddell Sea but are offset in time. Changes in sea ice concentration also play a role in modulating solar heating of the ocean near the continent. The time scale for the initial cooling is much longer than that seen in NCAR CCSM3.5, possibly reflecting differences in natural convective variability between that model (which has essentially no Southern Ocean deep convection) and the one used here (which has a large and possibly unrealistically regular mode of convection) or to differences in cloud feedbacks or in the location of the anomalous winds. © 2017 American Meteorological Society."
"43561261500;7404653593;8855923200;12040335900;36015299300;","Recent changes in winter Arctic clouds and their relationships with sea ice and atmospheric conditions",2016,"10.3402/tellusa.v68.29130","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84962359289&doi=10.3402%2ftellusa.v68.29130&partnerID=40&md5=c3fbb83059f7fec7f5c036b88907a0c2","Changes in Arctic clouds during boreal winter (December through February) and their relationship with sea ice and atmospheric conditions in recent decades have been examined using satellite and reanalysis data, and they are compared with output data from atmospheric general circulation model (AGCM) experiments. All the datasets used in this study consistently show that cloud amount over the Arctic Ocean (north of 67°N) decreased until the late 1990s but rapidly increased thereafter. Cloud increase in recent decade was a salient feature in the lower troposphere over a large part of the Arctic Sea, in association with obvious increase of lower tropospheric temperature and moisture. The comparison between the two periods before and after 1997 indicates that interannual covariability of Arctic clouds and lower tropospheric temperature and moisture was significantly enhanced after the late 1990s. Large reduction of sea ice cover during boreal winter decreased lower tropospheric static stability and deepened the planetary boundary layer. These changes led to an enhanced upward moisture transport and cloud formation, which led to considerable longwave radiative forcing and, as a result, strengthened the cloud-moisture-temperature relationship in the lower troposphere.AGCMexperiments under reduced sea ice conditions support those results obtained by satellite and reanalysis datasets reproducing the increases in cloud amount and lower tropospheric temperature and their enhanced covariability. © 2016 S.-Y. Jun et al."
"23008938100;56033135100;","How well do simulated last glacial maximum tropical temperatures constrain equilibrium climate sensitivity?",2015,"10.1002/2015GL064903","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938118156&doi=10.1002%2f2015GL064903&partnerID=40&md5=6474069232694aa11b21e10120de9f95","Previous work demonstrated a significant correlation between tropical surface air temperature and equilibrium climate sensitivity (ECS) in PMIP (Paleoclimate Modelling Intercomparison Project) phase 2 model simulations of the last glacial maximum (LGM). This implies that reconstructed LGM cooling in this region could provide information about the climate system ECS value. We analyze results from new simulations of the LGM performed as part of Coupled Model Intercomparison Project (CMIP5) and PMIP phase 3. These results show no consistent relationship between the LGM tropical cooling and ECS. A radiative forcing and feedback analysis shows that a number of factors are responsible for this decoupling, some of which are related to vegetation and aerosol feedbacks. While several of the processes identified are LGM specific and do not impact on elevated CO<inf>2</inf> simulations, this analysis demonstrates one area where the newer CMIP5 models behave in a qualitatively different manner compared with the older ensemble. The results imply that so-called Earth System components such as vegetation and aerosols can have a significant impact on the climate response in LGM simulations, and this should be taken into account in future analyses. Key Points New LGM simulations show no tropical temperature to climate sensitivity relation This is caused by a model complexity, especially due to Earth System components It is unclear how inferred ECS will change as more model components are included. © 2015. American Geophysical Union. All Rights Reserved."
"7003420726;35580303100;","A perspective on model-data surface temperature comparison at the Last Glacial Maximum",2015,"10.1016/j.quascirev.2014.09.019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910026075&doi=10.1016%2fj.quascirev.2014.09.019&partnerID=40&md5=93cc7050a696ea9d62a83bc25951dd3c","We review progress in model and proxy-based reconstruction of the surface temperature field of the Last Glacial Maximum. Both approaches have converged towards a climate state substantially colder than the present day, with the temperature anomaly field showing strong polar amplification and land-sea contrast. The magnitudes of the large-scale changes are increasingly well-constrained, with a recent model-data synthesis generating a value of 4°C, which suggests a moderate equilibrium climate sensitivity of about 2.5°C. However, significant areas of uncertainty remain, particularly in the tropical sea surface temperature change. At finer sub-continental spatial scales, there is limited agreement between models and data regarding the patterns of change. © 2014 Elsevier Ltd.All rights reserved."
"7004479957;8882641700;16029674800;","Cloud feedbacks on greenhouse warming in the superparameterized climate model SP-CCSM4",2014,"10.1002/2014MS000355","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027950951&doi=10.1002%2f2014MS000355&partnerID=40&md5=b7bb164ae9e2a943183ac3504e7f6c63","Cloud feedbacks on greenhouse warming are studied in a superparameterized version of the Community Climate System Model (SP-CCSM4) in an atmospheric component SP-CAM4 that explicitly simulates cumulus convection. A 150 year simulation in an abrupt quadrupling of CO2 is branched from a control run. It develops moderate positive global cloud feedback and an implied climate sensitivity of 2.8 K comparable to the conventionally parameterized CCSM4 and the median of other modern climate models. All of SP-CCSM4's positive shortwave cloud feedback is due to a striking decrease in low cloud over land, which is much more pronounced than in most other climate models, including CCSM4. Four other cloud responses - decreased midlevel cloud, more Arctic water and ice cloud, a slight poleward shift of midlatitude storm track cloud, and an upward shift of high clouds - are also typical of conventional global climate models. SP-CCSM4 does not simulate the large warming-induced decrease in Southern Ocean cloud found in CCSM4. Two companion uncoupled SP-CAM4 simulations, one with a uniform 4 K sea-surface temperature increase and one with quadrupled CO2 but fixed SST, suggest that SP-CCSM4's global-scale cloud changes are primarily mediated by the warming, rather than by rapid adjustments to increased CO2. SP-CAM4 show spatial patterns of cloud response qualitatively similar to the previous-generation superparameterized SP-CAM3, but with systematically more positive low cloud feedbacks over low-latitude land and ocean. Key Points: The superparameterized SP-CCSM4 has moderate positive cloud feedbacks It simulates less low cloud over land as climate warms SP-CCSM4 rapid cloud adjustments associated with abrupt CO2 increase are weak © 2014. The Authors."
"6603873829;7003638866;6701571700;","Comparison of model predicted cloud parameters and surface radiative fluxes with observations on the 100 km scale",2001,"10.1007/s007030170021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035533834&doi=10.1007%2fs007030170021&partnerID=40&md5=6d9a77c985c067bc2416265a7e242295","Cloud parameters and surface radiative fluxes predicted by regional atmospheric models are directly compared with observations for a 10-day period in late summer 1995 characterized by predominantly large-scale synoptic conditions. Observations of total cloud cover and vertical cloud structure are inferred from measurements with a ground-based network of Lidar ceilometers and IR-radiometers and from satellite observations on a 100 kilometer scale. Ground-based observations show that at altitudes below 3 km, implying liquid water clouds, there is a considerable portion of optically non-opaque clouds. Vertical distributions of cloud temperatures simultaneously inferred from the ground-based infrared radiometer network and from satellite can only be reconciled if the occurrence of optically thin cloud structures at mid-and high tropospheric levels is assumed to be frequent. Results of three regional atmospheric models, i.e. the GKSS-REMO, SMHI-HIRLAM, and KNMI-RACMO, are quantitatively compared with the observations. The main finding is that all models predict too much cloud amount at low altitude below 900 hPa, which is then compensated by an underestimation of cloud amount around 800 hPa. This is likely to be related with the finding that all models tend to underestimate the planetary boundary layer height. All models overpredict the high-level cloud amount albeit it is difficult to quantify to what extent due to the frequent presence of optically thin clouds. Whereas reasonably alike in cloud parameters, the models differ considerably in radiative fluxes. One model links a well matching incoming solar radiation to a radiatively transparent atmosphere over a too cool surface, another model underpredicts incoming solar radiation at the surface due to a too strong cloud feedback to radiation, the last model represents all surface radiative fluxes quite well on average, but underestimates the sensitivity of atmospheric transmissivity to cloud amount."
"7101823091;7103206141;6602806364;57208462871;7005808242;7201656946;55418799600;7005884486;56244473600;24528897900;8733579000;9846295300;56892869400;9939102400;57203864824;7004343004;57219988551;12809675900;55223995600;35310204900;6603715895;50261552200;7004473824;7401595141;56612517400;6508244744;57211520670;57211949675;7006003831;57203863932;23486734100;6603173671;57072934200;57159171700;56121625800;34974672900;6508175197;35184028700;56441062100;57219988615;7003802133;6602864692;8733579800;57219986306;55286185400;","The GFDL Earth System Model Version 4.1 (GFDL-ESM 4.1): Overall Coupled Model Description and Simulation Characteristics",2020,"10.1029/2019MS002015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85096417095&doi=10.1029%2f2019MS002015&partnerID=40&md5=0eb32459e57d686ee68747d604a659fa","We describe the baseline coupled model configuration and simulation characteristics of GFDL's Earth System Model Version 4.1 (ESM4.1), which builds on component and coupled model developments at GFDL over 2013–2018 for coupled carbon-chemistry-climate simulation contributing to the sixth phase of the Coupled Model Intercomparison Project. In contrast with GFDL's CM4.0 development effort that focuses on ocean resolution for physical climate, ESM4.1 focuses on comprehensiveness of Earth system interactions. ESM4.1 features doubled horizontal resolution of both atmosphere (2° to 1°) and ocean (1° to 0.5°) relative to GFDL's previous-generation coupled ESM2-carbon and CM3-chemistry models. ESM4.1 brings together key representational advances in CM4.0 dynamics and physics along with those in aerosols and their precursor emissions, land ecosystem vegetation and canopy competition, and multiday fire; ocean ecological and biogeochemical interactions, comprehensive land-atmosphere-ocean cycling of CO2, dust and iron, and interactive ocean-atmosphere nitrogen cycling are described in detail across this volume of JAMES and presented here in terms of the overall coupling and resulting fidelity. ESM4.1 provides much improved fidelity in CO2 and chemistry over ESM2 and CM3, captures most of CM4.0's baseline simulations characteristics, and notably improves on CM4.0 in (1) Southern Ocean mode and intermediate water ventilation, (2) Southern Ocean aerosols, and (3) reduced spurious ocean heat uptake. ESM4.1 has reduced transient and equilibrium climate sensitivity compared to CM4.0. Fidelity concerns include (1) moderate degradation in sea surface temperature biases, (2) degradation in aerosols in some regions, and (3) strong centennial scale climate modulation by Southern Ocean convection. ©2020. The Authors."
"57204217537;8696069500;","Emergent constraints on Earth’s transient and equilibrium response to doubled CO2 from post-1970s global warming",2019,"10.1038/s41561-019-0463-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074275874&doi=10.1038%2fs41561-019-0463-y&partnerID=40&md5=b844a41434a12dbfdca50be3250633b3","Future global warming is determined by both greenhouse gas emission pathways and Earth’s transient and equilibrium climate response to doubled atmospheric CO2. Energy-balance inference from the instrumental record typically yields central estimates for the transient response of around 1.3 K and the equilibrium response of 1.5–2.0 K, which is at the lower end of those from contemporary climate models. Uncertainty arises primarily from poorly known aerosol-induced cooling since the early industrialization era and a temporary cooling induced by evolving sea surface temperature patterns. Here we present an emergent constraint on post-1970s warming, taking advantage of the weakly varying aerosol cooling during this period. We derive a relationship between the transient response and the post-1970s warming in Coupled Model Intercomparison Project Phase 5 (CMIP5) models. We thereby constrain, with the observations, the transient response to 1.67 K (1.17–2.16 K, 5–95th percentiles). This is a 20% increase relative to energy-balance inference stemming from previously neglected upper-ocean energy storage. For the equilibrium climate sensitivity we obtain a best estimate of 2.83 K (1.72–4.12 K) contingent on the temporary pattern effects exhibited by climate models. If the real world’s surface temperature pattern effects are substantially stronger, then the upper-bound equilibrium sensitivity may be higher than found here. © 2019, The Author(s), under exclusive licence to Springer Nature Limited."
"57215699608;55177012900;8846887600;6602831555;15724543600;7004060399;","Stratospheric water vapor: an important climate feedback",2019,"10.1007/s00382-019-04721-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068825943&doi=10.1007%2fs00382-019-04721-4&partnerID=40&md5=c54efe4657e481a9102fbeeba63e96dd","The role of stratospheric water vapor (SWV) changes, in response to increasing CO 2, as a feedback component of quantitative significance for climate sensitivity has remained controversial. Here, we calculate the SWV climate feedback under abrupt CO 2 quadrupling in the CMIP5 ensemble of models. All models robustly show a moistening of the stratosphere, causing a global mean net stratosphere adjusted radiative perturbation of 0.89±0.27Wm-2 at the reference tropopause. The stratospheric temperature adjustment is a crucial component of this radiative perturbation. The associated climate feedback is 0.17±0.05Wm-2K-1, with a considerable inter-model range of 0.12–0.28 Wm-2K-1. Taking into account the rise in tropopause height under 4 × CO 2 slightly reduces the feedback to 0.15±0.04Wm-2K-1, with a range of 0.10–0.26Wm-2K-1. The SWV radiative perturbation peaks in the midlatitudes and not the tropics: this is due primarily to increases in SWV in the extratropical lowermost stratosphere, which cause the majority (over three quarters) of the global mean feedback. Based on these results, we suggest an increased focus on understanding drivers of water vapor trends in the extratropical lowermost stratosphere. We conclude that the SWV feedback is important, being on the same order of magnitude as the global mean surface albedo and cloud feedbacks in the multi-model mean. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature."
"57087451200;7103180783;","Anthropogenic impacts on recent decadal change in temperature extremes over China: relative roles of greenhouse gases and anthropogenic aerosols",2019,"10.1007/s00382-018-4342-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85049562867&doi=10.1007%2fs00382-018-4342-9&partnerID=40&md5=42fbd29d3bbc4c4ed8bb6763426ab2f8","Observational analysis indicates significant changes in some temperature extremes over China across the mid-1990s. The decadal changes in hot extremes are characterized as a rise in annual hottest day and night temperature (TXx and TNx) and an increase in frequencies of summer days (SU) and tropical night (TR). The decadal changes in cold extremes are distinguished by a rise in annual coldest day and night temperature (TXn and TNn) and a decrease in frequencies of ice days (ID) and frost days (FD). These decadal changes manifest not only over China as a whole, but also over individual climate sub-regions. An atmosphere-ocean-mixed-layer coupled model forced by changes in greenhouse gases (GHG) concentrations and anthropogenic aerosol (AA) emissions realistically reproduces the general spatial patterns and magnitudes of observed changes in both hot and cold extremes across the mid-1990s, suggesting a pronounced role of anthropogenic changes in these observed decadal changes. Separately, changes in GHG forcing lead to rise in TXx, TNx, TXn and TNn, increase in frequencies of SU and TR and decrease in frequencies of ID and FD over China through increased Greenhouse Effect with positive clear sky longwave radiation and play a dominant role in simulated changes of both hot and cold extremes over China. The AA forcing changes tend to cool Southern China and warm Northern China during summer via aerosol-radiation interaction and AA-induced atmosphere-cloud feedback and therefore lead to some weak decrease in hot extremes over Southeastern China and increase over Northern China. Meanwhile, AA changes lead to warming over China during winter through cloud feedbacks related to aerosol induced cooling over tropical Indian Ocean and western tropical Pacific, and also induce changes in cold extremes the same sign as those induced by GHG, but with weak magnitude. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature."
"7401945370;57212988186;56032970700;57190862866;22934904700;55471474500;6603345878;30767858100;","Toward reduction of the uncertainties in climate sensitivity due to cloud processes using a global non-hydrostatic atmospheric model",2018,"10.1186/s40645-018-0226-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055731023&doi=10.1186%2fs40645-018-0226-1&partnerID=40&md5=ab49b31d62e5ee40b875e53869990689","In estimates of climate sensitivity obtained from global models, the need to represent clouds introduces a great deal of uncertainty. To address this issue, approaches using a high-resolution global non-hydrostatic model are promising: the model captures cloud structure by explicitly simulating meso-scale convective systems, and the results compare reasonably well with satellite observations. We review the outcomes of a 5-year project aimed at reducing the uncertainty in climate models due to cloud processes using a global non-hydrostatic model. In our project, which was conducted as a subgroup of the Program for Risk Information on Climate Change, or SOUSEI, we use the non-hydrostatic icosahedral atmospheric model (NICAM) to study cloud processes related to climate change. NICAM performs numerical simulations with much higher resolution (about 7 km or 14 km mesh) than conventional global climate models (GCMs) using cloud microphysics schemes without a cumulus parameterization scheme, which causes uncertainties in climate projection. The subgroup had three research targets: analyzing cloud changes in global warming simulations with NICAM with the time-slice approach, sensitivity of the results to the cloud microphysics scheme employed, and evaluating circulation changes due to global warming. The research project also implemented a double-moment bulk cloud microphysics scheme and evaluated its results using satellite observation, as well as comparing it with a bin cloud microphysics scheme. The future projection simulations show in general increase in high cloud coverage, contrary to results with other GCMs. Changes in cloud horizontal-size distribution size and structures of tropical/extratropical cyclones can be discussed with high resolution simulations. At the conclusion of our review, we also describe the future prospects of research for global warming using NICAM in the program that followed SOUSEI, known as TOUGOU. © 2018, The Author(s)."
"13405561000;8918407000;7201485519;","Interpretation of factors controlling low cloud cover and low cloud feedback using a unified predictive index",2017,"10.1175/JCLI-D-16-0825.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032292536&doi=10.1175%2fJCLI-D-16-0825.1&partnerID=40&md5=d405a72a70535e70f4b6d40cbae1c58b","This paper reports on a new index for low cloud cover (LCC), the estimated cloud-top entrainment index (ECTEI), which is a modification of estimated inversion strength (EIS) and takes into account a cloud-top entrainment (CTE) criterion. Shipboard cloud observation data confirm that the index is strongly correlated with LCC. It is argued here that changes in LCC cannot be fully determined from changes in EIS only, but can be better determined from changes in both EIS and sea surface temperature (SST) based on the ECTEI. Furthermore, it is argued that various proposed predictors of LCC change, including the moist static energy vertical gradient, SST, and midlevel clouds, can be better understood from the perspective of the ECTEI. © 2017 American Meteorological Society."
"57212781009;57191914668;","On the relative strength of radiative feedbacks under climate variability and change",2017,"10.1007/s00382-016-3441-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84994761694&doi=10.1007%2fs00382-016-3441-8&partnerID=40&md5=452f86d7a2a2c9c20f1bf097ae308adb","Using the method of radiative ‘kernels’, an analysis is made of feedbacks in models participating in the World Climate Research Program Coupled Model Intercomparison Project phase 5. Feedbacks are calculated for RCP8.5 and abrupt4xCO2 experiments as well as for interannual and decadal variability from pre-industrial runs. Regressions across models are used to elicit relationships across experiments/timescales. Feedbacks between RCP8.5 and abrupt4xCO2 experiments show strong relationships, as expected from surface temperature response similarities arising from the two experiments. The analysis also reveals significant relationships between RCP8.5 and decadal and interannual lapse rate feedback, decadal water vapour and interannual total cloud—the latter confirming results elsewhere. To reveal the impact of warming pattern differences, ‘synthetic’ feedbacks are also generated, based on RCP8.5, whereby local feedbacks determined from that experiment are scaled by relative temperature changes (per degree of global warming) from the others. The synthetic feedbacks indicate that the (sometimes strongly) differing temperature response patterns themselves should not preclude strong correlations between variability and climate change feedbacks—indeed such correlations would be close if local feedbacks were a robust feature of the climate. Although such close correlations are not manifest, the synthetic feedbacks predict the interannual and decadal feedbacks to some extent (are correlated across models), and reveal the consistency, to a first approximation, of the mean model strength of variability feedbacks. Although cloud feedbacks at interannual timescales are correlated with those from RCP8.5, and show consistency with the strength of synthetic feedbacks, separate long and short wave components reveal very different, compensating, latitudinal patterns, suggesting the close correlation may be fortuitous. © 2016, Springer-Verlag Berlin Heidelberg."
"55838659500;6603422104;16202694600;7004060399;","CMIP5 models' shortwave cloud radiative response and climate sensitivity linked to the climatological Hadley cell extent",2017,"10.1002/2017GL073151","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020730383&doi=10.1002%2f2017GL073151&partnerID=40&md5=47b2530b75912b5152b009d7e433abb4","This study analyzes Coupled Model Intercomparison Project phase 5 (CMIP5) model output to examine the covariability of interannual Southern Hemisphere Hadley cell (HC) edge latitude shifts and shortwave cloud radiative effect (SWCRE). In control climate runs, during years when the HC edge is anomalously poleward, most models substantially reduce the shortwave radiation reflected by clouds in the lower midlatitude region (LML; ∼28°S–∼48°S), although no such reduction is seen in observations. These biases in HC-SWCRE covariability are linked to biases in the climatological HC extent. Notably, models with excessively equatorward climatological HC extents have weaker climatological LML subsidence and exhibit larger increases in LML subsidence with poleward HC edge expansion. This behavior, based on control climate interannual variability, has important implications for the CO2-forced model response. In 4×CO2-forced runs, models with excessively equatorward climatological HC extents produce stronger SW cloud radiative warming in the LML region and tend to have larger climate sensitivity values than models with more realistic climatological HC extents. ©2017. American Geophysical Union. All Rights Reserved."
"55345946200;55672545600;57191223500;57199509365;8538154900;7005191854;57188570624;","Behavior of predicted convective clouds and precipitation in the high-resolution Unified Model over the Indian summer monsoon region",2017,"10.1002/2016EA000242","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85038124033&doi=10.1002%2f2016EA000242&partnerID=40&md5=90211980972113286c62b99902308b92","National Centre for Medium Range Weather Forecasting high-resolution regional convective-scale Unified Model with latest tropical science settings is used to evaluate vertical structure of cloud and precipitation over two prominent monsoon regions: Western Ghats (WG) and Monsoon Core Zone (MCZ). Model radar reflectivity generated using Cloud Feedback Model Intercomparison Project Observation Simulator Package along with CloudSat profiling radar reflectivity is sampled for an active synoptic situation based on a new method using Budyko's index of turbulence (BT). Regime classification based on BT-precipitation relationship is more predominant during the active monsoon period when convective-scale model's resolution increases from 4 km to 1.5 km. Model predicted precipitation and vertical distribution of hydrometeors are found to be generally in agreement with Global Precipitation Measurement products and BT-based CloudSat observation, respectively. Frequency of occurrence of radar reflectivity from model implies that the low-level clouds below freezing level is underestimated compared to the observations over both regions. In addition, high-level clouds in the model predictions are much lesser over WG than MCZ. ©2017. The Authors."
"26642547700;6603081424;22635081500;","Regime-based evaluation of cloudiness in CMIP5 models",2017,"10.1007/s00382-016-3064-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84963748052&doi=10.1007%2fs00382-016-3064-0&partnerID=40&md5=8a2219f3b5b99ae1df3a7ede2651f9f3","The concept of cloud regimes (CRs) is used to develop a framework for evaluating the cloudiness of 12 fifth Coupled Model Intercomparison Project (CMIP5) models. Reference CRs come from existing global International Satellite Cloud Climatology Project (ISCCP) weather states. The evaluation is made possible by the implementation in several CMIP5 models of the ISCCP simulator generating in each grid cell daily joint histograms of cloud optical thickness and cloud top pressure. Model performance is assessed with several metrics such as CR global cloud fraction (CF), CR relative frequency of occurrence (RFO), their product [long-term average total cloud amount (TCA)], cross-correlations of CR RFO maps, and a metric of resemblance between model and ISCCP CRs. In terms of CR global RFO, arguably the most fundamental metric, the models perform unsatisfactorily overall, except for CRs representing thick storm clouds. Because model CR CF is internally constrained by our method, RFO discrepancies yield also substantial TCA errors. Our results support previous findings that CMIP5 models underestimate cloudiness. The multi-model mean performs well in matching observed RFO maps for many CRs, but is still not the best for this or other metrics. When overall performance across all CRs is assessed, some models, despite shortcomings, apparently outperform Moderate Resolution Imaging Spectroradiometer cloud observations evaluated against ISCCP like another model output. Lastly, contrasting cloud simulation performance against each model’s equilibrium climate sensitivity in order to gain insight on whether good cloud simulation pairs with particular values of this parameter, yields no clear conclusions. © 2016, Springer-Verlag Berlin Heidelberg."
"56766263400;24315205000;7003548068;55450672000;7401776640;","Cloud cover climatologies in the Mediterranean obtained from satellites, surface observations, reanalyses, and CMIP5 simulations: validation and future scenarios",2016,"10.1007/s00382-015-2834-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942026582&doi=10.1007%2fs00382-015-2834-4&partnerID=40&md5=51ca9c8d9096b9eed96800d755d9c3ba","Clouds are an important regulator of climate due to their connection to the water balance of the atmosphere and their interaction with solar and infrared radiation. In this study, monthly total cloud cover (TCC) records from different sources have been inter-compared on annual and seasonal basis for the Mediterranean region and the period 1984–2005. Specifically, gridded databases from satellite projects (ISCCP, CLARA, PATMOS-x), from reanalysis products (ERA-Interim, MERRA), and from surface observations over land (EECRA) and ocean (ICOADS) have been examined. Then, simulations from 44 climate runs of the Coupled Model Intercomparison Project phase 5 corresponding to the historical scenario have been compared against the observations. Overall, we find good agreement between the mean values of TCC estimated from the three satellite products and from surface observations, while reanalysis products show much lower values across the region. Nevertheless, all datasets show similar behavior regarding the annual cycle of TCC. In addition, our results indicate an underestimation of TCC from climate model simulations as compared to the satellite products, especially during summertime, although the annual cycle is well simulated by most models. This result is quite general and apparently independent of the cloud parameterizations included in each particular model. Equally, similar results are obtained if the ISCCP simulator included in the Cloud Feedback Model Intercomparison Project Observation Simulator Package is considered, despite only few models provide the post-processed results. Finally, GCM projections of TCC over the Mediterranean are presented. These projections predict a reduction of TCC during the 21st century in the Mediterranean. Specifically, for an extreme emission scenario (RCP8.5) the projected relative rate of TCC decrease is larger than 10 % by the end of the century. © 2015, Springer-Verlag Berlin Heidelberg."
"6701670597;","Gregarious convection and radiative feedbacks in idealized worlds",2016,"10.1002/2016MS000651","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84971449687&doi=10.1002%2f2016MS000651&partnerID=40&md5=26a717e0aa0096898ff0612f50ac1bba","What role does convection play in cloud feedbacks? What role does convective aggregation play in climate? A flurry of recent studies explores “self-aggregation” of moist convection in diverse simulations using explicit convection and interactive radiation. The implications involve upper level dry areas acting as infrared windows—the climate system's “radiator fins.” A positive feedback maintains these: dry columns undergo radiative cooling which drives descent and further drying. If the resulting clumpiness of vapor and cloud fields depends systematically on global temperature, then convective organization could be a climate system feedback. How reconcilable and how relevant are these interesting but idealized studies?. © 2016. The Authors."
"36701462300;10243650000;55686667100;57202301596;36728564200;","Robust cloud feedback over tropical land in a warming climate",2016,"10.1002/2015JD024525","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84964555392&doi=10.1002%2f2015JD024525&partnerID=40&md5=372a56f15a766a67aea21bea4bc334c8","Cloud-related radiative perturbations over land in a warming climate are of importance for human health, ecosystem, agriculture, and industry via solar radiation availability and local warming amplification. However, robustness and physical mechanisms responsible for the land cloud feedback were not examined sufficiently because of the limited contribution to uncertainty in global climate sensitivity. Here we show that cloud feedback in general circulation models over tropical land is robust, positive, and is relevant to atmospheric circulation change and thermodynamic constraint associated with water vapor availability. In a warming climate, spatial variations in tropospheric warming associated with climatological circulation pattern result in a general weakening of tropical circulation and a dynamic reduction of land cloud during summer monsoon season. Limited increase in availability of water vapor also reduces the land cloud. The reduction of land cloud depends on global-scale oceanic warming and is not sensitive to regional warming patterns. The robust positive feedback can contribute to the warming amplification and drying over tropical land in the future. © 2016. American Geophysical Union. All Rights Reserved."
"35119887100;7406250414;","Paleoclimate simulations of the mid-Holocene and last glacial maximum by FGOALS",2013,"10.1007/s00376-012-2177-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874506020&doi=10.1007%2fs00376-012-2177-6&partnerID=40&md5=b47aa4860fb758de39b7a0b7773032b9","Paleoclimate simulations of the mid-Holocene (MH) and Last Glacial maximum (LGM) by the latest versions of the Flexible Global Ocean-Atmosphere-Land System model, Spectral Version 2 and Grid-point Version 2 (FGOALS-s2 and g2) are evaluated in this study. The MH is characterized by changes of insolation induced by orbital parameters, and the LGM is a glacial period with large changes in greenhouse gases, sea level and ice sheets. For the MH, both versions of FGOALS simulate reasonable responses to the changes of insolation, such as the enhanced summer monsoon in African-Asian regions. Model differences can be identified at regional and seasonal scales. The global annual mean surface air temperature (TAS) shows no significant change in FGOALS-s2, while FGOALS-g2 shows a global cooling of about 0. 7°C that is related with a strong cooling during boreal winter. The amplitude of ENSO is weaker in FGOALS-g2, which agrees with proxy data. For the LGM, FGOALS-g2 captures the features of the cold and dry glacial climate, including a global cooling of 4. 6°C and a decrease in precipitation by 10%. The ENSO is weaker at the LGM, with a tendency of stronger ENSO cold events. Sensitivity analysis shows that the Equilibrium Climate Sensitivity (ECS) estimated for FGOALS ranges between 4. 23°C and 4. 59°C. The sensitivity of precipitation to the changes of TAS is ~2. 3% °C-1, which agrees with previous studies. FGOALS-g2 shows better simulations of the Atlantic Meridional Overturning Circulation (AMOC) and African summer monsoon precipitation in the MH when compared with FGOALS-g1. 0; however, it is hard to conclude any improvements for the LGM. © 2013 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"25031430500;57203030873;6602098362;","Spatial decomposition of climate feedbacks in the community earth system model",2013,"10.1175/JCLI-D-12-00497.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878961535&doi=10.1175%2fJCLI-D-12-00497.1&partnerID=40&md5=3dc456d71d754e763a294d53c5c9cb56","An ensemble of simulations from different versions of the Community Atmosphere Model in the Community Earth System Model (CESM) is used to investigate the processes responsible for the intermodel spread in climate sensitivity. In the CESM simulations, the climate sensitivity spread is primarily explained by shortwave cloud feedbacks on the equatorward flank of the midlatitude storm tracks. Shortwave cloud feedbacks have been found to explain climate sensitivity spread inprevious studies, but the location of feedback differences was in the subtropics rather than in the storm tracks as identified in CESM. The cloudfeedback relationships are slightly stronger in the winter hemisphere. The spread in climate sensitivity in this study is related both to the cloud-base state and to the cloud feedbacks. Simulated climate sensitivity is correlated with cloud-fraction changes on the equatorward side of the storm tracks, cloud condensate in the storm tracks, and cloud microphysical state on the poleward side of the storm tracks. Changes in the extent and water content of stratiform clouds (that make up cloud feedback) are regulated by the base-state vertical velocity, humidity, and deep convective mass fluxes. Within the storm tracks, the cloud-base state affects the cloud response to CO2-induced temperature changes and alters the cloud feedbacks, contributing to climate sensitivity spread within the CESM ensemble. © 2013 American Meteorological Society."
"56138750800;7003946703;","Investigating the impact of soil moisture and atmospheric stability on cloud development and distribution using a coupled large-eddy simulation and land surface model",2011,"10.1175/2011JHM1315.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-83455187084&doi=10.1175%2f2011JHM1315.1&partnerID=40&md5=5c13f59480eae9fd92aa885a9e3d06cc","The influence of soil moisture and atmospheric thermal stability on surface fluxes, boundary layer characteristics, and cloud development are investigated using a coupled large-eddy simulation (LES)-land surface model (LSM) framework. The study day from the Cabauw site in the central part of the Netherlands has been studied to examine the soil moisture-cloud feedback using a parameterized single-column model (SCM) in previous work. Good agreement is seen in the comparison between coupled model results and observations collected at the Cabauw eddy-covariance tower. Simulation results confirm the hypothesis that both surface fluxes and atmospheric boundary layer (ABL) states are strongly affected by soil moisture and atmospheric stability, which was proposed by a previous study using an SCM with simple parameterization. While the ABL-top cloud development is a nonmonotonic function of surface water content under different thermal stability conditions, coupled model simulations find that weak thermal stability has significant impacts on both thermal and moisture fluxes and variances near the entrainment zone, especially for the dry surface cases. Additionally, the impacts of ABL-top stability on thermal and moisture entrainment processes are in a different magnitude. The explicitly resolved cloud cover fraction increases with increasing soil moisture only occurs in cases with strong atmospheric stability, and an opposite result is seen when weak atmospheric stability exists. The elevation of cloud base highly depends on the strength of sensible heat flux. However, results of cloud thickness show that a dry surface with weak thermal stability is able to form a large amount of cumulus cloud, even if the soil provides less water vapor. © 2011 American Meteorological Society."
"55311589500;57202721532;","Decadal and seasonal dependence of North Pacific sea surface temperature persistence",2009,"10.1029/2008JD010723","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62149095695&doi=10.1029%2f2008JD010723&partnerID=40&md5=12f72519b0f60f9acfcfec043584ade3","Decadal and seasonal dependence of the persistence characteristics of area-averaged Sea surface temperature (SST) anomalies in the North Pacific (150°E-140°W, 20°N-60°N) are investigated using two different SST data sets for the period 1948-2005. It is found that a persistence barrier exists around July-September (especially in September). This July-September persistence barrier is accompanied by a summer decline in the wind stress. The results confirm the existence of the July-September persistence barrier in the North Pacific SST discovered by Namias and Born (1970). Besides the seasonal change, North Pacific SST persistence also exhibits a pronounced decadal change. Taking all calendar months into account, North Pacific SST persistence is relatively strong from the mid-1950s to the mid-1960s but then weak from the mid-1960s to the mid-1980s, and becomes stronger again from the mid-1980s until the mid-1990s, after which it tends to become weak again. The recurrence of SST anomalies from one winter to the next is obvious from the mid-1950s to mid-1960s, but no obvious recurrence occurs after the mid-1960s. Decadal changes of the Pacific-North America (PNA) pattern, the SST-clouds feedback, and the Southern Oscillation Index (SOI) are found to be related to those of North Pacific SST persistence. The PNA index shows a significant upward trend after the 1980s. Besides, the PNA pattern also exhibits a high persistence in winter from the mid-1980s to the mid-1990s. These changes of PNA pattern are favorable to the occurrence of strong SST persistence in winter from the mid-1980s to the mid-1990s. In summer, the positive feedback between the marine boundary clouds and SST enhances the SST persistence in the North Pacific. It is found that the positive feedback between the SST and clouds in the North Pacific during summer becomes stronger from the mid-1980s to the mid-1990s, which would contribute to the longer SST persistence in summer from the mid-1980s to the mid-1990s. The SOI shows negative correlation with the North Pacific SST persistence and the PNA index, indicating the remote forcing of ENSO on the North Pacific climate change. In addition, the high north Pacific SST persistence from the mid-1980s to the mid-1990s coincides with the warm phase of the Pacific Decadal Oscillation (PDO). We concluded that the changes in the tropical SST or the PDO phase might explain the origin of decadal changes of North Pacific SST persistence. Copyright 2009 by the American Geophysical Union."
"7005495256;7103060756;7005890514;","Local and global climate feedbacks in models with differing climate sensitivities",2006,"10.1175/JCLI3613.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644699286&doi=10.1175%2fJCLI3613.1&partnerID=40&md5=37211d47e4a1401b4a6a0ef18605cd51","The climatic response to a 5% increase in solar constant is analyzed in three coupled global ocean-atmosphere general circulation models, the NCAR Climate System Model version 1 (CSM1), the Community Climate System Model version 2 (CCSM2), and the Canadian Centre for Climate Modelling and Analysis (CCCma) Coupled General Circulation Model version 3 (CGCM3). For this simple perturbation the quantitative values of the radiative climate forcing at the top of the atmosphere can be determined very accurately simply from a knowledge of the shortwave fluxes in the control run. The climate sensitivity and the geographical pattern of climate feedbacks, and of the shortwave, longwave, clear-sky, and cloud components in each model, are diagnosed as the climate evolves. After a period of adjustment of a few years, both the magnitude and pattern of the feedbacks become reasonably stable with time, implying that they may be accurately determined from relatively short integrations. The global -mean forcing at the top of the atmosphere due to the solar constant change is almost identical in the three models. The exact value of the forcing in each case is compared with that inferred by regressing annual-mean top-of-the-atmosphere radiative imbalance against mean surface temperature change. This regression approach yields a value close to the directly diagnosed forcing for the CCCma model, but a value only within about 25% of the directly diagnosed forcing for the two NCAR models. These results indicate that this regression approach may have some practical limitation in its application, at least for some models. The global climate sensitivities differ among the models by almost a factor of 2, and, despite an overall apparent similarity, the spatial patterns of the climate feedbacks are only modestly correlated among the three models. An exception is the clear-sky shortwave feedback, which agrees well in both magnitude and spatial pattern among the models. The biggest discrepancies are in the shortwave cloud feedback, particularly in the tropical and subtropical regions where it is strongly negative in the NCAR models but weakly positive in the CCCma model. Almost all of the difference in the global-mean total feedback (and climate sensitivity) among the models is attributable to the shortwave cloud feedback component. All three models exhibit a region of positive feedb ack in the equatorial Pacific, which is surrounded by broad areas of negative feedback. These positive feedback regions appear to be associated with a local maximum of the surface warming. However, the models differ in the zonal structure of this surface warming, which ranges from a mean El Niño-like warming in the eastern Pacific in the CCCma model to a far-western Pacific maximum of warming in the NCAR CCSM2 model. A separate simulation with the CCSM2 model, in which these tropical Pacific zonal gradients of surface warming are artificially suppressed, shows no region of positive radiative feedback in the tropical Pacific. However, the global-mean feedback is only modestly changed in this constrained run, suggesting that the processes that produce the positive feedback in the tropical Pacific region may not contribute importantly to global-mean feedback and climate sensitivity. © 2006 American Meteorological Society."
"56157800800;","Early Earth's climate: Cloud feedback from reduced land fraction and ozone concentrations",1995,"10.1029/95GL00818","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029471881&doi=10.1029%2f95GL00818&partnerID=40&md5=b627b3528ef2047cb2cc25166ec3bb6d","Two features of early Earth—reduced ozone (O3) concentration and land fraction are investigated with a general circulation model (GCM). These features are components of a paradox (Faint‐Young Sun paradox) which has intrigued researchers for more than two decades. In this study, land fraction and O3 concentrations are uniformly reduced by 100 percent. The reduction in O3 takes place in the troposphere and stratosphere with all other variables held constant including present‐day land fraction. Two sensitivity tests under global ocean conditions are reported: one case with implied oceanic poleward transports of heat, the other case with no implied oceanic poleward transports of heat. The results show that the removal of land under present‐day conditions increases cloud fractions and cool surface temperatures, unless heat is transported poleward by oceans. In a third sensitivity test with zero O3 concentrations, global mean air temperatures are increased by 2 K because of an increase in upper tropospheric and lower stratospheric clouds. The clouds enhance the greenhouse effect within the troposphere, increasing downward longwave radiation to the surface, melting sea ice and snow. Similar studies using radiative‐convective models which do not include interactive clouds do not show such surface warming. Copyright 1995 by the American Geophysical Union."
"57212781009;6701715507;23080010200;6602929454;7801604834;","Snow and cloud feedbacks modelled by an atmospheric general circulation model",1994,"10.1007/BF00208257","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028327935&doi=10.1007%2fBF00208257&partnerID=40&md5=a8de51f16ffbf2bc31b183d11e729de2","One of the most important parametrizations in general circulation models used for climate change experiments is that of the surface albedo. The results of an albedo feedback experiment carried out under the auspices of the US Department of Energy are presented. An analysis of long and short wave components of the model response shows that short wave response dominates changes in fixed to variable albedo experiments, but that long wave response dominates in clear to cloudy sky changes. Cloud distribution changes are also discussed and are related to changes in global sensitivity. At the surface, the heat balance change for perturbed sea surface temperatures is dominated by changes in latent heat flux and downward long wave radiation. If albedo is freed up however, the major contrast lies in the change in surface reflected short wave radiation, amplified by changes in downward short wave radiation caused by cloud amount changes. © 1994 Springer-Verlag."
"57194876603;55803016100;30967646900;57203030873;","Do Southern Ocean Cloud Feedbacks Matter for 21st Century Warming?",2017,"10.1002/2017GL076339","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85038623422&doi=10.1002%2f2017GL076339&partnerID=40&md5=c2852a628d0e1eb440f4fb72abd776b4","Cloud phase improvements in a state-of-the-art climate model produce a large 1.5 K increase in equilibrium climate sensitivity (ECS, the surface warming in response to instantaneously doubled CO2) via extratropical shortwave cloud feedbacks. Here we show that the same model improvements produce only a small surface warming increase in a realistic 21st century emissions scenario. The small 21st century warming increase is attributed to extratropical ocean heat uptake. Southern Ocean mean-state circulation takes up heat while a slowdown in North Atlantic circulation acts as a feedback to slow surface warming. Persistent heat uptake by extratropical oceans implies that extratropical cloud biases may not be as important to 21st century warming as biases in other regions. Observational constraints on cloud phase and shortwave radiation that produce a large ECS increase do not imply large changes in 21st century warming. ©2017. American Geophysical Union. All Rights Reserved."
"15765851100;6701518904;12645767500;6701820543;7003696273;6603196991;55754577000;7005457526;56771426500;7003865921;","Emerging Technologies and Synergies for Airborne and Space-Based Measurements of Water Vapor Profiles",2017,"10.1007/s10712-017-9448-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85034663094&doi=10.1007%2fs10712-017-9448-9&partnerID=40&md5=f78b812f63978398b3bf12e797e926e3","A deeper understanding of how clouds will respond to a warming climate is one of the outstanding challenges in climate science. Uncertainties in the response of clouds, and particularly shallow clouds, have been identified as the dominant source of the discrepancy in model estimates of equilibrium climate sensitivity. As the community gains a deeper understanding of the many processes involved, there is a growing appreciation of the critical role played by fluctuations in water vapor and the coupling of water vapor and atmospheric circulations. Reduction of uncertainties in cloud-climate feedbacks and convection initiation as well as improved understanding of processes governing these effects will result from profiling of water vapor in the lower troposphere with improved accuracy and vertical resolution compared to existing airborne and space-based measurements. This paper highlights new technologies and improved measurement approaches for measuring lower tropospheric water vapor and their expected added value to current observations. Those include differential absorption lidar and radar, microwave occultation between low-Earth orbiters, and hyperspectral microwave remote sensing. Each methodology is briefly explained, and measurement capabilities as well as the current technological readiness for aircraft and satellite implementation are specified. Potential synergies between the technologies are discussed, actual examples hereof are given, and future perspectives are explored. Based on technical maturity and the foreseen near-mid-term development path of the various discussed measurement approaches, we find that improved measurements of water vapor throughout the troposphere would greatly benefit from the combination of differential absorption lidar focusing on the lower troposphere with passive remote sensors constraining the upper-tropospheric humidity. © 2017, The Author(s)."
"57040141000;57164106400;7408519295;35209683700;26324818700;","Process-based decomposition of the decadal climate difference between 2002-13 and 1984-95",2017,"10.1175/JCLI-D-15-0742.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020001048&doi=10.1175%2fJCLI-D-15-0742.1&partnerID=40&md5=4f758e79eb7abb9379440a03f727c7e5","This study examines at the process level the climate difference between 2002-13 and 1984-95 in ERA-Interim. A linearized radiative transfer model is used to calculate the temperature change such that its thermal radiative cooling would balance the energy flux perturbation associated with the change of an individual process, without regard to what causes the change of the process in the first place. The global mean error of the offline radiative transfer model calculations is 0.09 K, which corresponds to the upper limit of the uncertainties from a single term in the decomposition analysis. The process-based decomposition indicates that the direct effect of the increase of CO2 (0.15 K) is the largest contributor to the global warming between the two periods (about 0.27 K). The second and third largest contributors are the cloud feedback (0.14 K) and the combined effect of the oceanic heat storage and evaporation terms (0.11 K), respectively. The largest warming associated with the oceanic heat storage term is found in the tropical Pacific and Indian Oceans, with relatively weaker warming over the tropical Atlantic Ocean. The increase in atmospheric moisture adds another 0.1 K to the global surface warming, but the enhancement in tropical convections acts to reduce the surface warming by 0.17 K. The ice-albedo and atmospheric dynamical feedbacks are the two leading factors responsible for the Arctic polar warming amplification (PWA). The increase of atmospheric water vapor over the Arctic region also contributes substantially to the Arctic PWA pattern. © 2017 American Meteorological Society."
"57112070700;56014511300;56471281900;","On the role of the stratiform cloud scheme in the inter-model spread of cloud feedback",2017,"10.1002/2016MS000846","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85013020770&doi=10.1002%2f2016MS000846&partnerID=40&md5=f486f9b420f7330af03997d00c2fb851","This study explores the role of the stratiform cloud scheme in the inter-model spread of cloud feedback. Six diagnostic cloud schemes used in various CMIP (Coupled Model Intercomparison Experiment] climate models are implemented (at low and midlevels) into two testbed climate models, and the impacts on cloud feedback are investigated. Results suggest that the choice of stratiform cloud scheme may contribute up to roughly half of the intermodel spread of cloud radiative responses in stratocumulus (Sc) regions, and may determine or favor a given sign of the feedback there. Cloud schemes assuming a probability density function for total water content consistently predict a positive feedback in Sc regions in our experiments. A large negative feedback in Sc regions is obtained only with schemes that consider variables other than relative humidity (e.g., stability). The stratiform cloud scheme also significantly affects cloud feedback at the scale of the tropics and at global scale. Results are slightly less consistent for tropical means, likely indicating coupling with other boundary layer processes such as convective mixing. © 2017. The Authors."
"55537426400;55686667100;10241250100;35762238200;6603196127;56628141500;36701462300;","A review of progress towards understanding the transient global mean surface temperature response to radiative perturbation",2016,"10.1186/s40645-016-0096-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85017809881&doi=10.1186%2fs40645-016-0096-3&partnerID=40&md5=0b4a9ec4fb10a4031fc1f34ed5052337","The correct understanding of the transient response to external radiative perturbation is important for the interpretation of observed climate change, the prediction of near-future climate change, and committed warming under climate stabilization scenarios, as well as the estimation of equilibrium climate sensitivity based on observation data. It has been known for some time that the radiative damping rate per unit of global mean surface temperature increase varies with time, and this inconstancy affects the transient response. Knowledge of the equilibrium response alone is insufficient, but understanding the transient response of the global mean surface temperature has made rapid progress. The recent progress accompanies the relatively new concept of the efficacies of ocean heat uptake and forcing. The ocean heat uptake efficacy associates the temperature response induced by ocean heat uptake with equilibrium temperature response, and the efficacy of forcing compares the temperature response caused by non-CO2 forcing with that by CO2 forcing. In this review article, recent studies on these efficacies are discussed, starting from the classical global feedback framework and basis of the transient response. An attempt is made to structure different studies that emphasize different aspects of the transient response and to stress the relevance of those individual studies. The implications on the definition and computation of forcing and on the estimation of the equilibrium response in climate models are also discussed. Along with these discussions, examples are provided with MIROC climate model multi-millennial simulations. © 2016, The Author(s)."
"36866503400;36138641800;","On the limited ice intrusion in Alaska at the LGM",2016,"10.1002/2016GL071012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84995653358&doi=10.1002%2f2016GL071012&partnerID=40&md5=a9191e735eed9927ccc682bcd8867772","The Last Glacial Maximum (LGM) Laurentide Ice Sheet covered most of the North American continent poleward of 40°N, with the exception of Alaska that remained relatively warm, dry, and largely ice free. Experiments with a global atmospheric circulation model are in broad agreement with proxies: the Alaskan summer temperatures are comparable to the preindustrial, and the annual precipitation is reduced by 30–50%. The warm conditions are attributed to a lowering of the local planetary albedo—due to a decreased cloudiness in response to the cold LGM sea surface temperatures (SSTs) and a stationary anticyclone forced by the ice sheet—that allows more shortwave radiation to reach the surface. Stationary waves are shown to counteract the shortwave cloud feedback by converging less heat over the target region. The LGM SST field also yields an equatorward shifted Pacific stormtrack, which results in drier conditions in Alaska and abundant precipitation at the southern margin of the Laurentide Ice Sheet. ©2016. American Geophysical Union. All Rights Reserved."
"54982705800;7006304904;7004713805;7006784145;24343173500;8657166100;25522357400;","A new chemistry option in WRF-Chem v. 3.4 for the simulation of direct and indirect aerosol effects using VBS: Evaluation against IMPACT-EUCAARI data",2015,"10.5194/gmd-8-2749-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924731478&doi=10.5194%2fgmd-8-2749-2015&partnerID=40&md5=d9ff3dbd31ebb9f698b3c8827304f9f4","A parameterization for secondary organic aerosol (SOA) production based on the volatility basis set (VBS) approach has been coupled with microphysics and radiative schemes in the Weather Research and Forecasting model with Chemistry (WRF-Chem) model. The new chemistry option called ""RACM-MADE-VBS-AQCHEM"" was evaluated on a cloud resolving scale against ground-based and aircraft measurements collected during the IMPACT-EUCAARI (Intensive Cloud Aerosol Measurement Campaign - European Integrated project on Aerosol Cloud Climate and Air quality interaction) campaign, and complemented with satellite data from MODIS. The day-to-day variability and the diurnal cycle of ozone (O3) and nitrogen oxides (NOx) at the surface are captured by the model. Surface aerosol mass concentrations of sulfate (SO4), nitrate (NO3), ammonium (NH4), and organic matter (OM) are simulated with correlations larger than 0.55. WRF-Chem captures the vertical profile of the aerosol mass concentration in both the planetary boundary layer (PBL) and free troposphere (FT) as a function of the synoptic condition, but the model does not capture the full range of the measured concentrations. Predicted OM concentration is at the lower end of the observed mass concentrations. The bias may be attributable to the missing aqueous chemistry processes of organic compounds and to uncertainties in meteorological fields. A key role could be played by assumptions on the VBS approach such as the SOA formation pathways, oxidation rate, and dry deposition velocity of organic condensable vapours. Another source of error in simulating SOA is the uncertainties in the anthropogenic emissions of primary organic carbon. Aerosol particle number concentration (condensation nuclei, CN) is overestimated by a factor of 1.4 and 1.7 within the PBL and FT, respectively. Model bias is most likely attributable to the uncertainties of primary particle emissions (mostly in the PBL) and to the nucleation rate. Simulated cloud condensation nuclei (CCN) are also overestimated, but the bias is more contained with respect to that of CN. The CCN efficiency, which is a characterization of the ability of aerosol particles to nucleate cloud droplets, is underestimated by a factor of 1.5 and 3.8 in the PBL and FT, respectively. The comparison with MODIS data shows that the model overestimates the aerosol optical thickness (AOT). The domain averages (for 1 day) are 0.38 ± 0.12 and 0.42 ± 0.10 for MODIS and WRF-Chem data, respectively. The droplet effective radius (Re) in liquid-phase clouds is underestimated by a factor of 1.5; the cloud liquid water path (LWP) is overestimated by a factor of 1.1-1.6. The consequence is the overestimation of average liquid cloud optical thickness (COT) from a few percent up to 42 %. The predicted cloud water path (CWP) in all phases displays a bias in the range +41-80 %, whereas the bias of COT is about 15 %. In sensitivity tests where we excluded SOA, the skills of the model in reproducing the observed patterns and average values of the microphysical and optical properties of liquid and all phase clouds decreases. Moreover, the run without SOA (NOSOA) shows convective clouds with an enhanced content of liquid and frozen hydrometers, and stronger updrafts and downdrafts. Considering that the previous version of WRF-Chem coupled with a modal aerosol module predicted very low SOA content (secondary organic aerosol model (SORGAM) mechanism) the new proposed option may lead to a better characterization of aerosol-cloud feedbacks. © Author(s) 2015."
"57203694321;6603096324;15071907100;","Estimating climate sensitivity and future temperature in the presence of natural climate variability",2014,"10.1002/2013GL058532","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896691779&doi=10.1002%2f2013GL058532&partnerID=40&md5=47d097a9bf8394bd41913f04b3886f05","We use an initial condition ensemble of an Earth System Model as multiple realizations of the climate system to evaluate estimates of climate sensitivity and future temperature change derived with a climate model of reduced complexity under ""perfect"" conditions. In our setup, the mean and most likely estimate of equilibrium climate sensitivity vary by about 0.4-0.8°C (±1σ) due to internal variability. Estimates of the transient climate response vary much less; however, the effect of the spread and bias in the transient response on future temperature projections increases with lead time. Future temperature projections are shown to be more robust for central ranges (i.e., likely range) than for single percentiles. The estimates presented here strongly depend on a delicate balance between a particular realization of the climate system, the emerging constraints on the estimates as well as on the signal, and the decreasing uncertainties in ocean heat uptake observations. © 2014. American Geophysical Union. All Rights Reserved."
"16246205000;55738957800;26324818700;","Quantifying contributions of climate feedbacks to tropospheric warming in the NCAR CCSM3.0",2014,"10.1007/s00382-013-1805-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84895046534&doi=10.1007%2fs00382-013-1805-x&partnerID=40&md5=4d461d171d00f78643e4682cd5f036ab","In this study, a coupled atmosphere-surface ""climate feedback-response analysis method"" (CFRAM) was applied to the slab ocean model version of the NCAR CCSM3.0 to understand the tropospheric warming due to a doubling of CO2 concentration through quantifying the contributions of each climate feedback process. It is shown that the tropospheric warming displays distinct meridional and vertical patterns that are in a good agreement with the multi-model mean projection from the IPCC AR4. In the tropics, the warming in the upper troposphere is stronger than in the lower troposphere, leading to a decrease in temperature lapse rate, whereas in high latitudes the opposite it true. In terms of meridional contrast, the lower tropospheric warming in the tropics is weaker than that in high latitudes, resulting in a weakened meridional temperature gradient. In the upper troposphere the meridional temperature gradient is enhanced due to much stronger warming in the tropics than in high latitudes. Using the CFRAM method, we analyzed both radiative feedbacks, which have been emphasized in previous climate feedback analysis, and non-radiative feedbacks. It is shown that non-radiative (radiative) feedbacks are the major contributors to the temperature lapse rate decrease (increase) in the tropical (polar) region. Atmospheric convection is the leading contributor to temperature lapse rate decrease in the tropics. The cloud feedback also has non-negligible contributions. In the polar region, water vapor feedback is the main contributor to the temperature lapse rate increase, followed by albedo feedback and CO2 forcing. The decrease of meridional temperature gradient in the lower troposphere is mainly due to strong cooling from convection and cloud feedback in the tropics and the strong warming from albedo feedback in the polar region. The strengthening of meridional temperature gradient in the upper troposphere can be attributed to the warming associated with convection and cloud feedback in the tropics. Since convection is the leading contributor to the warming differences between tropical lower and upper troposphere, and between the tropical and polar regions, this study indicates that tropical convection plays a critical role in determining the climate sensitivity. In addition, the CFRAM analysis shows that convective process and water vapor feedback are the two major contributors to the tropical upper troposphere temperature change, indicating that the excessive upper tropospheric warming in the IPCC AR4 models may be due to overestimated warming from convective process or underestimated cooling due to water vapor feedback. © 2013 Springer-Verlag Berlin Heidelberg."
"10241250100;55686667100;10243650000;10241462700;7102857642;","Multi-parameter multi-physics ensemble (MPMPE): A new approach exploring the uncertainties of climate sensitivity",2014,"10.1002/asl2.472","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905919525&doi=10.1002%2fasl2.472&partnerID=40&md5=156651b7584295bbc05e320f6d3eb0c9","To explore both the parametric and structural uncertainties of climate sensitivity (CS), we have proposed a new general circulation model (GCM) ensemble termed the multi-parameter multi-physics ensemble (MPMPE). We used eight multi-physics ensemble (MPE) models in which the MIROC5 physics schemes were replaced by those of MIROC3. MPMPE consisted of perturbed-physics ensembles in which the parameter values were swept for each MPE model. MPMPE resulted in a wide range of CS, which was related to the shortwave cloud feedback (SWcld). Coupling between low- and mid-level clouds controlled the differences in the parametric spread of SWcld among the MPE models. © 2014 Royal Meteorological Society."
"56336403300;57202721532;35119688900;","Summer persistence barrier of sea surface temperature anomalies in the central western north pacific",2012,"10.1007/s00376-012-1253-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867777727&doi=10.1007%2fs00376-012-1253-2&partnerID=40&md5=16e8366200b72fc38fc983d7a099f5e8","The persistence barrier of sea surface temperature anomalies (SSTAs) in the North Pacific was investigated and compared with the ENSO spring persistence barrier. The results show that SSTAs in the central western North Pacific (CWNP) have a persistence barrier in summer: the persistence of SSTAs in the CWNP shows a significant decline in summer regardless of the starting month. Mechanisms of the summer persistence barrier in the CWNP are different from those of the spring persistence barrier of SSTAs in the central and eastern equatorial Pacific. The phase locking of SSTAs to the annual cycle does not explain the CWNP summer persistence barrier. Remote ENSO forcing has little linear influence on the CWNP summer persistence barrier, compared with local upper-ocean process and atmospheric forcing in the North Pacific. Starting in wintertime, SSTAs extend down to the deep winter mixed layer then become sequestered beneath the shallow summer mixed layer, which is decoupled from the surface layer. Thus, wintertime SSTAs do not persist through the following summer. Starting in summertime, persistence of summer SSTAs until autumn can be explained by the atmospheric forcing through a positive SSTAs-cloud/radiation feedback mechanism because the shallow summertime mixed layer is decoupled from the temperature anomalies at depth, then the following autumn-winter-spring, SSTAs persist. Thus, summer SSTAs in the CWNP have a long persistence, showing a significant decline in the following summer. In this way, SSTAs in the CWNP show a persistence barrier in summer regardless of the starting month. © 2012 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"55078244200;6701490531;7004154626;55077297800;35361704100;36006968000;","Aerosol and cloud feedbacks on surface energy balance over selected regions of the Indian subcontinent",2012,"10.1029/2011JD016363","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858057927&doi=10.1029%2f2011JD016363&partnerID=40&md5=728239fe4cda2022620ced7d57bda538","We investigate aerosol and cloud forcing on the surface energy balance over selected regions in India. Four regions were selected with different surface characteristics and have considerable differences in the long-term trends and seasonal distribution of clouds and aerosols. These regions are described as (1) northern semiarid, (2) humid subtropical, (3) populated central peninsula, and (4) northeast monsoon impacted. Modern Era Retrospective-analysis for Research and Applications (MERRA) data and Climate Forecast System Reanalysis version 2 (CFSR) data are used in this study. An intercomparison of cloud fractions from both data sets shows that CFSR systematically underestimates high-cloud fraction during premonsoon and monsoon seasons. However, there are fewer low-cloud fraction biases. The positive temporal trend over 31years (1979-2009) from MERRA in high clouds is greater than that of low clouds. This is due to positive anomalies in the cloud ice and supercooled liquid water content in MERRA. Biases in the radiative fluxes and surface fluxes show a strong relationship (correlations exceeding 0.8) with cloud fraction biases, more so for the high clouds. During the premonsoon season, aerosol forcing causes a change in surface shortwave radiation of -24.5, -25, -19, and -16Wm-2 over regions 1 -4, respectively. The corresponding longwave radiation decrease is -9.8, -6.8, -4.5, and -1.9Wm-2 over these same regions, respectively. The maximum surface shortwave reduction due to clouds, which is observed during the monsoon season, is -86, -113, -101, and -97Wm-2 for these same regions, respectively. A decreasing trend in the boundary layer height is noticed both in MERRA and CFSR. The variation in the Bowen ratio and its relation to aerosol and cloud effect anomalies are also discussed. Copyright 2012 by the American Geophysical Union."
"14049512800;35580303100;7003420726;35762238200;6603196127;6603378233;","Development of a system emulating the global carbon cycle in Earth system models",2010,"10.5194/gmd-3-365-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79956279269&doi=10.5194%2fgmd-3-365-2010&partnerID=40&md5=72cbfb6ad089a479559774b1c942dc71","Recent studies have indicated that the uncertainty in the global carbon cycle may have a significant impact on the climate. Since state of the art models are too computationally expensive for it to be possible to explore their parametric uncertainty in anything approaching a comprehensive fashion, we have developed a simplified system for investigating this problem. By combining the strong points of general circulation models (GCMs), which contain detailed and complex processes, and Earth system models of intermediate complexity (EMICs), which are quick and capable of large ensembles, we have developed a loosely coupled model (LCM) which can represent the outputs of a GCM-based Earth system model, using much smaller computational resources. We address the problem of relatively poor representation of precipitation within our EMIC, which prevents us from directly coupling it to a vegetation model, by coupling it to a precomputed transient simulation using a full GCM. The LCM consists of three components: an EMIC (MIROC-lite) which consists of a 2-D energy balance atmosphere coupled to a low resolution 3-D GCM ocean (COCO) including an ocean carbon cycle (an NPZD-type marine ecosystem model); a state of the art vegetation model (Sim-CYCLE); and a database of daily temperature, precipitation, and other necessary climatic fields to drive Sim-CYCLE from a precomputed transient simulation from a state of the art AOGCM. The transient warming of the climate system is calculated from MIROC-lite, with the global temperature anomaly used to select the most appropriate annual climatic field from the pre-computed AOGCM simulation which, in this case, is a 1% pa increasing CO2 concentration scenario. By adjusting the effective climate sensitivity (equivalent to the equilibrium climate sensitivity for an energy balance model) of MIROC-lite, the transient warming of the LCM could be adjusted to closely follow the low sensitivity (with an equilibrium climate sensitivity of 4.0 K) version of MIROC3.2. By tuning of the physical and biogeochemical parameters it was possible to reasonably reproduce the bulk physical and biogeochemical properties of previously published CO2 stabilisation scenarios for that model. As an example of an application of the LCM, the behavior of the high sensitivity version of MIROC3.2 (with a 6.3 K equilibrium climate sensitivity) is also demonstrated. Given the highly adjustable nature of the model, we believe that the LCM should be a very useful tool for studying uncertainty in global climate change, and we have named the model, JUMP-LCM, after the name of our research group (Japan Uncertainty Modelling Project). © Author(s) 2011."
"7101990351;","Integrated assessment for setting greenhouse gas emission targets under the condition of great uncertainty about the probability and impact of abrupt climate change",2009,"10.3808/jei.200900157","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73649132603&doi=10.3808%2fjei.200900157&partnerID=40&md5=0ec5ec45a6f8ee8a16fba39b0aa8a267","In this paper the mid-21st-century target level for industrial carbon dioxide emissions is analyzed, taking into account the very large uncertainty about abrupt climate change. Following a brief review of integrated assessments of abrupt climate change, this study introduces an extension of DICE-2007, an integrated assessment model for climate policy analysis, which contains a hazard function that connects the rise in air temperature with the probability of abrupt change. The probability of abrupt change under a certain air temperature conditions and the economic impact of abrupt change are treated as widely variable parameters. Graphic indications of the combination of these parameters for several emission targets using the extended model show the necessity of developing adaptation measures to control the economic loss from abrupt change to below 8%, as well as to restrain global industrial carbon emissions in 2055 to the same level as those in 2005, assuming a most likely equilibrium climate sensitivity of 3°C. Although a more stringent emissions target may be suggested in the spirit of precaution, it may lead to excessive carbon reduction from the viewpoint of cost-benefit balancing. © 2009 ISEIS."
"10241462700;8979277400;10240710000;10243650000;9535015400;55619302015;7007021059;6603378233;6603196127;7003967390;56284545500;7102857642;","Different transient climate responses of two versions of an atmosphere-ocean coupled general circulation model",2007,"10.1029/2006GL027966","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548043978&doi=10.1029%2f2006GL027966&partnerID=40&md5=593131e92d0ce7b17f2a44d7dbf82bcb","The Model for Interdisciplinary Research on Climate (MIROC), an atmosphere-ocean coupled general circulation model (AOGCM), has two versions with different resolutions, high (Hi-Res) and medium (Mid-Res). While their equilibrium climate sensitivities (ECS) to CO2 increases are similar, the transient climate response (TCR) of the Hi-Res version is larger than that of the Mid-Res version. The former shows the highest transient response among the Intergovernmental Panel on Climate Change (IPCC) fourth assessment report (AR4) climate models. Our climate feedback analysis indicates that the higher TCR of the Hi-Res version mainly comes from its larger ice-albedo feedback (SFC-SW) and lower ocean heat uptake (OHU). Since the Hi-Res version shows better agreement with observation than the Mid-Res version concerning the factors that affect the SFC-SW and OHU, the TCR of the Hi-Res version is not considered to be unrealistic compared to that of the Mid-Res version. On the other hand, the two versions have similar SFC-SW values and negligible OHU in ECS experiments performed by the atmosphere-slab ocean coupled general circulation model (ASGCM). In the ASGCM, the difference in SFC-SW between the two versions was likely suppressed due to artificial fluxes applied to the ocean and sea-ice system. Copyright 2007 by the American Geophysical Union."
"36862677400;7202145115;","Interactions among cloud, water vapor, radiation, and large-scale circulation in the tropical climate. Part II: Sensitivity to spatial gradients of sea surface temperature",2003,"10.1175/1520-0442-16.10.1441","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038467220&doi=10.1175%2f1520-0442-16.10.1441&partnerID=40&md5=0d094d46996187e46218244188c3a100","The responses of the large-scale circulation, clouds, and water vapor to an imposed sea surface temperature (SST) gradient are investigated. Simulations compare reasonably to averaged observations over the Pacific, considering the simplifications applied to the model. The model responses to sinusoidal SST patterns have distinct circulations in the upper and lower troposphere. The upper circulation is sensitive to the heating from deep convection over the warmest SST. Stronger SST gradients are associated with stronger longwave cooling above stratus clouds in the subsidence region, stronger lower-tropospheric large-scale circulation, a reduction of the rain area, and larger area coverage of low clouds. A similar SST gradient with a warmer mean temperature produces slightly weaker lower-tropospheric circulation, and slightly reduced low cloud coverage. The outgoing longwave radiation (OLR) is not sensitive to the mean SST or the range of the imposed sinusoidal SST gradient. The positive feedbacks of water vapor and decreasing high cloud OLR compensate for the increase in longwave emission with increasing mean temperature in these simulations. As the SST gradient is increased keeping the mean SST constant, the positive high cloud feedback is still active, but the air temperature increases in proportion to the maximum SST in the domain, increasing the clear-sky OLR value and keeping the average OLR constant. The net absorbed shortwave radiation (SWI) is found to be extremely sensitive to the SST gradient. The stronger lower-tropospheric large-scale circulation produces a higher water content in the high and low clouds, increasing the absolute magnitude of the shortwave cloud forcing. A 25% increase in the maximum zonal mass flux of the lower circulation of the 300-K mean, 4-K SST range simulation leads to a 7.4 W m-2 decrease in SWI. Increasing the mean SST creates a positive feedback in these simulations because of the decrease in the lower-tropospheric large-scale circulation and the resultant decrease in cloud optical depth."
"7403508241;7006783796;7005673120;","Cloud liquid water path variations with temperature observed during the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment",2003,"10.1029/2002jd002851","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0742305189&doi=10.1029%2f2002jd002851&partnerID=40&md5=596ff54e8ce53344c4d3eac078cebe61","Because clouds play such a significant role in climate, understanding their responses to climatic temperature changes is essential to determining the overall impact of a given climate forcing. Cloud liquid water path (LWP) over tropical and midlatitude oceans has been observed to decrease with increasing cloud temperature. The presence of an ice sheet over the Arctic Ocean alters the energy and moisture exchange between the ocean and the atmospheric boundary layer and thus may affect the relationship between LWP and temperature. The variations of LWP with cloud and surface temperatures are examined in this paper using a combination of surface and satellite data taken during the 1998 Surface Heat Budget of the Arctic Ocean and the FIRE Arctic Clouds Experiments. The results show that LWP increases with temperature primarily because of an increase in cloud thickness that is enabled by the rise in surface moisture during the melt season. Cloud base heights and lifting condensation levels decrease as a result of the greater surface relative humidity and temperature. The average change rate of LWP with cloud temperature is 3.3% K-1, a value slightly smaller than earlier observations taken over cold midlatitude land areas. This cloud LWP feedback with temperature differs significantly from that estimated over other marine environments and should be taken into account in all climate models with explicit cloud feedbacks."
"57212781009;","Seasonal contributions to climate feedbacks",2003,"10.1007/s00382-002-0301-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037929583&doi=10.1007%2fs00382-002-0301-5&partnerID=40&md5=6d965fb918e35bbb5a6385b37001a330","This study addresses the question: How do the contributions to feedbacks in a climate model vary over the seasonal cycle? To answer this the feedbacks are evaluated from an equilibrium doubled CO2 experiment performed using the Bureau of Meteorology Research Centre (BMRC) General Circulation Model. Monthly means of the top-of-atmosphere radiative perturbations (which together comprise the annual climate feedbacks) are extracted to produce a mean annual cycle. It is found that the radiative contributions to the total longwave (LW) feedback are fairly constant throughout the year. Those to the total shortwave (SW) feedback, on the other hand, vary by a factor of three, from a maximum in July to a minimum in November. Of the LW feedbacks, contributions to the lapse rate shows greatest seasonal variation, while those to water vapour and cloud feedbacks vary by relatively small amounts throughout the year. Contributions to the lapse rate feedback as a function of surface type and latitude reveal conflicting positive and negative radiative perturbations, which vary most strongly at high latitudes. Of the SW feedbacks, contributions to both albedo and cloud show large seasonal variations. Radiative perturbations contributing to albedo feedback vary in strength with snow and sea-ice retreat which occurs at different latitudes and in different months. They are shown to be highly sensitive to the amount of incident solar radiation in a given month. SW radiative perturbations due to cloud changes vary in sign between opposite seasons. Contributions to the seasonal variations of the cloud component feedbacks, which make up the total cloud feedback, are also examined. In the LW, the feedback is dominated by the total cloud water term. Radiative perturbations due to this component show relatively little variation throughout the year. In the SW, the main source of seasonal variation occurs for contributions to the cloud amount feedback: Radiative perturbations vary from strongly positive in July to close to zero in December. The seasonal cycle of the perturbations making up the other cloud component feedbacks is also considered. Implications for climate sensitivity, and for the diagnosis of climate feedbacks are discussed."
"23095483400;16444232500;56039057300;57208121852;36171703500;56250185400;57206038917;35235146400;6506718302;57203053317;","The global aerosol-climate model ECHAM6.3-HAM2.3-Part 2: Cloud evaluation, aerosol radiative forcing, and climate sensitivity",2019,"10.5194/gmd-12-3609-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85071235195&doi=10.5194%2fgmd-12-3609-2019&partnerID=40&md5=5b46beb191002250765800ba146684d3","The global aerosol-climate model ECHAM6.3-HAM2.3 (E63H23) as well as the previous model versions ECHAM5.5-HAM2.0 (E55H20) and ECHAM6.1-HAM2.2 (E61H22) are evaluated using global observational datasets for clouds and precipitation. In E63H23, the amount of low clouds, the liquid and ice water path, and cloud radiative effects are more realistic than in previous model versions. E63H23 has a more physically based aerosol activation scheme, improvements in the cloud cover scheme, changes in the detrainment of convective clouds, changes in the sticking efficiency for the accretion of ice crystals by snow, consistent ice crystal shapes throughout the model, and changes in mixed-phase freezing; an inconsistency in ice crystal number concentration (ICNC) in cirrus clouds was also removed. Common biases in ECHAM and in E63H23 (and in previous ECHAM-HAM versions) are a cloud amount in stratocumulus regions that is too low and deep convective clouds over the Atlantic and Pacific oceans that form too close to the continents (while tropical land precipitation is underestimated). There are indications that ICNCs are overestimated in E63H23. Since clouds are important for effective radiative forcing due to aerosol-radiation and aerosol-cloud interactions (ERFariCaci) and equilibrium climate sensitivity (ECS), differences in ERFariCaci and ECS between the model versions were also analyzed. ERFariCaci is weaker in E63H23 (-1:0 W m-2) than in E61H22 (-1:2 W m-2) (or E55H20;-1:1 W m-2). This is caused by the weaker shortwave ERFariCaci (a new aerosol activation scheme and sea salt emission parameterization in E63H23, more realistic simulation of cloud water) overcompensating for the weaker longwave ERFariCaci (removal of an inconsistency in ICNC in cirrus clouds in E61H22). The decrease in ECS in E63H23 (2.5 K) compared to E61H22 (2.8 K) is due to changes in the entrainment rate for shallow convection (affecting the cloud amount feedback) and a stronger cloud phase feedback. Experiments with minimum cloud droplet number concentrations (CDNCmin) of 40 cm-3 or 10 cm-3 show that a higher value of CDNCmin reduces ERFariCaci as well as ECS in E63H23. © 2019 The Author(s)."
"56893786200;55763471100;","What can the internal variability of CMIP5 models tell us about their climate sensitivity?",2018,"10.1175/JCLI-D-17-0736.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048466876&doi=10.1175%2fJCLI-D-17-0736.1&partnerID=40&md5=8d13d5840843897c8399e320d71ee2ec","The relationship between climate models' internal variability and their response to external forcings is investigated. Frequency-dependent regressions are performed between the outgoing top-of-atmosphere (TOA) energy fluxes and the global-mean surface temperature in the preindustrial control simulations of the CMIP5 archive. Two distinct regimes are found. At subdecadal frequencies the surface temperature and the outgoing shortwave flux are in quadrature, while the outgoing longwave flux is linearly related to temperature and acts as a negative feedback on temperature perturbations. On longer time scales the outgoing shortwave and longwave fluxes are both linearly related to temperature, with the longwave continuing to act as a negative feedback and the shortwave acting as a positive feedback on temperature variability. In addition to the different phase relationships, the two regimes can also be seen in estimates of the coherence and of the frequency-dependent regression coefficients. The frequency-dependent regression coefficients for the total cloudy-sky flux on time scales of 2.5 to 3 years are found to be strongly (r2 &gt; 0.6) related to the models' equilibrium climate sensitivities (ECSs), suggesting a potential ""emergent constraint"" for Earth's ECS. However, O(100) years of data are required for this relationship to become robust. A simple model for Earth's surface temperature variability and its relationship to the TOA fluxes is used to provide a physical interpretation of these results. © 2018 American Meteorological Society."
"56724051400;36182467000;57194589938;25645385100;8686475900;","Interactions between vegetation, atmospheric turbulence and clouds under a wide range of background wind conditions",2018,"10.1016/j.agrformet.2017.07.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85023594344&doi=10.1016%2fj.agrformet.2017.07.001&partnerID=40&md5=812f4634cc89e5de136e7e396a8f68f1","The effects of plant responses to cumulus (Cu) cloud shading are studied from free convective to shear-driven boundary-layer conditions. By using a large-eddy simulation (LES) coupled to a plant physiology embedded land-surface submodel, we study the vegetation–cloud feedbacks for a wide range (44) of atmospheric and plant stomatal conditions. The stomatal relaxation time is prescribed as an instantaneous, symmetrical (10, 15 and 20 min) and asymmetrical (5 min closing, 10 min opening) response, and the background wind ranges from 0 to 20 m s−1. We show that in free convective, non-shading (i.e. transparent) cloud conditions the near-surface updraft region is marked by an enhanced CO2 assimilation rate (An; 7%) and increased latent (LE; 9%) and sensible heat (H; 19%) fluxes. When we introduce Cu shading, we find an enhancement in plant transpiration and CO2 assimilation rates under optically thin clouds due to an increase in diffuse radiation. However, these effects vanish when a background wind is present and the Cu are advected. Optically thick clouds reduce the assimilation rate and surface fluxes under all simulated wind conditions. With increasing background wind, the shaded surface area is enlarged due to Cu tilting. The consequent decrease in surface fluxes by a reduction in incoming radiation, is partly offset due to an enhancement in the surface exchange and turbulent mixing as a result of stronger wind speeds. Different and non-linear processes control the H and LE response to shading. H is mainly radiation driven, whereas plant responses dampen the shading effects on LE. As a result, the regional averaged (48 km2) reduction in H and LE are found to be 18% and 5%, respectively, compared to non-shading cloud conditions. Surprisingly, a nearly uniform regional net radiation reduction of 11% is found, with only a deviation between all 35 Cu shading cases of 0.5% (i.e. 1.2 W m−2) at the moment of maximum cloud cover. By comparing four representative simulations that are equal in net available energy, but differ in interactive and prescribed surface energy fluxes, we find a relative reduction in cloud cover between 5 and 10% during the maximum cloud cover period when the dynamic surface heterogeneity is neglected. We conclude that the local and spatial dynamic surface heterogeneity influences Cu development, while the Cu–vegetation coupling becomes progressively weaker with increasing stomatal relaxation time and background wind. © 2017 Elsevier B.V."
"25031430500;56699083600;8866821900;57212416832;","Climate feedback variance and the interaction of aerosol forcing and feedbacks",2016,"10.1175/JCLI-D-16-0151.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84987958800&doi=10.1175%2fJCLI-D-16-0151.1&partnerID=40&md5=57781a3a466a4184c577c4fe45f0e4ba","Aerosols can influence cloud radiative effects and, thus, may alter interpretation of how Earth's radiative budget responds to climate forcing. Three different ensemble experiments from the same climate model with different greenhouse gas and aerosol scenarios are used to analyze the role of aerosols in climate feedbacks and their spread across initial condition ensembles of transient climate simulations. The standard deviation of global feedback parameters across ensemble members is low, typically 0.02 W m-2 K-1. Feedbacks from high (8.5 W m-2) and moderate (4.5 W m-2) year 2100 forcing cases are nearly identical. An aerosol kernel is introduced to remove effects of aerosol cloud interactions that alias into cloud feedbacks. Adjusted cloud feedbacks indicate an ""aerosol feedback"" resulting from changes to climate that increase sea-salt emissions, mostly in the Southern Ocean. Ensemble simulations also indicate higher tropical cloud feedbacks with higher aerosol loading. These effects contribute to a difference in cloud feedbacks of nearly 50% between ensembles of the same model. These two effects are also seen in aquaplanet simulations with varying fixed drop number. Thus aerosols can be a significant modifier of cloud feedbacks, and different representations of aerosols and their interactions with clouds may contribute to multimodel spread in climate feedbacks and climate sensitivity in multimodel archives. © 2016 American Meteorological Society."
"7007067997;6603700951;36781333600;6603808707;6604075852;6603452105;7004346367;","Indirect aerosol effect increases CMIP5 models' projected arctic warming",2016,"10.1175/JCLI-D-15-0362.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959458793&doi=10.1175%2fJCLI-D-15-0362.1&partnerID=40&md5=0e79b66d065af97a02ff321be5426641","Phase 5 of the CoupledModel Intercomparison Project (CMIP5) climate models' projections of the 2014-2100 Arctic warming under radiative forcing from representative concentration pathway 4.5 (RCP4.5) vary from 0.9° to 6.7°C. Climate models with or without a full indirect aerosol effect are both equally successful in reproducing the observed (1900-2014) Arctic warming and its trends. However, the 2014-2100 Arctic warming and the warming trends projected by models that include a full indirect aerosol effect (denoted here as AA models) are significantly higher (mean projected Arctic warming is about 1.5°C higher) than those projected by models without a full indirect aerosol effect (denoted here as NAA models). The suggestion is that, within models including full indirect aerosol effects, those projecting stronger future changes are not necessarily distinguishable historically because any stronger past warming may have been partially offset by stronger historical aerosol cooling. The CMIP5 models that include a full indirect aerosol effect follow an inverse radiative forcing to equilibrium climate sensitivity relationship, while models without it do not. © 2016 American Meteorological Society."
"6602098362;23486332900;7005578774;","Recent Progress in Constraining Climate Sensitivity With Model Ensembles",2015,"10.1007/s40641-015-0021-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85015268726&doi=10.1007%2fs40641-015-0021-7&partnerID=40&md5=509eaef7a330b683bd1a1966f9953d7f","Recently available model ensembles have created an unprecedented opportunity for exploring and narrowing uncertainty in one of climate’s benchmark indices, equilibrium climate sensitivity. A range of novel approaches for constraining the raw sensitivity estimates from these ensembles with observations has also been proposed, applied, and explored in a diversity of contexts. Through subsequent analysis, an increased understanding of the relative merits and limitations of these methods has been gained and their refinement and optimal implementation continue to be actively studied and debated with the hopes of reducing uncertainty in one of climate science’s most persistent and elusive measures. © 2015, Springer International Publishing AG."
"7401604360;55199339300;6701925357;55597088322;57188751935;52463601100;55555283600;","WRF multi-physics simulation of clouds in the African region",2015,"10.1002/qj.2560","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946482243&doi=10.1002%2fqj.2560&partnerID=40&md5=1793283a9da199c058a4fa0faef6cc50","The Weather Research and Forecasting (WRF) model has been used to simulate clouds, and their effects on precipitation and radiation, in Africa. The results have been compared with observational databases, mainly based on satellite measurements. The Cloud Feedback Model Intercomparison Project (CFMIP) Observation Simulator Package (COSP) has been used to consistently compare simulated clouds with satellite data, allowing us to evaluate not only the total cloud cover but also the cloud amount of different cloud types, classified according to their optical thickness and cloud-top pressure. Nine WRF simulations, for the 2002-2006 period, were carried out to evaluate the influence on cloud cover of different physical parametrizations and model configurations. In general, model simulations show similar results, underestimating total cloud cover in most of the studied region. In the tropical convective area, high clouds are underestimated, but the net effect on the radiation is partially compensated by the overestimation of cloud optical depth. Major differences appear over subtropical areas dominated by marine boundary-layer clouds, mainly off the coast of Namibia. In this area, simulations show too many thick clouds and too few clouds with lower optical thickness. The net result is an underestimation of low cloud cover. Also, the transition from stratocumulus to shallow cumulus away from the coast is not realistically modelled. © 2015 Royal Meteorological Society."
"7201485519;7005056279;13402835300;35509639400;8397494800;8918407000;13405561000;55389942900;6701815637;36187387300;7201504886;","The diurnal cycle of marine cloud feedback in climate models",2015,"10.1007/s00382-014-2234-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939881418&doi=10.1007%2fs00382-014-2234-1&partnerID=40&md5=958f57206bd907351ce2acb586d5e57e","We examine the diurnal cycle of marine cloud feedback using high frequency outputs in CFMIP-2 idealised uniform +4 K SST perturbation experiments from seven CMIP5 models. Most of the inter-model spread in the diurnal mean marine shortwave cloud feedback can be explained by low cloud responses, although these do not explain the model responses at the neutral/weakly negative end of the feedback range, where changes in mid and high level cloud properties are more important. All of the models show reductions in marine low cloud fraction in the warmer climate, and these are in almost all cases largest in the mornings when more cloud is present in the control simulations. This results in shortwave cloud feedbacks being slightly stronger and having the largest inter-model spread at this time of day. The diurnal amplitudes of the responses of marine cloud properties to the warming climate are however small compared to the inter-model differences in their diurnally meaned responses. This indicates that the diurnal cycle of cloud feedback is not strongly relevant to understanding inter-model spread in overall cloud feedback and climate sensitivity. A number of unusual behaviours in individual models are highlighted for future investigation. © 2014, Crown Copyright."
"56230988400;6603566335;6603606681;","Evaluation of low-cloud climate feedback through single-column model equilibrium states",2015,"10.1002/qj.2398","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928286280&doi=10.1002%2fqj.2398&partnerID=40&md5=acda455d43390b359cf49584964da882","The dependency of the boundary-layer cloud regime on the free tropospheric temperature and humidity is examined. Equilibrium state solutions obtained with the single-column model version of the climate model EC-EARTH are analysed in a phase space defined by the lower tropospheric stability (LTS) and a similar measure for humidity. The set-up comprises two experiments: one with large-scale subsidence which is constant in time and a second one with additional stochastic noise added to the subsidence. The dependency of the boundary-layer state on the free tropospheric conditions is qualitatively consistent between the two experiments. Well-mixed stratocumulus-topped boundary layers are found for high LTS and moist free tropospheric conditions. Cooler and dryer free tropospheric conditions favour the presence of shallow cumulus clouds. Subsequently the response to a sea surface warming of 2 K and a free atmospheric perturbation conserving both the LTS and the relative humidity is assessed. The model predicts an overall positive low-cloud feedback for both the constant subsidence experiment and the experiment with the additional stochastic noise. © 2014 Royal Meteorological Society."
"7004429984;","A minimal model for estimating climate sensitivity",2014,"10.1016/j.ecolmodel.2014.01.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893419810&doi=10.1016%2fj.ecolmodel.2014.01.006&partnerID=40&md5=48bddca196734dec69b536549296f294","Climate sensitivity summarizes the net effect of a change in forcing on Earth's surface temperature. Estimates based on energy balance calculations give generally lower values for sensitivity (&lt;2°C per doubling of forcing) than those based on general circulation models, but utilize uncertain historical data and make various assumptions about forcings. A minimal model was used that has the fewest possible assumptions and the least data uncertainty. Using only the historical surface temperature record, the periodic temperature oscillations often associated with the Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation were estimated and subtracted from the surface temperature data, leaving a linear warming trend identified as an anthropogenic signal. This estimated rate of warming was related to the fraction of a log CO2 doubling from 1959 to 2013 to give an estimated transient sensitivity of 1.093°C (0.96-1.23°C 95% confidence limits) and equilibrium climate sensitivity of 1.99°C (1.75-2.23°C). It is argued that higher estimates derived from climate models are incorrect because they disagree with empirical estimates. © 2014 Elsevier B.V."
"57196499374;","Insights on global warming",2011,"10.1002/aic.12780","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80355133224&doi=10.1002%2faic.12780&partnerID=40&md5=cdfe2e5bbc736b71d7b4ecfea47dbbd7","The global temperature increase over the last century and a half (~ 0.8°C), and the last three decades in particular, is well outside of that which can be attributed to natural climate fluctuations. The increase of atmospheric CO2 over this period has been conclusively demonstrated to be a result largely of fossil fuel burning. The global mean temperature change that results in response to a sustained perturbation of the Earth's energy balance after a time sufficiently long for both the atmosphere and oceans to come to thermal equilibrium is termed the Earth's climate sensitivity. The purely radiative (blackbody) warming from a doubling of CO2 from its preindustrial level of 280 parts-per-million (ppm) to 560 ppm is ~ 1.2°C; the actual warming that would result is considerably larger owing to amplification by climate feedbacks, including that owing to water vapor. Increases in greenhouse gas (GHG) levels are estimated to have contributed about +3.0 W m-2 perturbation (radiative forcing) to the Earth's energy balance. Particles (aerosols), on the whole, exert a cooling effect on climate, with a total forcing estimated by the Intergovernmental Panel on Climate Change (2007)1 as -1.2 W m-2, a value that is subject to considerable uncertainty. If the actual magnitude of aerosol forcing is close to the low end of its estimated uncertainty range, then it offsets a considerably smaller fraction of the GHG forcing and the total net forcing is at the high end of its range, ~ 2.4 W m-2; at the other extreme, if the actual aerosol cooling is at the high end of its range, then aerosol forcing is currently offsetting a major fraction of GHG forcing, and the total net forcing is only ~ 0.6 W m-2. To explain the actual global increase in temperature of ~ 0.8°C, these two extremes have major implications in terms of the Earth's climate sensitivity. Climate sensitivity is determined by the strength of feedbacks, of which cloud feedback is the most uncertain. That the Earth has warmed and that GHGs are responsible is unequivocal; the Earth's climate sensitivity and the effect of aerosols complicate answers to the question: how much warming and how soon? © 2011 American Institute of Chemical Engineers (AIChE)."
"7201504886;35509639400;22956930200;57204755628;11939918300;6701518904;6701606453;55626648300;57204833386;57209838184;49664027700;7003865921;7005035762;","Sugar, gravel, fish and flowers: Mesoscale cloud patterns in the trade winds",2020,"10.1002/qj.3662","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074279427&doi=10.1002%2fqj.3662&partnerID=40&md5=55f352422a8ffbb5aa288da1109296f8","An activity designed to characterise patterns of mesoscale (20 to 2,000 km) organisation of shallow clouds in the downstream trades is described. Patterns of mesoscale organisation observed from space were subjectively defined and learned by 12 trained scientists. The ability of individuals to communicate, learn and replicate the classification was evaluated. Nine-hundred satellite images spanning the area from 48°W to 58°W, 10°N to 20°N for the boreal winter months (December–February) over 10 years (2007/2008 to 2016/2017) were classified. Each scene was independently labelled by six scientists as being dominated by one of six patterns (one of which was “no-pattern”). Four patterns of mesoscale organisation could be labelled in a reproducible manner, and were labelled Sugar, Gravel, Fish and Flowers. Sugar consists of small, low clouds of low reflectivity, Gravel clouds form along apparent gust fronts, Fish are skeletal networks (often fishbone-like) of clouds, while Flowers are circular clumped features defined more by their stratiform cloud elements. Both Fish and Flowers are surrounded by large areas of clear air. These four named patterns were identified 40% of the time, with the most common pattern being Gravel. Sugar was identified the least and suggests that unorganised and very shallow convection is unlikely to dominate large areas of the downstream trade winds. Some of the patterns show signs of seasonal and interannual variability, and some degree of scale selectivity. Comparison of typical patterns with radar imagery suggests that even this subjective and qualitative visual inspection of imagery appears to capture several important physical differences between shallow cloud regimes, such as precipitation and radiative effects. © 2019 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"56417341400;16636807900;26536569500;","FAT or FiTT: Are Anvil Clouds or the Tropopause Temperature Invariant?",2019,"10.1029/2018GL080096","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061436550&doi=10.1029%2f2018GL080096&partnerID=40&md5=fbbc9d185b1bc30a5fbab2c10fb77fdd","The Fixed Anvil Temperature (FAT) hypothesis proposes that upper tropospheric cloud fraction peaks at a special isotherm that is independent of surface temperature. It has been argued that a FAT should result from simple ingredients: Clausius-Clapeyron, longwave emission from water vapor, and tropospheric energy and mass balance. Here the first cloud-resolving simulations of radiative-convective equilibrium designed to contain only these basic ingredients are presented. This setup does not produce a FAT: the anvil temperature varies by about 40% of the surface temperature range. However, the tropopause temperature varies by only 4% of the surface temperature range, which supports the existence of a Fixed Tropopause Temperature (FiTT). In full-complexity radiative-convective equilibrium simulations, the spread in anvil temperature is smaller by about a factor of 2, but the tropopause temperature remains more invariant than the anvil temperature by an order of magnitude. In other words, our simulations have a FiTT, not a FAT. ©2019. American Geophysical Union. All Rights Reserved."
"56417341400;16636807900;57206546852;26536569500;","Formation of Tropical Anvil Clouds by Slow Evaporation",2019,"10.1029/2018GL080747","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059908569&doi=10.1029%2f2018GL080747&partnerID=40&md5=0e0c340e32b6d81e5e1f990579aea91f","Tropical anvil clouds play a large role in the Earth's radiation balance, but their effect on global warming is uncertain. The conventional paradigm for these clouds attributes their existence to the rapidly declining convective mass flux below the tropopause, which implies a large source of detraining cloudy air there. Here we test this paradigm by manipulating the sources and sinks of cloudy air in cloud-resolving simulations. We find that anvils form in our simulations because of the long lifetime of upper-tropospheric cloud condensates, not because of an enhanced source of cloudy air below the tropopause. We further show that cloud lifetimes are long in the cold upper troposphere because the saturation specific humidity is much smaller there than the condensed water loading of cloudy updrafts, which causes evaporative cloud decay to act very slowly. Our results highlight the need for novel cloud-fraction schemes that align with this decay-centric framework for anvil clouds. ©2019. American Geophysical Union. All Rights Reserved."
"56520853700;7401945370;","Roles of Cloud Microphysics on Cloud Responses to Sea Surface Temperatures in Radiative-Convective Equilibrium Experiments Using a High-Resolution Global Nonhydrostatic Model",2018,"10.1029/2018MS001386","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052625880&doi=10.1029%2f2018MS001386&partnerID=40&md5=06de60c519fecbb68ad27026c0210d7a","The high-cloud amount responses to sea surface temperature (SST) changes were investigated based on simulations with radiative-convective equilibrium configuration using a high-resolution nonhydrostatic icosahedral atmospheric model. The radiative-convective equilibrium was calculated using a nonrotating sphere with Earth radius and a 14-km horizontal mesh with uniform SSTs of 300 and 304 K. Two types of cloud microphysics schemes (single- and double-moment bulk schemes) and two types of vertical layer configurations (38 and 78 layers) were tested. The radiatively driven circulation weakens with increasing SST in all simulation pairs due to the increase in the static stability, as suggested in previous studies. In contrast, the high-cloud amount increases in three simulation pairs and decreases in one pair. These indicate that the weakening of radiatively driven circulation with increasing SST does not always accompany the high-cloud amount decrease. We determined that the tropopause layer was wet (dry) in simulations that showed positive (negative) high-cloud cover responses. The radiatively driven upward moisture transport just below the wet tropopause layer increases with increasing SST in the simulation pairs with positive high-cloud amount responses, and this causes the supply of ice condensate to the lower layer through the sedimentation process, while this feedback was not observed in the simulation pair with the negative response. These indicate that the high-cloud cover response depends on the occurrence of the feedback and there is a feedback threshold among the variety of simulations. And furthermore, these speculate that whether the feedback mechanism is effective or not has the large impact on high-cloud responses in the real atmosphere. ©2018. The Authors."
"55623265200;18635208300;7004479957;","Variability in modeled cloud feedback tied to differences in the climatological spatial pattern of clouds",2018,"10.1007/s00382-017-3673-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85017174904&doi=10.1007%2fs00382-017-3673-2&partnerID=40&md5=7e5f85b7934fb5ac28f20c67a30ad195","Despite the increasing sophistication of climate models, the amount of surface warming expected from a doubling of atmospheric CO2 (equilibrium climate sensitivity) remains stubbornly uncertain, in part because of differences in how models simulate the change in global albedo due to clouds (the shortwave cloud feedback). Here, model differences in the shortwave cloud feedback are found to be closely related to the spatial pattern of the cloud contribution to albedo (α) in simulations of the current climate: high-feedback models exhibit lower (higher) α in regions of warm (cool) sea-surface temperatures, and therefore predict a larger reduction in global-mean α as temperatures rise and warm regions expand. The spatial pattern of α is found to be strongly predictive (r= 0.84) of a model’s global cloud feedback, with satellite observations indicating a most-likely value of 0.58 ± 0.31 Wm- 2 K- 1 (90% confidence). This estimate is higher than the model-average cloud feedback of 0.43 Wm- 2 K- 1, with half the range of uncertainty. The observational constraint on climate sensitivity is weaker but still significant, suggesting a likely value of 3.68 ± 1.30 K (90% confidence), which also favors the upper range of model estimates. These results suggest that uncertainty in model estimates of the global cloud feedback may be substantially reduced by ensuring a realistic distribution of clouds between regions of warm and cool SSTs in simulations of the current climate. © 2017, Springer-Verlag Berlin Heidelberg."
"57194201247;7004479957;6701346974;","Cloud and circulation feedbacks in a near-global aquaplanet cloud-resolving model",2017,"10.1002/2016MS000872","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019111827&doi=10.1002%2f2016MS000872&partnerID=40&md5=f56da88225433e8775d2af74657d3a3b","A near-global aquaplanet cloud-resolving model (NGAqua) with fixed meridionally varying sea-surface temperature (SST) is used to investigate cloud feedbacks due to three climate perturbations: a uniform 4 K SST increase, a quadrupled-CO2 concentration, and both combined. NGAqua has a horizontal resolution of 4 km with no cumulus parameterization. Its domain is a zonally periodic 20,480 km-long tropical channel, spanning 46°S–N. It produces plausible mean distributions of clouds, rainfall, and winds. After spin-up, 80 days are analyzed for the control and increased-SST simulations, and 40 days for those with quadrupled CO2. The Intertropical Convergence Zone width and tropical cloud cover are not strongly affected by SST warming or CO2 increase, except for the expected upward shift in high clouds with warming, but both perturbations weaken the Hadley circulation. Increased SST induces a statistically significant increase in subtropical low cloud fraction and in-cloud liquid water content but decreases midlatitude cloud, yielding slightly positive domain-mean shortwave cloud feedbacks. CO2 quadrupling causes a slight shallowing and a statistically insignificant reduction of subtropical low cloud fraction. Warming-induced low cloud changes are strongly correlated with changes in estimated inversion strength, which increases modestly in the subtropics but decreases in the midlatitudes. Enhanced clear-sky boundary layer radiative cooling in the warmer climate accompanies the robust subtropical low cloud increase. The probability distribution of column relative humidity across the tropics and subtropics is compared between the control and increased-SST simulations. It shows no evidence of bimodality or increased convective aggregation in a warmer climate. © 2017. The Authors."
"15319714800;7007107813;","Investigating the mechanisms of seasonal ENSO phase locking bias in the ACCESS coupled model",2016,"10.1007/s00382-015-2633-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957432408&doi=10.1007%2fs00382-015-2633-y&partnerID=40&md5=f040ae47fd113e99f15f0d830910fc77","The mechanisms of coupled model bias in seasonal ENSO phase locking are investigated using versions 1.0 and 1.3 of the CSIRO–BOM ACCESS coupled model (hereafter, ACCESS1.0 and ACCESS1.3, respectively). The two ACCESS coupled models are mostly similar in construction except for some differences, the most notable of which are in the cloud and land surface schemes used in the models. ACCESS1.0 simulates a realistic seasonal phase locking, with the ENSO variability peaking in December as in observations. On the other hand, the simulated ENSO variability in ACCESS1.3 peaks in March, a bias shown to be shared by many other CMIP5 models. To explore the mechanisms of this model bias, we contrast the atmosphere–ocean feedbacks associated with ENSO in both ACCESS model simulations and also compare the key feedbacks with those in other CMIP5 models. We find evidence that the ENSO phase locking bias in ACCESS1.3 is primarily caused by incorrect simulations of the shortwave feedback and the thermocline feedback in this model. The bias in the shortwave feedback is brought about by unrealistic SST–cloud interactions leading to a positive cloud feedback bias that is largest around March, in contrast to the strongest negative cloud feedback found in ACCESS1.0 simulations and observations at that time. The positive cloud feedback bias in ACCESS1.3 is the result of a dominant role played by the low-level clouds in its modeled SST–cloud interactions in the tropical eastern Pacific. Two factors appear to contribute to the dominance of low-level clouds in ACCESS1.3: the occurrence of a stronger mean descending motion bias and, to a lesser extent, a larger mean SST cold bias during March–April in ACCESS1.3 than in ACCESS1.0. A similar association is found between the positive cloud feedback bias and the biases in spring-time mean descending motion and SST for a group of CMIP5 models that show a seasonal phase locking bias similar to ACCESS1.3. Significant differences are also found between the thermocline feedbacks simulated by ACCESS1.0 and ACCESS1.3 that appear to reinforce the seasonal ENSO phase locking bias in the latter model. We discuss a mechanism by which the thermocline feedback differences could arise from atmospheric forcing differences in the two models. © 2015, Springer-Verlag Berlin Heidelberg."
"7401513228;","Estimating climate sensitivity using two-zone energy balance models",2016,"10.1002/2015EA000154","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85015081247&doi=10.1002%2f2015EA000154&partnerID=40&md5=81d1e7f88566d04feeab329516c91e4b","Estimates of 2 × CO2 equilibrium climate sensitivity (EqCS) derive from running global climate models (GCMs) to equilibrium. Estimates of effective climate sensitivity (EfCS) are the corresponding quantities obtained using transient GCM output or observations. The EfCS approach uses an accompanying energy balance model (EBM), the zero-dimensional model (ZDM) being standard. GCM values of EqCS and EfCS vary widely [Intergovernmental Panel on Climate Change range: (1.5, 4.5)°C] and have failed to converge over the past 35 years. Recently, attempts have been made to refine the EfCS approach by using two-zone (tropical/extratropical) EBMs. When applied using satellite radiation data, these give low and tightly constrained EfCS values, in the neighborhood of 1°C. These low observational EfCS/two-zone EBM values have been questioned because (a) they disagree with higher observational EfCS/ZDM values and (b) the EfCS/two-zone EBM values given by GCMs are poorly correlated with the standard GCM sensitivity estimates. The validity of the low observational EfCS/two-zone EBM values is here explored, with focus on the limitations of the observational EfCS/ZDM approach, the disagreement between the GCM and observational radiative responses to surface temperature perturbations in the tropics, and on the modified EfCS values provided by an extended two-zone EBM that includes an explicit parameterization of dynamical heat transport. The results support the low observational EfCS/two-zone EBM values, indicating that objections (a) and (b) to these values both need to be reconsidered. It is shown that in the EBM with explicit dynamical heat transport the traditional formulism of climate feedbacks can break down because of lack of additivity. ©2016. The Authors."
"57202891769;","An alternative method to calculate cloud radiative forcing: Implications for quantifying cloud feedbacks",2006,"10.1029/2005GL024723","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644631351&doi=10.1029%2f2005GL024723&partnerID=40&md5=123ed1054dc3c2309f92eef2e8743c7d","A modification to the traditional cloud radiative forcing (CRF) formula is presented. This alternative approach uses incident rather than absorbed-solar radiation to calculate shortwave cloud radiative forcing at the surface. By removing the competing influence of surface albedo on CRF, the new formula more effectively isolates the impact of clouds and cloud changes under different climatic regimes. The removal of surface albedo effects makes the change in CRF a more useful measure of cloud feedback, although other factors (such as changes in clearsky solar absorption) can still muddle the interpretation. I present examples from GCM greenhouse simulations that demonstrate how this new formula can help to differentiate between actual cloud feedbacks versus apparent ones induced by snow and ice meltback using the traditional CRF equation. The results suggest that changes in surface albedo contribute approximately 20 to 40% of the high-latitude CRF anomaly using the standard formula applied to an equilibrium 2 × CO2 simulation and about 50% to the greater Arctic when used on 21st-century transient greenhouse experiments. Copyright 2006 by the American Geophyical Union."
"7004171611;7103010852;","Observations of the infrared outgoing spectrum of the Earth from space: The effects of temporal and spatial sampling",2003,"10.1175/1520-0442(2003)016<3820:OOTIOS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346056663&doi=10.1175%2f1520-0442%282003%29016%3c3820%3aOOTIOS%3e2.0.CO%3b2&partnerID=40&md5=9381cc6250f9c12779b2891fb30b5893","A recent comparison between data taken by two different satellite instruments, the Interferometric Monitor of Greenhouse Gases (IMG) that flew in 1997 and the Infrared Interferometer Spectrometer (IRIS) that flew in 1970, showed evidence of a change in the clear-sky greenhouse radiative forcing due to the increase in greenhouse gas concentrations between those years. A possibly even more intriguing question is whether the data can be used to extract unambiguous information about the radiative feedback processes that accompany such a change of forcing, especially cloud feedback. This paper is an investigation of this question, with particular reference to the uncertainties introduced into the differences between IMG and IRIS spectra due to their different patterns of temporal and spatial sampling. This has been approached by modeling the sampling problem, using high-resolution proxy scenes of top-of-the-atmosphere 11-μm brightness temperature, TB11, taken from International Satellite Cloud Climatology Project (ISCCP) data, sampled according to the characteristics of IRIS and IMG, respectively. The results suggest that while the sampling pattern of the IRIS instrument is sufficiently well distributed and dense to generate monthly regional mean brightness temperatures that are within 1.5 K of the true all-sky values, the IMG sampling is too sparse and yields results that differ from the true case by up to 6.0 K. Under cloud-free conditions the agreement with the true field for both instruments improves to within a few tenths of a kelvin. Comparisons with the observed IMG-IRIS difference spectra show that these uncertainties due to sampling presently limit the conclusions that can be drawn about climatically significant feedback processes. However, further analysis using the sampling characteristics of the Advanced Infrared Sounder (AIRS) instrument suggests that as climate change progresses, spectral measurements may be able to pick out significant changes due to processes such as cloud feedback."
"7006174850;7101795549;","Unified treatment of thermodynamic and optical variability in a simple model of unresolved low clouds",2003,"10.1175/1520-0469(2003)60<1621:UTOTAO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0041845372&doi=10.1175%2f1520-0469%282003%2960%3c1621%3aUTOTAO%3e2.0.CO%3b2&partnerID=40&md5=84a9bb1aa63819b366ca65e9b97a880e","Comparative studies of global climate models have long shown a marked sensitivity to the parameterization of cloud properties. Early attempts to quantify this sensitivity were hampered by diagnostic schemes that were inherently biased toward the contemporary climate. Recently, prognostic cloud schemes based on an assumed statistical distribution of subgrid variability replaced the older diagnostic schemes in some models. Although the relationship between unresolved variability and mean cloud amount is known in principle, a corresponding relationship between ice-free low cloud thermodynamic and optical properties is lacking. The authors present a simple, analytically tractable statistical optical depth parameterization for boundary layer clouds that links mean reflectivity and emissivity to the underlying distribution of unresolved fluctuations in model thermodynamic variables. To characterize possible impacts of this parameterization on the radiative budget of a large-scale model, they apply it to a zonally averaged climatology, illustrating the importance of a coupled treatment of subgrid-scale condensation and optical variability. They derive analytic expressions for two response functions that characterize two potential low cloud feedback scenarios in a warming climate."
"7403318365;57193132723;","Effects of cloud parameterization on the simulation of climate changes in the GISS GCM. Part II: Sea surface temperature and cloud feedbacks",2002,"10.1175/1520-0442(2002)015<2491:EOCPOT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036748172&doi=10.1175%2f1520-0442%282002%29015%3c2491%3aEOCPOT%3e2.0.CO%3b2&partnerID=40&md5=8562ade099b35747874e955e78ea6e95","The influence of the sea surface temperature distribution on cloud feedbacks is studied by making two sets of doubled CO2 experiments with the Goddard Institute for Space Studies (GISS) GCM at 4° latitude 5° longitude resolution. One set uses Q fluxes obtained by prescribing observed sea surface temperatures (MODELII'), and the other set uses Q fluxes obtained by prescribing the simulated sea surface temperature of a coupled ocean-atmosphere model (MODELIIO). The global and annual mean surface air temperature change (Δ Ts) obtained in MODELII' is reduced from 4.11° to 3.02°C in MODELIIO. This reduced sensitivity, aside from reduced sea ice/snow-albedo feedback, is mainly due to cloud feedback that becomes nearly neutral in MODELIIO. Furthermore, the negative effect on climate sensitivity of anvil clouds of large optical thickness identified by Yao and Del Genio changes its sign in MODELIIO primarily due to sharply reduced increases of cloud water in the tropical upper troposphere. Colder tropical sea surface temperature in MODELIIO results in weaker deep convective activity and a more humid lower atmosphere in the warmer climate relative to MODELIIO', which then removes the negative feedback of anvil clouds and sharply reduces the positive feedback of low clouds. However, an overall positive cloud optical thickness feedback is still maintained in MODELIIO. It is suggested that the atmospheric climate sensitivity, partially due to changes in cloud feedbacks, may be significantly different for climate changes associated with different patterns of sea surface temperature change, as for example in warm versus cold paleoclimate epochs. Likewise, the climate sensitivity in coupled atmosphere-ocean models is also likely to be significantly different from the results obtained in Q-flux models due to the different simulations of sea surface temperature patterns in each type of model."
"6507587542;7406514318;","On the dependence of climate sensitivity on convective parametrization",1990,"10.1007/BF00208904","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025586845&doi=10.1007%2fBF00208904&partnerID=40&md5=15320ee2089ac680bb5d3e606e124aae","Two sensitivity experiments, in which CO2 is doubled and sea-surface temperatures are enhanced, were carried out using a general circulation model to determine the influence of the convective parametrization on simulated climate change. In the first experiment, a non-penetrative ""layer-swapping"" convection scheme is used; in the second, a penetrative scheme is used. It is found that the penetrative scheme gives the greater upper tropospheric warming (over 4.5 K compared to 4 K) and the greater reduction in upper tropospheric cloud, consistent with recent CO2 sensitivity studies. However, there is a 0.7 Wm-2 greater increase in net downward radiation at the top of the atmosphere in the experiment with the non-penetrative scheme, implying a larger tropical warming which is inconsistent with recent CO2 studies. Other possible explanations for discrepancies between recent studies of the equilibrium climate response to increasing CO2 are considered and discussed. The changes in the atmospheric fluxes of heat and moisture from the tropical continents in the model with the penetrative scheme differ from those found using the non-penetrative scheme, and those in an equilibrium experiment using the penetrative scheme. Thus, changes in circulation may explain the apparent discrepancy in the current experiments, but prescribed sea-surface temperature experiments may not provide a reliable indication of a model's equilibrium climate sensitivity. © 1990 Springer-Verlag."
"7003979342;","Cloud-radiation feedbacks in a climate model",1988,"10.1016/0169-8095(88)90032-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024193376&doi=10.1016%2f0169-8095%2888%2990032-4&partnerID=40&md5=f0071eb8dff476007fdc1f7b8280689b","Using a global coupled model of the atmosphere, the ocean mixed layer and sea ice, the atmospheric response to a 2% rise of the solar constant is studied with emphasis on cloud feedback processes. Clouds are computed on the basis of the cloud liquid water budget equation including simple parameterizations of cloud microphysics and partial cloud cover. The cloud liquid water content determines the optical properties of the clouds so that cloud optical depth feedbacks can be studied. The change of the cloud cover distribution results in a global and annual mean positive feedback. On the other hand, due to an increase of the cloud liquid water content by approximately 10%, the cloud optical depth feedback is negative at the surface. The atmosphere, however, is heated because of a substantial increase of high cloud infrared opacity, especially in the tropics. Thus, the net cloud feedback is positive for the atmosphere and for the whole planet but negative for the surface. © 1988."
"57109884900;35547807400;57191980050;35094424100;57212269695;24329376600;57203200427;12240390300;57110426700;36894599500;57189524073;12139043600;7102976560;35227762400;7003777747;6602414959;7003786872;6602988199;57196261945;7004214645;57208121852;7202079615;22986631300;36462180600;","Efficacy of Climate Forcings in PDRMIP Models",2019,"10.1029/2019JD030581","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076347242&doi=10.1029%2f2019JD030581&partnerID=40&md5=7ee53394edee2d2f3713ed1a9c6ae979","Quantifying the efficacy of different climate forcings is important for understanding the real-world climate sensitivity. This study presents a systematic multimodel analysis of different climate driver efficacies using simulations from the Precipitation Driver and Response Model Intercomparison Project (PDRMIP). Efficacies calculated from instantaneous radiative forcing deviate considerably from unity across forcing agents and models. Effective radiative forcing (ERF) is a better predictor of global mean near-surface air temperature (GSAT) change. Efficacies are closest to one when ERF is computed using fixed sea surface temperature experiments and adjusted for land surface temperature changes using radiative kernels. Multimodel mean efficacies based on ERF are close to one for global perturbations of methane, sulfate, black carbon, and insolation, but there is notable intermodel spread. We do not find robust evidence that the geographic location of sulfate aerosol affects its efficacy. GSAT is found to respond more slowly to aerosol forcing than CO2 in the early stages of simulations. Despite these differences, we find that there is no evidence for an efficacy effect on historical GSAT trend estimates based on simulations with an impulse response model, nor on the resulting estimates of climate sensitivity derived from the historical period. However, the considerable intermodel spread in the computed efficacies means that we cannot rule out an efficacy-induced bias of ±0.4 K in equilibrium climate sensitivity to CO2 doubling when estimated using the historical GSAT trend. ©2019. The Authors."
"57204755628;56524152600;55795049300;57191290414;7003748648;","Clouds in Convection-Resolving Climate Simulations Over Europe",2019,"10.1029/2018JD030150","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85063987862&doi=10.1029%2f2018JD030150&partnerID=40&md5=1860d6022c42ebd33d62d81fcc9e6819","Although crucial for the Earth's climate, clouds are poorly represented in current climate models, which operate at too coarse grid resolutions and rely on convection parameterizations. Thanks to advances in high-performance computing, it is becoming feasible to perform high-resolution climate simulations with explicitly resolved deep convection. The added value of such convection-resolving simulations for the representation of precipitation has already been demonstrated in a number of studies, but assessments about clouds are still rare. In the present study, we analyze the representation of clouds in decade-long convection-resolving climate simulations (2.2-km horizontal grid spacing) over a computational domain with 1,536 × 1,536 × 60 grid points covering Europe and compare it against coarser-resolution convection-parameterizing simulations (12-km horizontal spacing). The simulations have been performed with a version of the COSMO model that runs entirely on graphics processing units. The European Centre for Medium-Range Weather Forecasts Re-Analysis-Interim reanalysis-driven present climate simulations (1999–2008) show that biases in mean summertime cloudiness and top-of-the-atmosphere radiation budget are reduced when convection is resolved instead of parameterized. Especially, the typically underestimated midtropospheric cloud layer is enhanced, thanks to stronger vertical exchange. Future climate simulations (2079–2088) conducted using pseudo global warming experiments for a Representative Concentration Pathway 8.5 scenario show a predominating reduction in low-level and midlevel cloud cover fraction and an increase in cloud top height, implying positive cloud-amount and cloud-height feedbacks. These positive feedbacks are only partly compensated by the negative cloud-thickness feedback. Although the simulations exhibit substantial differences in terms of clouds in the present climate, the simulated cloud feedbacks are similar between the 2.2- and 12-km models. ©2019. American Geophysical Union. All Rights Reserved."
"56724051400;8686475900;","Substantial Reductions in Cloud Cover and Moisture Transport by Dynamic Plant Responses",2019,"10.1029/2018GL081236","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061668418&doi=10.1029%2f2018GL081236&partnerID=40&md5=cdc3e73217d9efdd24b09963d73697f9","Cumulus clouds make a significant contribution to the Earth's energy balance and hydrological cycle and are a major source of uncertainty in climate projections. Reducing uncertainty by expanding our understanding of the processes that drive cumulus convection is vital to the accurate identification of future global and regional climate impacts. Here we adopt an interdisciplinary approach that integrates interrelated scales from plant physiology to atmospheric turbulence. Our explicit simulations mimic the land-atmosphere approach implemented in current numerical weather prediction, and global climate models enable us to conclude that neglecting local plant dynamic responses leads to misrepresentations in the cloud cover and midtropospheric moisture convection of up to 21% and 56%, respectively. Our approach offers insights into the key role played by the active vegetation on atmospheric convective mixing that has recently been identified as the source of half of the variance in global warming projections (i.e., equilibrium climate sensitivity). ©2019. The Authors."
"57190858567;23082420800;8866821900;7006256622;","Cloud radiative feedbacks and El Niño-Southern Oscillation",2019,"10.1175/JCLI-D-18-0842.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068932325&doi=10.1175%2fJCLI-D-18-0842.1&partnerID=40&md5=d0321969c1cbda1a284576f71b076775","Cloud radiative feedbacks are disabled via ""cloud-locking"" in the Community Earth System Model, version 1.2 (CESM1.2), to result in a shift in El Niño-Southern Oscillation (ENSO) periodicity from 2-7 years to decadal time scales. We hypothesize that cloud radiative feedbacks may impact the periodicity in three ways: by 1) modulating heat flux locally into the equatorial Pacific subsurface through negative shortwave cloud feedback on sea surface temperature anomalies (SSTA), 2) damping the persistence of subtropical southeast Pacific SSTA such that the South Pacific meridional mode impacts the duration of ENSO events, or 3) controlling the meridional width of off-equatorial westerly winds, which impacts the periodicity of ENSO by initiating longer Rossby waves. The result of cloud-locking in CESM1.2 contrasts that of another study, which found that cloud-locking in a different global climate model led to decreased ENSO magnitude across all time scales due to a lack of positive longwave feedback on the anomalous Walker circulation. CESM1.2 contains this positive longwave feedback on the anomalous Walker circulation, but either its influence on the surface is decoupled from ocean dynamics or the feedback is only active on interannual time scales. The roles of cloud radiative feedbacks in ENSO in other global climate models are additionally considered. In particular, it is shown that one cannot predict the role of cloud radiative feedbacks in ENSO through a multimodel diagnostic analysis. Instead, they must be directly altered. © 2019 American Meteorological Society."
"57034069700;35509639400;","On the Interplay Between Convective Aggregation, Surface Temperature Gradients, and Climate Sensitivity",2018,"10.1029/2018MS001406","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058690710&doi=10.1029%2f2018MS001406&partnerID=40&md5=22e521dae65d78317cb87a9ba0c433ad","This study explores the extent to which convective aggregation interacts with sea surface temperature (SST) and affects climate sensitivity. For this purpose, radiative-convective equilibrium simulations are run with a general circulation model coupled to an ocean mixed layer, and several types of perturbations are imposed to the ocean-atmosphere system. Convective aggregation turns out to be much more sensitive to temperature in coupled experiments than in prescribed SST experiments. But changes in convective aggregation induced by a doubling of the CO 2 concentration are always smaller than changes associated with the transition from a non-aggregated to an aggregated state. If aggregation changes were acting alone, they would exert a strong negative feedback on global mean surface temperature. However, in a coupled framework, aggregation changes interact with the SST and generate SST gradients that strengthen the positive low-cloud feedback associated with changes in SST pattern. This overcompensates the negative feedback due to aggregation changes and leads to a larger equilibrium climate sensitivity than in the absence of SST gradients. Although this effect might be model specific, interactions between convective aggregation and the spatial distribution of SST appear crucial to assess the impact of convective aggregation on climate sensitivity. ©2018. The Authors."
"55816227500;56722821200;15755995900;7003666669;56162305900;","The importance of considering sub-grid cloud variability when using satellite observations to evaluate the cloud and precipitation simulations in climate models",2018,"10.5194/gmd-11-3147-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85051229367&doi=10.5194%2fgmd-11-3147-2018&partnerID=40&md5=7912fe0ebd0d570aaac8c16a71d865e3","Satellite cloud observations have become an indispensable tool for evaluating general circulation models (GCMs). To facilitate the satellite and GCM comparisons, the CFMIP (Cloud Feedback Model Inter-comparison Project) Observation Simulator Package (COSP) has been developed and is now increasingly used in GCM evaluations. Real-world clouds and precipitation can have significant sub-grid variations, which, however, are often ignored or oversimplified in the COSP simulation. In this study, we use COSP cloud simulations from the Super-Parameterized Community Atmosphere Model (SPCAM5) and satellite observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) and CloudSat to demonstrate the importance of considering the sub-grid variability of cloud and precipitation when using the COSP to evaluate GCM simulations. We carry out two sensitivity tests: SPCAM5 COSP and SPCAM5-Homogeneous COSP. In the SPCAM5 COSP run, the sub-grid cloud and precipitation properties from the embedded cloud-resolving model (CRM) of SPCAM5 are used to drive the COSP simulation, while in the SPCAM5-Homogeneous COSP run only grid-mean cloud and precipitation properties (i.e., no sub-grid variations) are given to the COSP. We find that the warm rain signatures in the SPCAM5 COSP run agree with the MODIS and CloudSat observations quite well. In contrast, the SPCAM5-Homogeneous COSP run which ignores the sub-grid cloud variations substantially overestimates the radar reflectivity and probability of precipitation compared to the satellite observations, as well as the results from the SPCAM5 COSP run. The significant differences between the two COSP runs demonstrate that it is important to take into account the sub-grid variations of cloud and precipitation when using COSP to evaluate the GCM to avoid confusing and misleading results. © Author(s) 2018."
"54399869900;7401836526;","Atmospheric dynamics feedback: Concept, simulations, and climate implications",2018,"10.1175/JCLI-D-17-0470.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042849303&doi=10.1175%2fJCLI-D-17-0470.1&partnerID=40&md5=6c8bf7b48ce659940c21bc7aa8229481","The regional climate response to radiative forcing is largely controlled by changes in the atmospheric circulation. It has been suggested that global climate sensitivity also depends on the circulation response, an effect called the ""atmospheric dynamics feedback."" Using a technique to isolate the influence of changes in atmospheric circulation on top-of-the-atmosphere radiation, the authors calculate the atmospheric dynamics feedback in coupled climate models. Large-scale circulation changes contribute substantially to all-sky and cloud feedbacks in the tropics but are relatively less important at higher latitudes. Globally averaged, the atmospheric dynamics feedback is positive and amplifies the near-surface temperature response to climate change by an average of 8% in simulations with coupled models. A constraint related to the atmospheric mass budget results in the dynamics feedback being small on large scales relative to feedbacks associated with thermodynamic processes. Idealized-forcing simulations suggest that circulation changes at high latitudes are potentially more effective at influencing global temperature than circulation changes at low latitudes, and the implications for past and future climate change are discussed. © 2018 American Meteorological Society."
"55831437900;57206503877;","Energy transport, polar amplification, and ITCZ shifts in the GeoMIP G1 ensemble",2018,"10.5194/acp-18-2287-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042146117&doi=10.5194%2facp-18-2287-2018&partnerID=40&md5=8a295c057da9b6de77fc5bdc95d59780","The polar amplification of warming and the ability of the Intertropical Convergence Zone (ITCZ) to shift to the north or south are two very important problems in climate science. Examining these behaviors in global climate models (GCMs) running solar geoengineering experiments is helpful not only for predicting the effects of solar geoengineering but also for understanding how these processes work under increased carbon dioxide (CO2). Both polar amplification and ITCZ shifts are closely related to the meridional transport of moist static energy (MSE) by the atmosphere. This study examines changes in MSE transport in 10 fully coupled GCMs in experiment G1 of the Geoengineering Model Intercomparison Project (GeoMIP), in which the solar constant is reduced to compensate for the radiative forcing from abruptly quadrupled CO2 concentrations. In G1, poleward MSE transport decreases relative to preindustrial conditions in all models, in contrast to the Coupled Model Intercomparison Project phase 5 (CMIP5) abrupt4xCO2 experiment, in which poleward MSE transport increases. We show that since poleward energy transport decreases rather than increases, and local feedbacks cannot change the sign of an initial temperature change, the residual polar amplification in the G1 experiment must be due to the net positive forcing in the polar regions and net negative forcing in the tropics, which arise from the different spatial patterns of the simultaneously imposed solar and CO2 forcings. However, the reduction in poleward energy transport likely plays a role in limiting the polar warming in G1. An attribution study with a moist energy balance model shows that cloud feedbacks are the largest source of uncertainty regarding changes in poleward energy transport in midlatitudes in G1, as well as for changes in cross-equatorial energy transport, which are anticorrelated with ITCZ shifts. © 2018 Author(s)."
"7003865921;6603925960;57207507108;57189386544;","Observational Constraints on Cloud Feedbacks: The Role of Active Satellite Sensors",2017,"10.1007/s10712-017-9452-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85035801783&doi=10.1007%2fs10712-017-9452-0&partnerID=40&md5=457c3231781fe4e5d43de3f27878b6f3","Cloud profiling from active lidar and radar in the A-train satellite constellation has significantly advanced our understanding of clouds and their role in the climate system. Nevertheless, the response of clouds to a warming climate remains one of the largest uncertainties in predicting climate change and for the development of adaptions to change. Both observation of long-term changes and observational constraints on the processes responsible for those changes are necessary. We review recent progress in our understanding of the cloud feedback problem. Capabilities and advantages of active sensors for observing clouds are discussed, along with the importance of active sensors for deriving constraints on cloud feedbacks as an essential component of a global climate observing system. © 2017, The Author(s)."
"7102284923;26656246100;8315173400;36772864900;7004326742;56695227400;","A State-Dependent Quantification of Climate Sensitivity Based on Paleodata of the Last 2.1 Million Years",2017,"10.1002/2017PA003190","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032951361&doi=10.1002%2f2017PA003190&partnerID=40&md5=e7a19592adecfc5b873aa4f413f337cc","The evidence from both data and models indicates that specific equilibrium climate sensitivity S[X]—the global annual mean surface temperature change (ΔTg) as a response to a change in radiative forcing X (ΔR[X])—is state dependent. Such a state dependency implies that the best fit in the scatterplot of ΔTg versus ΔR[X] is not a linear regression but can be some nonlinear or even nonsmooth function. While for the conventional linear case the slope (gradient) of the regression is correctly interpreted as the specific equilibrium climate sensitivity S[X], the interpretation is not straightforward in the nonlinear case. We here explain how such a state-dependent scatterplot needs to be interpreted and provide a theoretical understanding—or generalization—how to quantify S[X] in the nonlinear case. Finally, from data covering the last 2.1 Myr we show that—due to state dependency—the specific equilibrium climate sensitivity which considers radiative forcing of CO2 and land ice sheet (LI) albedo, S[co2,LI], is larger during interglacial states than during glacial conditions by more than a factor 2. ©2017. The Authors."
"56909327200;7401836526;36097134700;55351266200;","Large-eddy simulation of subtropical cloud-topped boundary layers: 2. Cloud response to climate change",2017,"10.1002/2016MS000804","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85010723113&doi=10.1002%2f2016MS000804&partnerID=40&md5=2b009944619031b192274fb0ae5a1321","How subtropical marine boundary layer (MBL) clouds respond to warming is investigated using large-eddy simulations (LES) of a wide range of warmer climates, with CO2 concentrations elevated by factors 2–16. In LES coupled to a slab ocean with interactive sea surface temperatures (SST), the surface latent heat flux (LHF) is constrained by the surface energy balance and only strengthens modestly under warming. Consequently, the MBL in warmer climates is shallower than in corresponding fixed-SST LES, in which LHF strengthens excessively and the MBL typically deepens. The inferred shortwave (SW) cloud feedback with a closed energy balance is weakly positive for cumulus clouds. It is more strongly positive for stratocumulus clouds, with a magnitude that increases with warming. Stratocumulus clouds generally break up above 6 K to 9 K warming, or above a four to eightfold increase in CO2 concentrations. This occurs because the MBL mixing driven by cloud-top longwave (LW) cooling weakens as the LW opacity of the free troposphere increases. The stratocumulus breakup triggers an abrupt and large SST increase and MBL deepening, which cannot occur in fixed-SST experiments. SW cloud radiative effects generally weaken while the lower-tropospheric stability increases under warming—the reverse of their empirical relation in the present climate. The MBL is deeper and stratocumulus persists into warmer climates if large-scale subsidence decreases as the climate warms. The contrasts between experiments with interactive SST and fixed SST highlight the importance of a closed surface energy balance for obtaining realizable responses of MBL clouds to warming. © 2016. The Authors."
"8882641700;7004479957;8977001000;55272477500;24173130300;7005056279;56033466400;","CGILS Phase 2 LES intercomparison of response of subtropical marine low cloud regimes to CO2 quadrupling and a CMIP3 composite forcing change",2016,"10.1002/2016MS000765","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84995968692&doi=10.1002%2f2016MS000765&partnerID=40&md5=d6a07a25d45cd216d6a2a3a76ef329e3","Phase 1 of the CGILS large-eddy simulation (LES) intercomparison is extended to understand if subtropical marine boundary-layer clouds respond to idealized climate perturbations consistently in six LES models. Here the responses to quadrupled carbon dioxide (“fast adjustment”) and to a composite climate perturbation representative of CMIP3 multimodel mean 2×CO2 near-equilibrium conditions are analyzed. As in Phase 1, the LES is run to equilibrium using specified steady summertime forcings representative of three locations in the Northeast Pacific Ocean in shallow well-mixed stratocumulus, decoupled stratocumulus, and shallow cumulus cloud regimes. The results are generally consistent with a single-LES study of Bretherton et al. () on which this intercomparison was based. Both quadrupled CO2 and the composite climate perturbation result in less cloud and a shallower boundary layer for all models in well-mixed stratocumulus and for all but a single LES in decoupled stratocumulus and shallow cumulus, corroborating similar findings from global climate models (GCMs). For both perturbations, the amount of cloud reduction varies across the models, but there is less intermodel scatter than in GCMs. The cloud radiative effect changes are much larger in the stratocumulus-capped regimes than in the shallow cumulus regime, for which precipitation buffering may damp the cloud response. In the decoupled stratocumulus and cumulus regimes, both the CO2 increase and CMIP3 perturbations reduce boundary-layer decoupling, due to the shallowing of inversion height. © 2016. The Authors."
"57190862866;56032970700;22934904700;7401945370;57212988186;55471474500;","High cloud responses to global warming simulated by two different cloud microphysics schemes implemented in the nonhydrostatic icosahedral atmospheric model (NICAM)",2016,"10.1175/JCLI-D-15-0668.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983543788&doi=10.1175%2fJCLI-D-15-0668.1&partnerID=40&md5=fa094d5f0fec8f32877ee6a23f89088b","This study examines cloud responses to global warming using a global nonhydrostatic model with two different cloud microphysics schemes. The cloud microphysics schemes tested here are the single- and doublemoment schemes with six water categories: these schemes are referred to as NSW6 and NDW6, respectively. Simulations of one year for NSW6 and one boreal summer for NDW6 are performed using the nonhydrostatic icosahedral atmospheric model with a mesh size of approximately 14 km. NSW6 and NDW6 exhibit similar changes in the visible cloud fraction under conditions of global warming. The longwave (LW) cloud radiative feedbacks inNSW6 and NDW6are within the upper half of the phase 5 of the CoupledModel Intercomparison Project (CMIP5)-Cloud Feedback Model Intercomparison Project 2 (CFMIP2) range. The LWcloud radiative feedbacks are mainly attributed to cirrus clouds, which prevail more in the tropics under global warming conditions. For NDW6, the LW cloud radiative feedbacks from cirrus clouds also extend to midlatitudes. The changes in cirrus clouds and their effects on LW cloud radiative forcing (LWCRF) are assessed based on changes in the effective radii of ice hydrometeors (Rei) and the cloud fraction. Itwas determined that an increase in Rei has a nonnegligible impact on LWCRF compared with an increase in cloud fraction. © 2016 American Meteorological Society."
"24528108000;44061090200;35547807400;","An intensified hydrological cycle in the simulation of geoengineering by cirrus cloud thinning using ice crystal fall speed changes",2016,"10.1002/2015JD024304","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977501539&doi=10.1002%2f2015JD024304&partnerID=40&md5=5b4d5b59e4dbe8ab9577b5ab5466fb0c","Proposals to geoengineer Earth’s climate by cirrus cloud thinning (CCT) potentially offer advantages over solar radiation management schemes: amplified cooling of the Arctic and smaller perturbations to global mean precipitation in particular. Using an idealized climate model implementation of CCT in which ice particle fall speeds were increased 2×, 4×, and 8× we examine the relationships between effective radiative forcing (ERF) at the top of atmosphere, near-surface temperature, and the response of the hydrological cycle. ERF was nonlinear with fall speed change and driven by the trade-off between opposing positive shortwave and negative longwave radiative forcings. ERF was-2.0Wm-2 for both 4× and 8× fall speeds. Global mean temperature decreased linearly with ERF, while Arctic temperature reductions were amplified compared with the global mean change. The change in global mean precipitation involved a rapid adjustment (~ 1%/Wm2), which was linear with the change in the net atmospheric energy balance, and a feedback response (~2%/°C). Global mean precipitation and evaporation increased strongly in the first year of CCT. Intensification of the hydrological cycle was promoted by intensification of the vertical overturning circulation of the atmosphere, changes in boundary layer climate favorable for evaporation, and increased energy available at the surface for evaporation (from increased net shortwave radiation and reduced subsurface storage of heat). Such intensification of the hydrological cycle is a significant side effect to the cooling of climate by CCT. Any accompanying negative cirrus cloud feedback response would implicitly increase the costs and complexity of CCT deployment. © 2016. The Authors."
"7005578774;57207969036;6602098362;","Relationships among top-of-atmosphere radiation and atmospheric state variables in observations and CESM",2015,"10.1002/2015JD023381","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945453810&doi=10.1002%2f2015JD023381&partnerID=40&md5=c3c299fa055dff84c238f7c50a2a97f1","A detailed examination is made in both observations and the Community Earth System Model (CESM) of relationships among top-of-atmosphere radiation, water vapor, temperatures, and precipitation for 2000–2014 to assess the origins of radiative perturbations and climate feedbacks empirically. The 30-member large ensemble coupled runs are analyzed along with one run with specified sea surface temperatures for 1994 to 2005 (to avoid volcanic eruptions). The vertical structure of the CESM temperature profile tends to be top heavy in the model, with too much deep convection and not enough lower stratospheric cooling as part of the response to tropospheric heating. There is too much absorbed solar radiation (ASR) over the Southern Oceans and not enough in the tropics, and El Niño–Southern Oscillation (ENSO) is too large in amplitude in this version of the model. However, the covariability of monthly mean anomalies produces remarkably good replication of most of the observed relationships. There is a lot more high-frequency variability in radiative fluxes than in temperature, highlighting the role of clouds and transient weather systems in the radiation statistics. Over the Warm Pool in the tropical western Pacific and Indian Oceans, where nonlocal effects from the Walker circulation driven by the ENSO events are important, several related biases emerge: in response to high SST anomalies there is more precipitation, water vapor, and cloud and less ASR and outgoing longwave radiation in the model than observed. Different model global mean trends are evident, however, possibly hinting at too much positive cloud feedback in the model. © 2015. American Geophysical Union. All rights reserved."
"56278161100;56457990000;26324818700;35209683700;","Feedback attribution of the land-sea warming contrast in a global warming simulation of the NCAR CCSM4",2014,"10.1088/1748-9326/9/12/124005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919665363&doi=10.1088%2f1748-9326%2f9%2f12%2f124005&partnerID=40&md5=3c8b9e1281718e4836efb9206ca7d582","One of the salient features in both observations and climate simulations is a stronger land warming than sea. This paper provides a quantitative understanding of the main processes that contribute to the land-sea warming asymmetry in a global warming simulation of the NCAR CCSM4. The CO2 forcing alone warms the surface nearly the same for both land and sea, suggesting that feedbacks are responsible for the warming contrast. Our analysis on one hand confirms that the principal contributor to the above-unity land-to-sea warming ratio is the evaporation feedback; on the other hand the results indicate that the sensible heat flux feedback has the largest land-sea warming difference that favors a greater ocean than land warming. Therefore, the results uniquely highlight the importance of other feedbacks in establishing the above-unity land-to-sea warming ratio. Particularly, the SW cloud feedback and the ocean heat storage in the transient response are key contributors to the greater warming over land than sea. © 2014 IOP Publishing Ltd."
"57001165400;7406250414;","Preliminary Evaluations of ENSO-Related Cloud and Water Vapor Feedbacks in FGOALS",2014,"10.1007/978-3-642-41801-3_23","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84994897045&doi=10.1007%2f978-3-642-41801-3_23&partnerID=40&md5=514b961218196a3b500aaf5873e6d45f","Previous studies have revealed two common biases in the simulation of the response of cloud and water vapor to El Niño warming in current models: an underestimation of the negative shortwave cloud radiative forcing (SWCRF) feedback and an overestimation of the positive water vapor feedback. In the present study, the performance of the FGOALS models in representing these feedbacks was evaluated. The major characteristics of the SWCRF and water vapor feedbacks over the tropical Pacific regions in response to ENSO forcing are generally well captured by the two FGOALS models. Specifically, FGOAS-g2.0 provides a more realistic simulation of SWCRF feedback than FGOALS-s2.0, particularly in the historical run. The bias of the SWCRF feedback in the FGOALS- s2.0 historical run can be attributed to two factors: the small bias in the FGOALS-s2.0 AMIP run is carried into its coupled counterpart and further amplified, and the excessive cold tongue in the FGOALS-s2.0 historical is another key factor behind the SWCRF feedback bias. Both FGOALS models overestimated the positive water vapor feedback, especially in their AMIP runs. This bias can be traced back to the overestimation of the response of water vapor in the upper troposphere. © Springer-Verlag Berlin Heidelberg 2014."
"10139389700;42161528200;","The value of information for integrated assessment models of climate change",2014,"10.1016/j.jeem.2014.01.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904552090&doi=10.1016%2fj.jeem.2014.01.002&partnerID=40&md5=848593118deb7bf9ed7e2ef31ddce97b","We estimate the value of information (VOI) for three key parameters of climate integrated assessment models (IAMs): marginal damages at low temperature anomalies, marginal damages at high temperature anomalies, and equilibrium climate sensitivity. Most empirical studies of climate damages have examined temperature anomalies up to 3. °C, while some recent theoretical studies emphasize the risks of ""climate catastrophes,"" which depend on climate sensitivity and on marginal damages at higher temperature anomalies. We use a new IAM to estimate the VOI for each parameter over a range of assumed levels of study precision based on prior probability distributions calibrated using results from previous studies. We measure the VOI as the maximum fixed fraction of consumption that a social planner would be willing to pay to conduct a new study before setting a carbon tax. Our central results suggest that the VOI is greatest for marginal damages at high temperature anomalies. © 2014."
"15729547600;7003876681;12240249100;7202367208;","Impact of climate sensitivity and polar amplification on projections of Greenland Ice Sheet loss",2014,"10.1007/s00382-014-2050-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892768880&doi=10.1007%2fs00382-014-2050-7&partnerID=40&md5=59254821887e10d522e669df6303964f","The future rate of Greenland Ice Sheet (GrIS) deglaciation and the future contribution of GrIS deglaciation to sea level rise will depend critically on the magnitude of northern hemispheric polar amplification and global equilibrium climate sensitivity. Here, these relationships are analyzed using an ensemble of multi-century coupled ice-sheet/climate model simulations seeded with observationally-constrained initial conditions and then integrated forward under tripled preindustrial CO2. Polar amplifications and climate sensitivities were varied between ensemble members in order to bracket current uncertainty in polar amplification and climate sensitivity. A large inter-ensemble spread in mean GrIS air temperature, albedo and surface mass balance trends stemming from this uncertainty resulted in GrIS ice volume loss ranging from 5 to 40 % of the original ice volume after 500 years. The large dependence of GrIS deglaciation on polar amplification and climate sensitivity that we find indicates that the representation of these processes in climate models will exert a strong control on any simulated predictions of multi-century GrIS evolution. Efforts to reduce polar amplification and equilibrium climate sensitivity uncertainty will therefore play a critical role in constraining projections of GrIS deglaciation and sea level rise in a future high-CO2 world. © 2014, Springer-Verlag (outside the USA)."
"25943390200;35201039100;","The contribution of timescales to the temperature response of climate models",2011,"10.1007/s00382-010-0753-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79551602685&doi=10.1007%2fs00382-010-0753-y&partnerID=40&md5=0bfce0c44217d3a4bbfd3be3f6b04f4b","Both the magnitude and timescale of climate change in response to anthropogenic forcing are important consideration in climate change decision making. Using a familiar, yet simple global energy balance model combined with a novel method for estimating the amount of gain in the global surface temperature response to radiative forcing associated with timescales in the range 100-103 years we show that the introduction of large-scale circulation such as meridional overturning leads to the emergence of discrete gain-timescale relationships in the dynamics of this model. This same feature is found in the response of both an intermediate complexity and two atmosphere-ocean general circulation models run to equilibrium. As a result of this emergent property of climate models, it is possible to offer credible partitioning of the full equilibrium gain of these models, and hence their equilibrium climate sensitivity, between two discrete timescales; one decadal associated with near surface ocean heat equilibration; and one centennial associated with deep ocean heat equilibration. Timescales of approximately 20 and 700 years with a 60:40 partitioning of the equilibrium gain are found for the models analysed here. A re-analysis of the emulation results of 19 AOGCMs presented by Meinshausen et al. (Atmos Chem Phys Discuss 8:6153-6272, 2008) indicates timescales of 20 and 580 years with an approximate 50:50 partition of the equilibrium gain between the two. This suggests near equal importance of both short and long timescales in determining equilibrium climate sensitivity. © 2010 Springer-Verlag."
"7201724034;7003499257;19337904400;7402331145;19337201300;37061989400;55858477800;44561045800;57202396417;36149741000;6603370049;8612652300;55619302054;36842329100;36017183900;12647654300;6505890285;26531444800;8604965200;55686667100;10241250100;10240710000;57201565982;8507223000;7102857642;","Impact of the assimilation of sea ice concentration data on an atmosphere-ocean-sea ice coupled simulation of the Arctic Ocean climate",2011,"10.2151/sola.2011-010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878308564&doi=10.2151%2fsola.2011-010&partnerID=40&md5=7f397e41a16b72687ad363b40320489c","We have investigated the effects of assimilating sea ice concentration (SIC) data on a simulation of Arctic Ocean climate using an atmosphere-ocean-sea ice coupled model. Our results show that the normal overestimation of summertime SIC in the East Siberian Sea and the Beaufort Sea in simulations without sea-ice data input can be greatly reduced by assimilating seaice data and that this improvement is also evident in a following hindcast experiment for 3-4 years after the initialization of the assimilation. In the hindcast experiment, enhanced heat storage in both sea ice and in the ocean surface layer plays a central role in improving the accuracy of the sea ice distribution, particularly in summer. Our detailed investigation suggests that the ice-albedo feedback and the feedback associated with the atmospheric pressure pattern generated by the improved estimation of SIC work more effectively to retain the heat signal after initialization for a coupled atmosphere-ocean-sea ice system prediction. In addition, comparison with field observations confirms that the model fails to produce a realistic feedback loop, which is (presumably) due to inadequacies in both the ice-cloud feedback model and the feedback via the Beaufort Gyre circulation. Further development of coupled models is thus required to better define Arctic Ocean climate processes and to improve the accuracy of their predictions. © 2011, the Meteorological Society of Japan."
"12801992200;","Planetary albedo in strongly forced climate, as simulated by the CMIP3 models",2011,"10.1007/s00704-011-0411-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052707202&doi=10.1007%2fs00704-011-0411-2&partnerID=40&md5=490309ca70604d4d40f8773f2155a9a8","In an ensemble of general circulation models, the global mean albedo significantly decreases in response to strong CO2 forcing. In some of the models, the magnitude of this positive feedback is as large as the CO2 forcing itself. The models agree well on the surface contribution to the trend, due to retreating snow and ice cover, but display large differences when it comes to the contribution from shortwave radiative effects of clouds. The ""cloud contribution"" defined as the difference between clear-sky and all-sky albedo anomalies and denoted as ΔCC is correlated with equilibrium climate sensitivity in the models (correlation coefficient 0. 76), indicating that in high sensitivity models the clouds to a greater extent act to enhance the negative clear-sky albedo trend, whereas in low sensitivity models the clouds rather counteract this trend. As a consequence, the total albedo trend is more negative in more sensitive models (correlation coefficient 0. 73). This illustrates in a new way the importance of cloud response to global warming in determining climate sensitivity in models. The cloud contribution to the albedo trend can primarily be ascribed to changes in total cloud fraction, but changes in cloud albedo may also be of importance. © 2011 The Author(s)."
"7004033942;7102604282;7403531523;","Observed and modeled evolution of the tropical mean radiation budget at the top of the atmosphere since 1985",2009,"10.1029/2008JD011560","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350074389&doi=10.1029%2f2008JD011560&partnerID=40&md5=3074050ae4c43f524d29431dbc48f8de","We have used satellite-based broadband radiation observations to construct a longterm continuous 1985-2005 record of the radiative budget components at the top of the atmosphere for the tropical region (20°S-20°N). On the basis of the constructed record we have derived the most conservative estimate of their trends. We compared the interannual variability of the net radiative fluxes at the top of the tropical atmosphere with model simulations from the Intergovernmental Panel on Climate Change fourth assessment report (AR4) archive available up to 2000 and showed that most of the models capture the 1991 Mount Pinatubo eruption signal in both its timing and amplitude; however, none of them simulate the observed trends. Further comparison showed that among the ""best skilled"" models, which are those that showed the highest value of the correlation in simulating one or all of the observed net, shortwave, and longwave radiative fluxes at the top of the atmosphere, the model with an equilibrium climate sensitivity ~3.4°C for the doubling CO<inf>2</inf> represents the observed amplifying total feedback effect in the tropical atmosphere better than the models with a climate sensitivity ~2.7°C or 4.3°C. This total feedback effect was calculated on the basis of an assumed simplified system of interactions between the near-surface temperature and the net radiation at the top of the atmosphere. Copyright 2009 by the American Geophysical Union."
"7004932211;6602438250;6701508267;10243910600;","Seasonal correlations of SST, water vapor, and convective activity in tropical oceans: A new hyperspectral data set for climate model testing",2007,"10.1029/2006GL029191","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34948880742&doi=10.1029%2f2006GL029191&partnerID=40&md5=92ebcab540ff8c47bdde3a4cd58bd28c","The analysis of the response of the Earth Climate System to the seasonal changes of solar forcing in the tropical oceans using four years of the Atmospheric Infrared Sounder (AIRS) and Advanced Microwave Sounding Unit (AMSU) data between 2002 and 2006 gives new insight into amplitude and phase relationships between surface and tropospheric temperatures, humidity, and convective activity. The intensity of the convective activity is measured by counting deep convective clouds. The peaks of convective activity, temperature in the mid-troposphere, and water vapor in the 0-30 N and 0-30 S tropical ocean zonal means occur about two months after solstice, all leading the peak of the sea surface temperature by several weeks. Phase is key to the evaluation of feedback. The evaluation of climate models in terms of zonal and annual means and annual mean deviations from zonal means can now be supplemented by evaluating the phase of key atmospheric and surface parameters relative to solstice. The ability of climate models to reproduce the statistical flavor of the observed amplitudes and relative phases for broad zonal means should lead to increased confidence in the realism of their water vapor and cloud feedback algorithms. AIRS and AMSU were launched into a 705 km altitude polar sun-synchronous orbit on the EOS Aqua spacecraft on May 4, 2002, and have beeen routine data gathering mode since September 2002. Copyright 2007 by the American Geophysical Union."
"35917252100;7005814217;7005513582;","Diagnosing cloud feedbacks in general circulation models",2007,"10.1175/JCLI4140.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250821102&doi=10.1175%2fJCLI4140.1&partnerID=40&md5=7145d4601e7f1733477a3f09328448d2","In this study, it is shown that the NCAR and GFDL GCMs exhibit a marked difference in climate sensitivity of clouds and radiative fluxes in response to doubled CO2 and ±2-K SST perturbations. The GFDL model predicted a substantial decrease in cloud amount and an increase in cloud condensate in the warmer climate, but produced a much weaker change in net cloud radiative forcing (CRF) than the NCAR model. Using a multiple linear regression (MLR) method, the full-sky radiative flux change at the top of the atmosphere was successfully decomposed into individual components associated with the clear sky and different types of clouds. The authors specifically examined the cloud feedbacks due to the cloud amount and cloud condensate changes involving low, mid-, and high clouds between 60°S and 60°N. It was found that the NCAR and GFDL models predicted the same sign of individual longwave and shortwave feedbacks resulting from the change in cloud amount and cloud condensate for all three types of clouds (low, mid, and high) despite the different cloud and radiation schemes used in the models. However, since the individual longwave and shortwave feedbacks resulting from the change in cloud amount and cloud condensate generally have the opposite signs, the net cloud feedback is a subtle residual of all. Strong cancellations between individual cloud feedbacks may result in a weak net cloud feedback. This result is consistent with the findings of the previous studies, which used different approaches to diagnose cloud feedbacks. This study indicates that the proposed MLR approach provides an easy way to efficiently expose the similarity and discrepancy of individual cloud feedback processes between GCMs, which are hidden in the total cloud feedback measured by CRF. Most importantly, this method has the potential to be applied to satellite measurements. Thus, it may serve as a reliable and efficient method to investigate cloud feedback mechanisms on short-term scales by comparing simulations with available observations which may provide a useful way to identify the cause for the wide spread of cloud feedbacks in GCMs. © 2007 American Meteorological Society."
"56862398800;55715215300;7404976222;","Cloud Feedback on SST Variability in the Western Equatorial Pacific in GOALS / LASG Model",1998,"10.1007/s00376-998-0011-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2742563111&doi=10.1007%2fs00376-998-0011-y&partnerID=40&md5=1d3b84bbc0ab39c7d3dabe54486a991d","The cloud feedback on the SST variability in the western equatorial Pacific in GOALS / LASG model is studied in this paper. Two versions of the model, one with the diagnostic cloud and another with the prescribed cloud, are used. Both versions are integrated for 45 years. It is found that in the prescribed cloud run, the SST variability in the western equatorial Pacific is mainly of interdecadal time scale and the interannual variability is very weak. In the diagnostic cloud run, however, the interdecadal SST variability is depressed much and the interannual SST variability becomes much significant. The mechanism for the feedback is then explored. The variability of sea surface temperature (SST) in the western equatorial Pacific is found to be controlled mainly by the zonal wind anomaly, through the process of upwelling / downwelling in both versions. Then it is found that in the diagnostic cloud case, the negative feedback of the solar short wave (SW) flux acts significantly to balance the effect of upwelling / downwelling in addition to the latent flux. In addition, the variability of the SW flux is shown to be closely related to the variability of the middle and high cloud covers. Therefore, the negative feedback of the SW surface flux may have significant contribution to the cloud feedback on the SST variability."
"7004169476;","MODELLING CLOUD FEEDBACKS ON CLIMATE CHANGE",1989,"10.1002/j.1477-8696.1989.tb07057.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024782468&doi=10.1002%2fj.1477-8696.1989.tb07057.x&partnerID=40&md5=184b9607b0f5caeb63f8e012d0fbdcbd",[No abstract available]
"57203401530;55424975000;6603783890;7202991355;","Decadal global temperature variability increases strongly with climate sensitivity",2019,"10.1038/s41558-019-0527-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85069736721&doi=10.1038%2fs41558-019-0527-4&partnerID=40&md5=0496126b315b0a700160a7fcc9910981","Climate-related risks are dependent not only on the warming trend from GHGs, but also on the variability about the trend. However, assessment of the impacts of climate change tends to focus on the ultimate level of global warming1, only occasionally on the rate of global warming, and rarely on variability about the trend. Here we show that models that are more sensitive to GHGs emissions (that is, higher equilibrium climate sensitivity (ECS)) also have higher temperature variability on timescales of several years to several decades2. Counter-intuitively, high-sensitivity climates, as well as having a higher chance of rapid decadal warming, are also more likely to have had historical ‘hiatus’ periods than lower-sensitivity climates. Cooling or hiatus decades over the historical period, which have been relatively uncommon, are more than twice as likely in a high-ECS world (ECS = 4.5 K) compared with a low-ECS world (ECS = 1.5 K). As ECS also affects the background warming rate under future scenarios with unmitigated anthropogenic forcing, the probability of a hyper-warming decade—over ten times the mean rate of global warming for the twentieth century—is even more sensitive to ECS. © 2019, The Author(s), under exclusive licence to Springer Nature Limited."
"25031430500;7801492228;6701431208;36856321600;7102696626;6506848305;34771961800;","The Single Column Atmosphere Model Version 6 (SCAM6): Not a Scam but a Tool for Model Evaluation and Development",2019,"10.1029/2018MS001578","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85066027317&doi=10.1029%2f2018MS001578&partnerID=40&md5=22f8b7087778c160e3562273c3377bac","The Single Column Atmosphere Model (SCAM) is a single column model version of the Community Atmosphere Model (CAM). Here we describe the functionality and features of SCAM6, available as part of CAM6 in the Community Earth System Model, version 2 (CESM2). SCAM6 features a wide selection of standard cases, as well as the ability to easily configure a case specified by the user based on a particular point in a CAM 3-D simulation. This work illustrates how SCAM6 reproduces CAM6 results for physical parameterizations, mostly of moisture and clouds. We demonstrate how SCAM6 can be used for model development through different physics selections, as well as with parameter sweep experiments to highlight the sensitivity of cloud properties to the specification of the vapor deposition process in the cloud microphysics. Furthermore, we use SCAM6 to illustrate the sensitivity of CAM6 cloud radiative properties and precipitation to variable drop number (cloud microphysics properties). Finally, we illustrate how SCAM6 can be used to explore critical emergent processes such as cloud feedbacks and show that CAM6 cloud responses to surface warming in stratus and stratocumulus regimes are similar to those in CAM5. CAM6 has a larger response in the shallow cumulus regime than CAM5. CAM6 cloud feedbacks in the shallow cumulus regime are sensitive to turbulence parameters. SCAM6 is thus a valuable tool for model development, evaluation, and scientific analy sis and an important part of the model hierarchy in Community Earth System Model, version 2. ©2019. The Authors."
"55915126600;6603060770;","Atmospheric Variability Driven by Radiative Cloud Feedback in Brown Dwarfs and Directly Imaged Extrasolar Giant Planets",2019,"10.3847/1538-4357/ab0c07","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064448201&doi=10.3847%2f1538-4357%2fab0c07&partnerID=40&md5=0c502efe7a2898a523064f2f9bd0f83e","Growing observational evidence has suggested active meteorology in the atmospheres of brown dwarfs (BDs) and directly imaged extrasolar giant planets (EGPs). In particular, a number of surveys have shown that near-infrared brightness variability is common among L and T dwarfs. Despite the likelihood from previous studies that atmospheric dynamics is the major cause of the variability, the detailed mechanism of the variability remains elusive, and we need to seek a natural, self-consistent mechanism. Clouds are important in shaping the thermal structure and spectral properties of these atmospheres via their opacity, and we expect the same for inducing atmospheric variability. In this work, using a time-dependent one-dimensional model that incorporates a self-consistent coupling between the thermal structure, convective mixing, cloud radiative heating/cooling, and condensation/evaporation of clouds, we show that radiative cloud feedback can drive spontaneous atmospheric variability in both temperature and cloud structure under conditions appropriate for BDs and directly imaged EGPs. The typical periods of variability are 1 to tens of hr, with a typical amplitude of the variability up to hundreds of K in effective temperature. The existence of variability is robust over a wide range of parameter space, but the detailed evolution of the variability is sensitive to model parameters. Our novel, self-consistent mechanism has important implications for the observed flux variability of BDs and directly imaged EGPs, especially for objects whose variability evolves on short timescales. It is also a promising mechanism for cloud breaking, which has been proposed to explain the L/T transition of BDs. © 2019. The American Astronomical Society. All rights reserved.."
"51864663400;23991212200;7004479957;55232897900;6602878057;6701346974;55544607500;","Insensitivity of the Cloud Response to Surface Warming Under Radical Changes to Boundary Layer Turbulence and Cloud Microphysics: Results From the Ultraparameterized CAM",2018,"10.1029/2018MS001409","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058702303&doi=10.1029%2f2018MS001409&partnerID=40&md5=3632887d08c1d53eac968ed95a206f7c","We study the cloud response to a +4K surface warming in a new multiscale climate model that uses enough interior resolution to begin explicitly resolving boundary layer turbulence (i.e., ultraparameterization or UP). UP's predictions are compared against those from standard superparameterization (SP). The mean cloud radiative effect feedback turns out to be remarkably neutral across all of our simulations, despite some radical changes in both cloud microphysical parameter settings and cloud-resolving model grid resolution. The overall low cloud response to warming is a positive low cloud feedback over land, a negative feedback (driven by cloud optical depth increase) at high latitudes, and weak feedback over the low-latitude oceans. The most distinct effects of UP result from tuning decisions impacting high-latitude cloud feedback. UP's microphysics is tuned to optimize the model present-day, top-of-atmosphere radiation fluxes against CERES observations, by lowering the cloud ice-liquid phase shift temperature ramp, adjusting the ice/liquid autoconversion rate, and increasing the ice fall speed. This reduces high-latitude low cloud amounts and damps the optical depth feedback at high latitudes, leading to a slightly more positive global cloud feedback compared to SP. A sensitivity test that isolates these microphysical impacts from UP's grid resolution confirms that the microphysical settings are mostly responsible for the differences between SP and UP cloud feedback. ©2018. The Authors."
"57201828043;","On the Time Evolution of Climate Sensitivity and Future Warming",2018,"10.1029/2018EF000889","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053939580&doi=10.1029%2f2018EF000889&partnerID=40&md5=0c8820197d91ff1f854adda5885c50a1","The Earth's climate sensitivity to radiative forcing remains a key source of uncertainty in future warming projections. There is a growing realization in recent literature that research must go beyond an equilibrium and CO2-only viewpoint, toward considering how climate sensitivity will evolve over time in response to anthropogenic and natural radiative forcing from multiple sources. Here the transient behavior of climate sensitivity is explored using a modified energy balance model, in which multiple climate feedbacks evolve independently over time to multiple sources of radiative forcing, combined with constraints from observations and from the Climate Model Intercomparison Project phase 5 (CMIP5). First, a large initial ensemble of 107 simulations is generated, with a distribution of climate feedback strengths from subannual to 102-year timescales constrained by the CMIP5 ensemble, including the Planck feedback, the combined water vapor lapse rate feedback, snow and sea ice albedo feedback, fast cloud feedbacks, and the cloud response to sea surface temperature adjustment feedback. These 107 simulations are then tested against observational metrics representing decadal trends in warming, heat and carbon uptake, leaving only 4.6 × 103 history-matched simulations consistent with both the CMIP5 ensemble and historical observations. The results reveal an annual timescale climate sensitivity of 2.1 °C (ranging from 1.6 to 2.8 °C at 95% uncertainty), rising to 2.9 °C (from 1.9 to 4.6 °C) on century timescales. These findings provide a link between lower estimates of climate sensitivity, based on the current transient state of the climate system, and higher estimates based on long-term behavior of complex models and palaeoclimate evidence. ©2018. The Authors."
"36105812700;6701597468;6603711967;7004038301;56250938500;6602741207;","Aerosol-Climate Interactions During the Last Glacial Maximum",2018,"10.1007/s40641-018-0100-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85051713478&doi=10.1007%2fs40641-018-0100-7&partnerID=40&md5=ed0e86c826171dfe92e6575150ead20d","Purpose of Review: Natural archives are imprinted with signs of the past variability of some aerosol species in connection to major climate changes. In certain cases, it is possible to use these paleo-observations as a quantitative tool for benchmarking climate model simulations. Where are we on the path to use observations and models in connection to define an envelope on aerosol feedback onto climate? Recent Findings: On glacial-interglacial time scales, the major advances in our understanding refer to mineral dust, in terms of quantifying its global mass budget, as well as in estimating its direct impacts on the atmospheric radiation budget and indirect impacts on the oceanic carbon cycle. Summary: Even in the case of dust, major uncertainties persist. More detailed observational studies and model intercomparison experiments such as in the Paleoclimate Modelling Intercomparison Project phase 4 will be critical in advancing the field. The inclusion of new processes such as cloud feedbacks and studies focusing on other aerosol species are also envisaged. © 2018, The Author(s)."
"13402835300;","Cloud Condensate and Radiative Feedbacks at Midlatitudes in an Aquaplanet",2018,"10.1002/2018GL077217","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045844073&doi=10.1002%2f2018GL077217&partnerID=40&md5=d8b21e762c605500c036663134595d33","Climate models show a robust negative feedback in the midlatitudes, coincident with an increase in cloud liquid in the mixed-phase region of the control climate. This “mixed-phase feedback” is normally attributed to a feedback caused by a phase change feedback (ice to liquid). Here we use an aquaplanet configuration to investigate this in more detail. We use high-frequency instantaneous diagnostics and composite them in ascending and descending regimes. We find that a large fraction of the increase in cloud liquid water in the mixed-phase region does not significantly contribute to the radiative feedback due to a masking effect of the ice cloud above. Using some simple arguments and approximate calculations, we estimate that about one third of the total shortwave negative radiative feedback is driven by a phase change feedback, whereas the rest of the feedback is driven by changes in ice and warm liquid clouds. © 2018 Crown copyright. This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland."
"55894937000;7004544454;55796430300;","Coupling between marine boundary layer clouds and summer-to-summer sea surface temperature variability over the North Atlantic and Pacific",2018,"10.1007/s00382-017-3651-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85016474214&doi=10.1007%2fs00382-017-3651-8&partnerID=40&md5=c71a27ee542cf107e5e85e8e817f10af","Climate modes of variability over the Atlantic and Pacific may be amplified by a positive feedback between sea-surface temperature (SST) and marine boundary layer clouds. However, it is well known that climate models poorly simulate this feedback. Does this deficiency contribute to model-to-model differences in the representation of climate modes of variability? Over both the North Atlantic and Pacific, typical summertime interannual to interdecadal SST variability exhibits horseshoe-like patterns of co-located anomalies of shortwave cloud radiative effect (CRE), low-level cloud fraction, SST, and estimated inversion strength over the subtropics and midlatitudes that are consistent with a positive cloud feedback. During winter over the midlatitudes, this feedback appears to be diminished. Models participating in the Coupled Model Intercomparison Project phase 5 that simulate a weak feedback between subtropical SST and shortwave CRE produce smaller and less realistic amplitudes of summertime SST and CRE variability over the northern oceans compared to models with a stronger feedback. The change in SST amplitude per unit change in CRE amplitude among the models and observations may be understood as the temperature response of the ocean mixed layer to a unit change in radiative flux over the course of a season. These results highlight the importance of boundary layer clouds in interannual to interdecadal atmosphere–ocean variability over the northern oceans during summer. The results also suggest that deficiencies in the simulation of these clouds in coupled climate models contribute to underestimation in their simulation of summer-to-summer SST variability. © 2017, Springer-Verlag Berlin Heidelberg."
"7007021059;54893098900;7402064802;55366637500;55339081600;7202660824;7404142321;56014511300;8067118800;26645289600;","The Cloud Feedback Model Intercomparison Project (CFMIP) Diagnostic Codes Catalogue - Metrics, diagnostics and methodologies to evaluate, understand and improve the representation of clouds and cloud feedbacks in climate models",2017,"10.5194/gmd-10-4285-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85035353094&doi=10.5194%2fgmd-10-4285-2017&partnerID=40&md5=7f3bbfa2f5ec3aec4d9e75c63b8a3fe5","The CFMIP Diagnostic Codes Catalogue assembles cloud metrics, diagnostics and methodologies, together with programs to diagnose them from general circulation model (GCM) outputs written by various members of the CFMIP community. This aims to facilitate use of the diagnostics by the wider community studying climate and climate change. This paper describes the diagnostics and metrics which are currently in the catalogue, together with examples of their application to model evaluation studies and a summary of some of the insights these diagnostics have provided into the main shortcomings in current GCMs. Analysis of outputs from CFMIP and CMIP6 experiments will also be facilitated by the sharing of diagnostic codes via this catalogue.<br><br>Any code which implements diagnostics relevant to analysing clouds - including cloud-circulation interactions and the contribution of clouds to estimates of climate sensitivity in models - and which is documented in peer-reviewed studies, can be included in the catalogue. We very much welcome additional contributions to further support community analysis of CMIP6 outputs."
"30667558200;11940329900;54893098900;","On the Dependence of Cloud Feedbacks on Physical Parameterizations in WRF Aquaplanet Simulations",2017,"10.1002/2017GL074820","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85034025810&doi=10.1002%2f2017GL074820&partnerID=40&md5=b54e02f55e204d838a7eeeb45015e615","We investigate the effects of physical parameterizations on cloud feedback uncertainty in response to climate change. For this purpose, we construct an ensemble of eight aquaplanet simulations using the Weather Research and Forecasting (WRF) model. In each WRF-derived simulation, we replace only one parameterization at a time while all other parameters remain identical. By doing so, we aim to (i) reproduce cloud feedback uncertainty from state-of-the-art climate models and (ii) understand how parametrizations impact cloud feedbacks. Our results demonstrate that this ensemble of WRF simulations, which differ only in physical parameterizations, replicates the range of cloud feedback uncertainty found in state-of-the-art climate models. We show that microphysics and convective parameterizations govern the magnitude and sign of cloud feedbacks, mostly due to tropical low-level clouds in subsidence regimes. Finally, this study highlights the advantages of using WRF to analyze cloud feedback mechanisms owing to its plug-and-play parameterization capability. ©2017. American Geophysical Union. All Rights Reserved."
"57192663547;25649175400;6602831555;","Can feedback analysis be used to uncover the physical origin of climate sensitivity and efficacy differences?",2017,"10.1007/s00382-016-3476-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007180337&doi=10.1007%2fs00382-016-3476-x&partnerID=40&md5=530659c5f215451a18bb4e739832e501","Different strengths and types of radiative forcings cause variations in the climate sensitivities and efficacies. To relate these changes to their physical origin, this study tests whether a feedback analysis is a suitable approach. For this end, we apply the partial radiative perturbation method. Combining the forward and backward calculation turns out to be indispensable to ensure the additivity of feedbacks and to yield a closed forcing-feedback-balance at top of the atmosphere. For a set of CO2-forced simulations, the climate sensitivity changes with increasing forcing. The albedo, cloud and combined water vapour and lapse rate feedback are found to be responsible for the variations in the climate sensitivity. An O3-forced simulation (induced by enhanced NOx and CO surface emissions) causes a smaller efficacy than a CO2-forced simulation with a similar magnitude of forcing. We find that the Planck, albedo and most likely the cloud feedback are responsible for this effect. Reducing the radiative forcing impedes the statistical separability of feedbacks. We additionally discuss formal inconsistencies between the common ways of comparing climate sensitivities and feedbacks. Moreover, methodical recommendations for future work are given. © 2016, The Author(s)."
"23990276200;7006256622;23082420800;57193084799;","Model evidence for low-level cloud feedback driving persistent changes in atmospheric circulation and regional hydroclimate",2017,"10.1002/2016GL071978","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85010637404&doi=10.1002%2f2016GL071978&partnerID=40&md5=d480688d2d2cd56a5aaf0da2c5d8c130","Recent studies suggest that low clouds in the Pacific play an important role in the observed decadal climate variability and future climate change. In this study, we implement a novel modeling experiment designed to isolate how interactions between local and remote feedbacks associated with low cloud, SSTs, and the large-scale circulation play a significant role in the observed persistence of tropical Pacific SST and associated North American drought. The modeling approach involves the incorporation of observed patterns of satellite-derived shortwave cloud radiative effect (SWCRE) into the coupled model framework and is ideally suited for examining the role of local and large-scale coupled feedbacks and ocean heat transport in Pacific decadal variability. We show that changes in SWCRE forcing in eastern subtropical Pacific alone reproduces much of the observed changes in SST and atmospheric circulation over the past 16 years, including the observed changes in precipitation over much of the Western Hemisphere. ©2016. The Authors."
"7004364155;8891521600;56493740900;","Understanding Climate Feedbacks and Sensitivity Using Observations of Earth’s Energy Budget",2016,"10.1007/s40641-016-0047-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030564406&doi=10.1007%2fs40641-016-0047-5&partnerID=40&md5=c076b7d842a963c6723bfb1ea5ec39bc","While climate models and observations generally agree that climate feedbacks collectively amplify the surface temperature response to radiative forcing, the strength of the feedback estimates varies greatly, resulting in appreciable uncertainty in equilibrium climate sensitivity. Because climate feedbacks respond differently to different spatial variations in temperature, short-term observational records have thus far only provided a weak constraint for climate feedbacks operating under global warming. Further complicating matters is the likelihood of considerable time variation in the effective global climate feedback parameter under transient warming. There is a need to continue to revisit the underlying assumptions used in the traditional forcing-feedback framework, with an emphasis on how climate models and observations can best be utilized to reduce the uncertainties. Model simulations can also guide observational requirements and provide insight on how the observational record can most effectively be analyzed in order to make progress in this critical area of climate research. © 2016, The Author(s)."
"55758496500;","Implications of recent multimodel attribution studies for climate sensitivity",2016,"10.1007/s00382-015-2653-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959145474&doi=10.1007%2fs00382-015-2653-7&partnerID=40&md5=bfa3cd27c2ea3616244c50bfc8f7b51a","Equilibrium climate sensitivity (ECS) is inferred from estimates of instrumental-period warming attributable solely to greenhouse gases (AW), as derived in two recent multi-model detection and attribution (D&A) studies that apply optimal fingerprint methods with high spatial resolution to 3D global climate model simulations. This approach minimises the key uncertainty regarding aerosol forcing without relying on low-dimensional models. The “observed” AW distributions from the D&A studies together with an observationally-based estimate of effective planetary heat capacity (EHC) are applied as observational constraints in (AW, EHC) space. By varying two key parameters—ECS and effective ocean diffusivity—in an energy balance model forced solely by greenhouse gases, an invertible map from the bivariate model parameter space to (AW, EHC) space is generated. Inversion of the constrained (AW, EHC) space through a transformation of variables allows unique recovery of the observationally-constrained joint distribution for the two model parameters, from which the marginal distribution of ECS can readily be derived. The method is extended to provide estimated distributions for transient climate response (TCR). The AW distributions from the two D&A studies produce almost identical results. Combining the two sets of results provides best estimates (5–95 % ranges) of 1.66 (0.7–3.2) K for ECS and 1.37 (0.65–2.2) K for TCR, in line with those from several recent studies based on observed warming from all causes but with tighter uncertainty ranges than for some of those studies. Almost identical results are obtained from application of an alternative profile likelihood statistical methodology. © 2015, Springer-Verlag Berlin Heidelberg."
"14049512800;36522733500;6603378233;","Increase of uncertainty in transient climate response to cumulative carbon emissions after stabilization of atmospheric CO2 concentration",2015,"10.1088/1748-9326/10/12/125018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84952775869&doi=10.1088%2f1748-9326%2f10%2f12%2f125018&partnerID=40&md5=60c4651b2d2d7bd53fc6da30e9123c8f","We analyzed a dataset from an experiment of an earth system model of intermediate complexity, focusing on the change in transient climate response to cumulative carbon emissions (TCRE) after atmospheric CO2 concentration was stabilized in the Representative Concentration Pathway (RCP) 4.5. We estimated the TCRE in 2005 at 0.3-2.4 K/TtC for an unconstrained case and 1.1-1.7 K/TtC when constrained with historical and present-day observational data, the latter result being consistent with other studies. The range of TCRE increased when the increase of CO2 concentration was moderated and then stabilized. This is because the larger (smaller) TCRE members yield even greater (less) TCRE. An additional experiment to assess the equilibrium state revealed significant changes in temperature and cumulative carbon emissions after 2300. We also found that variation of land carbon uptake is significant to the total allowable carbon emissions and subsequent change of the TCRE. Additionally, in our experiment, we revealed that equilibrium climate sensitivity (ECS), one of the 12 parameters perturbed in the ensemble experiment, has a strong positive relationship with the TCRE at the beginning of the stabilization and its subsequent change. We confirmed that for participant models in the Coupled Model Intercomparison Project Phase 5, ECS has a strong positive relationship with TCRE. For models using similar experimental settings, there is a positive relationship with TCRE for the start of the period of stabilization in CO2 concentration, and rate of change after stabilization. The results of this study are influential regarding the total allowable carbon emissions calculated from the TCRE and the temperature increase set as the mitigation target. © 2015 IOP Publishing Ltd."
"6701455548;","Consistent differences in climate feedbacks between Atmosphere-ocean GCMs and atmospheric GCMs with slab-ocean models",2013,"10.1175/JCLI-D-12-00519.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880261516&doi=10.1175%2fJCLI-D-12-00519.1&partnerID=40&md5=36419942f17be33f2e207e67e3326b62","Climate sensitivity is generally studied using two types of models. Atmosphere-ocean general circulation models (AOGCMs) include interactive ocean dynamics and detailed heat uptake. Atmospheric GCMs (AGCMs) with slab ocean models (SOMs) cannot fully simulate the ocean's response to and influence on climate. However, AGCMs are computationally cheaper and thus are often used to quantify and understand climate feedbacks and sensitivity. Here, physical climate feedbacks are compared between AOGCMs and SOM-AGCMs from the Coupled Model Intercomparison Project phase 3 (CMIP3) using the radiative kernel technique. Both the global-average (positive) water vapor and (negative) lapse-rate feedbacks are consistently stronger in AOGCMs. Water vapor feedback differences result from an essentially constant relative humidity and peak in the tropics, where temperature changes are larger for AOGCMs. Differences in lapserate feedbacks extend to midlatitudes and correspond to a larger ratio of tropical- to global-average temperature changes. Global-average surface albedo feedbacks are similar between models types because of a near cancellation of Arctic and Antarctic differences. In AOGCMs, the northern high latitudes warm faster than the southern latitudes, resulting in interhemispheric differences in albedo, water vapor, and lapse-rate feedbacks lacking in the SOM-AGCMs. Meridional heat transport changes also depend on the model type, although there is a large intermodel spread. However, there are no consistent global or zonal differences in cloud feedbacks. Effects of the forcing scenario [Special Report on Emissions Scenarios A1B (SRESa1b) or the 1% CO2 increase per year to doubling (1%to2x) experiments] on feedbacks are model dependent and generally of lesser importance than the model type. Care should be taken when using SOM-AGCMs to understand AOGCM feedback behavior. © 2013 American Meteorological Society."
"55788929500;55686667100;36701462300;","Mechanism of tropical low-cloud response to surface warming using weather and climate simulations",2013,"10.1002/grl.50474","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879936850&doi=10.1002%2fgrl.50474&partnerID=40&md5=c5b52c54497c13a883b6ec3459833b27","To understand mechanisms of shortwave cloud-radiative feedback to global warming in a general circulation model (GCM), we analyzed the response of tropical clouds to uniform increase of sea surface temperature in an atmospheric GCM with two different experimental designs: a single Atmospheric Model Intercomparison Project (AMIP) run for 30 years and a series of 10 day weather hindcasts following the Transpose AMIP II (TAMIP). Given the fast time scale of cloud processes, the hindcast ensemble can capture initial transient responses toward equilibrium obtained in the AMIP experiment, which shows a reduction of low clouds over tropical subsidence regions. The reduction of clouds occurs in the first 10 days in TAMIP when the marine boundary layer (MBL) is destabilized because of contrast between fast and slow warming in the MBL and aloft. Enhanced evaporation from the sea surface that should moisten the MBL through turbulent mixing is suppressed by a reduced surface wind speed associated with a slowdown of the Walker circulation. The sign of the low-cloud change over the subsidence regime is thus determined roughly by competition between convective drying and turbulent moistening of the MBL. © 2013 American Geophysical Union. All Rights Reserved."
"8846887600;6602729528;","The vertical distribution of climate forcings and feedbacks from the surface to top of atmosphere",2012,"10.1007/s00382-011-1233-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864394230&doi=10.1007%2fs00382-011-1233-8&partnerID=40&md5=f07ad469b712dd8e0d34bf62be03cacb","The radiative forcings and feedbacks that determine Earth's climate sensitivity are typically defined at the top-of-atmosphere (TOA) or tropopause, yet climate sensitivity itself refers to a change in temperature at the surface. In this paper, we describe how TOA radiative perturbations translate into surface temperature changes. It is shown using first principles that radiation changes at the TOA can be equated with the change in energy stored by the oceans and land surface. This ocean and land heat uptake in turn involves an adjustment of the surface radiative and non-radiative energy fluxes, with the latter being comprised of the turbulent exchange of latent and sensible heat between the surface and atmosphere. We employ the radiative kernel technique to decompose TOA radiative feedbacks in the IPCC Fourth Assessment Report climate models into components associated with changes in radiative heating of the atmosphere and of the surface. (We consider the equilibrium response of atmosphere-mixed layer ocean models subjected to an instantaneous doubling of atmospheric CO2). It is shown that most feedbacks, i. e., the temperature, water vapor and cloud feedbacks, (as well as CO2 forcing) affect primarily the turbulent energy exchange at the surface rather than the radiative energy exchange. Specifically, the temperature feedback increases the surface turbulent (radiative) energy loss by 2.87 W m-2 K-1 (0.60 W m-2 K-1) in the multimodel mean; the water vapor feedback decreases the surface turbulent energy loss by 1.07 W m-2 K-1 and increases the surface radiative heating by 0.89 W m-2 K-1; and the cloud feedback decreases both the turbulent energy loss and the radiative heating at the surface by 0.43 and 0.24 W m-2 K-1, respectively. Since changes to the surface turbulent energy exchange are dominated in the global mean sense by changes in surface evaporation, these results serve to highlight the fundamental importance of the global water cycle to Earth's climate sensitivity. © 2011 Springer-Verlag."
"7202733689;7003543851;23082420800;","Diagnosing Climate Feedbacks in Coupled Ocean-Atmosphere Models",2012,"10.1007/s10712-012-9187-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862662745&doi=10.1007%2fs10712-012-9187-x&partnerID=40&md5=8367081ce2f300aacad0edfe2ee645af","We review the methodologies used to quantify climate feedbacks in coupled models. The method of radiative kernels is outlined and used to illustrate the dependence of lapse rate, water vapor, surface albedo, and cloud feedbacks on (1) the length of the time average used to define two projected climate states and (2) the time separation between the two climate states. Except for the shortwave component of water vapor feedback, all feedback processes exhibit significant high-frequency variations and intermodel variability of feedback strengths for sub-decadal time averages. It is also found that the uncertainty of lapse rate, water vapor, and cloud feedback decreases with the increase in the time separation. The results suggest that one can substantially reduce the uncertainty of cloud and other feedbacks with the accumulation of accurate, long-term records of satellite observations; however, several decades may be required. © 2012 Springer Science+Business Media B.V."
"26638958100;16423822700;26638773300;26638612200;36928400600;","Study on the mixed layer, entrain ment zone, and cloud feedback based on lidar exploration of nanjing city",2009,"10.1029/2008GL036768","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66149163246&doi=10.1029%2f2008GL036768&partnerID=40&md5=316eb9408cb30440b4a19d761f81b500","An experiment devoted to the lidar (Light Detection And Ranging) study of the urban boundary layer (UBL) over Nanjing city was executed from February 20 to March 5, 2006. Many other techniques including radiosonde, meteorological towers, and turbulence measurements were also performed in order to explore the UBL. In this paper, the results of the lidar experiment with other observation data are presented. The experimental results demonstrate the daily transition features of the mixed layer (ML) and the entrainment zone (EZ). The different features of the ML between urban and suburban areas have been revealed by comparison. Furthermore, cloud feedback on the mixed layer depth (MLD) and the entrainment zone thickness (EZT) has been analyzed © 2009."
"7801693068;7403282069;","Sensitivity of a large ensemble of tropical convective systems to changes in the thermodynamic and dynamic forcings",2008,"10.1175/2007JAS2446.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45849089206&doi=10.1175%2f2007JAS2446.1&partnerID=40&md5=8519c6b198d1659c5ad2cb06298792a8","A two-dimensional cloud-resolving model (CRM) is used to perform five sets of simulations of 68 deep convective cloud objects identified with Clouds and the Earth's Radiant Energy System (CERES) data to examine their sensitivity to changes in thermodynamic and dynamic forcings. The control set of simulations uses observed sea surface temperatures (SSTs) and is forced by advective cooling and moistening tendencies derived from a large-scale model analysis matched to the time and location of each cloud object. Cloud properties, such as albedo, effective cloud height, cloud ice and snow path, and cloud radiative forcing (CRF), are analyzed in terms of their frequency distributions rather than their mean values. Two sets of simulations, F+50% and F-50%, use advective tendencies that are 50% greater and 50% smaller than the control tendencies, respectively. The increased cooling and moistening tendencies cause more widespread convection in the F+50% set of simulations, resulting in clouds that are optically thicker and higher than those produced by the control and F-50% sets of simulations. The magnitudes of both longwave and shortwave CRF are skewed toward higher values with the increase in advective forcing. These significant changes in overall cloud properties are associated with a substantial increase in deep convective cloud fraction (from 0.13 for the F-50% simulations to 0.34 for the F+50% simulations) and changes in the properties of non-deep convective clouds, rather than with changes in the properties of deep convective clouds. Two other sets of simulations, SST+2K and SST-2K, use SSTs that are 2 K higher and 2 K lower than those observed, respectively. The updrafts in the SST+2K simulations tend to be slightly stronger than those of the control and SST-2K simulations, which may cause the SST+2K cloud tops to be higher. The changes in cloud properties, though smaller than those due to changes in the dynamic forcings, occur in both deep convective and non-deep convective cloud categories. The overall changes in some cloud properties are moderately significant when the SST is changed by 4 K. The changes in the domain-averaged shortwave and longwave CRFs are larger in the dynamic forcing sensitivity sets than in the SST sensitivity sets. The cloud feedback effects estimated from the SST-2K and SST+2K sets are comparable to prior studies. © 2008 American Meteorological Society."
"7102268722;6604075289;7004079572;7402386828;","Climate change and cloud feedback: the possible radiative effects of latitudinal redistribution.",1981,"10.1175/1520-0469(1981)038<0489:CCACFT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019678126&doi=10.1175%2f1520-0469%281981%29038%3c0489%3aCCACFT%3e2.0.CO%3b2&partnerID=40&md5=df5d7eb4f4339a56c7fc1b0afd3d5fc3","In a recent zonal atmospheric model experiment the global value of dF/dAc was different in sign than in other calculations. This difference in behaviour was traced to a latitudianl redistribution of cloud amount and height that occurred in the doubled CO2 experiment. However, when dF/dAc was evaluated at individual latitudes and then weighted globally, the value of this parameter was consistent with those found by Cess (1976) and Budyko (1974). -from Authors"
"55823659900;7403076014;","A test of emergent constraints on cloud feedback and climate sensitivity using a calibrated single-model ensemble",2018,"10.1175/JCLI-D-17-0682.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052973920&doi=10.1175%2fJCLI-D-17-0682.1&partnerID=40&md5=ecda73d3deeeda317595a1e570d1e4da","A calibrated single-model ensemble (SME) derived from the NCAR Community Atmosphere Model, version 3.1, is used to test two hypothesized emergent constraints on cloud feedback and equilibrium climate sensitivity (ECS). The Fasullo and Trenberth relative humidity (RH) metric and the Sherwood et al. lowertropospheric mixing (LTMI) metric are computed for the present-day climate of the SME, and the relationships between the metrics, ECS, and cloud and other climate feedbacks are examined. The tropical convergence zone relative humidity (RHM) and the parameterized lower-tropospheric mixing (LTMIS) are positively correlated to ECS, and each is associated with a different spatial pattern of tropical shortwave cloud feedback in the SME. However, neither of those metrics is linked to the type of cloud response hypothesized by its authors. The resolved lower-tropospheric mixing (LTMID) is positively correlated to ECS for a subset of the SME having LTMID over a threshold value. LTMI and the RH for the dry, descending branch of the Hadley cell (RHD) narrow and shift upward the posterior estimates of ECS in the SME, but the SME bias in RHD and concerns over poorly understood physical mechanisms suggest the narrowing could be spurious for both constraints. While calibrated SME results may not generalize to multimodel ensembles, they can enhance the process understanding of emergent constraints and serve as out-of-sample tests of robustness. © 2018 American Meteorological Society."
"57202680564;6603749963;6603362421;7102163440;7003777747;","Climate sensitivity estimates - Sensitivity to radiative forcing time series and observational data",2018,"10.5194/esd-9-879-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85049005035&doi=10.5194%2fesd-9-879-2018&partnerID=40&md5=4946e63081c9ec11e35c1647dc556adc","Inferred effective climate sensitivity (ECSinf) is estimated using a method combining radiative forcing (RF) time series and several series of observed ocean heat content (OHC) and near-surface temperature change in a Bayesian framework using a simple energy balance model and a stochastic model. The model is updated compared to our previous analysis by using recent forcing estimates from IPCC, including OHC data for the deep ocean, and extending the time series to 2014. In our main analysis, the mean value of the estimated ECSinf is 2.0°C, with a median value of 1.9°C and a 90% credible interval (CI) of 1.2-3.1°C. The mean estimate has recently been shown to be consistent with the higher values for the equilibrium climate sensitivity estimated by climate models. The transient climate response (TCR) is estimated to have a mean value of 1.4°C (90% CI 0.9-2.0°C), and in our main analysis the posterior aerosol effective radiative forcing is similar to the range provided by the IPCC. We show a strong sensitivity of the estimated ECSinf to the choice of a priori RF time series, excluding pre-1950 data and the treatment of OHC data. Sensitivity analysis performed by merging the upper (0-700m) and the deep-ocean OHC or using only one OHC dataset (instead of four in the main analysis) both give an enhancement of the mean ECSinf by about 50% from our best estimate. © Author(s) 2018."
"36657850900;55688930000;55087038900;30967646900;56162305900;55720018700;15755995900;7006705919;","Local Radiative Feedbacks Over the Arctic Based on Observed Short-Term Climate Variations",2018,"10.1029/2018GL077852","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048988350&doi=10.1029%2f2018GL077852&partnerID=40&md5=fbf46fd35caf8f3e0f26de7ba9db79db","We compare various radiative feedbacks over the Arctic (60–90°N) estimated from short-term climate variations occurring in reanalysis, satellite, and global climate model data sets using the combined Kernel-Gregory approach. The lapse rate and surface albedo feedbacks are positive, and their magnitudes are comparable. Relative to the tropics (30°S–30°N), the lapse rate feedback is the largest contributor to Arctic amplification among all feedbacks, followed by surface albedo feedback and Planck feedback deviation from its global mean. Both shortwave and longwave water vapor feedbacks are positive, leading to a significant positive net water vapor feedback over the Arctic. The net cloud feedback has large uncertainties including its sign, which strongly depends on the data used for all-sky and clear-sky radiative fluxes at the top of the atmosphere, the time periods considered, and the methods used to estimate the cloud feedback. ©2018. American Geophysical Union. All Rights Reserved."
"57192180109;56250119900;7004587644;57211565887;55796882100;","Regional Regime-Based Evaluation of Present-Day General Circulation Model Cloud Simulations Using Self-Organizing Maps",2018,"10.1002/2017JD028196","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047472096&doi=10.1002%2f2017JD028196&partnerID=40&md5=bfe7e7c1a6122da8bc0f85aedfc0304c","Global clusters are derived by applying the self-organizing map technique to the Moderate Resolution Imaging Spectroradiometer cloud top pressure-cloud optical thickness joint histograms. These cloud clusters are then used to classify Cloud Feedback Model Intercomparison Project Observation Simulator Package output from the HadGEM3 (Global Atmosphere version 7) atmosphere-only climate model. Discrepancies in the Global Atmosphere version 7 representation of particular clusters can be established by examining the two sets of cluster's occurrence rate and radiative effect. The overall differences in the occurrence rates show major discrepancies in several of the clusters, resulting in a shift from five dominant clusters in Moderate Resolution Imaging Spectroradiometer (above 10% occurrence rate) to two dominant clusters in the model. A comparison of the geographic distributions of occurrence rate shows that the differences are strongly regional and unique to each cluster. While comparisons of the global mean longwave and shortwave cloud radiative effect (CRE) show strong agreement, examination of the CRE of individual cloud types reveals larger errors that highlight the role of compensating errors in masking model deficiencies. CRE data for each of the clusters is further partitioned into regions. This establishes that the bias associated with a cluster is highly variable globally, with no clusters showing consistent biases across all regions. Therefore, regional level phenomena likely play an important role in the creation of these errors. ©2018. American Geophysical Union. All Rights Reserved."
"56492516000;7006151875;","State-Dependence of the Climate Sensitivity in Earth System Models of Intermediate Complexity",2017,"10.1002/2017GL075457","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032278825&doi=10.1002%2f2017GL075457&partnerID=40&md5=23bf36b38cd73d14abccdffc86d54b5f","Growing evidence from general circulation models (GCMs) indicates that the equilibrium climate sensitivity (ECS) depends on the magnitude of forcing, which is commonly referred to as state-dependence. We present a comprehensive assessment of ECS state-dependence in Earth system models of intermediate complexity (EMICs) by analyzing millennial simulations with sustained 2×CO2 and 4×CO2 forcings. We compare different extrapolation methods and show that ECS is smaller in the higher-forcing scenario in 12 out of 15 EMICs, in contrast to the opposite behavior reported from GCMs. In one such EMIC, the Bern3D-LPX model, this state-dependence is mainly due to the weakening sea ice-albedo feedback in the Southern Ocean, which depends on model configuration. Due to ocean-mixing adjustments, state-dependence is only detected hundreds of years after the abrupt forcing, highlighting the need for long model integrations. Adjustments to feedback parametrizations of EMICs may be necessary if GCM intercomparisons confirm an opposite state-dependence. ©2017. The Authors."
"56031683500;12765822400;56111699000;7401672948;55419212600;","Quantifying snow albedo radiative forcing and its feedback during 2003-2016",2017,"10.3390/rs9090883","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029355024&doi=10.3390%2frs9090883&partnerID=40&md5=62bf6226e07991ca19c56b982c3ec3b0","Snow albedo feedback is one of the most crucial feedback processes that control equilibrium climate sensitivity, which is a central parameter for better prediction of future climate change. However, persistent large discrepancies and uncertainties are found in snow albedo feedback estimations. Remotely sensed snow cover products, atmospheric reanalysis data and radiative kernel data are used in this study to quantify snow albedo radiative forcing and its feedback on both hemispheric and global scales during 2003-2016. The strongest snow albedo radiative forcing is located north of 30 ° N, apart from Antarctica. In general, it has large monthly variation and peaks in spring. Snow albedo feedback is estimated to be 0.18-0.08 Wm-2°C-1 and 0.04-0.02Wm-2°C-1 on hemispheric and global scales, respectively. Compared to previous studies, this paper focuses specifically on quantifying snow albedo feedback and demonstrates three improvements: (1) used high spatial and temporal resolution satellite-based snow cover data to determine the areas of snow albedo radiative forcing and feedback; (2) provided detailed information for model parameterization by using the results from (1), together with accurate description of snow cover change and constrained snow albedo and snow-free albedo data; and (3) effectively reduced the uncertainty of snow albedo feedback and increased its confidence level through the block bootstrap test. Our results of snow albedo feedback agreed well with other partially observation-based studies and indicate that the 25 Coupled Model Intercomparison Project Phase 5 (CMIP5) models might have overestimated the snow albedo feedback, largely due to the overestimation of surface albedo change between snow-covered and snow-free surface in these models. © 2017 by the authors. Licensee MDPI, Basel, Switzerland."
"56940125000;7004299063;55207713000;56418532300;35096299800;","The G4Foam Experiment: Global climate impacts of regional ocean albedo modification",2017,"10.5194/acp-17-595-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85009454856&doi=10.5194%2facp-17-595-2017&partnerID=40&md5=ecdd63596a4bc8065813e853a2906b48","Reducing insolation has been proposed as a geoengineering response to global warming. Here we present the results of climate model simulations of a unique Geoengineering Model Intercomparison Project Testbed experiment to investigate the benefits and risks of a scheme that would brighten certain oceanic regions. The National Center for Atmospheric Research CESM CAM4-Chem global climate model was modified to simulate a scheme in which the albedo of the ocean surface is increased over the subtropical ocean gyres in the Southern Hemisphere. In theory, this could be accomplished using a stable, nondispersive foam, comprised of tiny, highly reflective microbubbles. Such a foam has been developed under idealized conditions, although deployment at a large scale is presently infeasible. We conducted three ensemble members of a simulation (G4Foam) from 2020 through to 2069 in which the albedo of the ocean surface is set to 0.15 (an increase of 150 %) over the three subtropical ocean gyres in the Southern Hemisphere, against a background of the RCP6.0 (representative concentration pathway resulting in +6 W mg-2 radiative forcing by 2100) scenario. After 2069, geoengineering is ceased, and the simulation is run for an additional 20 years. Global mean surface temperature in G4Foam is 0.6 K lower than RCP6.0, with statistically significant cooling relative to RCP6.0 south of 30° N. There is an increase in rainfall over land, most pronouncedly in the tropics during the June-July-August season, relative to both G4SSA (specified stratospheric aerosols) and RCP6.0. Heavily populated and highly cultivated regions throughout the tropics, including the Sahel, southern Asia, the Maritime Continent, Central America, and much of the Amazon experience a statistically significant increase in precipitation minus evaporation. The temperature response to the relatively modest global average forcing of g-1.5 W mg-2 is amplified through a series of positive cloud feedbacks, in which more shortwave radiation is reflected. The precipitation response is primarily the result of the intensification of the southern Hadley cell, as its mean position migrates northward and away from the Equator in response to the asymmetric cooling. © 2017 Author(s)."
"7005849273;","Quantification of temperature response to CO2 forcing in atmosphere–ocean general circulation models",2017,"10.1007/s10584-016-1832-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84994361361&doi=10.1007%2fs10584-016-1832-9&partnerID=40&md5=074d5991baba4e1f5fdb04ece8b0f627","The present study establishes a general formulation to represent the behavior and variation of an ensemble of complex climate models in terms of the global mean surface temperature response to atmospheric CO2 increase. The response parameters of this formulation provide a set of metrics that extends the conventional concept of climate sensitivity and quantifies transient temperature changes with sufficient simplicity and transparency to serve studies on climate change mitigation. Two commonly used metrics for transient and equilibrium climate sensitivity are analytically derived from the formulation, such that conventional estimates of equilibrium climate sensitivity based on standard numerical experiments for quadrupling CO2 increase are properly scaled down to the reference level of doubling CO2. The characteristics and variations of a specific ensemble of complex climate models can be simulated with a statistical model built using the principal components (PCs) of the response parameters. This approach is applied to the probabilistic assessment of temperature changes as well as to the diagnosis of the base ensemble. In current complex climate models, the ratio of transient-to-equilibrium sensitivity decreases with an increase of equilibrium sensitivity, as identified in variations associated with two specific PCs that characterize coherence between transient temperature response and properties of heat uptake by the ocean. © 2016, Springer Science+Business Media Dordrecht."
"56278161100;26324818700;","Isolating the temperature feedback loop and its effects on surface temperature",2016,"10.1175/JAS-D-15-0287.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84982262304&doi=10.1175%2fJAS-D-15-0287.1&partnerID=40&md5=cf73c1380721611284b50d8b4ee338b7","Climate feedback processes are known to substantially amplify the surface warming response to an increase of greenhouse gases. When the forcing and feedbacks modify the temperature response they trigger temperature feedback loops that amplify the direct temperature changes due to the forcing and nontemperature feedbacks through the thermal-radiative coupling between the atmosphere and surface. This study introduces a new feedback-response analysis method that can isolate and quantify the effects of the temperature feedback loops of individual processes on surface temperature from their corresponding direct surface temperature responses. The authors analyze a 1% yr-1 increase of CO2 simulation of the NCAR CCSM4 at the time of CO2 doubling to illustrate the new method. The Planck sensitivity parameter, which indicates colder regions experience stronger surface temperature responses given the same change in surface energy flux, is the inherent factor that leads to polar warming amplification (PWA). This effect explains the PWA in the Antarctic, while the direct temperature response to the albedo and cloud feedbacks further explains the greater PWA of the Arctic. Temperature feedback loops, particularly the one associated with the albedo feedback, further amplify the Arctic surface warming relative to the tropics. In the tropics, temperature feedback loops associated with the CO2 forcing and water vapor feedback cause most of the surface warming. Overall, the temperature feedback is responsible for most of the surface warming globally, accounting for nearly 76% of the global-mean surface warming. This is 3 times larger than the next largest warming contribution, indicating that the temperature feedback loop is the preeminent contributor to the surface warming. © 2016 American Meteorological Society."
"7202970886;6603631763;","Entering the era of 130-year satellite cloud climatologies: A North American case study",2014,"10.1175/JCLI-D-14-00068.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906871572&doi=10.1175%2fJCLI-D-14-00068.1&partnerID=40&md5=bf90c510747fd952039415f1c614b8ad","The emergence of satellite-based cloud records of climate length and quality hold tremendous potential for climate model development, climate monitoring, and studies on global water cycling and its subsequent energetics. This article examines the more than 30-yr Pathfinder Atmospheres-Extended (PATMOS-x) Advanced Very High Resolution Radiometer (AVHRR) cloudiness record over North America and assesses its suitability as a climate-quality data record. A loss of ̃4.2% total cloudiness is observed between 1982 and 2012 over a North American domain centered over the contiguous United States. While ENSO can explain some of the observed change, a weather state clustering analysis identifies shifts in weather patterns that result in loss of water cloud over the Great Lakes and cirrus over southern portions of the United States. The radiative properties of the shifting weather states are characterized, and the results suggest that extended cloud satellite records may prove useful tools for increasing knowledge of cloud feedbacks, a long-standing issue in the climate change community. © 2014 American Meteorological Society."
"55389942900;6701815637;","Changes in the cloud properties in response to El Niño: A bivariate approach",2013,"10.1007/s00382-012-1645-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878112547&doi=10.1007%2fs00382-012-1645-0&partnerID=40&md5=a513a2518589fe60f6bc4594c00221e7","We analyse the dependence of the cloud radiative effect (CRE) and cloud amount on mid-tropospheric pressure velocity (ω 500) and sea surface temperature (SST) and point out the shortcomings of using these two proxies separately as means to separate cloud regimes. A bivariate approach is proposed to overcome these shortcomings and it is used to systematically investigate marine cloud properties at different spatial and time scales in the present-day (1985-2001) tropical climate. During the 1997-1998 El Niño, the greatest regional change in CRE and cloud cover coincides with the greatest local change in circulation and SST. In addition, we find that the cooling effect of the stratiform low clouds reduces at the rate of approximately 1 W/m2 per percent of cloudiness reduction in the subsident cold pools of the Pacific ocean. During El Niño, the transition between different cloud regimes gives rise to opposing cloud feedbacks. The sign of the total feedback is controlled by the cloud optical thickness. More generally, we find that the largest part of the cloud response to El Niño, when averaged over the tropical Pacific, is not directly associated with ω 500 and SST changes, so other factors must play a role as well. © 2013 Springer-Verlag Berlin Heidelberg."
"7202299505;55241232500;7102202012;7005973015;56528677800;","Transient climate response in coupled atmospheric-ocean general circulation models",2013,"10.1175/JAS-D-12-0338.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877667483&doi=10.1175%2fJAS-D-12-0338.1&partnerID=40&md5=e28691a65a650829e5e2ffe45874562a","The equilibrium climate sensitivity (ECS) has a large uncertainty range among models participating in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) and has recently been presented as ""inherently unpredictable."" One way to circumvent this problem is to consider the transient climate response (TCR). However, the TCR among AR4 models also differs by more than a factor of 2. The authors argue that the situation may not necessarily be so pessimistic, because much of the intermodel difference may be due to the fact that the models were run with their oceans at various stages of flux adjustment with their atmosphere. This is shown by comparing multimillennium-long runs of the Goddard Institute for Space Studies model, version E, coupled with the Hybrid Coordinate Ocean Model (GISS-EH) and the Community Climate System Model, version 4 (CCSM4) with what were reported to AR4. The long model runs here reveal the range of variability (~30%) in their TCR within the same model with the same ECS. The commonly adopted remedy of subtracting the ""climate drift"" is ineffective and adds to the variability. The culprit is the natural variability of the control runs, which exists even at quasi equilibration. Fortunately, for simulations with multidecadal time horizon, robust solutions can be obtained by branching off thousand-year-long control runs that reach ""quasi equilibration"" using a new protocol, which takes advantage of the fact that forced solutions to radiative forcing forget their initial condition after 30-40 yr and instead depend mostly on the trajectory of the radiative forcing. © 2013 American Meteorological Society."
"57196752024;","On the determination of the global cloud feedback from satellite measurements",2012,"10.5194/esd-3-97-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870577111&doi=10.5194%2fesd-3-97-2012&partnerID=40&md5=988680b1d1abb722350d7ff87849b3f4","A detailed analysis is presented in order to determine the sensitivity of the estimated short-term cloud feedback to choices of temperature datasets, sources of top-ofatmosphere (TOA) clear-sky radiative flux data, and temporal averaging. It is shown that the results of a previous analysis, which suggested a likely positive value for the short-term cloud feedback, depended upon combining all-sky radiative fluxes from NASA's Clouds and Earth's Radiant Energy System (CERES) with reanalysis clear-sky forecast fluxes when determining the cloud radiative forcing (CRF). These results are contradicted when ACRF is derived using both all-sky and clear-sky measurements from CERES over the same period. The differences between the radiative flux data sources are thus explored, along with the potential problems in each. The largest discrepancy is found when including the first two years (2000-2002), and the diagnosed cloud feedback from each method is sensitive to the time period over which the regressions are run. Overall, there is little correlation between the changes in the ACRF and surface temperatures on these timescales, suggesting that the net effect of clouds varies during this time period quite apart from global temperature changes. Given the large uncertainties generated from this method, the limited data over this period are insufficient to rule out either the positive feedback present in most climate models or a strong negative cloud feedback. ©Author(s) 2012."
"55998327100;6507224579;7006184606;7004247643;","Correlation between present-day model simulation of Arctic cloud radiative forcing and sea ice consistent with positive winter convective cloud feedback",2012,"10.1029/2012MS000153","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867737015&doi=10.1029%2f2012MS000153&partnerID=40&md5=69b0a3cd2cd47eb9e9884bb96bf19055","A positive feedback on winter sea-ice loss, based on warming due to radiative forcing caused by the onset of convective clouds in response to sea-ice loss, has recently been proposed. This feedback has thus far been investigated using a hierarchy of climate models in high CO<inf>2</inf> scenarios. This paper examines the possibility that such feedback may be active within present-day like Arctic variability, using model output from two reanalysis models. It is emphasized that Arctic surface fluxes, radiative fluxes and clouds are effectively unconstrained by observations in reanalysis products. Consequently, the results here should be viewed only as a model study of the feedback in present-day model climate variability. Model winter sea ice and cloud radiative forcing are found to co-vary strongly and locally, consistent with a strong convective cloud feedback, which may contribute to sea ice variability. Furthermore, the anticorrelation between the two variables is found to be as strong in the model output analyzed here as in the IPCC global climate models that simulate the convective cloud feedback most strongly at high CO<inf>2</inf>. In those IPCC models the convective cloud feedback contributes to a total loss of winter sea ice in a CO<inf>2</inf> quadrupling scenario. These results do not necessarily prove that this feedback exists in the present-day Arctic and demonstrating this will require further study using actual Arctic observations. © 2012. American Geophysical Union."
"57212020923;57212020453;57212026611;57212024035;57212023802;","Preliminary Evaluation of Cloud Fraction Simulations by GAMIL2 Using COSP",2012,"10.1080/16742834.2012.11447002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876442798&doi=10.1080%2f16742834.2012.11447002&partnerID=40&md5=f7e32b5f68ae46b08f73c9af27b3c61d","The Cloud Feedback Model Intercomparisons Project (CFMIP) Observation Simulator Package (COSP) is adopted in the Grid-point Atmospheric Model of IAP LASG (GAMIL2) during CFMIP at Phase II to evaluate the model cloud fractions in a consistent way with satellite observations. The cloud simulation results embedded in the Atmospheric Model Intercomparison Project (AMIP) control experiment are presented using three satellite simulators: International Satellite Cloud Climatology Project (ISCCP), Moderate Resolution Imaging Spectroradiometer (MODIS), and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) lidar onboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). Overall, GAMIL2 can produce horizontal distributions of the low cloud fraction that are similar to the satellite observations, and its similarities to the observations on different levels are shown in Taylor diagrams. The discrepancies among satellite observations are also shown, which should be considered during evaluation. © 2012, © Institute of Atmospheric Physics, Chinese Academy of Sciences."
"36024555900;36127012800;7005523706;","Impact of sub-grid variability of precipitation and canopy water storage on hydrological processes in a coupled land - Atmosphere model",2009,"10.1007/s00382-008-0435-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60349101979&doi=10.1007%2fs00382-008-0435-1&partnerID=40&md5=b6ed6427179fd245bf5a7bd4bff2a928","The impact of sub-grid variability of precipitation and canopy water storage is investigated by applying a new canopy interception scheme into the Community Atmosphere Model version 3 (CAM3) coupled with the Community Land Model version 3 (CLM3). Including such sub-grid variability alters the partitioning of net radiation between sensible heat flux and latent heat flux on land surface, which leads to changes in precipitation through various pathways/mechanisms. The areas with most substantial changes are Amazonia and Central Africa where convective rain is dominant and vegetation is very dense. In these areas, precipitation during December - January - February is increased by up to 2 mm/day. This increase is due to the enhanced large-scale circulation and atmospheric instability caused by including the sub-grid variability. Cloud feedback plays an important role in modifying the large-scale circulation and atmospheric instability. Turning off cloud feedback mitigates the changes in surface convergence and boundary layer height caused by inclusion of sub-grid variability of precipitation and water storage canopy, which moderate the effect on precipitation. © Springer-Verlag 2008."
"7102731389;7403508241;7004325649;7407116104;7403282069;","Reply to comments on ""The Iris Hypothesis: A negative or positive cloud feedback?""",2002,"10.1175/1520-0442(2002)015<2716:r>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037106763&doi=10.1175%2f1520-0442%282002%29015%3c2716%3ar%3e2.0.co%3b2&partnerID=40&md5=920785573985d38be9261df0352741a3",[No abstract available]
"7005449794;35122577300;","The role of clouds in the surface energy balance over the Amazon forest",1998,"10.1002/(SICI)1097-0088(19981130)18:14<1575::AID-JOC316>3.0.CO;2-U","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032583288&doi=10.1002%2f%28SICI%291097-0088%2819981130%2918%3a14%3c1575%3a%3aAID-JOC316%3e3.0.CO%3b2-U&partnerID=40&md5=2de9ac36487b21a761a6918a446be171","Deforestation in the Amazon region will initially impact the energy balance at the land surface through changes in land cover and surface hydrology. However, continuation of this human activity will eventually lead to atmospheric feedbacks, including changes in cloudiness which may play an important role in the final equilibrium of solar and terrestrial radiation at the surface. In this study, the different components of surface radiation over an undisturbed forest in the Amazon region are computed using data from the Amazon region micrometerological experiment (ARME). Several measures of cloudiness are defined: two estimated from the terrestrial radiation measurements, and one from the solar radiation measurements. The sensitivity of the surface fluxes of solar and terrestrial radiation to natural variability in cloudiness is investigated to infer the potential role of the cloudiness feedback in the surface energy balance. The results of this analysis indicate that a 1% decrease in cloudiness would increase net solar radiation by ca. 1.6 W/m2. However, the overall magnitude of this feedback, due to total deforestation of the Amazon forest, is likely to be of the same order as the magnitude of the decrease in net solar radiation due to the observed increase in surface albedo following deforestation. Hence, the total change in net solar radiation is likely to have a negligible magnitude. In contrast to this conclusion, we find that terrestrial radiation is likely to be more strongly affected; reduced cloudiness will decrease net terrestrial radiation; a 1% decrease in cloudiness induces a reduction in net terrestrial radiation of ca. 0.7 W/m2; this process augments the similar effects of the predicted warming and drying in the boundary layer. Due to the cloudiness feedback, the most significant effect of large-scale deforestation on the surface energy balance is likely to be in the modification of the terrestrial radiation field rather than the classical albedo effect on solar radiation fields. The net effect of clouds is to reduce net radiation; a 1% increase in cloudiness induces a reduction in net radiation of ca. 1 W/m2. The implications of this negative feedback on large-scale land-atmosphere interactions over rainforests are discussed."
"6602178158;55885662200;7408519438;6603710604;36098422200;6603002398;","On the increased climate sensitivity in the EC-Earth model from CMIP5 to CMIP6",2020,"10.5194/gmd-13-3465-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089582341&doi=10.5194%2fgmd-13-3465-2020&partnerID=40&md5=4aee4b5434c505cfb111b9f7131c10ee","Many modelling groups that contribute to CMIP6 (Coupled Model Intercomparison Project Phase 6) have found a larger equilibrium climate sensitivity (ECS) with their latest model versions compared with the values obtained with the earlier versions used in CMIP5. This is also the case for the EC-Earth model. Therefore, in this study, we investigate what developments since the CMIP5 era could have caused the increase in the ECS in this model. Apart from increases in the horizontal and vertical resolution, the EC-Earth model has also substantially changed the representation of aerosols; in particular, it has introduced a more sophisticated description of aerosol indirect effects. After testing the model with some of the recent updates switched off, we find that the ECS increase can be attributed to the more advanced treatment of aerosols, with the largest contribution coming from the effect of aerosols on cloud microphysics (cloud lifetime or second indirect effect). The increase in climate sensitivity is unrelated to model tuning, as all experiments were performed with the same tuning parameters and only the representation of the aerosol effects was changed. These results cannot be generalised to other models, as their CMIP5 and CMIP6 versions may differ with respect to aspects other than the aerosol-cloud interaction, but the results highlight the strong sensitivity of ECS to the details of the aerosol forcing. © 2020 Copernicus GmbH. All rights reserved."
"7402989545;57215667319;36060938100;57131609600;7406250414;56424145700;15830929400;57216142129;57199888745;55220443400;57201697889;57218273453;55899884100;25823927100;57209611475;9845350200;36093295000;35115649600;55430046100;7403590757;7404815507;14059214300;57216240807;55745955800;","Development of Climate and Earth System Models in China: Past Achievements and New CMIP6 Results",2020,"10.1007/s13351-020-9164-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081552178&doi=10.1007%2fs13351-020-9164-0&partnerID=40&md5=ef2e424b3bf43141050112293eb0626c","The Earth-Climate System Model (ECSM) is an important platform for multi-disciplinary and multi-sphere integration research, and its development is at the frontier of international geosciences, especially in the field of global change. The research and development (R&D) of ECSM in China began in the 1980s and have achieved great progress. In China, ECSMs are now mainly developed at the Chinese Academy of Sciences, ministries, and universities. Following a brief review of the development history of Chinese ECSMs, this paper summarized the technical characteristics of nine Chinese ECSMs participating in the Coupled Model Intercomparison Project Phase 6 and preliminarily assessed the basic performances of four Chinese models in simulating the global climate and the climate in East Asia. The projected changes of global precipitation and surface air temperature and the associated relationship with the equilibrium climate sensitivity under four shared socioeconomic path scenarios were also discussed. Finally, combined with the international situation, from the perspective of further improvement, eight directions were proposed for the future development of Chinese ECSMs. © 2020, The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg."
"16644246500;","Self-Aggregation of Deep Convection and its Implications for Climate",2019,"10.1007/s40641-019-00120-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060695648&doi=10.1007%2fs40641-019-00120-3&partnerID=40&md5=a20cc50d867fcad0ffd5509247a9a4b8","Purpose of Review: This paper reviews the self-aggregation of deep convection, its impact on the large-scale environment, its dependence on surface temperature, and its implications for climate. Recent Findings: Self-aggregation generates significant humidity variability, dries the mean state, reduces high cloud cover, and increases the ability of the atmosphere to cool to space. Some studies find that convection is more self-aggregated at warmer temperatures but other studies, or other ways of measuring the degree of self-aggregation, disagree. There is not a simple, monotonic relationship between self-aggregation and surface temperature. Summary: Self-aggregation, through its effect on the humidity distribution and radiative budget, can affect climate. However, there is uncertainty over how strong the modulation of climate by self-aggregation is, in part because of the ambiguity over its temperature dependence. There are some indications that self-aggregation may modestly reduce climate sensitivity even without a dramatic temperature dependence, but more research is needed to understand this behavior. © 2019, Springer Nature Switzerland AG."
"57212781009;7101785401;","What can decadal variability tell us about climate feedbacks and sensitivity?",2018,"10.1007/s00382-018-4113-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042544228&doi=10.1007%2fs00382-018-4113-7&partnerID=40&md5=169a6ced24e2745f18c7e8ebdabd6c2a","Radiative feedbacks are known to determine climate sensitivity. Global top-of-atmosphere radiation correlations with surface temperature performed here show that decadal variability in surface temperature is also reinforced by strong positive feedbacks in models, both in the long wave (LW) and short wave (SW), offsetting much of the Planck radiative damping. Net top-of-atmosphere feedback is correlated with the magnitude of decadal temperature variability, particularly in the tropics. This indicates decadal-timescale radiative reinforcement of surface temperature variability. Assuming a simple global ocean mixed layer response, the reinforcement is found to be of a magnitude comparable to that required for typical decadal global scale anomalies. The magnitude of decadal variability in the tropics is uncorrelated with LW feedbacks, but it is correlated with total SW feedbacks, which are, in turn, correlated with tropical SW cloud feedback. Globally, water vapour/lapse rate, surface albedo and cloud feedbacks on decadal timescales are, on average, as strong as those operating under climate change. Together these results suggest that some of the physical processes responsible for setting the magnitude of global temperature change in the twenty-first century and climate sensitivity also help set the magnitude of the natural decadal variability. Furthermore, a statistically significant correlation exists between climate sensitivity and decadal variability in the tropics across CMIP5 models, although this is not apparent in the earlier generation of CMIP3 models. Thus although the link to sensitivity is not conclusive, this opens up potential paths to improve our understanding of climate feedbacks, climate sensitivity and decadal climate variability, and has the potential to reduce the associated uncertainty. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature."
"55686667100;36701462300;10241250100;55746365900;8067118800;","Low clouds link equilibrium climate sensitivity to hydrological sensitivity",2018,"10.1038/s41558-018-0272-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053659830&doi=10.1038%2fs41558-018-0272-0&partnerID=40&md5=3284d96ee0bbf7b63d50af389d983f5a","Equilibrium climate sensitivity (ECS) and hydrological sensitivity describe the global mean surface temperature and precipitation responses to a doubling of atmospheric CO2. Despite their connection via the Earth’s energy budget, the physical linkage between these two metrics remains controversial. Here, using a global climate model with a perturbed mean hydrological cycle, we show that ECS and hydrological sensitivity per unit warming are anti-correlated owing to the low-cloud response to surface warming. When the amount of low clouds decreases, ECS is enhanced through reductions in the reflection of shortwave radiation. In contrast, hydrological sensitivity is suppressed through weakening of atmospheric longwave cooling, necessitating weakened condensational heating by precipitation. These compensating cloud effects are also robustly found in a multi-model ensemble, and further constrained using satellite observations. Our estimates, combined with an existing constraint to clear-sky shortwave absorption, suggest that hydrological sensitivity could be lower by 30% than raw estimates from global climate models. © 2018, The Author(s), under exclusive licence to Springer Nature Limited."
"56230988400;6602364115;","Can We Use Single-Column Models for Understanding the Boundary Layer Cloud-Climate Feedback?",2018,"10.1002/2017MS001113","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041196991&doi=10.1002%2f2017MS001113&partnerID=40&md5=d602b85595fab0d7d00c7168f4f1c5b0","This study explores how to drive Single-Column Models (SCMs) with existing data sets of General Circulation Model (GCM) outputs, with the aim of studying the boundary layer cloud response to climate change in the marine subtropical trade wind regime. The EC-EARTH SCM is driven with the large-scale tendencies and boundary conditions as derived from two different data sets, consisting of high-frequency outputs of GCM simulations. SCM simulations are performed near Barbados Cloud Observatory in the dry season (January–April), when fair-weather cumulus is the dominant low-cloud regime. This climate regime is characterized by a near equilibrium in the free troposphere between the long-wave radiative cooling and the large-scale advection of warm air. In the SCM, this equilibrium is ensured by scaling the monthly mean dynamical tendency of temperature and humidity such that it balances that of the model physics in the free troposphere. In this setup, the high-frequency variability in the forcing is maintained, and the boundary layer physics acts freely. This technique yields representative cloud amount and structure in the SCM for the current climate. Furthermore, the cloud response to a sea surface warming of 4 K as produced by the SCM is consistent with that of the forcing GCM. © 2017. The Authors."
"57193321502;6603925960;57207507108;57193321831;6701705691;7003865921;56493740900;","The link between outgoing longwave radiation and the altitude at which a spaceborne lidar beam is fully attenuated",2017,"10.5194/amt-10-4659-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85037619961&doi=10.5194%2famt-10-4659-2017&partnerID=40&md5=49c11595dc830ea4a2e2e74b451031fb","According to climate model simulations, the changing altitude of middle and high clouds is the dominant contributor to the positive global mean longwave cloud feedback. Nevertheless, the mechanisms of this longwave cloud altitude feedback and its magnitude have not yet been verified by observations. Accurate, stable, and long-term observations of a metric-characterizing cloud vertical distribution that are related to the longwave cloud radiative effect are needed to achieve a better understanding of the mechanism of longwave cloud altitude feedback. This study shows that the direct measurement of the altitude of atmospheric lidar opacity is a good candidate for the necessary observational metric. The opacity altitude is the level at which a spaceborne lidar beam is fully attenuated when probing an opaque cloud. By combining this altitude with the direct lidar measurement of the cloud-top altitude, we derive the effective radiative temperature of opaque clouds which linearly drives (as we will show) the outgoing longwave radiation. We find that, for an opaque cloud, a cloud temperature change of 1 K modifies its cloud radiative effect by 2 W m-2. Similarly, the longwave cloud radiative effect of optically thin clouds can be derived from their top and base altitudes and an estimate of their emissivity. We show with radiative transfer simulations that these relationships hold true at single atmospheric column scale, on the scale of the Clouds and the Earth's Radiant Energy System (CERES) instantaneous footprint, and at monthly mean 2° × 2° scale. Opaque clouds cover 35 % of the ice-free ocean and contribute to 73 % of the global mean cloud radiative effect. Thin-cloud coverage is 36 % and contributes 27 % of the global mean cloud radiative effect. The link between outgoing longwave radiation and the altitude at which a spaceborne lidar beam is fully attenuated provides a simple formulation of the cloud radiative effect in the longwave domain and so helps us to understand the longwave cloud altitude feedback mechanism."
"12040335900;25723417400;7402085600;7006614696;57194553129;55890394800;55814053500;","Revisiting the iris effect of tropical cirrus clouds with trmm and a-train satellite data",2017,"10.1002/2016JD025827","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020785188&doi=10.1002%2f2016JD025827&partnerID=40&md5=5112221dc3ce3ea33d483449bd8a58b3","Just as the iris of human eye controls the light influx (iris effect), tropical anvil cirrus clouds may regulate the Earth’s surface warming by controlling outgoing longwave radiation. This study examines this possible effect with monthly satellite observations such as Tropical Rainfall Measuring Mission (TRMM) precipitation, Moderate Resolution Imaging Spectroradiometer cirrus fraction, and Clouds and the Earth’s Radiant Energy System top-of-the-atmosphere radiative fluxes averaged over different tropical domains from March 2000 to October 2014. To confirm that high-level cirrus is relevant to this study, Cloud-Aerosol Lidar with Orthogonal Polarization high cloud observations were also analyzed from June 2006 to December 2015. Our analysis revealed that the increase in sea surface temperature in the tropical western Pacific tends to concentrate convective cloud systems. This concentration effect very likely induces the significant reduction of both stratiform rain rate and cirrus fraction, without appreciable change in the convective rain rate. This reduction of stratiform rain rate and cirrus fraction cannot be found over its subregion or the tropical eastern Pacific, where the concentration effect of anvil cirrus is weak. Consistently, over the tropical western Pacific, the higher ratio of convective rain rate to total rain rate (i.e., precipitation efficiency) significantly correlates with warmer sea surface temperature and lower cirrus fraction. The reduced cirrus eventually increased outgoing longwave radiation to a greater degree than absorbed solar radiation. Finally, the negative relationship between precipitation efficiency and cirrus fraction tends to correspond to a low global equilibrium climate sensitivity in the models in the Coupled Model Intercomparison Project Phase 5. This suggests that tropical anvil cirrus clouds exert a negative climate feedback in strong association with precipitation efficiency. © 2017. American Geophysical Union. All Rights Reserved."
"37027011900;6603925960;7102410621;57207507108;30667558200;35203328900;6507495053;8669401600;","An EarthCARE/ATLID simulator to evaluate cloud description in climate models",2015,"10.1002/2015JD023919","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84956775517&doi=10.1002%2f2015JD023919&partnerID=40&md5=d3b11c64643a9d276ee42fe3b14c8b71","Clouds still remain the largest source of uncertainty in model-based predictions of future climate; thus, the description of the clouds in climate models needs to be evaluated. In particular, the cloud detailed vertical distribution that impacts directly the cloud radiative effect needs to be evaluated. Active satellite sensors directly measure the cloud vertical distribution with high accuracy; their observations should be used for model evaluation together with a satellite simulator in order to allow fair comparison between models and observations. The next cloud lidar in space, EarthCARE/ATmospheric LIDar (ATLID), is planned for launch in 2018, while the current spaceborne cloud lidar CALIPSO/CALIOP is expected to stop collecting data within the next coming years. Here we describe the characteristics of the ATLID on board the EarthCARE satellite (spatial resolution, signal-to-noise ratio, wavelength, field of view, pulse repetition frequency, orbit, and high-spectral resolution lidar) that need to be taken into account to build a Cloud Feedback Model Intercomparison Project Observation Simulator Package (COSP)/ATLID simulator. We then present the COSP/ATLID simulator, and the low-, middle-, high-level cloud covers it produces, as well as the zonal mean cloud fraction profiles and the height-intensity histograms that are simulated by COSP/ATLID when overflying an atmosphere predicted by LMDZ5 global circulation model. Finally, we compare the clouds simulated by COSP/ATLID with those simulated by COSP/CALIPSO when overflying the same atmosphere. As the main differences between ATLID and CALIOP are taken into account in the simulators, the differences between COSP/ATLID and COSP/CALIPSO cloud covers are less than 1% in nighttime conditions Key Point EarthCARE simulator to evaluate cloud in climate models. © 2015. American Geophysical Union. All Rights Reserved."
"54585176800;7004978125;7801642934;","Cloud-radiation feedback and atmosphere-ocean coupling in a stochastic multicloud model",2015,"10.1016/j.dynatmoce.2015.05.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84931263082&doi=10.1016%2fj.dynatmoce.2015.05.003&partnerID=40&md5=07302337a5612e5f223ca1182b04767c","Despite recent advances in supercomputing, current general circulation models (GCMs) have significant problems in representing the variability associated with organized tropical convection. Furthermore, due to high sensitivity of the simulations to the cloud radiation feedback, the tropical convection remains a major source of uncertainty in long-term weather and climate forecasts. In a series of recent studies, it has been shown, in paradigm two-baroclinic-mode systems and in aquaplanet GCMs, that a stochastic multicloud convective parameterization based on three cloud types (congestus, deep and stratiform) can be used to improve the variability and the dynamical structure of tropical convection, including intermittent coherent structures such as synoptic and mesoscale convective systems. Here, the stochastic multicloud model is modified with a parameterized cloud radiation feedback mechanism and atmosphere-ocean coupling. The radiative convective feedback mechanism is shown to increase the mean and variability of the Walker circulation. The corresponding intensification of the circulation is associated with propagating synoptic scale systems originating inside of the enhanced sea surface temperature area. In column simulations, the atmosphere ocean coupling introduces pronounced low frequency convective features on the time scale associated with the depth of the mixed ocean layer. However, in the presence of the gravity wave mixing of spatially extended simulations, these features are not as prominent. This highlights the deficiency of the column model approach at predicting the behavior of multiscale spatially extended systems. Overall, the study develops a systematic framework for incorporating parameterized radiative cloud feedback and ocean coupling which may be used to improve representation of intraseasonal and seasonal variability in GCMs. © 2015 Elsevier B.V."
"9635764200;","Cloud responses in the AMIP simulations of CMIP5 models in the southeastern Pacific marine subsidence region",2015,"10.1002/joc.4181","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938854585&doi=10.1002%2fjoc.4181&partnerID=40&md5=79fed06511b2d3f81cf183a02e4d2bc6","The sensitivity of regimes dominated by low clouds has been identified as the largest contributor to uncertainties in tropical cloud feedback estimates in climate models. The Atmospheric Model Intercomparison Project simulations of the low cloud response to sea surface temperature (SST) are compared with satellite observations in the southeastern Pacific subsidence region. The model ensemble annual average cloud fraction is only about 10% lower than Moderate Resolution Imaging Spectroradiometer observations; however, many models compensate by overestimating the cloud liquid water path (LWP), especially in areas typically associated with shallow cumulus. Analysis of the monthly distribution also shows that models have considerable difficulty in simulating the annual cycle in the cloud radiative effect (CRE), cloud fraction, and LWP likely due in part to underestimation of the strength of lower tropospheric stability and the depth of the boundary layer. The interannual sensitivity of CRE to SST agrees with observations in about half of the models, with the other half generally underestimating the cloud radiative forcing sensitivity. Model-observational differences are driven by the varying interannual responses in cloud fraction and LWP. Most models, including those that capture the mean interannual sensitivity of CRE to SST, have lower sensitivity in cloud fraction that is compensated by oversensitivity in the cloud LWP, especially in areas of more frequent shallow cumulus. Results presented here also highlight the possibility of using the vertical gradient of moist static energy (MSE) to test the fidelity of a model's representation of clouds and cloud sensitivity. Models that reproduce the observed distribution of cloud fraction with the lower tropospheric MSE gradient not only show better regional distribution and annual cycle in clouds and radiative forcing, but also demonstrate cloud and radiative sensitivities to SST that are more well correlated with the observed cloud sensitivities. © 2015 Royal Meteorological Society."
"9246029600;15026371500;7004647146;","The influence of regional feedbacks on circulation sensitivity",2014,"10.1002/2014GL059336","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896551772&doi=10.1002%2f2014GL059336&partnerID=40&md5=ca26da995697862b06626fe7a6871e87","Weakening of the tropical overturning circulation in a warmer world is a robust feature in climate models. Here an idealized representation of ocean heat flux drives a Walker cell in an aquaplanet simulation. A goal of the study is to assess the influence of the Walker circulation on the magnitude and structure of climate feedbacks, as well as to global sensitivity. We compare two CO 2 perturbation experiments, one with and one without a Walker circulation, to isolate the differences attributable to tropical circulation and associated zonal asymmetries. For an imposed Walker circulation, the subtropical shortwave cloud feedback is reduced, which manifests as a weaker tropical-subtropical anomalous energy gradient and consequently a weaker slow down of the Hadley circulation, relative to the case without a Walker circulation. By focusing on the coupled feedback circulation system, these results offer insights into understanding changes in atmospheric circulation and hence the hydrological cycle under global warming. © 2014. American Geophysical Union. All Rights Reserved."
"16246205000;55738957800;26324818700;","Characterizing the climate feedback pattern in the NCAR CCSM3-SOM using hourly data",2014,"10.1175/JCLI-D-13-00567.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898026917&doi=10.1175%2fJCLI-D-13-00567.1&partnerID=40&md5=8e2349233ed35cb19b864425f56685de","The climate feedback-response analysis method (CFRAM) was applied to 10-yr hourly output of the NCAR Community Climate System Model, version 3, using the slab ocean model (CCSM3-SOM), to analyze the strength and spatial distribution of climate feedbacks and to characterize their contributions to the global and regional surface temperature Ts changes in response to a doubling of CO2. The global mean bias in the sum of partial Ts changes associated with the CO2 forcing, and each feedback derived with the CFRAM analysis is about 2% of Ts change obtained directly from the CCSM3-SOM simulations. The pattern correlation between the two is 0.94, indicating that the CFRAManalysis using hourlymodel output is accurate and thus is appropriate for quantifying the contributions of climate feedback to the formation of global and regional warming patterns. For global mean Ts, the largest contributor to the warming is water vapor feedback, followed by the direct CO2 forcing and albedo feedback. The albedo feedback exhibits the largest spatial variation, followed by shortwave cloud feedback. In terms of pattern correlation and RMS difference with the modeled global surface warming, longwave cloud feedback contributes the most. On zonal average, albedo feedback is the largest contributor to the stronger warming in high latitudes than in the tropics. The longwave cloud feedback further amplifies the latitudinal warming contrast. Both the land-ocean warming difference and contributions of climate feedbacks to it vary with latitude. Equatorward of 50°, shortwave cloud feedback and dynamical advection are the two largest contributors. The land-ocean warming difference on the hemispheric scale is mainly attributable to longwave cloud feedback and convection. © 2014 American Meteorological Society."
"12769875100;","The Role of Clouds: An Introduction and Rapporteur Report",2012,"10.1007/s10712-012-9182-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862668973&doi=10.1007%2fs10712-012-9182-2&partnerID=40&md5=124ff0d440120d2c7c758b9e3beed101","This paper presents an overview of discussions during the Cloud's Role session at the Observing and Modelling Earth's Energy FlowsWorkshop. N. Loeb and B. Soden convened this session including 10 presentations by B. Stevens, B. Wielicki, G. Stephens, A. Clement, K. Sassen, D. Hartmann, T. Andrews, A. Del Genio, H. Barker, and M. Sugi addressing critical aspects of the role of clouds in modulating Earth energy flows. Presentation topics covered a diverse range of areas from cloud microphysics and dynamics, cloud radiative transfer, and the role of clouds in large-scale atmospheric circulations patterns in both observations and atmospheric models. The presentations and discussions, summarized below, are organized around several key questions raised during the session. (1) What is the best way to evaluate clouds in climate models? (2) How well do models need to represent clouds to be acceptable for making climate predictions? (3) What are the largest uncertainties in clouds? (4) How can these uncertainties be reduced? (5) What new observations are needed to address these problems? Answers to these critical questions are the topics of ongoing research and will guide the future direction of this area of research. © 2012 The Author(s)."
"25226945400;56014511300;","Erroneous relationships among humidity and cloud forcing variables in three global climate models",2008,"10.1175/2008JCLI1969.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53649107313&doi=10.1175%2f2008JCLI1969.1&partnerID=40&md5=5b79563aa6f2ccf0b5366913aa855c3f","Links are examined between time-averaged cloud radiative properties, particularly the longwave and shortwave components of cloud radiative forcing (CRF), and properties of the long-term averages of atmospheric soundings, in particular upper-tropospheric humidity (UTH), lower-tropospheric precipitable water (PW), and static stability (SS). The joint distributions of moisture measures and the composite or conditional mean CRF for different moisture and stability combinations are computed. This expands on previous studies that have examined cloud properties versus vertical velocity and surface temperature. These computations are done for satellite observations and for three representative coupled climate models from major modeling centers. Aside from mean biases reported previously, several departures are identified between the modeled and observed joint distributions that are qualitative and significant. Namely, the joint distribution of PW and UTH is very compact in observations but less so in models, cloud forcings are tightly related to PW in the data but to UTH in the models, and strong negative net CRF in marine stratocumulus regions occurs only for high SS and low UTH in the data but violates one or both of these restrictions in each of the models. All three errors are preliminarily interpreted as symptoms of inadequate dependence of model convective development on ambient humidity above the boundary layer. In any case, the character of the errors suggests utility for model testing and future development. A set of scalar metrics for quantifying some of the problems is presented; these metrics can be easily applied to standard model output. Finally, an examination of doubled-CO2 simulations suggests that the errors noted here are significantly affecting cloud feedback in at least some models. For example, in one model a strong negative feedback is found from clouds forming in model conditions that never occur in the observations. © 2008 American Meteorological Society."
"55686667100;","Two regimes of the equatorial warm pool. Part II: Hybrid coupled GCM experiments",2008,"10.1175/2007JCLI2152.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53649107310&doi=10.1175%2f2007JCLI2152.1&partnerID=40&md5=ac4a9f06f14a45382abe18f9a08c2c21","In this second of a two-part study, the two regimes in a simple tropical climate model identified in Part I are verified using a hybrid coupled general circulation model (HCM) that can reproduce the observed climatology and the interannual variability reasonably well. Defining a ratio of basin width between the Pacific and Indian Oceans, a series of parameter sweep experiments was conducted with idealized tropical land geometry. Consistent with the simple model, the HCM simulates two distinct states: the split warm pool regime with large vacillation between the two ocean basins and the single warm pool regime representing current climate. The former is suddenly switched to the latter as the Pacific becomes wider than the Indian Ocean. Furthermore, the vacillation in the split regime reveals a preferred transition route that the warm phase in the Pacific follows that in the Indian Ocean. This route occurs due to convectively coupled Kelvin waves that accompany precipitation anomalies over land. Additional experiments show that the inclusion of the idealized Eurasian continent stabilizes the split regime by reducing the Bjerknes feedback in the Indian Ocean, suggesting the atmosphere-ocean-land interaction at work in maintaining the observed warm pool. No difference in cloud feedback was found between two regimes; this feature may, however, be model dependent. Both the simple model and the HCM results suggest that the tropical atmosphere-ocean system inherently involves multiple solutions, which may have an implication on climate modeling as well as on the understanding of the observed mean climate. © 2008 American Meteorological Society."
"57195549023;","Gravity waves and convection cells resulting from feedback heating of Venus' lower clouds",2003,"10.2151/jmsj.81.885","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0344466446&doi=10.2151%2fjmsj.81.885&partnerID=40&md5=d420c47397f8e6b4b40bd68f2b0ec82b","A radiative-dynamical cloud feedback heating (CFH) is incorporated into a two-dimensional mechanistic model in an equatorial longitude-height plane of Venus. For a typical basic field, the CFH triggered by random disturbance results in the formation of convection cells with various scales in the low-stability layer (∼ 55 km) sandwiched between stable layers, and the convection cells generate vertically propagating gravity waves. The wave-generation mechanism by convection cells resulting from CFH is different from previous mechanisms, in which waves were directly forced by CFH. If the cloud feedback process works in real atmosphere, the convection resulting from the perturbed CFH should be considered as a possible formation mechanism of gravity waves in Venus' cloud layer."
"7003869084;7004604556;","Cloud feedback examined using a two-component time-dependent climate model",1995,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028806844&partnerID=40&md5=e6a49b391351edfe70e0651c06021815","A zero-dimensional, time-dependent, two-component atmosphere-ocean climate model shows that water vapor and snow-ice albedo feedbacks may lead to multiple stable equilibria. A sensitivity study shows that depending on the rate of change of cloud infrared emissivity and cloud albedo with temperature, several regimes with differing stability characteristics may be identified. In the model, the cloud water content and cloud altitude feedbacks, coupled with enhanced greenhouse longwave forcing, lead to the formation of a new warm stable equilibrium. In a time-dependent simulation with a single layer ocean, the global mean surface temperature rises gradually, then rapidly, finally reaching a value approximately 14 K warmer than at present, when an enhanced greenhouse flux of 4 Wm-2 is added. -Authors"
"7005793728;7003991093;","An energy balance climate model with cloud feedbacks.",1984,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021598285&partnerID=40&md5=5e2dddec13c7049a06908d650f43024a","A simple two-level global climate model based on the energy balance of the atmosphere and surface is described. Several model integrations are described. It is found that cloudiness is generally constant with changing temperature in low latitudes. In high latitudes cloudiness increases with increasing temperature but because of compensating effects on the thermal and solar radiation, the cloud feedback effect on the radiation field is small. The net global feedback by the cloud field is negative but small.-from Authors"
"7403577184;7409376438;7401701196;7202772927;7003397919;6701845806;","Impact of radiation frequency, precipitation radiative forcing, and radiation column aggregation on convection-permitting West African monsoon simulations",2020,"10.1007/s00382-018-4187-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044472381&doi=10.1007%2fs00382-018-4187-2&partnerID=40&md5=6bc073dbd34ad85f357acbd567b39a04","In this study, the impact of different configurations of the Goddard radiation scheme on convection-permitting simulations (CPSs) of the West African monsoon (WAM) is investigated using the NASA-Unified WRF (NU-WRF). These CPSs had 3 km grid spacing to explicitly simulate the evolution of mesoscale convective systems (MCSs) and their interaction with radiative processes across the WAM domain and were able to reproduce realistic precipitation and energy budget fields when compared with satellite data, although low clouds were overestimated. Sensitivity experiments reveal that (1) lowering the radiation update frequency (i.e., longer radiation update time) increases precipitation and cloudiness over the WAM region by enhancing the monsoon circulation, (2) deactivation of precipitation radiative forcing suppresses cloudiness over the WAM region, and (3) aggregating radiation columns reduces low clouds over ocean and tropical West Africa. The changes in radiation configuration immediately modulate the radiative heating and low clouds over ocean. On the 2nd day of the simulations, patterns of latitudinal air temperature profiles were already similar to the patterns of monthly composites for all radiation sensitivity experiments. Low cloud maintenance within the WAM system is tightly connected with radiation processes; thus, proper coupling between microphysics and radiation processes must be established for each modeling framework. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature."
"7003707266;25030776200;8606857600;35502560300;55568513229;7003681353;7103033688;","The global and regional impacts of climate change under representative concentration pathway forcings and shared socioeconomic pathway socioeconomic scenarios",2019,"10.1088/1748-9326/ab35a6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85072730726&doi=10.1088%2f1748-9326%2fab35a6&partnerID=40&md5=f0e725d6b950458670f1b044230be057","This paper presents an evaluation of the global and regional consequences of climate change for heat extremes, water resources, river and coastal flooding, droughts, agriculture and energy use. It presents change in hazard and resource base under different rates of climate change (representative concentration pathways (RCP)), and socio-economic impacts are estimated for each combination of RCP and shared socioeconomic pathway. Uncertainty in the regional pattern of climate change is characterised by CMIP5 climate model projections. The analysis adopts a novel approach using relationships between level of warming and impact to rapidly estimate impacts under any climate forcing. The projections provided here can be used to inform assessments of the implications of climate change. At the global scale all the consequences of climate change considered here are adverse, with large increases under the highest rates of warming. Under the highest forcing the global average annual chance of a major heatwave increases from 5% now to 97% in 2100, the average proportion of time in drought increases from 7% to 27%, and the average chance of the current 50 year flood increases from 2% to 7%. The socio-economic impacts of these climate changes are determined by socio-economic scenario. There is variability in impact across regions, reflecting variability in projected changes in precipitation and temperature. The range in the estimated impacts can be large, due to uncertainty in future emissions and future socio-economic conditions and scientific uncertainty in how climate changes in response to future emissions. For the temperature-based indicators, the largest source of scientific uncertainty is in the estimated magnitude of equilibrium climate sensitivity, but for the indicators determined by precipitation the largest source is in the estimated spatial and seasonal pattern of changes in precipitation. By 2100, the range across socio-economic scenario is often greater than the range across the forcing levels. © 2019 The Author(s). Published by IOP Publishing Ltd."
"23492864500;6603566335;","Boundary Layer Clouds and Convection over Subtropical Oceans in our Current and in a Warmer Climate",2019,"10.1007/s40641-019-00126-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065421570&doi=10.1007%2fs40641-019-00126-x&partnerID=40&md5=6c07875bf284617d00ac375bbd5cffce","Purpose of Review: We review our understanding of mechanisms underlying the response of (sub)tropical clouds to global warming, highlight mechanisms that challenge our understanding, and discuss simulation strategies that tackle them. Recent Findings: Turbulence-resolving models and emergent constraints provide probable evidence, supported by theoretical understanding, that the cooling cloud radiative effect (CRE) of low clouds weakens with warming: a positive low-cloud feedback. Nevertheless, an uncertainty in the feedback remains. Climate models may not adequately represent changing SST and circulation patterns, which determine future cloud-controlling factors and how these couple to clouds. Furthermore, we do not understand what mesoscale organization implies for the CRE, and how moisture-radiation interactions, horizontal advection, and the profile of wind regulate low cloud, in our current and in our warmer climate. Summary: Clouds in nature are more complex than the idealized cloud types that have informed our understanding of the cloud feedback. Remaining major uncertainties are the coupling of clouds to large-scale circulations and to the ocean, and mesoscale aggregation of clouds. © 2019, The Author(s)."
"57131609600;55913183200;7402989545;55899884100;36093295000;36648197400;25226875800;24382049500;","Climate Sensitivity and Feedbacks of a New Coupled Model CAMS-CSM to Idealized CO 2 Forcing: A Comparison with CMIP5 Models",2019,"10.1007/s13351-019-8074-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061185748&doi=10.1007%2fs13351-019-8074-5&partnerID=40&md5=9179b3b2adc57ffa49cb89ecdcf3b891","Climate sensitivity and feedbacks are basic and important metrics to a climate system. They determine how large surface air temperature will increase under CO 2 forcing ultimately, which is essential for carbon reduction policies to achieve a specific warming target. In this study, these metrics are analyzed in a climate system model newly developed by the Chinese Academy of Meteorological Sciences (CAMS-CSM) and compared with multi-model results from the Coupled Model Comparison Project phase 5 (CMIP5). Based on two idealized CO 2 forcing scenarios, i.e., abruptly quadrupled CO 2 and CO 2 increasing 1% per year, the equilibrium climate sensitivity (ECS) and transient climate response (TCR) in CAMS-CSM are estimated to be about 2.27 and 1.88 K, respectively. The ECS is near the lower bound of CMIP5 models whereas the TCR is closer to the multi-model ensemble mean (MME) of CMIP5 due to compensation of a relatively low ocean heat uptake (OHU) efficiency. The low ECS is caused by an unusually negative climate feedback in CAMS-CSM, which is attributed to cloud shortwave feedback (λ SWCL ) over the tropical Indo-Pacific Ocean. The CMIP5 ensemble shows that more negative λ SWCL is related to larger increase in low-level (925–700 hPa) cloud over the tropical Indo-Pacific under warming, which can explain about 90% of λ SWCL in CAMS-CSM. Static stability of planetary boundary layer in the pre-industrial simulation is a critical factor controlling the low-cloud response and λ SWCL across the CMIP5 models and CAMS-CSM. Evidently, weak stability in CAMS-CSM favors lowcloud formation under warming due to increased low-level convergence and relative humidity, with the help of enhanced evaporation from the warming tropical Pacific. Consequently, cloud liquid water increases, amplifying cloud albedo, and eventually contributing to the unusually negative λ SWCL and low ECS in CAMS-CSM. Moreover, the OHU may influence climate feedbacks and then the ECS by modulating regional sea surface temperature responses. © 2019, The Chinese Meteorological Society and Springer-Verlag GmbH Germany, part of Springer Nature."
"23009736100;6508048114;57204687415;7004270629;6602867359;","Emergent scale invariance and climate sensitivity",2018,"10.3390/cli6040093","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059380198&doi=10.3390%2fcli6040093&partnerID=40&md5=731dea6e331cc06ca22c666660a9f8b0","Earth's global surface temperature shows variability on an extended range of temporal scales and satisfies an emergent scaling symmetry. Recent studies indicate that scale invariance is not only a feature of the observed temperature fluctuations, but an inherent property of the temperature response to radiative forcing, and a principle that links the fast and slow climate responses. It provides a bridge between the decadal- and centennial-scale fluctuations in the instrumental temperature record, and the millennial-scale equilibration following perturbations in the radiative balance. In particular, the emergent scale invariance makes it possible to infer equilibrium climate sensitivity (ECS) from the observed relation between radiative forcing and global temperature in the instrumental era. This is verified in ensembles of Earth system models (ESMs), where the inferred values of ECS correlate strongly to estimates from idealized model runs. For the range of forcing data explored in this paper, the method gives best estimates of ECS between 1.8 and 3.7 K, but statistical uncertainties in the best estimates themselves will provide a wider likely range of the ECS. © 2018 by the authors."
"55558809100;54400559100;6603400519;55688930000;57207228835;7006705919;","Climatic Responses to Future Trans-Arctic Shipping",2018,"10.1029/2018GL078969","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054074555&doi=10.1029%2f2018GL078969&partnerID=40&md5=19567c8436518e6669763fcd177b4626","As global temperatures increase, sea ice loss will increasingly enable commercial shipping traffic to cross the Arctic Ocean, where the ships' gas and particulate emissions may have strong regional effects. Here we investigate impacts of shipping emissions on Arctic climate using a fully coupled Earth system model (CESM 1.2.2) and a suite of newly developed projections of 21st-century trans-Arctic shipping emissions. We find that trans-Arctic shipping will reduce Arctic warming by nearly 1 °C by 2099, due to sulfate-driven liquid water cloud formation. Cloud fraction and liquid water path exhibit significant positive trends, cooling the lower atmosphere and surface. Positive feedbacks from sea ice growth-induced albedo increases and decreased downwelling longwave radiation due to reduced water vapor content amplify the cooling relative to the shipping-free Arctic. Our findings thus point to the complexity in Arctic climate responses to increased shipping traffic, justifying further study and policy considerations as trade routes open. ©2018. The Authors."
"55669579000;57196143493;","The Radiative Feedback During the ENSO Cycle: Observations Versus Models",2018,"10.1029/2018JD028401","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052852973&doi=10.1029%2f2018JD028401&partnerID=40&md5=90d52d29895306c9eb95f08b9e8be85d","Observational and model data are used to study the radiative feedbacks during the El Niño–Southern Oscillation (ENSO) cycle. We extend the previous works by analyzing the feedbacks with respect to not only top-of-atmosphere (TOA) but also the surface and atmospheric radiation budgets, using a newly developed set of radiation kernels. We find that the tropical radiative budgets undergo distinctive variations during ENSO. The radiative perturbation is especially significant for the atmospheric energy budget. We find that the cloud feedback during the developing phase of ENSO heats the atmosphere over the west and central Pacific differentially, which acts to strengthen the development. We also find that a prominent cloud feedback bias persists in the newer version global climate models. This bias results from wrong extent of compensation between longwave and shortwave effects, which points to the importance of validating the radiative sensitivity of clouds in the general circulation models. ©2018. American Geophysical Union. All Rights Reserved."
"57191343618;56250119900;23479549200;","An energy balance model exploration of the impacts of interactions between surface albedo, cloud cover and water vapor on polar amplification",2018,"10.1007/s00382-017-3974-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85033463505&doi=10.1007%2fs00382-017-3974-5&partnerID=40&md5=5bd7bbf29657f8a5049e67184b723469","We examine the effects of non-linear interactions between surface albedo, water vapor and cloud cover (referred to as climate variables) on amplified warming of the polar regions, using a new energy balance model. Our simulations show that the sum of the contributions to surface temperature changes due to any variable considered in isolation is smaller than the temperature changes from coupled feedback simulations. This non-linearity is strongest when all three climate variables are allowed to interact. Surface albedo appears to be the strongest driver of this non-linear behavior, followed by water vapor and clouds. This is because increases in longwave radiation absorbed by the surface, related to increases in water vapor and clouds, and increases in surface absorbed shortwave radiation caused by a decrease in surface albedo, amplify each other. Furthermore, our results corroborate previous findings that while increases in cloud cover and water vapor, along with the greenhouse effect itself, warm the polar regions, water vapor also significantly warms equatorial regions, which reduces polar amplification. Changes in surface albedo drive large changes in absorption of incoming shortwave radiation, thereby enhancing surface warming. Unlike high latitudes, surface albedo change at low latitudes are more constrained. Interactions between surface albedo, water vapor and clouds drive larger increases in temperatures in the polar regions compared to low latitudes. This is in spite of the fact that, due to a forcing, cloud cover increases at high latitudes and decreases in low latitudes, and that water vapor significantly enhances warming at low latitudes. © 2017, Springer-Verlag GmbH Germany."
"24081888700;6603081424;57208765879;7401793588;","Observations of Local Positive Low Cloud Feedback Patterns and Their Role in Internal Variability and Climate Sensitivity",2018,"10.1029/2018GL077904","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046655987&doi=10.1029%2f2018GL077904&partnerID=40&md5=5d4acd1b048755a06e6a61dce3438bdb","Modeling studies have shown that cloud feedbacks are sensitive to the spatial pattern of sea surface temperature (SST) anomalies, while cloud feedbacks themselves strongly influence the magnitude of SST anomalies. Observational counterparts to such patterned interactions are still needed. Here we show that distinct large-scale patterns of SST and low-cloud cover (LCC) emerge naturally from objective analyses of observations and demonstrate their close coupling in a positive local SST-LCC feedback loop that may be important for both internal variability and climate change. The two patterns that explain the maximum amount of covariance between SST and LCC correspond to the Interdecadal Pacific Oscillation and the Atlantic Multidecadal Oscillation, leading modes of multidecadal internal variability. Spatial patterns and time series of SST and LCC anomalies associated with both modes point to a strong positive local SST-LCC feedback. In many current climate models, our analyses suggest that SST-LCC feedback strength is too weak compared to observations. Modeled local SST-LCC feedback strength affects simulated internal variability so that stronger feedback produces more intense and more realistic patterns of internal variability. To the extent that the physics of the local positive SST-LCC feedback inferred from observed climate variability applies to future greenhouse warming, we anticipate significant amount of delayed warming because of SST-LCC feedback when anthropogenic SST warming eventually overwhelm the effects of internal variability that may mute anthropogenic warming over parts of the ocean. We postulate that many climate models may be underestimating both future warming and the magnitude of modeled internal variability because of their weak SST-LCC feedback. ©2018. The Authors."
"7201485519;7005056279;56575686800;","No access interactions between hydrological sensitivity, radiative cooling, stability, and low-level cloud amount feedback",2018,"10.1175/JCLI-D-16-0895.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041946426&doi=10.1175%2fJCLI-D-16-0895.1&partnerID=40&md5=7285f2fc205aee6c8ea6d475377b3aa5","Low-level cloud feedbacks vary in magnitude but are positive in most climate models, due to reductions in low-level cloud fraction. This study explores the impact of surface evaporation on low-level cloud fraction feedback by performing climate change experiments with the aquaplanet configuration of the HadGEM2-A climate model, forcing surface evaporation to increase at different rates in two ways. Forcing the evaporation diagnosed in the surface scheme to increase at 7% K-1 with warming (more than doubling the hydrological sensitivity) results in an increase in global mean low-level cloud fraction and a negative global cloud feedback, reversing the signs of these responses compared to the standard experiments. The estimated inversion strength (EIS) increases more rapidly in these surface evaporation forced experiments, which is attributed to additional latent heat release and enhanced warming of the free troposphere. Stimulating a 7% K-1 increase in surface evaporation via enhanced atmospheric radiative cooling, however, results in a weaker EIS increase compared to the standard experiments and a slightly stronger low-level cloud reduction. The low-level cloud fraction response is predicted better by EIS than surface evaporation across all experiments. This suggests that surface-forced increases in evaporation increase low-level cloud fraction mainly by increasing EIS. Additionally, the results herein show that increases in surface evaporation can have a very substantial impact on the rate of increase in radiative cooling with warming, by modifying the temperature and humidity structure of the atmosphere. This has implications for understanding the factors controlling hydrological sensitivity. © 2018 American Meteorological Society."
"56524474400;21744127000;","Climate Engineering and Abatement: A ‘flat’ Relationship Under Uncertainty",2018,"10.1007/s10640-016-0104-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85009278910&doi=10.1007%2fs10640-016-0104-5&partnerID=40&md5=b762bbc7782ffe36742e40bef0484a27","The potential of climate engineering to substitute or complement abatement of greenhouse gas emissions has been increasingly debated over the last years. The scientific assessment is driven to a large extent by assumptions regarding its effectiveness, costs, and impacts, all of which are profoundly uncertain. We investigate how this uncertainty about climate engineering affects the optimal abatement policy in the near term. Using a two period model of optimal climate policy under uncertainty, we show that although abatement decreases in the probability of success of climate engineering, this relationship is concave implying a rather ‘flat’ level of abatement as the probability of climate engineering becomes a viable policy option. Using a stochastic version of an integrated assessment model, the results are found to be robust to a wide range of specifications. Moreover, we numerically evaluate different correlation structures between climate engineering and the equilibrium climate sensitivity. © 2017, Springer Science+Business Media Dordrecht."
"7202660824;7403288995;55746365900;26645289600;7402064802;56537463000;8525144100;22959252400;","On the emergent constraints of climate sensitivity",2018,"10.1175/JCLI-D-17-0482.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040610855&doi=10.1175%2fJCLI-D-17-0482.1&partnerID=40&md5=7cdd7d441265e8d5448bd6ba9c0788e3","Differences among climate models in equilibrium climate sensitivity (ECS; the equilibrium surface temperature response to a doubling of atmospheric CO2) remain a significant barrier to the accurate assessment of societally important impacts of climate change. Relationships between ECS and observable metrics of the current climate in model ensembles, so-called emergent constraints, have been used to constrain ECS. Here a statistical method (including a backward selection process) is employed to achieve a better statistical understanding of the connections between four recently proposed emergent constraint metrics and individual feedbacks influencing ECS. The relationship between each metric and ECS is largely attributable to a statistical connection with shortwave low cloud feedback, the leading cause of intermodel ECS spread. This result bolsters confidence in some of the metrics, which had assumed such a connection in the first place. Additional analysis is conducted with a few thousand artificial metrics that are randomly generated but are well correlated with ECS. The relationships between the contrived metrics and ECS can also be linked statistically to shortwave cloud feedback. Thus, any proposed or forthcoming ECS constraint based on the current generation of climate models should be viewed as a potential constraint on shortwave cloud feedback, and physical links with that feedback should be investigated to verify that the constraint is real. In addition, any proposed ECS constraint should not be taken at face value since other factors influencing ECS besides shortwave cloud feedback could be systematically biased in the models. © 2018 American Meteorological Society."
"24757696000;6602600408;7004020627;57194586250;26632168400;55326237100;35611334800;56060986400;56250185400;","Implementation of aerosol-cloud interactions in the regional atmosphere-aerosol model COSMO-Muscat(5.0) and evaluation using satellite data",2017,"10.5194/gmd-10-2231-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021101500&doi=10.5194%2fgmd-10-2231-2017&partnerID=40&md5=18a77e2265e0942f40347709d3e61bad","The regional atmospheric model Consortium for Small-scale Modeling (COSMO) coupled to the Multi-Scale Chemistry Aerosol Transport model (Muscat) is extended in this work to represent aerosol-cloud interactions. Previously, only one-way interactions (scavenging of aerosol and in-cloud chemistry) and aerosol-radiation interactions were included in this model. The new version allows for a microphysical aerosol effect on clouds. For this, we use the optional two-moment cloud microphysical scheme in COSMO and the online-computed aerosol information for cloud condensation nuclei concentrations (Cccn), replacing the constant Cccn profile. In the radiation scheme, we have implemented a droplet-size-dependent cloud optical depth, allowing now for aerosol-cloud-radiation interactions. To evaluate the models with satellite data, the Cloud Feedback Model Intercomparison Project Observation Simulator Package (COSP) has been implemented. A case study has been carried out to understand the effects of the modifications, where the modified modeling system is applied over the European domain with a horizontal resolution of 0.25°g × g0.25°. To reduce the complexity in aerosol-cloud interactions, only warm-phase clouds are considered. We found that the online-coupled aerosol introduces significant changes for some cloud microphysical properties. The cloud effective radius shows an increase of 9.5g%, and the cloud droplet number concentration is reduced by 21.5g%."
"13405218400;6603036806;57194716852;","Empirically constrained climate sensitivity and the social cost of carbon",2017,"10.1142/S2010007817500063","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021807771&doi=10.1142%2fS2010007817500063&partnerID=40&md5=409e35f8155262e227925545c4e86f7e","Integrated Assessment Models (IAMs) require parameterization of both economic and climatic processes. The latter includes Equilibrium Climate Sensitivity (ECS), or the temperature response to doubling CO2 levels, and Ocean Heat Uptake (OHU) efficiency. ECS distributions in IAMs have been drawn from climate model runs that lack an empirical basis, and in Monte Carlo experiments may not be constrained to consistent OHU values. Empirical ECS estimates are now available, but have not yet been applied in IAMs. We incorporate a new estimate of the ECS distribution conditioned on observed OHU efficiency into two widely used IAMs. The resulting Social Cost of Carbon (SCC) estimates are much lower than those from models based on simulated ECS parameters. In the DICE model, the average SCC falls by approximately 40-50% depending on the discount rate, while in the FUND model the average SCC falls by over 80%. The span of estimates across discount rates also shrinks substantially. © 2017 World Scientific Publishing Company."
"57193803894;7004325649;6506827279;7006783796;","Quantifying the dependence of satellite cloud retrievals on instrument uncertainty",2017,"10.1175/JCLI-D-16-0429.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027247940&doi=10.1175%2fJCLI-D-16-0429.1&partnerID=40&md5=3c90cfe69d4cb3f2e1fdaeada95c190c","Cloud response to Earth's changing climate is one of the largest sources of uncertainty among global climate model (GCM) projections. Two of the largest sources of uncertainty are the spread in equilibrium climate sensitivity (ECS) and uncertainty in radiative forcing due to uncertainty in the aerosol indirect effect. Satellite instruments with sufficient accuracy and on-orbit stability to detect climate change-scale trends in cloud properties will improve confidence in the understanding of the relationship between observed climate change and cloud property trends, thus providing information to better constrain ECS and radiative forcing. This study applies a climate change uncertainty framework to quantify the impact of measurement uncertainty on trend detection times for cloud fraction, effective temperature, optical thickness, and water cloud effective radius. Although GCMs generally agree that the total cloud feedback is positive, disagreement remains on its magnitude. With the climate uncertainty framework, it is demonstrated how stringent measurement uncertainty requirements for reflected solar and infrared satellite measurements enable improved constraint of SW and LW cloud feedbacks and the ECS by significantly reducing trend uncertainties for cloud fraction, optical thickness, and effective temperature. The authors also demonstrate improved constraint on uncertainty in the aerosol indirect effect by reducing water cloud effective radius trend uncertainty. © 2017 American Meteorological Society."
"36701462300;10243650000;10241250100;55686667100;","Recent progress toward reducing the uncertainty in tropical low cloud feedback and climate sensitivity: a review",2016,"10.1186/s40562-016-0053-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018480049&doi=10.1186%2fs40562-016-0053-4&partnerID=40&md5=22ca2628d47dfdca47d4cb41af935ef5","Equilibrium climate sensitivity (ECS) to doubling of atmospheric CO2 concentration is a key index for understanding the Earth’s climate history and prediction of future climate changes. Tropical low cloud feedback, the predominant factor for uncertainty in modeled ECS, diverges both in sign and magnitude among climate models. Despite its importance, the uncertainty in ECS and low cloud feedback remains a challenge. Recently, researches based on observations and climate models have demonstrated a possibility that the tropical low cloud feedback in a perturbed climate can be constrained by the observed relationship between cloud, sea surface temperature and atmospheric dynamic and thermodynamic structures. The observational constraint on the tropical low cloud feedback suggests a higher ECS range than raw range obtained from climate model simulations. In addition, newly devised modeling frameworks that address both spreads among different model structures and parameter settings have contributed to evaluate possible ranges of the uncertainty in ECS and low cloud feedback. Further observational and modeling approaches and their combinations may help to advance toward dispelling the clouds of uncertainty. © 2016, The Author(s)."
"13405561000;8918407000;35104877900;36655323000;9838847000;","Changes in marine fog in a warmer climate",2016,"10.1002/asl.691","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84984678066&doi=10.1002%2fasl.691&partnerID=40&md5=d379edaefae7deb88b08bc6ff00f8d1d","Changes in marine fog in a warmer climate are investigated through simulations using the atmospheric component of a global climate model, with both observed and perturbed sea surface temperature forcing. Global changes in marine fog occurrence in different seasons are compared. We show that the changes in marine fog occurrence correspond well to changes in horizontal temperature advection near the surface in a warmer climate. Therefore, the changes in marine fog can be well explained by large-scale circulation changes. Regarding changes in the characteristics of marine fog, we show that the in-cloud liquid water content of marine fog is consistently increased in a warmer climate, for a given horizontal surface temperature advection. It is also confirmed that the contribution of changes in marine fog to cloud feedback is not negligible, but is small. © 2016 The Authors. Atmospheric Science Letters published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"35580303100;7003420726;","Could the Pliocene constrain the equilibrium climate sensitivity?",2016,"10.5194/cp-12-1591-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84980390221&doi=10.5194%2fcp-12-1591-2016&partnerID=40&md5=b8b0947927c8b6fa2f4edd032c420c73","The mid-Pliocene Warm Period (mPWP) is the most recent interval in which atmospheric carbon dioxide was substantially higher than in modern pre-industrial times. It is, therefore, a potentially valuable target for testing the ability of climate models to simulate climates warmer than the pre-industrial state. The recent Pliocene Model Intercomparison Project (PlioMIP) presented boundary conditions for the mPWP and a protocol for climate model experiments. Here we analyse results from the PlioMIP and, for the first time, discuss the potential for this interval to usefully constrain the equilibrium climate sensitivity. We observe a correlation in the ensemble between their tropical temperature anomalies at the mPWP and their equilibrium sensitivities. If the real world is assumed to also obey this relationship, then the reconstructed tropical temperature anomaly at the mPWP can in principle generate a constraint on the true sensitivity. Directly applying this methodology using available data yields a range for the equilibrium sensitivity of 1.9-3.7 °C, but there are considerable additional uncertainties surrounding the analysis which are not included in this estimate. We consider the extent to which these uncertainties may be better quantified and perhaps lessened in the next few years. © Author(s) 2016."
"55767119300;8654071800;","Bayesian estimation of climate sensitivity using observationally constrained simple climate models",2016,"10.1002/wcc.397","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84963960001&doi=10.1002%2fwcc.397&partnerID=40&md5=58fdc19280b0436d8cd5f77918bc7e60","One-dimensional simple climate models (SCMs) play an important role within a hierarchy of climate models. They have largely been used to investigate alternative emission scenarios and estimate global-mean temperature change. This role has expanded through the incorporation of techniques that include Monte Carlo methods and Bayesian statistics, adding the ability to generate probabilistic temperature change projections and diagnose key uncertainties, including equilibrium climate sensitivity (ECS). The latter is the most influential parameter within this class of models where it is ordinarily prescribed, rather than being an emergent property. A series of recent papers based on SCMs and Bayesian statistical methods have endeavored to estimate ECS by using instrumental observations and results from other more complex models to constrain the parameter space. Distributions for ECS depend on a variety of parameters, such as ocean diffusivity and aerosol forcing, so that conclusions cannot be drawn without reference to the joint parameter distribution. Results are affected by the treatment of natural variability, observational uncertainty, and the parameter space being explored. In addition, the highly simplified nature of SCMs means that they contain a number of implicit assumptions that do not necessarily reflect adequately the true nature of Earth's nonlinear quasi-chaotic climate system. Differences in the best estimate and range for ECS may be partly due to variations in the structure of the SCMs reviewed in this study, along with the selection of data and the calibration details, including the choice of priors. Further investigations and model intercomparisons are needed to clarify these issues. © 2016 Wiley Periodicals, Inc."
"7005103514;55466396900;7103331758;","The uncertainty of climate sensitivity and its implication for the Paris negotiation",2016,"10.1007/s11625-015-0339-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944705300&doi=10.1007%2fs11625-015-0339-z&partnerID=40&md5=9f093a998c808a2bb762a6a2d1e9ed17","Uncertainty of climate sensitivity is one of the critical issues that may affect climate response strategies. Whereas the equilibrium climate sensitivity (ECS) was specified as 2–4.5 °C with the best estimate of 3 °C in the 4th Assessment Report of IPCC, it was revised to 1.5–4.5 °C in the 5th Assessment Report. The authors examined the impact of a difference in ECS assuming a best estimate of 2.5 °C, instead of 3 °C. The current pledges of several countries including the U.S., EU and China on emission reductions beyond 2020 are not on track for the 2 °C target with an ECS of 3 °C but are compatible with the target with an ECS of 2.5 °C. It is critically important for policymakers in Paris to know that they are in a position to make decisions under large uncertainty of ECS. © 2015, Springer Japan."
"56492516000;7006151875;","Earth system commitments due to delayed mitigation",2016,"10.1088/1748-9326/11/1/014010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84956617388&doi=10.1088%2f1748-9326%2f11%2f1%2f014010&partnerID=40&md5=8b6c8415eda5af8d8c05ddd60d1c1a0f","As long as global CO2 emissions continue to increase annually, long-term committed Earth system changes grow much faster than current observations. A novel metric linking this future growth to policy decisions today is the mitigation delay sensitivity (MDS), but MDS estimates for Earth system variables other than peak temperature (ΔT max) are missing. Using an Earth System Model of Intermediate Complexity, we show that the current emission increase rate causes a ΔT max increase roughly 3-7.5 times as fast as observed warming, and a millenial steric sea level rise (SSLR) 7-25 times as fast as observed SSLR, depending on the achievable rate of emission reductions after the peak of emissions. These ranges are only slightly affected by the uncertainty range in equilibrium climate sensitivity, which is included in the above values. The extent of ocean acidification at the end of the century is also strongly dependent on the starting time and rate of emission reductions. The preservable surface ocean area with sufficient aragonite supersaturation for coral reef growth is diminished globally at an MDS of roughly 25%-80% per decade. A near-complete loss of this area becomes unavoidable if mitigation is delayed for a few years to decades. Also with respect to aragonite, 12%-18% of the Southern Ocean surface become undersaturated per decade, if emission reductions are delayed beyond 2015-2040. We conclude that the consequences of delaying global emission reductions are much better captured if the MDS of relevant Earth system variables is communicated in addition to current trends and total projected future changes. © 2016 IOP Publishing Ltd."
"55913183200;7402989545;","Why does FGOALS-gl reproduce a weak Medieval Warm Period but a reasonable Little Ice Age and 20th century warming?",2013,"10.1007/s00376-013-2227-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886872259&doi=10.1007%2fs00376-013-2227-8&partnerID=40&md5=aa81fbbaa7170150542c51b0139627cf","To understand the strengths and limitations of a low-resolution version of Flexible Global Ocean-Atmosphere-Land-Sea-ice (FGOALS-gl) to simulate the climate of the last millennium, the energy balance, climate sensitivity and absorption feedback of the model are analyzed. Simulation of last-millennium climate was carried out by driving the model with natural (solar radiation and volcanic eruptions) and anthropogenic (greenhouse gases and aerosols) forcing agents. The model feedback factors for (model sensitivity to) different forcings were calculated. The results show that the system feedback factor is about 2.5 (W m-2) K-1 in the pre-industrial period, while 1.9 (W m-2) K-1 in the industrial era. Thus, the model's sensitivity to natural forcing is weak, which explains why it reproduces a weak Medieval Warm Period. The relatively reasonable simulation of the Little Ice Age is caused by both the specified radiative forcing and unforced linear cold drift. The model sensitivity in the industrial era is higher than that of the pre-industrial period. A negative net cloud radiative feedback operates during whole-millennial simulation and reduces the model's sensitivity to specified forcing. The negative net cloud radiative forcing feedback under natural forcing in the period prior to 1850 is due to the underestimation (overestimation) of the response of cloudiness (in-cloud water path). In the industrial era, the strong tropospheric temperature response enlarges the effective radius of ice clouds and reduces the fractional ice content within cloud, resulting in a weak negative net cloud feedback in the industrial period. The water vapor feedback in the industrial era is also stronger than that in the pre-industrial period. Both are in favor of higher model sensitivity and thus a reasonable simulation of the 20th century global warming. © 2013 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"57195574170;57212972452;56520921400;","On the usage of spectral and broadband satellite instrument measurements to differentiate climate models with different cloud feedback strengths",2013,"10.1175/JCLI-D-12-00378.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883182441&doi=10.1175%2fJCLI-D-12-00378.1&partnerID=40&md5=0b1151d6c92345d2c3bafa97e2fe1b6c","Top-of-atmosphere radiometric signals associated with different high- and low-cloud-radiative feedbacks have been examined through the use of an observing system simulation experiment (OSSE). The OSSE simulates variations in the spectrally resolved and spectrally integrated signals that are due to a range of plausible feedbacks of the climate system when forced withCO2 concentrations that increase at1% yr21. This initial version of the OSSE is based on the Community Climate System Model, version 3 (CCSM3), and exploits the fact that CCSM3 exhibits different cloud feedback strengths for different model horizontal resolutions. In addition to the conventional broadband shortwave albedos and outgoing longwave fluxes, a dataset of shortwave spectral reflectance and longwave spectral radiance has been created. These data have been analyzed to determine simulated satellite instrument signals of poorly constrained cloud feedbacks for three plausible realizations of Earth's climate system produced by CCSM3. These data have been analyzed to estimate the observational record length of albedo, outgoing longwave radiation, shortwave reflectance, or longwave radiance required to differentiate these dissimilar Earth system realizations. Shortwave spectral measurements in visible and near-infrared water vapor overtone lines are best suited to differentiate model results, and a 33% difference in shortwave-cloud feedbacks can be detected with 20 years of continuous measurements. Nevertheless, at most latitudes and with most wavelengths, the difference detection time is more than 30 years. This suggests that observing systems of sufficiently stable calibration would be useful in addressing the contribution of low clouds to the spread of climate sensitivities currently exhibited by the models that report to the Intergovernmental Panel on Climate Change (IPCC). © 2013 American Meteorological Society."
"13405561000;","Examples of mechanisms for negative cloud feedback of stratocumulus and stratus in cloud parameterizations",2012,"10.2151/sola.2012-037","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920933805&doi=10.2151%2fsola.2012-037&partnerID=40&md5=a5ef485d2893cc77afd50048130d6104","Mechanisms of cloud feedback for marine boundary layer clouds in GCMs (General Circulation Models) to the sea surface temperature increase, which can depend on parameterization, were investigated using single column model version of a GCM with two different low cloud schemes. Both schemes showed negative cloud feedbacks and they were attributed to the increase of the liquid water path (LWP) with the future climate forcing for stratocumulus and stratus. The mechanisms of the LWP increase in the two schemes were investigated respectively through simple numerical experiments. The experimental results imply that in the first scheme, the increase of saturation specific humidity due to the temperature increase in the future climate forcing contributes to the negative cloud feedback through the parameterization determining in-cloud cloud water content (CWC). The results also imply that the increase of latent heat flux in the future climate contributes to increased LWP and hence negative cloud feedback in the other scheme. © 2012, the Meteorological Society of Japan."
"54403961000;24468389200;15830929400;22137065500;","Climate sensitivity and cloud feedback processes imposed by two different external forcings in an aquaplanet GCM",2012,"10.1007/s00704-012-0607-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857404705&doi=10.1007%2fs00704-012-0607-0&partnerID=40&md5=22d2eb82b19e574d56cda7e3c4c4f58f","The sensitivity of climate to an increase in sea surface temperature (SST) and CO2, as well as cloud feedback processes, is analyzed through a series of aquaplanet experiments listed in the Coupled Model Intercomparison Project. Rainfall is strengthened in a +4K anomaly SST experiment due to the enhanced surface evaporation; while in a quadruple CO2 experiment, precipitation and total cloud cover are appreciably weakened. In both the +4K and quadruple CO2 (4xCO2) experiments, the Hadley cell is impaired, with an increase in moderate subsidence and a decrease in the frequency of strong convective activity. Regarding cloud radiation forcing (CRF), the analysis technique of Bony et al. (Climate Dynamics, 22:71-86, 2004) is used to sort cloud variables by dynamic regimes using the 500-hPa vertical velocity in tropical areas (30°S-30°N). Results show that the tropically averaged CRF change is negative and is dominated mainly by the thermodynamic component. Within convective regimes, the behavior of longwave CRF is different in the +4K and 4xCO2 experiments, with positive and negative changes, respectively. The globally averaged CRF also reveals a negative change in both aquaplanet and Earthlike experiments, implying that clouds may play a role in decelerating global warming. The calculated climate sensitivity demonstrates that our results are close to those obtained from other models, with 0. 384 and 0. 584 Km2 W-1 for aquaplanet and Earthlike experiments, respectively. © 2012 Springer-Verlag."
"57203213108;7404243086;38362385200;","Cloud and water vapor feedbacks in a vertrical energy-balance model with maximum entropy production",2008,"10.1175/2008JCLI2349.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60749136548&doi=10.1175%2f2008JCLI2349.1&partnerID=40&md5=1c80c51a22dfdced334d434b3c1d071d","A vertically one-dimensional model is developed with cloud fraction constrained by the maximum entropy production (MEP) principle. The model reasonably reproduces the global mean climate with its surface temperature, radiation and heat fluxes, cloud fraction, and lapse rate. The maximum convection hypothesis in Paltridge's models is related to the MEP principle, and the MEP state of climate is approximately equivalent to that with the maximum lapse rate. The sensitivity investigation about the model assumptions and the prescribed parameters show that the model is considerably robust in simulating the global mean climate. With the MEP constraint, the feedbacks of cloud and water vapor to external forcings, such as changes of CO'2 concentration, solar incidence, and surface albedo, are evaluated. While water vapor always behaves as a strong positive feedback, cloud feedbacks to the different forcings are different, in both magnitude and sign. The modeled feedback of cloud fraction to the forcing resulting from surface albedo variation seems in good agreement with the observed seasonal variation of the global cloud fraction. © 2008 American Meteorological Society."
"7202208382;7202496599;7005561168;6603752490;56586869000;6701652286;","Cloud feedbacks",2006,"10.1017/CBO9780511535857.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349166470&doi=10.1017%2fCBO9780511535857.009&partnerID=40&md5=8cb9c7c4511f17ba746085f6d3a63e16","Introduction As discussed in Chapter 1, climate feedbacks are an integral aspect of the climate system. This chapter investigates the importance of cloud feedbacks. Although many of the best-known early climate models used prescribed clouds (e.g., Manabe and Bryan, 1969), the importance of potential changes in cloudiness for the problem of climate change has been recognized as a key factor since the 1970s (e.g., Arakawa, 1975; Charney et al., 1979). In particular, it is now widely appreciated that “cloud feedback” is a key source of uncertainty limiting the reliability of simulations of anthropogenic climate change (e.g., Houghton et al., 1990). Nevertheless the whole concept of cloud feedback continues to be obscure, in part because the term “cloud feedback” is often used without being properly defined at all, and is rarely given a definition precise enough to show how it can be quantitatively measured. Further confusion arises from the fact that there are in fact many types of cloud feedbacks (e.g., Schneider, 1972; Schlesinger, 1985; 1988; 1989; Wielicki et al., 1995). In addition, it is widely perceived that existing atmospheric general circulation models (AGCMs) are incapable of making quantitatively realistic simulations of cloudiness. The purposes of this chapter are to give a definition of cloud feedback, to discuss some particular types of cloud feedback, and to assess the prospects for simulations of cloud feedback on anthropogenic climate change. © Cambridge University Press 2006 and Cambridge University Press, 2009."
"7006518289;","Climate change commitment in the twenty-first and twenty-second centuries",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-17644404067&partnerID=40&md5=3bc664fe857454c89070feff9d8926cf","The newly developed Community Climate System Model Version 3 (CCSM3) with increased horizontal resolution was used to address climate-change commitment. It was found that even if concentrations of all greenhouse gases (GHGs) were stabilized at year 2000 levels, 0.4°C more warming could still occur by the end of 21st century. At the end of 21st century, the warming in the tropical Pacific will resemble an El Nino-like response, likely due to cloud feedbacks in the model."
"7003802133;6602806364;7101823091;7005808242;8733579000;55286185400;50261552200;6508244744;55418799600;7003554208;23486734100;55437450100;57218150582;","Climate Sensitivity of GFDL's CM4.0",2020,"10.1029/2019MS001838","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078820857&doi=10.1029%2f2019MS001838&partnerID=40&md5=bb21ee3847a6ea00e6396aa57b073688","GFDL's new CM4.0 climate model has high transient and equilibrium climate sensitivities near the middle of the upper half of CMIP5 models. The CMIP5 models have been criticized for excessive sensitivity based on observations of present-day warming and heat uptake and estimates of radiative forcing. An ensemble of historical simulations with CM4.0 produces warming and heat uptake that are consistent with these observations under forcing that is at the middle of the assessed distribution. Energy budget-based methods for estimating sensitivities based on these quantities underestimate CM4.0's sensitivities when applied to its historical simulations. However, we argue using a simple attribution procedure that CM4.0's warming evolution indicates excessive transient sensitivity to greenhouse gases. This excessive sensitivity is offset prior to recent decades by excessive response to aerosol and land use changes. ©2020. The Authors."
"55581675600;57212101779;35227762400;35611334800;6602600408;","Climate models disagree on the sign of total radiative feedback in the Arctic",2020,"10.1080/16000870.2019.1696139","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075953533&doi=10.1080%2f16000870.2019.1696139&partnerID=40&md5=73ddc82d4387859c9c41558ee13ef023","Climate feedbacks have been found to strongly impact the observed amplified Arctic warming. However, Arctic amplification is modeled with a wide spread which partly arises from intermodel differences of the various feedbacks. To explain the spread in modeled Arctic warming, feedback uncertainties and their origins are investigated in 13 climate models in an experiment with abruptly quadrupled CO2. While intermodel differences in the cloud feedback, being strongest in the Tropics, have been found to determine the spread of global mean effective climate sensitivity, we find that in the Arctic the cloud feedback is not responsible for the spread of Arctic warming as its contribution is too small. Instead, the spread of Arctic warming is explained by differing estimates of surface albedo and Planck feedbacks which show the largest intermodel differences. Our results indicate that these uncertainties not only arise from different degrees of simulated Arctic warming but also are partly related to the large differences in initial sea ice cover and surface temperatures which contribute to the increased spread in estimated warming compared to lower latitudes. Further investigations of feedback dependencies to the base state are needed to constrain the impact of initial uncertainties and to obtain robust results. The most significant distinction between models is the sign of the total feedback parameter. While all models investigated here simulate a negative global mean total feedback, only half of them also show negative Arctic feedbacks which implies that Arctic local feedbacks alone suffice to stably adjust Arctic surface temperatures in response to a radiative perturbation. The other half exhibits positive total Arctic feedbacks indicating local runaway systems which need to be balanced by decreased meridional heat transports. Whether or not a model features such a behaviour depends upon the strength of the simulated positive surface albedo versus the negative Planck feedback. © 2019, © 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group."
"57087451200;7103180783;53880473700;53879901600;12787547600;6602080205;","Attribution of recent trends in temperature extremes over China: Role of changes in anthropogenic aerosol emissions over asia",2019,"10.1175/JCLI-D-18-0777.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074927588&doi=10.1175%2fJCLI-D-18-0777.1&partnerID=40&md5=07d873a68f0f46904fcaebbde3ad5564","Observations indicate large changes in temperature extremes over China during the last four decades, exhibiting as significant increases in the amplitude and frequency of hot extremes and decreases in the amplitude and frequency of cold extremes.An ensemble of transient experimentswith the fully coupled atmosphere-ocean model HadGEM3-GC2, including both anthropogenic forcing and natural forcing, successfully reproduces the spatial pattern andmagnitude of observed historical trends in both hot and cold extremes. Themodel-simulated trends in temperature extremes primarily come fromthe positive trends in clear-sky longwave radiation,which is mainly due to the increases in greenhouse gases (GHGs). An ensemble of sensitivity experiments with Asian anthropogenic aerosol (AA) emissions fixed at their 1970s levels tends to overestimate the trends in temperature extremes, indicating that local AA emission changes have moderated the trends in these temperature extremes over China. The recent increases in Asian AA drive cooling trends over China by inducing negative clear-sky shortwave radiation directly through the aerosol-radiation interaction, which partly offsets the strong warming effect by GHG changes. The cooling trends induced by Asian AA changes are weaker over northern China during summer, which is due to the warming effect by the positive shortwave cloud radiative effect through the AA-induced atmosphere-cloud feedback. This accounts for the observed north-south gradients of the historical trends in some temperature extremes over China, highlighting the importance of local Asian AA emission changes on spatial heterogeneity of trends in temperature extremes. © 2019 American Meteorological Society."
"55531609200;56537463000;57200702127;55802732200;7404829395;7006417494;","Relationships Between Tropical Ascent and High Cloud Fraction Changes With Warming Revealed by Perturbation Physics Experiments in CAM5",2019,"10.1029/2019GL083026","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85071317038&doi=10.1029%2f2019GL083026&partnerID=40&md5=cb8cc659cdaacddb5843cd33aa0952a7","Tropical ascent area (Aa) and high cloud fraction (HCF) are projected to decrease with surface warming in most Coupled Model Intercomparison Project Phase 5 (CMIP5) models. Perturbing deep convective parameters in the Community Atmosphere Model (CAM5) results in a similar spread and correlation between HCF and Aa responses to interannual warming compared to the CMIP5 ensemble, with a narrower Aa corresponding to greater HCF reduction. Perturbing cloud physics parameters produces a comparatively smaller range of Aa responses to warming and a dissimilar HCF-Aa relation to that in CMIP5; a narrower Aa corresponds to less HCF reduction, likely due to cloud radiative effects. A narrowing of Aa corresponds to a regime shift toward stronger precipitation in both experiments. We infer that model differences in deep convection parameterization likely play a greater role than differing cloud physics in determining the diverse responses of Aa and HCF to warming in CMIP5. © 2019. American Geophysical Union. All Rights Reserved."
"23012746800;57112070700;16445110800;7004468723;12761291000;55885528600;26645901500;10339477400;26635870100;","Fast-Forward to Perturbed Equilibrium Climate",2019,"10.1029/2019GL083031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070762683&doi=10.1029%2f2019GL083031&partnerID=40&md5=df849ff30057b030e691745365995276","The equilibrium climate sensitivity, that is, the global-mean surface-air temperature change in response to a doubling of the carbon dioxide concentration is a widely used metric in climate change studies. Its exact value is rarely known because its estimation requires a long integration time of several thousand years. We propose a method to estimate an accurate value of the equilibrium response from fully coupled climate models at a reasonable computational cost. Using this method, our state-of-the-art climate model CNRM-CM6-1 reaches a stationary state after only few hundred of years of integration. This “Fast-Forward” method consists of an optimal two-step forcing pathway designed using the framework of a two-layer energy balance model. It can be applied easily to any coupled climate model. ©2019. American Geophysical Union. All Rights Reserved."
"7006263321;","An Observational Constraint on CMIP5 Projections of the East African Long Rains and Southern Indian Ocean Warming",2019,"10.1029/2019GL082847","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067648490&doi=10.1029%2f2019GL082847&partnerID=40&md5=d33481e56d4bcbe99309ba6dacf0c86e","Two outlying projections of the East African Long Rains suggest the seasonal rainfall may double by the late 21st century. Previous work has linked these extremes—found in the IPSL-CM5A model—to an exceptional March to May warming of the southern Indian Ocean. The current study shows a strong feedback between sea surface temperature (SST) increases and reduced low-level cloud cover (with similar behavior in other southern subtropical oceans). An observational constraint is developed by demonstrating a correlation across 28 models between the strength of present-day interannual SST-cloud sensitivity and future SST response. Verification of the present-day sensitivity finds that IPSL-CM5A's feedbacks are very likely overestimated. It is therefore suggested its projections should be discounted for the March to May southern Indian Ocean and East African Long Rains. This narrows the CMIP5 plausible range of Long Rains totals by a third. ©2019. The Authors."
"57200083124;14051038900;24080132800;57194003391;57194275819;","Impacts of Observational Constraints Related to Sea Level on Estimates of Climate Sensitivity",2019,"10.1029/2018EF001082","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067842907&doi=10.1029%2f2018EF001082&partnerID=40&md5=3c1e30f943ec0836ed0c57841f1904d6","Reduced complexity climate models are useful tools for quantifying decision-relevant uncertainties, given their flexibility, computational efficiency, and suitability for large-ensemble frameworks necessary for statistical estimation using resampling techniques (e.g., Markov chain Monte Carlo). Here we document a new version of the simple, open-source, global climate model Hector, coupled with a 1-D diffusive heat and energy balance model (Diffusion Ocean Energy balance CLIMate model) and a sea level change module (Building blocks for Relevant Ice and Climate Knowledge) that also represents contributions from thermal expansion, glaciers and ice caps, and polar ice sheets. We apply a Bayesian calibration approach to quantify model uncertainties surrounding 39 model parameters with prescribed radiative forcing, using observational information from global surface temperature, thermal expansion, and other contributors to sea level change. We find the addition of thermal expansion as an observational constraint sharpens inference for the upper tail of posterior equilibrium climate sensitivity estimates (the 97.5 percentile is tightened from 7.1 to 6.6 K), while other contributors to sea level change play a lesser role. The thermal expansion constraint also has implications for probabilistic projections of global surface temperature (the 97.5 percentile for RCP8.5 2100 temperature decreases 0.3 K). Due to the model's parameterization of thermal expansion as an uncertain function of global ocean heat, we note a trade-off between two ways of incorporating thermal expansion information: Ocean heat data provide a somewhat sharper equilibrium climate sensitivity estimate while thermal expansion data allow for constrained sea level projections. ©2019. The Authors."
"57201896263;57002856000;7003543851;6701606453;","Observation-Based Radiative Kernels From CloudSat/CALIPSO",2019,"10.1029/2018JD029021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85066487497&doi=10.1029%2f2018JD029021&partnerID=40&md5=9b9ae1c93fb48d8b6a4e1974745cb431","Radiative kernels describe the differential response of radiative fluxes to small perturbations in state variables and are widely used to quantify radiative feedbacks on the climate system. Radiative kernels have traditionally been generated using simulated data from a global climate model, typically sourced from the model's base climate. Consequently, these radiative kernels are subject to model bias from the climatological fields used to produce them. Here, we introduce the first observation-based temperature, water vapor, and surface albedo radiative kernels, developed from CloudSat's fluxes and heating rates data set, 2B-FLXHR-LIDAR, which is supplemented with cloud information from the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). We compare the radiative kernels to a previously published set generated from the Geophysical Fluid Dynamics Laboratory (GFDL) model and find general agreement in magnitude and structure. However, several key differences illustrate the sensitivity of radiative kernels to the distribution of clouds. The radiative kernels are used to quantify top-of-atmosphere and surface cloud feedbacks in an ensemble of global climate models from the Climate Model Intercomparison Project Phase 5, showing that biases in the GFDL low clouds likely cause the GFDL kernel to underestimate longwave surface cloud feedback. Since the CloudSat kernels are free of model bias in the base state, they will be ideal for future analysis of radiative feedbacks and forcing in both models and observations and for evaluating biases in model-derived radiative kernels. ©2019. American Geophysical Union. All Rights Reserved."
"56457851700;7103016965;25924878400;13402835300;7102171439;26645289600;22934904700;8696069500;55325157500;7404029779;6602887222;23012746800;55885528600;6603718837;24764483400;7801353107;18635820300;","Cloud feedbacks in extratropical cyclones: Insight from long-term satellite data and high-resolution global simulations",2019,"10.5194/acp-19-1147-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060956582&doi=10.5194%2facp-19-1147-2019&partnerID=40&md5=02664cbd6068789bdc44ae62953a0269","A negative extratropical shortwave cloud feedback driven by changes in cloud optical depth is a feature of global climate models (GCMs). A robust positive trend in observed liquid water path (LWP) over the last two decades across the warming Southern Ocean supports the negative shortwave cloud feedback predicted by GCMs. This feature has been proposed to be due to transitions from ice to liquid with warming. To gain insight into the shortwave cloud feedback we examine extratropical cyclone variability and the response of extratropical cyclones to transient warming in GCM simulations. Multi-Sensor Advanced Climatology Liquid Water Path (MAC-LWP) microwave observations of cyclone properties from the period 1992-2015 are contrasted with GCM simulations, with horizontal resolutions ranging from 7&thinsp;km to hundreds of kilometers. We find that inter-cyclone variability in LWP in both observations and models is strongly driven by the moisture flux along the cyclone's warm conveyor belt (WCB). Stronger WCB moisture flux enhances the LWP within cyclones. This relationship is replicated in GCMs, although its strength varies substantially across models. It is found that more than 80&thinsp;% of the enhancement in Southern Hemisphere (SH) extratropical cyclone LWP in GCMs in response to a transient 4&thinsp;K warming can be predicted based on the relationship between the WCB moisture flux and cyclone LWP in the historical climate and their change in moisture flux between the historical and warmed climates. Further, it is found that that the robust trend in cyclone LWP over the Southern Ocean in observations and GCMs is consistent with changes in the moisture flux. We propose two cloud feedbacks acting within extratropical cyclones: a negative feedback driven by Clausius-Clapeyron increasing water vapor path (WVP), which enhances the amount of water vapor available to be fluxed into the cyclone, and a feedback moderated by changes in the life cycle and vorticity of cyclones under warming, which changes the rate at which existing moisture is imported into the cyclone. Both terms contribute to increasing LWP within the cyclone. While changes in moisture flux predict<span idCombining double low line""page1148""/> cyclone LWP trends in the current climate and the majority of changes in LWP in transient warming simulations, a portion of the LWP increase in response to climate change that is unexplained by increasing moisture fluxes may be due to phase transitions. The variability in LWP within cyclone composites is examined to understand what cyclonic regimes the mixed-phase cloud feedback is relevant to. At a fixed WCB moisture flux cyclone LWP increases with increasing sea surface temperature (SST) in the half of the composite poleward of the low and decreases in the half equatorward of the low in both GCMs and observations. Cloud-top phase partitioning observed by the Atmospheric Infrared Sounder (AIRS) indicates that phase transitions may be driving increases in LWP in the poleward half of cyclones. © Author(s) 2019."
"55745955800;","CLOUD-CLIMATE FEEDBACK: HOW MUCH DO WE KNOW?",2019,"10.1142/9789812791139_0008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85071481764&doi=10.1142%2f9789812791139_0008&partnerID=40&md5=d063f147f8a5d119164bc97fedf1faea","This paper introduces the concept of cloud-climate feedback along with its role in the sensitivity of the climate system. It reviews available cloud feedback diagnostic methods and representative results in three-dimensional atmospheric general circulation models. A case study is presented to analyze physical processes responsible for cloud feedbacks that control the sensitivity of the NCAR Community Climate Model. The paper further discusses weaknesses of current numerical models and areas of required research on this subject. © 2004 World Scientific Publishing Co. Pte. Ltd."
"7005528388;7102171439;6603126554;15726427000;36095558300;56219284300;","Temporal and spatial characteristics of short-term cloud feedback on global and local interannual climate fluctuations from A-Train observations",2019,"10.1175/JCLI-D-18-0335.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85063006709&doi=10.1175%2fJCLI-D-18-0335.1&partnerID=40&md5=eb257455d14a9c29c65c4e8b6f4c8f9a","Observations from multiple sensors on the NASA Aqua satellite are used to estimate the temporal and spatial variability of short-term cloud responses (CR) and cloud feedbacks λ for different cloud types, with respect to the interannual variability within the A-Train era (July 2002-June 2017). Short-term cloud feedbacks by cloud type are investigated both globally and locally by three different definitions in the literature: 1) the global-mean cloud feedback parameter λGG from regressing the global-mean cloud-induced TOA radiation anomaly ΔRG with the global-mean surface temperature change ΔTGS; 2) the local feedback parameter λLL from regressing the local ΔR with the local surface temperature change ΔTS; and 3) the local feedback parameter λGL from regressing global ΔRG with local ΔTS. Observations show significant temporal variability in the magnitudes and spatial patterns in λGG and λGL, whereas λLL remains essentially time invariant for different cloud types. The global-mean net λGG exhibits a gradual transition from negative to positive in the A-Train era due to a less negative λGG from low clouds and an increased positive λGG from high clouds over the warm pool region associated with the 2015/16 strong El Niño event. Strong temporal variability in λGL is intrinsically linked to its dependence on global ΔRG, and the scaling of λGL with surface temperature change patterns to obtain global feedback λGG does not hold. Despite the shortness of the A-Train record, statistically robust signals can be obtained for different cloud types and regions of interest. © 2019 American Meteorological Society."
"36241005100;22134910200;7006329853;","Evaluating Climate Sensitivity to CO2 Across Earth's History",2018,"10.1029/2018JD029262","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056078644&doi=10.1029%2f2018JD029262&partnerID=40&md5=27f3bb13d6a118196cff50bca8360ef4","CO2-driven changes to climate have occurred during many epochs of Earth's history when the solar insolation, atmospheric CO2 concentration, and surface temperature of the planet were all significantly different than today. Each of these aspects affects the implied radiative forcings, climate feedbacks, and resultant changes in global mean surface temperature. Here we use a three-dimensional climate system model to study the effects of increasing CO2 on Earth's climate, across many orders of magnitude of variation, and under solar inputs relevant for paleo, present, and future Earth scenarios. We find that the change in global mean surface temperature from doubling CO2 (i.e., the equilibrium climate sensitivity) may vary between 2.6 and 21.6 K over the course of Earth's history. In agreement with previous studies, we find that the adjusted radiative forcing from doubling CO2 increases at high concentrations up to about 1.5 bars partial pressure, generally resulting in larger changes in the surface temperature. We also find that the cloud albedo feedback causes an abrupt transition in climate for warming atmospheres that depends both on the mean surface temperature and the total solar insolation. Climate sensitivity to atmospheric CO2 has probably varied considerably across Earth's history. ©2018. American Geophysical Union. All Rights Reserved."
"57204637584;56162305900;55913183200;55332348600;7402989545;55802246600;7005920812;7003666669;55405340400;6506848305;25031430500;","Low-Cloud Feedback in CAM5-CLUBB: Physical Mechanisms and Parameter Sensitivity Analysis",2018,"10.1029/2018MS001423","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056465273&doi=10.1029%2f2018MS001423&partnerID=40&md5=92bd41fc1cf873cd06fc8afdb573d2c5","The physical mechanism of low-cloud feedbacks is examined by using perturbed-parameter ensemble experiments in a unified scheme of boundary layer turbulence and shallow convection, named Cloud Layers Unified by Binormals (CLUBB) coupled to Community Atmosphere Model version 5 (CAM5). The shortwave cloud feedbacks in CAM5-CLUBB are positive in the most stable tropical regime, which is related to the weaker turbulence in the planetary boundary layer (PBL) in a warmer climate that is possibly triggered by the strengthened stability of the cloud layer. The positive feedback between low cloud cover (LCC), cloud top radiative cooling, and PBL turbulent mixing may further enhance the decrease in LCC. The stronger inversion stability of PBL partly counters the decrease in LCC, and a recently developed index, the estimated cloud-top entrainment index, is a better predictor for LCC changes than conventional stability indices. The relative strength of shallow convection increases in the warmer climate, but its effect on low-cloud feedback is complicated by the unified treatment of shallow convection and PBL turbulence in CLUBB. Stronger shallow convection means more convective drying but also less PBL turbulence and less LCC in the present climate, which leads to less reduction in LCC. The parameters related to dynamic turbulent structure and double Gaussian closure in CLUBB are the most influential parameters on low-cloud feedbacks. Our results suggest that a unified treatment of shallow convection and turbulence may give rise to the predominate role of the PBL turbulent mixing in determining low-cloud feedback. ©2018. The Authors."
"26323066900;35742922300;6602845217;25723647800;","An ensemble of AMIP simulations with prescribed land surface temperatures",2018,"10.5194/gmd-11-3865-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054082692&doi=10.5194%2fgmd-11-3865-2018&partnerID=40&md5=281bef0c10fcd8124a16fab8757c7eaf","General circulation models (GCMs) are routinely run under Atmospheric Modelling Intercomparison Project (AMIP) conditions with prescribed sea surface temperatures (SSTs) and sea ice concentrations (SICs) from observations. These AMIP simulations are often used to evaluate the role of the land and/or atmosphere in causing the development of systematic errors in such GCMs. Extensions to the original AMIP experiment have also been developed to evaluate the response of the global climate to increased SSTs (prescribed) and carbon dioxide (CO2) as part of the Cloud Feedback Model Intercomparison Project (CFMIP). None of these international modelling initiatives has undertaken a set of experiments where the land conditions are also prescribed, which is the focus of the work presented in this paper. Experiments are performed initially with freely varying land conditions (surface temperature, and soil temperature and moisture) under five different configurations (AMIP, AMIP with uniform 4&thinsp;K added to SSTs, AMIP SST with quadrupled CO2, AMIP SST and quadrupled CO2 without the plant stomata response, and increasing the solar constant by 3.3&thinsp;%). Then, the land surface temperatures from the free land experiments are used to perform a set of <q>AMIP prescribed land</q> (PL) simulations, which are evaluated against their free land counterparts. The PL simulations agree well with the free land experiments, which indicates that the land surface is prescribed in a way that is consistent with the original free land configuration. Further experiments are also performed with different combinations of SSTs, CO2 concentrations, solar constant and land conditions. For example, SST and land conditions are used from the AMIP simulation with quadrupled CO2 in order to simulate the atmospheric response to increased CO2 concentrations without the surface temperature changing. The results of all these experiments have been made publicly available for further analysis. The main aims of this paper are to provide a description of the method used and an initial validation of these AMIP prescribed land experiments. © Crown copyright 2018."
"57203866755;36809017200;7004647146;55623265200;9246029600;","Sources of Uncertainty in the Meridional Pattern of Climate Change",2018,"10.1029/2018GL079429","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053273714&doi=10.1029%2f2018GL079429&partnerID=40&md5=2a8514fa1dd147a87bb3d5026f56d459","We employ a moist energy balance model (MEBM), representing atmospheric heat transport as the diffusion of near-surface moist static energy, to evaluate sources of uncertainty in the meridional pattern of surface warming. Given zonal mean patterns of radiative forcing, radiative feedbacks, and ocean heat uptake, the MEBM accurately predicts zonal mean warming as simulated by general circulation models under increased CO2. Over a wide range of latitudes, the MEBM captures approximately 90% of the variance in zonal mean warming across the general circulation models, with approximately 70% of the variance attributable to differences in radiative feedbacks alone. Partitioning the radiative feedbacks into individual components shows that the majority of the uncertainty in the meridional pattern of warming arises from uncertainty in cloud feedbacks. Isolating feedback uncertainty within specific regions demonstrates that tropical feedback uncertainty leads to surface warming uncertainty that is global and nearly uniform with latitude, whereas polar feedback uncertainty leads to surface warming uncertainty that is largely confined to the poles. ©2018. American Geophysical Union. All Rights Reserved."
"55894937000;7004544454;55796430300;","Importance of positive cloud feedback for tropical Atlantic interhemispheric climate variability",2018,"10.1007/s00382-017-3978-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032375069&doi=10.1007%2fs00382-017-3978-1&partnerID=40&md5=f7319741f81e50849ef2fe89053df037","Over the tropical Atlantic during boreal spring, average interhemispheric differences in sea-surface temperature (SST) coincide with a coherent pattern of interannual climate variability often referred to as the Atlantic Meridional Mode. This includes anomalous SST and sea-level pressure roughly anti-symmetric about the equator, as well as cross-equatorial near-surface winds directed toward the warmer hemisphere. Within subtropical marine boundary layer cloud regions in both hemispheres, enhanced cloudiness associated with this variability is co-located with cool SST, a strong temperature inversion, and cold horizontal surface temperature advection, while reduced cloudiness is associated with the opposite meteorological conditions. This is indicative a positive cloud feedback that reinforces the underlying SST anomalies. The simulation of this feedback varies widely among models participating in phase 5 of the Coupled Model Intercomparison Project. Models that fail to simulate this feedback substantially underestimate the amplitudes of typical tropical Atlantic interhemispheric variability in cloudiness off of the equator, SST, and atmospheric circulation. Models that correctly reproduce a positive cloud feedback generally produce higher and more realistic amplitudes of variability, but with substantial scatter. Marine boundary layer clouds therefore appear to be a key element of springtime coupled atmosphere–ocean variability over the tropical Atlantic. A markedly more successful simulation of this variability in climate models may be obtained by better representing boundary layer cloud processes. © 2017, Springer-Verlag GmbH Germany."
"57195576398;25941200000;35572096100;9239331500;24337947000;56009810800;35317714900;7003557662;6602681732;6602922400;12800966700;7003535385;8397494800;35567153700;6603631763;","Evaluation of a high-resolution numerical weather prediction model's simulated clouds using observations from CloudSat, GOES-13 and in situ aircraft",2018,"10.1002/qj.3318","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054533459&doi=10.1002%2fqj.3318&partnerID=40&md5=a777a4a748952ef2711a1970af7f1d10","This study aimed to assess tropical cloud properties predicted by Environment and Climate Change Canada's Global Environmental Multiscale (GEM) model when run with the Milbrandt–Yau double-moment cloud microphysical scheme and one-way nesting that culminated at a (∼300 km)2 inner domain with 0.25 km horizontal grid spacing. The assessment utilized satellite and in situ data collected during the High Ice Water Content (HIWC) and High Altitude Ice Crystals (HAIC) projects for a mesoscale convective system on 16 May 2015 over French Guiana. Data from CloudSat's cloud-profiling radar and GOES-13's imager were compared to data either simulated directly by GEM or produced by operating on GEM's cloud data with both the CFMIP (Cloud Feedback Model Intercomparison Project) Observation Simulator Package (COSP) instrument simulator and a three-dimensional Monte Carlo solar radiative transfer model. In situ observations were made from research aircraft – Canada's National Research Council Convair-580 and the French SAFIRE Falcon-20 – whose flight paths were aligned with CloudSat's ground-track. Spatial and temporal shifts of clouds simulated by GEM compared well to GOES-13 imagery. There are, however, differences between simulated and observed amounts of high and low cloud. While GEM did well at predicting ranges of ice-water content (IWC) near 11 km altitude (Falcon-20), it produces too much graupel and snow near 7 km (Convair-580). This produced large differences between CloudSat's and COSP-generated radar reflectivities and two-way attenuations. On the other hand, CloudSat's inferred values of IWC agree well with in situ samples at both altitudes. Generally, GEM's visible reflectances exceeded GOES-13's on account of having produced too much low-level liquid cloud. It is expected that GEM's disproportioning of cloud hydrometeors will improve once it includes a better representation of secondary ice production. © 2018 Her Majesty the Queen in Right of Canada. Quarterly Journal of the Royal Meteorological Society © 2018 Royal Meteorological Society"
"56159401000;57195248265;55930003300;55544443300;7402425067;57207436906;36015299300;","Vegetation-cloud feedbacks to future vegetation changes in the Arctic regions",2018,"10.1007/s00382-017-3840-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85026552770&doi=10.1007%2fs00382-017-3840-5&partnerID=40&md5=18c3a01d1c6945c855fa89d660c63885","This study investigates future changes in the Arctic region and vegetation-cloud feedbacks simulated using the National Center for Atmospheric Research Community Atmosphere Model Version 3 coupled with a mixed layer ocean model. Impacts of future greening of the Arctic region are tested using altered surface boundary conditions for hypothetical vegetation distributions: (1) grasslands poleward of 60°N replaced by boreal forests and (2) both grasslands and shrubs replaced by boreal forests. Surface energy budget analysis reveals that future greening induces a considerable surface warming effect locally and warming is largely driven by an increase in short wave radiation. Both upward and downward shortwave radiation contribute to positive surface warming: upward shortwave radiation decreases mainly due to the decreased surface albedo (a darker surface) and downward shortwave radiation increases due to reduced cloud cover. The contribution of downward shortwave radiation at surface due to cloud cover reduction is larger than the contribution from surface albedo alone. The increased roughness length also transported surface fluxes to upper layer more efficiently and induce more heating and dry lower atmosphere. A relatively smaller increase in water vapor compared to the large increase in low-level air temperature in the simulation reduces relative humidity and results in reduced cloud cover. Therefore, vegetation-cloud feedbacks induced from land cover change significantly amplify Arctic warming. In addition to previously suggested feedback mechanisms, we propose that the vegetation-cloud feedback should be considered as one of major components that will give rise to an additional positive feedback to Arctic amplification. © 2017, Springer-Verlag GmbH Germany."
"7004390019;","Inferred Net Aerosol Forcing Based on Historical Climate Changes: a Review",2018,"10.1007/s40641-018-0085-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85051773368&doi=10.1007%2fs40641-018-0085-2&partnerID=40&md5=ae69479c3be2d7643af6e41c5777d083","Purpose of Review: This review summarizes the inverse methods used to estimate the net aerosol forcing inferred from the historical climate change records for the Earth. Recent Findings: The available methods are similar in design while differing in their assumptions. Primary differences are (a) the complexity of the earth system model used for forward simulations of the historical period (~ 1850 to the present), (b) the uncertainty sampling methodology, and (c) the representation of internal climate variability in the statistical approach. All methods, in some fashion, include the net aerosol radiative forcing as a residual forcing that is scaled to find simulations that match the observed records of surface air and deep ocean temperatures. Inverse methods also require sampling the model response uncertainty in the equilibrium climate sensitivity and the transient climate response (i.e., the delay due to mixing heat into the deep ocean), and therefore, a joint probability distribution is estimated that includes uncertainty across multiple components. Summary: The resulting estimates of the net aerosol forcing and its uncertainty are, by construction, necessarily linked to the earth system model, its response characteristics, and the estimates of the internal chaotic variability. Summary results indicate that the net aerosol forcing during the late twentieth century was − 0.77 Wm−2 with a 5–95% range of − 1.15 to − 0.31 Wm−2 based on 19 results from simple- to full-complexity climate system models. © 2018, Springer International Publishing AG, part of Springer Nature."
"7202733689;7003543851;","On the compensation between cloud feedback and cloud adjustment in climate models",2018,"10.1007/s00382-017-3682-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85017449980&doi=10.1007%2fs00382-017-3682-1&partnerID=40&md5=63459187e634405dc95b95b50a9b436a","Intermodel compensation between cloud feedback and rapid cloud adjustment has important implications for the range of model-inferred climate sensitivity. Although this negative intermodel correlation exists in both realistic (e.g., coupled ocean–atmosphere models) and idealized (e.g., aqua-planet) model configurations, the compensation appears to be stronger in the latter. The cause of the compensation between feedback and adjustment, and its dependence on model configuration remain poorly understood. In this study, we examine the characteristics of the cloud feedback and adjustment in model simulations with differing complexity, and analyze the causes responsible for their compensation. We show that in all model configurations, the intermodel compensation between cloud feedback and cloud adjustment largely results from offsetting changes in marine boundary-layer clouds. The greater prevalence of these cloud types in aqua-planet models is a likely contributor to the larger correlation between feedback and adjustment in those configurations. It is also shown that differing circulation changes in the aqua-planet configuration of some models act to amplify the intermodel range and sensitivity of the cloud radiative response by about a factor of 2. © 2017, Springer-Verlag Berlin Heidelberg."
"8918407000;7006165316;13405561000;6603412788;","Evaluation of relationships between subtropical marine low stratiform cloudiness and estimated inversion strength in CMIP5 models using the satellite simulator package COSP",2018,"10.2151/sola.2018-005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045668814&doi=10.2151%2fsola.2018-005&partnerID=40&md5=9043c0f794e091350ac7153df49d83a1","Using the Cloud Feedback Model Intercomparison Project Observation Simulator Package (COSP) outputs, subtropical marine low stratiform cloud (LSC) amounts simulated in 12 Coupled Model Intercomparison Project phase 5 (CMIP5) models are robustly evaluated in terms of the relationship with the estimated inversion strength (EIS). The International Satellite Cloud Climatology Project (ISCCP) low-plus-middle cloud amounts with optical thickness &gt; 3.6, corrected with the random-overlap assumption, are defined as the LSC amount. Although EISs are well-simulated in all the models, more than half of the models show weaker responses of the LSC amount to EIS (2%-3% K-1) than the observations (~4.5% K-1), and some models even show negative responses. The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) cloud amounts and layered EISs reveal that most models simulate inversion levels lower than observed, and that the vertical structure of LSCs has a key role for improvement in the modeled relationships. © The Author(s) 2018."
"7403282069;8977001000;","Understanding the tropical cloud feedback from an analysis of the circulation and stability regimes simulated from an upgraded multiscale modeling framework",2016,"10.1002/2016MS000767","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85006287864&doi=10.1002%2f2016MS000767&partnerID=40&md5=b6a561d44ed6b8417e2b52b7d6ee8c0f","As revealed from studies using conventional general circulation models (GCMs), the thermodynamic contribution to the tropical cloud feedback dominates the dynamic contribution, but these models have difficulty in simulating the subsidence regimes in the tropics. In this study, we analyze the tropical cloud feedback from a 2 K sea surface temperature (SST) perturbation experiment performed with a multiscale modeling framework (MMF). The MMF explicitly represents cloud processes using 2-D cloud-resolving models with an advanced higher-order turbulence closure in each atmospheric column of the host GCM. We sort the monthly mean cloud properties and cloud radiative effects according to circulation and stability regimes. We find that the regime-sorted dynamic changes dominate the thermodynamic changes in terms of the absolute magnitude. The dynamic changes in the weak subsidence regimes exhibit strong negative cloud feedback due to increases in shallow cumulus and deep clouds while those in strongly convective and moderate-to-strong subsidence regimes have opposite signs, resulting in a small contribution to cloud feedback. On the other hand, the thermodynamic changes are large due to decreases in stratocumulus clouds in the moderate-to-strong subsidence regimes with small opposite changes in the weak subsidence and strongly convective regimes, resulting in a relatively large contribution to positive cloud feedback. The dynamic and thermodynamic changes contribute equally to positive cloud feedback and are relatively insensitive to stability in the moderate-to-strong subsidence regimes. But they are sensitive to stability changes from the SST increase in convective and weak subsidence regimes. These results have implications for interpreting cloud feedback mechanisms. Published 2016. This article is a U.S. Government work and is in the public domain in the USA."
"57196171548;12040335900;36015299300;57216619452;","Influence of altered low cloud parameterizations for seasonal variation of Arctic cloud amount on climate feedbacks",2016,"10.1007/s00382-015-2926-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949568449&doi=10.1007%2fs00382-015-2926-1&partnerID=40&md5=558280a94fb2414dabbdf7644b13d6c0","This study investigates the alteration of climate feedbacks due to overestimated wintertime low-level cloud amount bias over the Arctic region (60°N–90°N) in a climate model. The climate feedback was quantitatively examined through radiative kernels that are pre-calculated radiative responses of climate variables to doubling of carbon dioxide concentration in NCAR Community Atmosphere Model version 3 (CAM3). Climate models have various annual cycle of the Arctic cloud amount at the low-level particularly with large uncertainty in winter and CAM3 may tend to overestimate the Arctic low-level cloud. In this study, the seasonal variation of low-level cloud amount was modified by reducing the wintertime cloud amount by up to 35 %, and then compared with the original without seasonal variation. Thus, we investigate how that bias may affect climate feedbacks and the projections of future Arctic warming. The results show that the decrease in low-level cloud amount slightly affected the radiation budgets because of a small amount of incident solar insolation in winter, but considerably changed water vapor and temperature profiles. Consequently, the most distinctive was decreases in water vapor feedback and contribution of heat transport (by −0.20 and −0.55 W m−2 K−1, respectively) and increases in the lapse rate feedback and cloud feedback (by 0.13 and 0.58 W m−2 K−1, respectively) during winter in this model experiment. This study suggests that the change in Arctic cloud amount effectively reforms the contributions of individual climate feedbacks to Arctic climate system and leads to opposing effects on different feedbacks, which cancel out in the model. © 2015, Springer-Verlag Berlin Heidelberg."
"55389942900;6701815637;6603566335;","Impact of changes in the formulation of cloud-related processes on model biases and climate feedbacks",2014,"10.1002/2014MS000341","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027918346&doi=10.1002%2f2014MS000341&partnerID=40&md5=91d78f6fedae273aff1a8a79996dce81","To test the impact of modeling uncertainties and biases on the simulation of cloud feedbacks, several configurations of the EC-Earth climate model are built altering physical parameterizations. An overview of the various radiative feedbacks diagnosed from the reference EC-Earth configuration is documented for the first time. The cloud feedback is positive and small. While the total feedback parameter is almost insensitive to model configuration, the cloud feedback, in particular its shortwave (SW) component, can vary considerably depending on the model settings. The lateral mass exchange rate of penetrative convection and the conversion rate from condensed water to precipitation are leading uncertain parameters affecting the radiative feedbacks diagnosed. Consistent with other studies, we find a strong correlation between low-cloud model fidelity and low-cloud response under global warming. It is shown that this relationship holds only for stratocumulus regimes and is contributed by low-cloud cover, rather than low-cloud optical thickness. Model configurations simulating higher stratocumulus cover, which is closer to the observations, exhibit a stronger positive SW cloud feedback. This feedback is likely underestimated in the reference EC-Earth configuration, over the eastern basins of the tropical oceans. In addition, connections between simulated high-cloud top altitude in present-day climate and longwave cloud feedback are discussed. © 2014. The Authors."
"54998077400;7003449707;24780215400;57203059498;","Cloud angular momentum and effective viscosity in global SPH simulations with feedback",2014,"10.1093/mnras/stu1121","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904542302&doi=10.1093%2fmnras%2fstu1121&partnerID=40&md5=f62b5f17eae4031b4fabefacce15a834","We examine simulations of isolated galaxies to analyse the effects of localized feedback on the formation and evolution of molecular clouds. Feedback contributes to turbulence and the destruction of clouds, leading to a population of clouds that is younger, less massive, and with more retrograde rotation. We investigate the evolution of clouds as they interact with each other and the diffuse interstellar medium, and determine that the role of cloud interactions differs strongly with the presence of feedback: in models without feedback, scattering events dramatically increase the retrograde fraction, but in models with feedback, mergers between clouds may slightly increase the prograde fraction.We also produce an estimate of the viscous time-scale due to cloud-cloud collisions, which increases with increasing strength of feedback (tν ̃ 20 Gyr versus tν ̃ 10 Gyr), but is still much smaller than previous estimates (tν ̃ 1000 Gyr); although collisions become more frequent with feedback, less energy is lost in each collision than in the models without feedback.© 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society."
"8718425100;55915206300;7103060756;7601492669;","Modeling the response of marine boundary layer clouds to global warming: The impact of subgrid-scale precipitation formation",2012,"10.1175/JCLI-D-11-00623.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867662357&doi=10.1175%2fJCLI-D-11-00623.1&partnerID=40&md5=8e9ab96b6a2d3f1c3fca32ced70069a3","An important parameter often adjusted to achieve agreement between simulated and observed radiative fluxes in climate models is the rain formation efficiency. This adjustment has been justified as accounting for the effects of subgrid-scale variability in cloud properties, but this tuning approach is rather arbitrary. This study examines results from a regional climate model with precipitation formation schemes that have been conventionally tuned, and it compares them with simulations employing a recently developed scheme that uses satellite observations to explicitly account for the subgrid-scale variability of clouds (""integral constraint method""). Simulations with the International Pacific Research Center's Regional Atmospheric Model (iRAM) show that the integral constraint method is capable of simulating cloud fields over the eastern Pacific that are in good agreement with observations, without requiring model tuning. A series of global warming simulations for late twenty-first-century conditions is performed to investigate the impact of the treatment of the precipitation formation efficiency on modeled cloud-climate feedbacks. The results with the integral constraint method show that the simulated cloud feedbacks have similar patterns at all the model resolutions considered (grid spacings of 50, 100, and 200 km), but there are some quantitative differences (with smaller feedbacks at finer resolution). The cloud responses to global warming in simulations with a conventionally tuned autoconversion scheme and with the integral constraint method were found to be quite consistent, although differences in individual regions of ~10%-30% are evident. No conclusions can be drawn from this study on the validity of model tuning for thick clouds and mixed phase or ice clouds, however. © 2012 American Meteorological Society."
"7402489842;56238118600;","Perspectives of parameter and state estimation in paleoclimatology",2012,"10.1007/978-3-7091-0973-1_7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948117789&doi=10.1007%2f978-3-7091-0973-1_7&partnerID=40&md5=4f5c59f3037dc45e888b8299400fe73a","Past climates provide a means for evaluating the response of the climate system to large perturbations. Our ultimate goal is to constrain climate models rigorously by paleoclimate data. For illustration, we used a conceptual climate model (a classical energy balance model) and applied the so-called “adjoint method” to minimize the misfit between our model and sea-surface temperature data for the Last Glacial Maximum (LGM, between 19,000 and 23,000 years before present). The “adjoint model” (derivative code) was generated by an “adjoint compiler.” We optimized parameters controlling the thermal diffusion and the sensitivity of the outgoing longwave radiation to changes in the zonal-mean surface temperature and the atmospheric CO2 concentration. As a result, we estimated that an equilibrium climate sensitivity between 2.2 °C and 2.5 °C was consistent with the reconstructed glacial cooling, and we were able to infer structural deficits of the simple model where the fit to current observations and paleo data was not successful. © Springer-Verlag Wien 2012."
"10243650000;7201485519;13402835300;7404142321;10241462700;7410084319;","Comparison of cloud response to CO2 doubling in two GCMS",2008,"10.2151/sola.2008-008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42449137373&doi=10.2151%2fsola.2008-008&partnerID=40&md5=16de2c2c950c03bbbb240f8147860239","The source terms of the cloud condensate tendency equation are analyzed for two general circulation models to clarify the effect of model differences on the non-convective cloud response to CO2 doubling. This analysis investigates the differences in the mechanism of cloud feedback between models, which is considered a major source of uncertainty in climate change projections. The two GCMs, the Hadley Centre model and MIROC, exhibit marked differences in cloud response in the mixed-phase region: cloud in middle to low latitudes decreases in the former and increases in the latter. The source terms indicate that the difference is attributable to the condensation-evaporation response. Discussions on the inter-model variance of cloud feedback may thus be assisted by developing a better understanding and evaluation of condensation-evaporation. The difference in the cloud response is also related to the relative importance of ice sedimentation compared to other microphysical processes: the former tends to increase mixedphase cloud while the latter tends to decrease the cloud. Physically based modeling of the relevant microphysical processes is thus considered essential for having more confidence in the simulated cloud feedback."
"7004201700;7402363038;7102403008;","Origin of climate sensitivity differences: Role of selected radiative processes in two GCMs",2007,"10.1111/j.1600-0870.2006.00224.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247601523&doi=10.1111%2fj.1600-0870.2006.00224.x&partnerID=40&md5=a8427e1362cdf74cf0bafd5e52c9a4d5","Model differences in projections of global mean and regional climate change due to increasing greenhouse gases are investigated using two atmospheric general circulation models (AGCMs): ECHAM4 (Max Planck Institute, version 4) and CCM3 (National Center for Atmospheric Research Community Climate Model version 3). We replace the ECHAM4 short-wave processes (including routines for short-wave radiation, aerosols, cloud liquid water path and cloud droplet size distribution) with the corresponding parametrizations from CCM3. We also eliminate sea-ice in both models. We find that the resulting 'hybrid'-ECHAM4 model has the same global mean temperature sensitivity (defined as the difference in temperature between the 2 × CO2 and 1 × CO2 integrations at equilibrium) and similar regional temperature change patterns as CCM3. The global mean precipitation sensitivity was only slightly affected; indicating different processes control this. Investigation of top of the atmosphere radiative feedbacks in the standard-ECHAM4 and hybrid-ECHAM4 models show that the differences in global mean temperature sensitivity and regional temperature change patterns can be attributed primarily to a stronger, negative, cloud short-wave feedback in the tropics of the hybrid-ECHAM4 model. However, comparison of the hybrid-ECHAM4 model to CCM3 reveals large differences in partitioning of the cloud feedbacks between long-wave and short-wave in the two models. This suggests that the global mean temperature sensitivity and regional temperature change patterns respond primarily to the magnitude and distribution of the top of the atmosphere feedbacks and are relatively insensitive to the partitioning between individual processes. © 2007 The Authors Journal compilation © 2007 Blackwell Munksgaard."
"35593927100;","The DMS-cloud albedo feedback effect: Greatly underestimated?",1992,"10.1007/BF00141380","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027040225&doi=10.1007%2fBF00141380&partnerID=40&md5=e304da632b52b5526ea2f846a7853d40","There are a number of ways by which the biosphere may counter any impetus for global warming that might be produced by the rising CO2 content of earth's atmosphere. Evidence for one of these phenomena, the DMS-cloud feedback effect, is discussed in light of recent claims that it is not of sufficient strength to be of much importance. © 1992 Kluwer Academic Publishers."
"7003499456;56684259500;","Regional Climate Sensitivity of Climate Extremes in CMIP6 Versus CMIP5 Multimodel Ensembles",2020,"10.1029/2019EF001474","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091423950&doi=10.1029%2f2019EF001474&partnerID=40&md5=c2465e1dd6305478e9880b1d368ffb6d","We analyze projected changes in climate extremes (extreme temperatures and heavy precipitation) in the multimodel ensembles of the fifth and sixth Coupled Model Intercomparison Projects (CMIP5 and CMIP6). The results reveal close similarity between both ensembles in the regional climate sensitivity of the projected multimodel mean changes in climate extremes, that is, their projected changes as a function of global warming. This stands in contrast to widely reported divergences in global (transient and equilibrium) climate sensitivity in the two multimodel ensembles. Some exceptions include higher warming in the South America monsoon region, lower warming in Southern Asia and Central Africa, and higher increases in heavy precipitation in Western Africa and the Sahel region in the CMIP6 ensemble. The multimodel spread in regional climate sensitivity is found to be large in both ensembles. In particular, it contributes more to intermodel spread in projected regional climate extremes compared with the intermodel spread in global climate sensitivity in CMIP6. Our results highlight the need to consider regional climate sensitivity as a distinct feature of Earth system models and a key determinant of projected regional impacts, which is largely independent of the models' response in global climate sensitivity. ©2020. The Authors."
"7006518289;6701508272;25921086700;12761052200;57206487279;25031430500;8866821900;6701431208;56585990000;6508089485;7201520140;7202699757;55259660400;7201488063;12795560600;","Characteristics of Future Warmer Base States in CESM2",2020,"10.1029/2020EA001296","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091410640&doi=10.1029%2f2020EA001296&partnerID=40&md5=b68d23f20cea84ef62f1d52b1ad2aafb","Simulations of 21st century climate with Community Earth System Model version 2 (CESM2) using the standard atmosphere (CAM6), denoted CESM2(CAM6), and the latest generation of the Whole Atmosphere Community Climate Model (WACCM6), denoted CESM2(WACCM6), are presented, and a survey of general results is described. The equilibrium climate sensitivity (ECS) of CESM2(CAM6) is 5.3°C, and CESM2(WACCM6) is 4.8°C, while the transient climate response (TCR) is 2.1°C in CESM2(CAM6) and 2.0°C in CESM2(WACCM6). Thus, these two CESM2 model versions have higher values of ECS than the previous generation of model, the CESM (CAM5) (hereafter CESM1), that had an ECS of 4.1°C, though the CESM2 versions have lower values of TCR compared to the CESM1 with a somewhat higher value of 2.3°C. All model versions produce credible simulations of the time evolution of historical global surface temperature. The higher ECS values for the CESM2 versions are reflected in higher values of global surface temperature increase by 2,100 in CESM2(CAM6) and CESM2(WACCM6) compared to CESM1 between comparable emission scenarios for the high forcing scenario. Future warming among CESM2 model versions and scenarios diverges around 2050. The larger values of TCR and ECS in CESM2(CAM6) compared to CESM1 are manifested by greater warming in the tropics. Associated with a higher climate sensitivity, for CESM2(CAM6) the first instance of an ice-free Arctic in September occurs for all scenarios and ensemble members in the 2030–2050 time frame, but about a decade later in CESM2(WACCM6), occurring around 2040–2060. ©2020 The Authors."
"57217286339;8696069500;6603183022;23012151700;55651471000;57190435285;","Multiple drivers of the North Atlantic warming hole",2020,"10.1038/s41558-020-0819-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087033446&doi=10.1038%2fs41558-020-0819-8&partnerID=40&md5=77d59e929ff39ac4e524fc264203efe6","Despite global warming, a region in the North Atlantic ocean has been observed to cool, a phenomenon known as the warming hole. Its emergence has been linked to a slowdown of the Atlantic meridional overturning circulation, which leads to a reduced ocean heat transport into the warming hole region. Here we show that, in addition to the reduced low-latitude heat import, increased ocean heat transport out of the region into higher latitudes and a shortwave cloud feedback dominate the formation and temporal evolution of the warming hole under greenhouse gas forcing. In climate model simulations of the historical period, the low-latitude Atlantic meridional overturning circulation decline does not emerge from natural variability, whereas the accelerating heat transport to higher latitudes is clearly attributable to anthropogenic forcing. Both the overturning and the gyre circulation contribute to the increased high-latitude ocean heat transport, and therefore are critical to understand the past and future evolutions of the warming hole. © 2020, The Author(s), under exclusive licence to Springer Nature Limited."
"56695227400;55569698000;6507224579;","Spatial radiative feedbacks from internal variability using multiple regression",2020,"10.1175/JCLI-D-19-0396.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085468956&doi=10.1175%2fJCLI-D-19-0396.1&partnerID=40&md5=f06f437aa907d39e6f5a5d1511614513","The sensitivity of the climate to CO2 forcing depends on spatially varying radiative feedbacks that act both locally and nonlocally. We assess whether a method employing multiple regression can be used to estimate local and nonlocal radiative feedbacks from internal variability. We test this method on millennial-length simulations performed with six coupled atmosphere-ocean general circulation models (AOGCMs). Given the spatial pattern of warming, the method does quite well at recreating the top-of-atmosphere flux response for most regions of Earth, except over the Southern Ocean where it consistently overestimates the change, leading to an overestimate of the sensitivity. For five of the six models, the method finds that local feedbacks are positive due to cloud processes, balanced by negative nonlocal shortwave cloud feedbacks associated with regions of tropical convection. For four of these models, the magnitudes of both are comparable to the Planck feedback, so that changes in the ratio between them could lead to large changes in climate sensitivity. The positive local feedback explains why observational studies that estimate spatial feedbacks using only local regressions predict an unstable climate. The method implies that sensitivity in these AOGCMs increases over time due to a reduction in the share of warming occurring in tropical convecting regions and the resulting weakening of associated shortwave cloud and longwave clear-sky feedbacks. Our results provide a step toward an observational estimate of time-varying climate sensitivity by demonstrating that many aspects of spatial feedbacks appear to be the same between internal variability and the forced response. © 2020 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"56250448700;","Diagnosing Transient Response to CO2 Forcing in Coupled Atmosphere-Ocean Model Experiments Using a Climate Model Emulator",2020,"10.1029/2019GL085844","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083509934&doi=10.1029%2f2019GL085844&partnerID=40&md5=491c872ae59a47838cbec2ee4dab3fc4","A climate model emulator that mimics an ensemble of state-of-the-art coupled climate models has been used for probabilistic climate projections. To emulate and compare the latest and previous multimodel ensembles, this study establishes a new method to diagnose a set of parameters of effective radiative forcing, feedback, and impulse response functions by fitting a minimal emulator to time series of individual models in response to step- and ramp-shaped CO2 forcing up to a quadrupling concentration level. The diagnosed CO2 forcing is scaled down to a doubling level, leading to an unbiased estimate of equilibrium climate sensitivity. The average climate sensitivity of the latest ensemble is 18% and 13% greater than that of the previous ensemble for equilibrium and transient states. Although these increases are subject to data availability, the latter smaller rate is significant and is consistent with the relationship between feedback strength and response timescales. ©2020. The Authors."
"35423103700;57203199846;7201785152;55014468500;55544443300;57202073722;24831179300;7202733689;55418587000;6602558284;36809017200;56576951600;","Strong remote control of future equatorial warming by off-equatorial forcing",2020,"10.1038/s41558-019-0667-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078597487&doi=10.1038%2fs41558-019-0667-6&partnerID=40&md5=44cebf0cf09ea34bdae39e1ad4315384","The tropical climate response to GHG forcing is spatially non-uniform1–3. Even though enhanced equatorial and eastern Pacific warming is simulated by most climate models, the underlying mechanisms—including the relative roles of atmospheric and oceanic feedbacks—remain debated. Here, we use a climate model with idealized CO2-radiative forcing patterns to show that off-equatorial radiative forcing and corresponding coupled circulation/cloud adjustments are responsible for much of equatorial warming in response to global CO2 forcing. For equatorial forcing, the atmosphere responds by enhancing atmospheric heat export to the extra-tropics, an associated strengthening of the ascending Hadley circulation branch and strong negative equatorial cloud feedbacks. These processes together greatly dampen equatorial surface warming. Intensification of the oceanic subtropical cells and increased cold subsurface water upwelling in the eastern tropical Pacific provide an additional negative feedback for surface temperatures. In contrast, applying off-equatorial forcing, the atmosphere responds by exporting less heat from the tropics, Hadley circulation weakening and weaker negative equatorial cloud feedbacks, while the subtropical cells slow down in the ocean. Our results demonstrate a delicate balance in the coupled climate system between remote circulation adjustments and regional feedbacks that create the patterns of future climate change. © 2020, The Author(s), under exclusive licence to Springer Nature Limited."
"55220443400;7406250414;15830929400;37022493200;35201784100;57207883166;57203825369;24468389200;7404976222;57215735395;57216858298;57207820825;57209799522;37105010900;57199944934;","CAS FGOALS-f3-L model dataset descriptions for CMIP6 DECK experiments [CAS FGOALS-f3-L 参加CMIP6 DECK 试验数据介绍]",2020,"10.1080/16742834.2020.1778419","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087635707&doi=10.1080%2f16742834.2020.1778419&partnerID=40&md5=04007ec3c2deea0a112ec8353b2e830e","The datasets of the Chinese Academy of Sciences (CAS) Flexible Global Ocean–Atmosphere–Land System (FGOALS-f3-L) model for the baseline experiment of the fully coupled runs in the Diagnostic, Evaluation and Characterization of Klima (DECK) common experiments of phase 6 of the Coupled Model Intercomparison Project (CMIP6) are described in this study. The CAS FGOALS-f3-L model team submitted the piControl run with a near equilibrium ocean state for 561 model years, and 160-year integrations for three ensemble members of abrupt-4× CO2 and 1pctCO2, respectively. The ensemble members restart from the 600, 650 and 700 model years in the piControl run, respectively. The baseline performances of the model are validated in this article. The preliminary evaluation suggests that the CAS FGOALS-f3-L model can preserve the long-term stability well for a mean net radiation flux of 0.31 W m−2 at the top of the atmosphere, and a limited decreasing trend of −0.03 W m−2/100 yr. The global annual mean SST is 16.45°C for the 561-year mean, with an increase of 0.03°C/100 yr. The model captures the basic spatial patterns of climate-mean SST and precipitation, but still underestimates the SST over the warm pool. The coupled model mitigates the precipitation bias in the ITCZ compared with the results from CMIP5. Moreover, the model’s climate sensitivity represented by the equilibrium climate sensitivity has been reduced from 4.5°C in CMIP5 to 3.0°C in CMIP6. All these datasets contribute to the benchmark of model behaviors for the desired continuity of CMIP. © 2020, © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group."
"57195065818;57211623938;7003696273;7404732357;7201504886;","Re-examining the first climate models: Climate sensitivity of a modern radiative–convective equilibrium model",2019,"10.1175/JCLI-D-18-0774.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074671889&doi=10.1175%2fJCLI-D-18-0774.1&partnerID=40&md5=7958c88ebd07d4a2de1faf4689f5c314","We revisit clear-sky one-dimensional radiative–convective equilibrium (1D-RCE) and determine its equilibrium climate sensitivity to a CO2 doubling (ECS) and associated uncertainty. Our 1D-RCE model, named konrad, uses the Rapid Radiative Transfer Model for GCMs (RRTMG) to calculate radiative fluxes in the same way as in comprehensive climate models. The simulated radiative feedbacks are verified by a line-by-line radiative transfer model, with which we also investigate their spectral distribution. Changing the model configuration of konrad enables a clear separation between the water vapor and the lapse rate feedbacks, as well as the interaction between the two. We find that the radiative feedback and ECS are sensitive to the chosen relative humidity profile, resulting in an ECS range of 2.09–2.40 K. Using larger CO2 forcings we find that the radiative feedback changes up to 10% for surface temperatures of 291–299 K. Although the ECS is similar to previous studies, it arises from the compensation of a larger clear-sky forcing (4.7 W m22) and more strongly negative feedbacks (22.3 W m22 K21). The lapse rate feedback and the feedback from the interaction of lapse rate and humidity compensate each other, but the degree of compensation depends on the relative humidity profile. Additionally, the temperature profile is investigated in a warming climate. The temperature change at the convective top is half as large as at the surface, consistent with the proportionally higher anvil temperature hypothesis, as long as the humidity is consistently coupled to the temperature profile. Ó 2019 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"57190858567;23082420800;8866821900;","Contributions of atmospheric and oceanic feedbacks to subtropical northeastern sea surface temperature variability",2019,"10.1007/s00382-019-04964-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85071884882&doi=10.1007%2fs00382-019-04964-1&partnerID=40&md5=60db7c94fcc2c38550018d4486ad1d93","Previous studies show that the dominant mode of variability in the Northeastern subtropical Pacific and Atlantic are analogous. Most attention has been given to the wind-evaporation-sea surface temperature (WES) feedback, but more recent studies suggest that clouds and ocean play a role. Here, it is shown that, while the mode of variability is similar, the quantitative role of clouds and ocean are different. Using Community Earth System Model, version 1.2, cloud feedbacks and interactive ocean dynamics are disabled separately to diagnose the relative contributions of each to sea surface temperature (SST) variability in subtropical northeastern ocean basins. Results from four experiments show that the relative contributions from WES and cloud radiative feedback depend on the role of the ocean. Positive cloud radiative feedback is evident in both basins but has less impact on SST variance in the Atlantic than in the Pacific. The reason for this is that ocean processes strongly damp SST anomalies in the Pacific and weakly enhance SST anomalies in the Atlantic. When cloud feedbacks are disabled, ocean processes become a larger driver of SST variability in the Atlantic. In line with previous studies, the Northeast Pacific SST variability may be understood as a white-noise-forced linear stochastic system with positive feedback from cloud and damping by latent heat flux and ocean processes, while Atlantic SST is driven partially by variations in ocean circulation and requires vertical mixing for rendition. Between these two regions, different ocean dynamics lead to different roles for atmospheric feedbacks but still result in similar patterns of SST variability. © 2019, The Author(s)."
"57201297359;57201896263;7003543851;","Radiative feedbacks associated with the Madden–Julian oscillation",2019,"10.1175/JCLI-D-19-0144.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074630333&doi=10.1175%2fJCLI-D-19-0144.1&partnerID=40&md5=cff1df29b650d22305e567ec67ffdb16","Radiative kernels derived from CloudSat/CALIPSO measurements are used to diagnose radiative feedbacks induced by the Madden–Julian oscillation (MJO). Over the Indo-Pacific warm pool, positive cloud and water vapor feedbacks are coincident with the convective envelope of the MJO during its active phases, whereas the lapse rate feedback shows faster eastward propagation than the convective envelope. During phase 2/3, when the convective envelope is over the Indian Ocean, water vapor exhibits a vertically coherent response, with the largest anomalies and strongest feedback in the midtroposphere. Though spatial structures of the feedbacks vary, the most prominent difference lies in the magnitude. Cloud changes induce the largest radiative perturbations associated with the MJO. It is also found that the strength of the cloud feedback per unit of precipitation is greater for strong MJO events, suggesting that the strength of individual MJO events is largely dictated by the magnitude of cloud radiative heating of the atmosphere. In addition, stronger radiative heating due to water vapor and clouds helps the MJO survive the barrier effect of the Maritime Continent, leading to farther eastward propagation. These results offer process-oriented metrics that could help to improve model simulations and predictions of the MJO in the future. © 2019 American Meteorological Society."
"7202145115;8882641700;57209244069;","Convection and Climate: What Have We Learned from Simple Models and Simplified Settings?",2019,"10.1007/s40641-019-00136-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067030032&doi=10.1007%2fs40641-019-00136-9&partnerID=40&md5=c43d81c70ad49a8c250270e2129a708c","Purpose of Review: We ask what fundamental insights about the relationship of tropical convection to climate have arisen from recent investigations using simplified models. Recent Findings: The vertical distribution of relative humidity should remain approximately constant in a changed climate. The temperature of clouds in the upper troposphere should also remain effectively constant for climate changes likely to occur in response to human-induced warming. The fractional coverage of convective clouds will likely decrease slightly with warming, but it is not known how the albedo and net radiative effect of tropical convective clouds will change. The areal extent and net radiative effect of tropical convective clouds depend on the interactions of radiation, cloud physics, and turbulence within the extended upper-level ice clouds. SST gradients develop naturally as a result of the aggregation of convection and large-scale thermodynamics and circulation act to couple the cloud properties and the SST. Summary: Radiative-convective equilibrium continues to provide insight into the structure and energy balance of the atmosphere by incorporating the interactions among radiation, cloud physics, and atmospheric motion. © 2019, Springer Nature Switzerland AG."
"57211627795;13403622000;57203053066;12040335900;","A positive iris feedback: Insights from climate simulations with temperature-sensitive cloud-rain conversion",2019,"10.1175/JCLI-D-18-0845.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074653563&doi=10.1175%2fJCLI-D-18-0845.1&partnerID=40&md5=7c1a841b1d10593a7a295d0041010c26","Estimates for equilibrium climate sensitivity from current climate models continue to exhibit a large spread, from 2.1 to 4.7 K per carbon dioxide doubling. Recent studies have found that the treatment of precipitation efficiency in deep convective clouds-specifically the conversion rate from cloud condensate to rain Cp-may contribute to the large intermodel spread. It is common for convective parameterization in climate models to carry a constant Cp, although its values are model and resolution dependent. In this study, we investigate how introducing a potential iris feedback, the cloud-climate feedback introduced by parameterizing Cp to increase with surface temperature, affects future climate simulations within a slab ocean configuration of the Community Earth System Model. Progressively stronger dependencies of Cp on temperature unexpectedly increase the equilibrium climate sensitivity monotonically from 3.8 to up to 4.6 K. This positive iris feedback puzzle, in which a reduction in cirrus clouds increases surface temperature, is attributed to changes in the opacity of convectively detrained cirrus. Cirrus clouds reduced largely in ice content and marginally in horizontal coverage, and thus the positive shortwave cloud radiative feedback dominates. The sign of the iris feedback is robust across different cloud macrophysics schemes, which control horizontal cloud cover associated with detrained ice. These results suggest a potentially strong but highly uncertain connection among convective precipitation, detrained anvil cirrus, and the high cloud feedback in a climate forced by increased atmospheric carbon dioxide concentrations. © 2019 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"55622453600;","An update on the thermosteric sea level rise commitment to global warming",2019,"10.1088/1748-9326/ab1c31","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068883848&doi=10.1088%2f1748-9326%2fab1c31&partnerID=40&md5=b437d0a9bb712058464db308953d9233","The equilibrium thermosteric sea level rise caused by global warming is evaluated in several coupled climate models. The thermosteric sea level rise is found to be well approximated as a linear function of the mean ocean temperature increase in the models. However, the mean ocean temperature increase as a function of the mean surface temperature increase differs between the models. Our models can be divided into two branches; models with an Atlantic meridional overturning circulation that increases with warming have large mean ocean temperature increases and vice versa. These two different branches give estimates of the equilibrium thermosteric sea level rise per degree of surface warming that are respectively 98% and 21% larger than the estimate given in the IPCC Fifth Assessment Report. Our estimates of the equilibrium thermosteric sea level rise are also used to infer an equilibrium sea level sensitivity, a parameter akin to the often used equilibrium climate sensitivity metric. © 2019 The Author(s). Published by IOP Publishing Ltd."
"56463153400;8920681600;","The strength of low-cloud feedbacks and tropical climate: A CESM sensitivity study",2019,"10.1175/JCLI-D-18-0551.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065784261&doi=10.1175%2fJCLI-D-18-0551.1&partnerID=40&md5=e6a145e113fddef6551e5fca2e1f31e9","Variability in the strength of low-cloud feedbacks across climate models is the primary contributor to the spread in their estimates of equilibrium climate sensitivity (ECS). This raises the question: What are the regional implications for key features of tropical climate of globally weak versus strong low-cloud feedbacks in response to greenhouse gas-induced warming? To address this question and formalize our understanding of cloud controls on tropical climate, we perform a suite of idealized fully coupled and slab-ocean climate simulations across which we systematically scale the strength of the low-cloud-cover feedback under abrupt 2 × CO2 forcing within a single model, thereby isolating the impact of low-cloud feedback strength. The feedback strength is varied by modifying the stratus cloud fraction so that it is a function of not only local conditions but also global temperature in a series of abrupt 2 × CO2 sensitivity experiments. The unperturbed decrease in low cloud cover (LCC) under 2 × CO2 is greatest in the mid- and high-latitude oceans, and the subtropical eastern Pacific and Atlantic, a pattern that is magnified as the feedback strength is scaled. Consequently, sea surface temperature (SST) increases more in these regions as well as the Pacific cold tongue. As the strength of the low-cloud feedback increases this results in not only increased ECS, but also an enhanced reduction of the large-scale zonal and meridional SST gradients (structural climate sensitivity), with implications for the atmospheric Hadley and Walker circulations, as well as the hydrological cycle. The relevance of our results to simulating past warm climate is also discussed. © 2019 American Meteorological Society."
"36165781900;7402689885;7004490499;","Role of cloud feedback in regulating the “pool of inhibited cloudiness” over the Bay of Bengal",2019,"10.1007/s00703-017-0560-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85031913758&doi=10.1007%2fs00703-017-0560-7&partnerID=40&md5=ed47767f06024439a71ff94f83b02642","Cloud-circulation feedback by latent heating (LH) is a major contributor for driving atmospheric circulation. This study examines the potential role of spatial variations of LH in driving a mini-circulation for generating the “pool of inhibited cloudiness”, where cloud formation in the lower and middle troposphere is significantly inhibited over the southwest Bay of Bengal (BoB) during the Indian summer monsoon. Spaceborne observations show that LH rates in the deep convective regions of the head BoB are as high as 0.2 K/h, while that over the “pool” are about 5 times smaller. This differential heating results in modulating the mean circulation. 20 years of reanalysis data show good correlation between (a) upper troposphere (300 hPa) convergence and lower tropospheric (1000 hPa) divergence at the “pool” and (b) lower tropospheric divergence at the “pool” and lower tropospheric convergence at the head BoB as well as at the west coast of India. Besides the orographic influence, a portion of the air mass descending at the “pool” arises from deep convective regions in the north BoB and equatorial trough. This subsidence is responsible for the persistent inhibition to cloud formation at the “pool”. This case forms a classic example of the cloud-circulation feedback. © 2017, Springer-Verlag GmbH Austria."
"55232897900;9132948500;7402064802;26645289600;25624545600;7004057920;","Mechanisms Behind the Extratropical Stratiform Low-Cloud Optical Depth Response to Temperature in ARM Site Observations",2019,"10.1029/2018JD029359","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061817875&doi=10.1029%2f2018JD029359&partnerID=40&md5=695de84f7012590f91ff6ebcfc463c19","Ground-based observations from three middle- and high-latitude sites managed by the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) program are used to determine the sensitivity of the low-cloud optical depth to temperature and to test whether observations support mechanisms previously proposed to affect the optical depth feedback. Analysis of cloud optical depth retrievals support previous satellite findings that the optical depth decreases or stays constant with increases in temperature when the cloud is warm but increases when the cloud is cold. The cloud liquid water path sensitivity to warming largely explains the optical depth sensitivity at all sites. Mechanisms examined in this study involve the temperature dependence of (a) the moist-adiabatic lapse rate, (b) cloud phase partitioning, (c) drying efficiency of cloud top mixing, (d) cloud top inversion strength, and (e) boundary layer decoupling. Mechanism (a) is present across all clouds and explains 30% to 50% of the increase in liquid water path with warming at temperatures below 0 °C. However, the cloud's adiabaticity, the ratio between the liquid water path and its theoretical maximum, is at least as important and determines how the liquid water path sensitivity to temperature varies with temperature. At temperatures below 0 °C, the adiabaticity increases with warming, and the data support mechanism (b). At warmer temperatures, the adiabaticity decreases with warming, overwhelming mechanism (a) and resulting in the liquid water path decreasing with warming. This adiabaticity decrease arises primarily because of mechanism (d), and to a lesser degree because of mechanism (e). No evidence is found supporting mechanism (c). ©2019. American Geophysical Union. All Rights Reserved."
"57196437869;8696069500;11939918300;","Climate Change Feedbacks in Aquaplanet Experiments With Explicit and Parametrized Convection for Horizontal Resolutions of 2,525 Up to 5 km",2019,"10.1029/2019MS001677","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068517056&doi=10.1029%2f2019MS001677&partnerID=40&md5=0e6bf97c110c0504d9155f1a20dbaa1c","Earth's equilibrium climate sensitivity (ECS) is the long-term response to doubled atmospheric CO2 and likely between 1.5 and 4.5 K. Conventional general circulation models do not convincingly narrow down this range, and newly developed nonhydrostatic models with relatively fine horizontal resolutions of a few kilometers have thus far delivered diverse results. Here we use the nonhydrostatic ICON model with the physics package normally used for climate simulations at resolutions as fine as 5 km to study the response to a uniform surface warming in an aquaplanet configuration. We apply the model in two setups: one with convection parametrization employed and one with explicit convection. ICON exhibits a negative total feedback independent of convective representation, thus providing a stable climate with an ECS comparable to other general circulation models, though three interesting new results are found. First, ECS varies little across resolution for both setups but runs with explicit convection have systematically lower ECS than the parametrized case, mainly due to more negative tropical clear-sky longwave feedbacks. These are a consequence of a drier mean state of about 6% relative humidity for explicit convection and less midtropospheric moistening with global warming. Second, shortwave feedbacks switch from positive to negative with increasing resolution, originating foremost in the tropics and high latitudes. Third, the model shows no discernible high cloud area feedback (iris effect) in any configuration. It is possible that ICON's climate model parametrizations applied here are less appropriate for cloud resolving scales, and therefore, ongoing developments aim at implementing a more advanced prognostic cloud microphysics scheme. © 2019. The Authors."
"55831437900;57206503877;","Changes in clouds and thermodynamics under solar geoengineering and implications for required solar reduction",2018,"10.5194/acp-18-11905-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85051952447&doi=10.5194%2facp-18-11905-2018&partnerID=40&md5=a90e83613457029a24067131b30753bc","The amount of solar constant reduction required to offset the global warming from an increase in atmospheric CO2 concentration is an interesting question with implications for assessing the feasibility of solar geoengineering scenarios and for improving our theoretical understanding of Earth's climate response to greenhouse gas and solar forcings. This study investigates this question by analyzing the results of 11 coupled atmosphere-ocean global climate models running experiment G1 of the Geoengineering Model Intercomparison Project, in which CO2 concentrations are abruptly quadrupled and the solar constant is simultaneously reduced by an amount tuned to maintain the top-of-atmosphere energy balance and pre-industrial global mean temperature. The required solar constant reduction in G1 is between 3.2&thinsp;% and 5.0&thinsp;%, depending on the model, and is uncorrelated with the models' equilibrium climate sensitivity, while a formula from the experiment specifications based on the models' effective CO2 forcing and planetary albedo is well correlated with but consistently underpredicts the required solar reduction. We propose an explanation for the required solar reduction based on CO2 instantaneous forcing and the sum of radiative adjustments to the combined CO2 and solar forcings. We quantify these radiative adjustments in G1 using established methods and explore changes in atmospheric temperature, humidity, and cloud fraction in order to understand the causes of these radiative adjustments.</p>The zonal mean temperature response in G1 exhibits cooling in the tropics and warming in high latitudes at the surface; greater cooling in the upper troposphere at all latitudes; and stratospheric cooling which is mainly due to the CO2 increase. Tropospheric specific humidity decreases due to the temperature decrease, while stratospheric humidity may increase or decrease depending on the model's temperature change in the tropical tropopause layer. Low cloud fraction decreases in all models in G1, an effect that is robust and widespread across ocean and vegetated land areas. We attribute this to a reduction in boundary layer inversion strength over the ocean, and a reduction in the release of water from plants due to the increased CO2. High cloud fraction increases in the global mean in most models. The low cloud fraction reduction and atmospheric temperature decrease have strong warming effects on the planet, due to reduced reflection of shortwave radiation and reduced emission of longwave radiation, respectively. About 50&thinsp;% to 75&thinsp;% of the temperature effect is caused by the stratospheric cooling, while the reduction in atmospheric humidity results in increased outgoing longwave radiation that roughly offsets the tropospheric temperature effect. The longwave (LW) effect of the cloud changes is small in the global mean, despite the increase in high cloud fraction. Taken together, the sum of the diagnosed radiative adjustments and the CO2 instantaneous forcing explains the required solar forcing in G1 to within about 6&thinsp;%. The cloud fraction response to the G1 experiment raises interesting questions about cloud rapid adjustments and feedbacks under solar versus greenhouse forcings, which would be best explored in a model intercomparison framework with a solar-forcing-only experiment. © 2018 Author(s)"
"6603925960;57207507108;6507495053;7004325649;7003865921;7004364155;24722339600;","The Potential of a Multidecade Spaceborne Lidar Record to Constrain Cloud Feedback",2018,"10.1002/2017JD027742","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047618446&doi=10.1002%2f2017JD027742&partnerID=40&md5=e41a62d7c6c2cff583e63c0c37ea61ea","Synthetic multidecadal spaceborne lidar records are used to examine when a cloud response to anthropogenic forcing would be detectable from spaceborne lidar observations. The synthetic records are generated using long-term cloud changes predicted by two Coupled Model Intercomparison Program 5 models seen through the COSP/lidar (CFMIP, Cloud Feedback Model Intercomparison Project, Observation Simulators Package) and cloud interannual variability observed by the CALIPSO (Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations) spaceborne lidar during the past decade. CALIPSO observations do not show any significant trend yet. Our analysis of the synthetic time series suggests that the tropical cloud longwave feedback and the Southern Ocean cloud shortwave feedback might be constrained with 70% confidence with, respectively, a 20-year and 29-year uninterrupted lidar-in-space record. A 27-year record might be needed to separate the two different model predictions in the tropical subsidence clouds. Assuming that combining the CALIPSO and Earth-CARE (Earth Clouds, Aerosols and Radiation Explorer) missions will lead to a spaceborne lidar record of at least 16 years, we examine the impact of gaps and calibration offsets between successive missions. A 2-year gap between Earth-CARE and the following spaceborne lidar would have no significant impact on the capability to constrain the cloud feedback if all the space lidars were perfectly intercalibrated. Any intercalibration shift between successive lidar missions would delay the capability to constrain the cloud feedback mechanisms, larger shifts leading to longer delays. ©2018. American Geophysical Union. All Rights Reserved."
"57194876603;57188924386;57203030873;57193321831;6603925960;","The Combined Influence of Observed Southern Ocean Clouds and Sea Ice on Top-of-Atmosphere Albedo",2018,"10.1029/2018JD028505","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046536342&doi=10.1029%2f2018JD028505&partnerID=40&md5=a3e358b45a00162bbb6c5dbc37e6f08a","When sea ice concentration decreases, surface albedo decreases. Yet the impact of Southern Ocean sea ice concentration decreases on top-of-atmosphere albedo is uncertain. Why? The cloud cover and opacity response to Southern Ocean sea ice variability has been challenging to quantify. Here we use observations to constrain the cloud response to Southern Ocean sea ice variability and assess the combined influence of sea ice and clouds on top-of-atmosphere albedo. We focus on the spring and summer seasons that dominate the high-latitude shortwave energy budget. To isolate the influence of sea ice concentration on clouds, we analyze spaceborne light detection and ranging (LIDAR) observations in regions where present-day sea ice concentration varies. During spring, low cloud cover is slightly (4%) higher over open water compared to sea ice. During summer, sea ice variability does not affect low cloud cover. During both spring and summer, cloud opacity is larger over open water than over sea ice due to a cloud phase shift from ice toward liquid with warming. Independent ship-based visual and radiosonde observations available during summer corroborate the LIDAR results. Even with the cloud response, satellite-observed top-of-atmosphere albedo is lower over open water than over sea ice. The observations show the cloud response to sea ice retreat with warming will not mask the surface albedo decrease. In other words, more shortwave radiation will be absorbed when Southern Ocean sea ice is lost. ©2018. American Geophysical Union. All Rights Reserved."
"57200162560;13806362800;7003859790;7402587163;","Anomalously low δ18O values of high-latitude Permo-Triassic paleosol siderite",2018,"10.1016/j.palaeo.2017.11.062","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85039997881&doi=10.1016%2fj.palaeo.2017.11.062&partnerID=40&md5=ac33a15e591e8fc596ee298e903a093d","The most severe extinction in Earth history occurred during a time of extreme climate change, caused in part by a massive release of carbon into the atmosphere. Isotopic measurements of siderite occurring in paleosols during intervals of global warming suggest high-latitude depletions in δ18O of precipitation, often attributed to an amplified hydrologic cycle. Here, Late Permian and Early Triassic paleosol siderite from Alaska, Antarctica, eastern Australia, Siberia, and South Africa indicate similar or greater meridional gradients in siderite δ18O compared to other past warm intervals. An isotope-tracer-enabled version of the Global Environmental and Ecological Simulation of Interactive Systems (GENESIS) general circulation model (GCM) was used to compare to siderite δ18O data. The model, when deriving siderite δ18O at a specified paleoatmospheric CO2 concentration of 12.7 × the preindustrial atmospheric level (PAL), matches a small subset of relatively less depleted high-latitude siderites but does not produce the conditions necessary to explain the most depleted siderite δ18O values. Siderite has been thought to record mean annual precipitation δ18O, though this study suggests that many may not. A seasonal bias, where siderite growth occurs in the summertime in wetlands that receive most of their recharge from melting winter precipitation, may be responsible. GENESIS indicates soil moisture recharge during the spring ahead of the rainy season for high-latitude Permo-Triassic (PT) siderite localities that reach below freezing winter temperatures. Drainage from high altitude regions throughout the growing season may also be responsible. Biological cloud feedbacks and monsoon-related amount effects are not likely the cause for low siderite δ18O because the enrichment of water vapor δ18O associated with warming is too significant. © 2017 Elsevier B.V."
"56457851700;7202145115;26645289600;","Mixed-Phase Cloud Feedbacks",2018,"10.1016/B978-0-12-810549-8.00009-X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041228946&doi=10.1016%2fB978-0-12-810549-8.00009-X&partnerID=40&md5=d23faf7f134a3739997f5d3e94fc9634","This chapter introduces cloud feedbacks and describes salient features of their structure. One particularly pronounced feature simulated by global climate models (GCMs), is the contrast between the subtropics where cloud cover decreases with warming (a positive feedback) and the mid- and high-latitudes where cloud albedo increases with warming (a negative feedback). This increase in cloud albedo appears to be due to mixed-phase clouds (MPCs) transitioning from a more ice-dominated to more liquid-dominated state. The representation of this behavior in GCMs is discussed and is compared to satellite observations. Observational constraints on the MPC feedback show that the current generation of GCMs have too strong an increase in planetary albedo due to ice transitioning to liquid in the mid- and high-latitudes, indicating a potential underestimation of climate sensitivity. This behavior appears to be at least partially due to an inability to maintain supercooled liquid water at sufficiently low temperatures. © 2018 Elsevier Inc. All rights reserved."
"36499025700;55955453800;","The application of machine learning for evaluating anthropogenic versus natural climate change",2017,"10.1016/j.grj.2017.08.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028312816&doi=10.1016%2fj.grj.2017.08.001&partnerID=40&md5=b27050fe5aae1032086e4fa47e3af3a1","Time-series profiles derived from temperature proxies such as tree rings can provide information about past climate. Signal analysis was undertaken of six such datasets, and the resulting component sine waves used as input to an artificial neural network (ANN), a form of machine learning. By optimizing spectral features of the component sine waves, such as periodicity, amplitude and phase, the original temperature profiles were approximately simulated for the late Holocene period to 1830 CE. The ANN models were then used to generate projections of temperatures through the 20th century. The largest deviation between the ANN projections and measured temperatures for six geographically distinct regions was approximately 0.2 °C, and from this an Equilibrium Climate Sensitivity (ECS) of approximately 0.6 °C was estimated. This is considerably less than estimates from the General Circulation Models (GCMs) used by the Intergovernmental Panel on Climate Change (IPCC), and similar to estimates from spectroscopic methods. © 2017 Elsevier Ltd"
"35494005000;55795535700;","Using Active Remote Sensing to Evaluate Cloud-Climate Feedbacks: a Review and a Look to the Future",2017,"10.1007/s40641-017-0067-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85051595042&doi=10.1007%2fs40641-017-0067-9&partnerID=40&md5=5d17d9f7ca785aa6d966c8833cc97c48","Uncertainty in the equilibrium climate sensitivity (ECS) of the Earth continues to be large. Aspects of the cloud feedback problem have been identified as fundamental to the uncertainty in ECS. Recent analyses have shown that changes to cloud forcing with climate change can be decomposed into contributions from changes in cloud occurrence that are proportional to globally averaged temperature change and changes associated with rapid adjustments in the system that are independent of changes to globally averaged surface temperature. Together these responses enhance warming due to (1) cloud feedback from increasing cloud altitude by upper tropospheric clouds and (2) decreases in cloud coverage by marine boundary layer clouds. We argue that active remote sensing from space can play a unique and crucial role in constraining our understanding of these separate phenomena. For 1, the feedback associated with changing tropical cirrus is predicted to emerge from the statistical noise of the climate system within the next one to two decades. However, active remote sensing will need to continue for that signal to be observed since accurate placement of these clouds in the vertical dimension is necessary. For 2, the processes associated with changes to marine boundary layer clouds have been linked to the coupling between cloud and precipitation microphysics and air motions over remote ocean basins where precipitation formation in shallow convection is modulated by changes to aerosols and thermodynamics. Exploiting the synergy in combined active and passive remote sensing is likely one of the only ways of constraining our evolving theoretical understanding of low-level cloud processes as represented in cloud-resolving models and for validating global-scale models. © 2017, The Author(s)."
"35490341500;9536598800;8942525300;","Observations of increased cloud cover over irrigated agriculture in an arid environment",2017,"10.1175/JHM-D-16-0208.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027987274&doi=10.1175%2fJHM-D-16-0208.1&partnerID=40&md5=c8fc19190522ad9fd1319cdad9081cd2","Irrigated agriculture accounts for 20% of global cropland area and may alter climate locally and globally, but feedbacks on clouds and rainfall remain highly uncertain, particularly in arid regions. Nonrenewable groundwater in arid regions accounts for 20% of global irrigation water demand, and quantifying these feedbacks is crucial for the prediction of long-term water use in a changing climate. Here, satellite data are used to show how irrigated crops in an arid environment alter land surface properties, cloud cover, and rainfall patterns. Land surface temperatures (LSTs) over the cropland are 5-7 K lower than their surroundings, despite a lower albedo, suggesting that Bowen ratio is strongly reduced (and latent heat fluxes increased) over the irrigated cropland. Daytime cloud cover is increased by up to 15% points (a relative increase of 60%), with increased cloud development in the morning and a greater afternoon peak in cloud. Cloud cover is significantly correlated with interannual variations in vegetation and LST. Afternoon rainfall also appears to be enhanced around the irrigation. The cloud feedback is the opposite of what has been previously observed in tropical and semiarid regions, suggesting different processes drive land-atmosphere feedbacks in very dry environments. Increased cloud and rainfall, and associated increases in diffuse radiation and reductions in temperature, are likely to benefit vegetation growth. Predictions of changes in crop productivity due to climate change and the impacts of global land-use change on climate and the use of water resources would therefore benefit from including these effects. © 2017 American Meteorological Society."
"55399935700;7006248174;","Which way will the circulation shift in a changing climate? Possible nonlinearity of extratropical cloud feedbacks",2017,"10.1007/s00382-016-3301-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84982957461&doi=10.1007%2fs00382-016-3301-6&partnerID=40&md5=58cecc3135163c36176f979c87bedbec","In a suite of idealized experiments with the Community Atmospheric Model version 3 coupled to a slab ocean, we show that the atmospheric circulation response to CO2 increase is sensitive to extratropical cloud feedback that is potentially nonlinear. Doubling CO2 produces a poleward shift of the Southern Hemisphere (SH) midlatitude jet that is driven primarily by cloud shortwave feedback and modulated by ice albedo feedback, in agreement with earlier studies. More surprisingly, for CO2 increases smaller than ~25 %, the SH jet shifts equatorward. Nonlinearities are also apparent in the Northern Hemisphere, but with less zonal symmetry. Baroclinic instability theory and climate feedback analysis suggest that as the CO2 forcing amplitude is reduced, there is a transition from a regime in which cloud and circulation changes are largely decoupled to a regime in which they are highly coupled. In the dynamically coupled regime, there is an apparent cancellation between cloud feedback due to warming and cloud feedback due to the shifting jet, and this allows the ice albedo feedback to dominate in the high latitudes. The extent to which dynamical coupling effects exceed thermodynamic forcing effects is strongly influenced by cloud microphysics: an alternate model configuration with slightly increased cloud liquid (LIQ) produces poleward jet shifts regardless of the amplitude of CO2 forcing. Altering the cloud microphysics also produces substantial spread in the circulation response to CO2 doubling: the LIQ configuration produces a poleward SH jet shift approximately twice that produced under the default configuration. Analysis of large ensembles of the Canadian Earth System Model version 2 demonstrates that nonlinear, cloud-coupled jet shifts are also possible in comprehensive models. We still expect a poleward trend in SH jet latitude for timescales on which CO2 increases by more than ~25 %. But on shorter timescales, our results give good reason to expect significant equatorward deviations. We also discuss the implications for understanding the circulation response to small external forcings from other sources, such as the solar cycle. © 2016, Springer-Verlag Berlin Heidelberg."
"8654071800;57193674464;","Reconciling the signal and noise of atmospheric warming on decadal timescales",2017,"10.5194/esd-8-177-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85015700409&doi=10.5194%2fesd-8-177-2017&partnerID=40&md5=3ece4278d45afd4fa890471bd7c67ae2","Interactions between externally forced and internally generated climate variations on decadal timescales is a major determinant of changing climate risk. Severe testing is applied to observed global and regional surface and satellite temperatures and modelled surface temperatures to determine whether these interactions are independent, as in the traditional signal-to-noise model, or whether they interact, resulting in step-like warming. The multistep bivariate test is used to detect step changes in temperature data. The resulting data are then subject to six tests designed to distinguish between the two statistical hypotheses, hstep and htrend. Test 1: since the mid-20th century, most observed warming has taken place in four events: in 1979/80 and 1997/98 at the global scale, 1988/89 in the Northern Hemisphere and 1968-70 in the Southern Hemisphere. Temperature is more step-like than trend-like on a regional basis. Satellite temperature is more step-like than surface temperature. Warming from internal trends is less than 40ĝ€ % of the total for four of five global records tested (1880-2013/14). Test 2: correlations between step-change frequency in observations and models (1880-2005) are 0.32 (CMIP3) and 0.34 (CMIP5). For the period 1950-2005, grouping selected events (1963/64, 1968-70, 1976/77, 1979/80, 1987/88 and 1996-98), the correlation increases to 0.78. Test 3: steps and shifts (steps minus internal trends) from a 107-member climate model ensemble (2006-2095) explain total warming and equilibrium climate sensitivity better than internal trends. Test 4: in three regions tested, the change between stationary and non-stationary temperatures is step-like and attributable to external forcing. Test 5: step-like changes are also present in tide gauge observations, rainfall, ocean heat content and related variables. Test 6: across a selection of tests, a simple stepladder model better represents the internal structures of warming than a simple trend, providing strong evidence that the climate system is exhibiting complex system behaviour on decadal timescales. This model indicates that in situ warming of the atmosphere does not occur; instead, a store-and-release mechanism from the ocean to the atmosphere is proposed. It is physically plausible and theoretically sound. The presence of step-like - rather than gradual - warming is important information for characterising and managing future climate risk."
"57189755950;7005137442;","Observational evidence against strongly stabilizing tropical cloud feedbacks",2017,"10.1002/2016GL072202","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85012104637&doi=10.1002%2f2016GL072202&partnerID=40&md5=e12c094a1dd4398a4818942a8682e35b","We present a method to attribute cloud radiative feedbacks to convective processes, using subcloud layer buoyancy as a diagnostic of stable and deep convective regimes. Applying this approach to tropical remote sensing measurements over years 2000–2016 shows that an inferred negative short-term cloud feedback from deep convection was nearly offset by a positive cloud feedback from stable regimes. The net cloud feedback was within statistical uncertainty of the National Center for Atmospheric Research Community Atmosphere Model (CAM5) with historical forcings, with discrepancies in the partitioning of the cloud feedback into convective regimes. Compensation between high-cloud responses to tropics-wide warming in stable and unstable regimes resulted in smaller net changes in high-cloud fraction with warming. In addition, deep convection and associated high clouds set in at warmer temperatures in response to warming, as a consequence of nearly invariant subcloud buoyancy. This invariance further constrained the magnitude of cloud radiative feedbacks and is consistent with climate model projections. Published 2017. This article is a US Government work and is in the public domain in the United States of America."
"57191171271;57191166952;56967261800;7006432040;6701316538;","The response of phanerozoic surface temperature to variations in atmospheric oxygen concentration",2016,"10.1002/2016JD025459","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84987725248&doi=10.1002%2f2016JD025459&partnerID=40&md5=6b55f3f1050c53c55dbd1086648e4f16","Recently, Poulsen et al. (2015) suggested that O2 has played a major role in climate forcing during the Phanerozoic. Specifically, they argued that decreased O2 levels during the Cenomanian stage of the middle Cretaceous (94-100 Ma) could help explain the extremely warm climate during that time. The postulated warming mechanism involves decreased Rayleigh scattering by a thinner atmosphere, which reduces the planetary albedo and allows greater surface warming. This warming effect is then amplified by cloud feedbacks within their 3-D climate model. This increase in shortwave surface forcing, in their calculations, exceeds any decrease in the greenhouse effect caused by decreased O2. Here we use a 1-D radiative-convective climate model (with no cloud feedback) to check their results. We also include a self-consistent calculation of the change in atmospheric ozone and its effect on climate. Our results are opposite to those of Poulsen et al.: we find that the climate warms by 1.4 K at 35% O2 concentrations as a result of increased pressure broadening of CO2 and H2O absorption lines and cools by 0.8 K at 10% O2 as a result of decreased pressure broadening. The surface temperature changes are only about 1 K either way, though, for reasonable variations in Phanerozoic O2 concentrations (10%-35% by volume). Hence, it seems unlikely that changes in atmospheric O2 account for the warm climate of the Cenomanian. Other factors, such as a higher-than-expected sensitivity of climate to increased CO2 concentrations, may be required to obtain agreement with the paleoclimate data. © 2016. American Geophysical Union."
"56464971600;7004479957;15026371500;","Time scales of response to antisymmetric surface fluxes in an aquaplanet GCM",2015,"10.1002/2015GL063372","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928694587&doi=10.1002%2f2015GL063372&partnerID=40&md5=6af2104123b3d86499335c76e565f145","The intertropical convergence zone (ITCZ) shifts in response to hemispheric asymmetries in extratropical energy forcings. This study investigates the response time scale of this shift in an aquaplanet global climate model coupled to a slab ocean. A steady antisymmetric perturbation is abruptly added to the slab-ocean heat flux convergence in midlatitudes. The time scale of the ITCZ shift scales linearly with the heat capacity of the combined ocean-atmosphere system, and the shift is amplified by subtropical clear-sky radiation and cloud radiative feedbacks. Key Points ITCZ shift time scale increases linearly with model heat capacity Radiative feedbacks amplify ITCZ response to midlatitude heat flux forcing Equilibration time is 8 years for realistic slab-ocean mixed layer depth ©2015. American Geophysical Union. All Rights Reserved."
"36655445400;35849722200;41362078500;25652997700;","A numerical investigation of the impacts of anthropogenic sulfate aerosol on regional climate in East Asia",2014,"10.1007/s13143-014-0026-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904253009&doi=10.1007%2fs13143-014-0026-5&partnerID=40&md5=4e5c2104404d9a3eb90e0d63b15af20d","Aerosol and its effects, especially its indirect effects, on climate have drawn more and more attention in recent years. In this study, the first indirect radiative forcing (RF) of sulfate aerosol and its impacts on the regional climate in East Asia during the period from December 2008 to November 2009 were investigated. Affected by the general circulation and the conversion efficiency from SO2 to SO42-? in aqueous phase, a remarkable seasonal variation of sulfate was found. The results show that the highest sulfate concentration as large as 24 g m-2 appears in the summer. The indirect RF due to sulfate aerosol at the top of atmosphere (TOA) and the surface is negative, which leads to a cooling effect on the surface by 0.12°C and a reduction of precipitation by 0.01 mm d-1. The tendencies of temperature and rainfall have significant diversity in space and time. The cloud feedback, associated with the hydrologic cycle and energy budget, is responsible for this discordant distribution. The variation of low cloud dominates the change of surface temperature. The subsidence due to the cooling effect in the mid atmosphere restrained and reduced the low clouds, leading to an apparent warm effect on the surface in Northeast Mongolia. © 2014 The Korean Meteorological Society and Springer."
"55446458900;7102948986;","Decoupled response of ocean acidification to variations in climate sensitivity",2013,"10.1175/JCLI-D-12-00290.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874798537&doi=10.1175%2fJCLI-D-12-00290.1&partnerID=40&md5=2b9838033d0dcd21bd72a727379d732d","It is now well understood that the global surface ocean, whose pH has been reduced by ;0.1 in response to rising atmospheric CO2 since industrialization, will continue to become more acidic as fossil fuel CO2 emissions escalate. However, it is unclear how uncertainties in climate sensitivity to future CO2 emissions will alter the manifestation of ocean acidification. Using an earth system model of intermediate complexity, this study performs a set of simulations that varies equilibrium climate sensitivity by 1.08-4.58C for a given CO2 emissions scenario and finds two unexpected and decoupled responses. First, the greater the climate sensitivity, the larger the surface mixed layer acidification signal but the smaller the subsurface acidification. However, taken throughout the ocean, the highest climate sensitivity will paradoxically cause greater global warming while buffering whole-ocean pH by up to 24% on centennial time scales. Second, this study finds a large decoupling between pH and carbonate ion concentration in surface waters whereby these chemical properties show opposite effects under variable climate sensitivity. For every 1°C increase in climate sensitivity, the surface ocean pH reduction grows by 4%, while surface ocean carbonate ion reduction shrinks by 2%. The chemical and spatialdecoupling found here highlights the importance of distinguishing the biological impacts of pH and aragonite saturation and understanding the spatial extent of important calcifying biomes so as to truly understand the long-term impacts of ocean acidification. © 2013 American Meteorological Society."
"55758131600;55806642700;36863441600;8633784600;7404105326;","Climate system properties determining the social cost of carbon",2013,"10.1088/1748-9326/8/2/024032","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880911271&doi=10.1088%2f1748-9326%2f8%2f2%2f024032&partnerID=40&md5=796882b90aba516345e23ec94a7926d5","The choice of an appropriate scientific target to guide global mitigation efforts is complicated by uncertainties in the temperature response to greenhouse gas emissions. Much climate policy discourse has been based on the equilibrium global mean temperature increase following a concentration stabilization scenario. This is determined by the equilibrium climate sensitivity (ECS) which, in many studies, shows persistent, fat-tailed uncertainty. However, for many purposes, the equilibrium response is less relevant than the transient response. Here, we show that one prominent policy variable, the social cost of carbon (SCC), is generally better constrained by the transient climate response (TCR) than by the ECS. Simple analytic expressions show the SCC to be directly proportional to the TCR under idealized assumptions when the rate at which we discount future damage equals 2.8%. Using ensemble simulations of a simple climate model we find that knowing the true value of the TCR can reduce the relative uncertainty in the SCC substantially more, up to a factor of 3, than knowing the ECS under typical discounting assumptions. We conclude that the TCR, which is better constrained by observations, less subject to fat-tailed uncertainty and more directly related to the SCC, is generally preferable to the ECS as a single proxy for the climate response in SCC calculations. © 2013 IOP Publishing Ltd."
"8906055900;56142281300;7201404844;57203939102;36015299300;7405437902;36924657100;57196174591;","Climate response over Asia/Arctic to change in orbital parameters for the last interglacial maximum",2010,"10.1007/s12303-010-0017-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954568362&doi=10.1007%2fs12303-010-0017-1&partnerID=40&md5=5faf3e45a10962eee074612eb1a91621","The climate response over Asia/Arctic to the change in orbital parameters for the last interglacial maximum (LIGM) is investigated using the NCAR CCM3. After implementing LIGM orbital parameters, the insolation decreases in January and increases in July in the northern hemisphere in comparison to present values. The reduced net short-wave radiative heat fluxes in January lead to the surface cooling in low to mid latitudes of Asia, whereas a warming is obtained in northern Asia where the net short-wave radiative heat fluxes change little. The January warming in northern Asia/Arctic in the LIGM, consistent with proxy records, is mainly due to the marked increase in downward long wave heat fluxes associated with the increase in cloud and in part by the increase in the Arctic Oscillation polarity. In July, the increased insolation leads to the surface warming over most Asia, even though a slight cooling is obtained in low latitudes in spite of the increase in insolation, due to the decrease in the short-wave heat fluxes at the surface by the increase in the cloud amount. Precipitation overall increases at South and East Asia in July, due to the stronger southwest and southerly winds. The change in insolation due to the orbital parameters determines the climate change pattern in low- to mid-latitudes over Asia in the LIGM, even though the degree of climate change is much lower than suggested by proxy estimates. The results obtained in this study implies that, under the different climate background such as future global warming, the change in greenhouse effect associated with cloud feedback could play an important role in determining the climate change over Asia/Arctic. © 2010 The Association of Korean Geoscience Societies and Springer-Verlag Berlin Heidelberg."
"7103001269;","On the confusion of planck feedback parameters",2009,"10.1260/095830509789876835","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70450161854&doi=10.1260%2f095830509789876835&partnerID=40&md5=7e561ff9d6f625674094068a08e4c843","The Planck feedback parameter λ0 is the most fundamental quantity in the theory of global warming, because the surface temperature change ΔTs,0 is calculated by- (radiative forcing due to CO2 doubling)/λ0 in the absence of feedbacks other than that of surface temperature change. The following three groups of Planck feedback parameters are found in the literature depending on the choice of temperature Ts and the outgoing long wave radiation (OLR) at the top of atmosphere in equation of λ0 = -4OLR/Ts, which is derived from the Stefan-Boltzmann Law. This study shows that λ0 of GROUP C is a theoretically relevant choice for Ts and OLR, rather than those of GROUP A and GROUP B, while the IPCC adopted λ0 of GROUP A. Although the surface temperature change Δ Ts is 3.0K with λ0 = -3.21(W/m2)/K for CO2 doubling when lapse rate, water vapor, surface albedo and cloud feedbacks are included in the IPCC AR4, it is shown to be 0.5-0.75K with λ0 = -6.8(W/m2)/K in the present study. Since the IPCC overestimates the threat of carbon dioxide by 4-6 times, the revaluation will be needed for the CO2 reduction policies in terms of cost and potential hazards."
"7003869084;7004604556;7103259185;","A stochastic model of global atmospheric response to enhanced greenhouse warming with cloud feedback",1998,"10.1016/S0169-8095(98)00037-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031695543&doi=10.1016%2fS0169-8095%2898%2900037-4&partnerID=40&md5=814b2f40b6a8469ddd4202f9368718cc","An atmosphere-ocean climate box model is used to examine the influence of cloud feedback on the change in the climate system's variability in response to enhanced greenhouse warming. The model consists of three nonlinear stochastic differential equations that are simplified forms of the first law of thermodynamics for the atmosphere and ocean and the continuity equation for the atmospheric component of the hydrological cycle. The model is driven by random fluctuations in the mean evaporative flux, which is routed and distributed among the components of the system through the fluxes of energy and moisture. The model suggests that cloud feedback can lead to the occurrence of two climatic regimes into which the present climate may evolve as a result of an enhanced greenhouse warming. In the first regime, the mean values of the model parameters, such as temperature, precipitation and cloudiness, as well as the amplitude and timescale of their fluctuations, all increase moderately. In the second regime, these mean values increase substantially, and the amplitude and timescale of their fluctuations rise sharply. The model also predicts the existence of climatic hysteresis; that is, for the climate system to return from either of these regimes back to the present regime, a substantial decrease in the long-wave forcing is required."
"16644246500;57219201388;56450100300;36992744000;55823467500;57212215393;35509639400;6701835010;57210719777;6602176524;6603606681;56925245400;11939918300;57194693620;24335361400;37107744600;6701346974;57204886915;57208054058;57218450611;8866821900;25647939800;22954298000;57195349030;56520853700;56471429200;57192174561;7202208382;42262516200;54881950900;36187387300;26536569500;55940978200;7401945370;55437450100;55469523400;7201504886;24485834000;25645385100;36054921000;55286185400;","Clouds and Convective Self-Aggregation in a Multimodel Ensemble of Radiative-Convective Equilibrium Simulations",2020,"10.1029/2020MS002138","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086879900&doi=10.1029%2f2020MS002138&partnerID=40&md5=a471402d55ec9d5e9e85478030e3d140","The Radiative-Convective Equilibrium Model Intercomparison Project (RCEMIP) is an intercomparison of multiple types of numerical models configured in radiative-convective equilibrium (RCE). RCE is an idealization of the tropical atmosphere that has long been used to study basic questions in climate science. Here, we employ RCE to investigate the role that clouds and convective activity play in determining cloud feedbacks, climate sensitivity, the state of convective aggregation, and the equilibrium climate. RCEMIP is unique among intercomparisons in its inclusion of a wide range of model types, including atmospheric general circulation models (GCMs), single column models (SCMs), cloud-resolving models (CRMs), large eddy simulations (LES), and global cloud-resolving models (GCRMs). The first results are presented from the RCEMIP ensemble of more than 30 models. While there are large differences across the RCEMIP ensemble in the representation of mean profiles of temperature, humidity, and cloudiness, in a majority of models anvil clouds rise, warm, and decrease in area coverage in response to an increase in sea surface temperature (SST). Nearly all models exhibit self-aggregation in large domains and agree that self-aggregation acts to dry and warm the troposphere, reduce high cloudiness, and increase cooling to space. The degree of self-aggregation exhibits no clear tendency with warming. There is a wide range of climate sensitivities, but models with parameterized convection tend to have lower climate sensitivities than models with explicit convection. In models with parameterized convection, aggregated simulations have lower climate sensitivities than unaggregated simulations. ©2020. The Authors."
"7101823091;7003802133;6701431208;6602688130;25031430500;6701752471;36876405100;35561911800;55418799600;57215614911;56203249800;35184028700;57217680314;57198379031;","Comparison of Equilibrium Climate Sensitivity Estimates From Slab Ocean, 150-Year, and Longer Simulations",2020,"10.1029/2020GL088852","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089830000&doi=10.1029%2f2020GL088852&partnerID=40&md5=67798107f45719fcdc548efa306ed6e7","We compare equilibrium climate sensitivity (ECS) estimates from pairs of long (≥800-year) control and abruptly quadrupled CO2 simulations with shorter (150- and 300-year) coupled atmosphere-ocean simulations and slab ocean models (SOMs). Consistent with previous work, ECS estimates from shorter coupled simulations based on annual averages for years 1–150 underestimate those from SOM (−8% ± 13%) and long (−14% ± 8%) simulations. Analysis of only years 21–150 improved agreement with SOM (−2% ± 14%) and long (−8% ± 10%) estimates. Use of pentadal averages for years 51–150 results in improved agreement with long simulations (−4% ± 11%). While ECS estimates from current generation U.S. models based on SOM and coupled annual averages of years 1–150 range from 2.6°C to 5.3°C, estimates based longer simulations of the same models range from 3.2°C to 7.0°C. Such variations between methods argues for caution in comparison and interpretation of ECS estimates across models. ©2020. The Authors."
"57203401530;55424975000;7202991355;","Emergent constraints on transient climate response (TCR) and equilibrium climate sensitivity (ECS) from historical warming in CMIP5 and CMIP6 models",2020,"10.5194/esd-11-737-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85090173070&doi=10.5194%2fesd-11-737-2020&partnerID=40&md5=1d0bc84483c39c1e395d92ddd6ff7b81","Climate sensitivity to CO2remains the key uncertainty in projections of future climate change. Transient climate response (TCR) is the metric of temperature sensitivity that is most relevant to warming in the next few decades and contributes the biggest uncertainty to estimates of the carbon budgets consistent with the Paris targets. Equilibrium climate sensitivity (ECS) is vital for understanding longer-term climate change and stabilisation targets. In the IPCC 5th Assessment Report (AR5), the stated ""likely"" ranges (16 %-84% confidence) of TCR (1.0-2.5 K) and ECS (1.5-4.5 K) were broadly consistent with the ensemble of CMIP5 Earth system models (ESMs) available at the time. However, many of the latest CMIP6 ESMs have larger climate sensitivities, with 5 of 34 models having TCR values above 2.5K and an ensemble mean TCR of 2.0-0.4 K. Even starker, 12 of 34 models have an ECS value above 4.5 K. On the face of it, these latest ESM results suggest that the IPCC likely ranges may need revising upwards, which would cast further doubt on the feasibility of the Paris targets. Here we show that rather than increasing the uncertainty in climate sensitivity, the CMIP6 models help to constrain the likely range of TCR to 1.3-2.1 K, with a central estimate of 1.68 K. We reach this conclusion through an emergent constraint approach which relates the value of TCR linearly to the global warming from 1975 onwards. This is a period when the signal-to-noise ratio of the net radiative forcing increases strongly, so that uncertainties in aerosol forcing become progressively less problematic. We find a consistent emergent constraint on TCR when we apply the same method to CMIP5 models. Our constraints on TCR are in good agreement with other recent studies which analysed CMIP ensembles. The relationship between ECS and the post-1975 warming trend is less direct and also non-linear. However, we are able to derive a likely range of ECS of 1.9-3.4K from the CMIP6 models by assuming an underlying emergent relationship based on a two-box energy balance model. Despite some methodological differences; this is consistent with a previously published ECS constraint derived from warming trends in CMIP5 models to 2005. Our results seem to be part of a growing consensus amongst studies that have applied the emergent constraint approach to different model ensembles and to different aspects of the record of global warming © 2020 EDP Sciences. All rights reserved."
"56044817200;6701853567;26643043700;6508089485;","Increased Climate Response and Earth System Sensitivity From CCSM4 to CESM2 in Mid-Pliocene Simulations",2020,"10.1029/2019MS002033","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089846095&doi=10.1029%2f2019MS002033&partnerID=40&md5=9545d6d069e37a47e67db9e0b43bf0dd","Three new equilibrium mid-Pliocene (MP) simulations are implemented with the Community Climate System Model version 4 (CCSM4) and Community Earth System Model versions 1.2 (CESM1.2) and 2 (CESM2). All simulations are carried out with the same boundary and forcing conditions following the protocol of Pliocene Model Intercomparison Project Phase 2 (PlioMIP2). These simulations reveal amplified MP climate change relative to the preindustrial going from CCSM4 to CESM2, seen in global and polar averages of surface warming, sea ice reduction in both the Arctic and the Antarctic, and weakened Hadley circulation. The enhanced global mean warming arises from enhanced Earth system sensitivity (ESS) to not only CO2 change but also changes in boundary conditions primarily from vegetation and ice sheets. ESS is amplified by up to 70% in CCSM4 and up to 100% in CESM1.2 and CESM2 relative to the equilibrium climate sensitivity of respective models. Simulations disagree on several climate metrics. Different from CCSM4, both CESM1.2 and CESM2 show reduction of cloud cover, and weakened Walker circulation accompanied by an El Niño-like mean state of the tropical Pacific in MP simulations relative to the preindustrial. This El Niño-like mean state is consistent with paleo-observational sea surface temperatures, suggesting an improvement upon CCSM4. The performances of MP simulations are assessed with a new compilation of observational MP sea surface temperature. The model-data comparison suggests that CCSM4 is not sensitivity enough to the MP forcings, but CESM2 is likely too sensitive, especially in the tropics. © 2020. The Authors."
"57201820235;7103373205;35113718100;55171972400;24329376600;24168416900;7003976079;7007021059;","The impact of performance filtering on climate feedbacks in a perturbed parameter ensemble",2020,"10.1007/s00382-020-05281-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085898489&doi=10.1007%2fs00382-020-05281-8&partnerID=40&md5=bee3af7e966276c902cb0b13ea37a295","A key contribution to the latest generation of climate projections for the UK (UKCP18) was a perturbed parameter ensemble (PPE) of global coupled models based on HadGEM3-GC3.05. Together with 13 CMIP5 simulations, this PPE provides users with a dataset that samples modelling uncertainty and is ideal for use in impacts studies. Evaluations of global mean surface temperatures for this PPE have shown twenty-first century warming rates consistently at the top end of the CMIP5 range. Here we investigate one potential contributory factor to this lack of spread: that the methodology to select plausible members from a larger, related PPE of atmosphere-only experiments preferentially ruled out those predicted to have more negative climate feedbacks (i.e. lower climate sensitivities). We confirm that this is indeed the case. We show that performance in extratropical long-wave cloud forcing played a key role in this by constraining ice cloud parameters, which in turn constrained the feedback distribution (though causal links are not established). The relatively weak relationship driving this constraint is shown to arise from stronger relationships for the long-wave and short-wave cloud feedback components, which largely cancel out due to changes in tropical high clouds. Moreover, we show that the strength of these constraints is due to a structural bias in extratropical long-wave cloud forcing across the PPE. We discuss how choices made in the methodology to pick the plausible PPE members may result in an overly strong constraint when there is a structural bias and possible improvements to this methodology for the future. © 2020, The Author(s)."
"13405218400;6603036806;57214481486;","Climate sensitivity, agricultural productivity and the social cost of carbon in FUND",2020,"10.1007/s10018-020-00263-w","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078298879&doi=10.1007%2fs10018-020-00263-w&partnerID=40&md5=349dce75e7c7e83b0bb4e9ce30b69457","We explore the implications of recent empirical findings about CO2 fertilization and climate sensitivity on the social cost of carbon (SCC) in the FUND model. New compilations of satellite and experimental evidence suggest larger agricultural productivity gains due to CO2 growth are being experienced than are reflected in FUND parameterization. We also discuss recent studies applying empirical constraints to the probability distribution of equilibrium climate sensitivity and we argue that previous Monte Carlo analyses in IAMs have not adequately reflected the findings of this literature. Updating the distributions of these parameters under varying discount rates is influential on SCC estimates. The lower bound of the social cost of carbon is likely negative and the upper bound is much lower than previously claimed, at least through the mid-twenty-first century. Also the choice of discount rate becomes much less important under the updated parameter distributions. © 2020, The Author(s)."
"56898618600;7005202019;56996271000;57210784145;36116390600;","Evaluation of cloud base height in the North American Regional Reanalysis using ceilometer observations",2020,"10.1002/joc.6389","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075234102&doi=10.1002%2fjoc.6389&partnerID=40&md5=38c5f48a1a2241ce089706ebf25647f0","Future climate change predictions by global climate models or earth system models diverge significantly, most likely due to their different cloud responses to global warming. There is an uncertainty as to how the cloud frequency (or cloud fraction) and height will change, in turn, affecting the sign, and amount of cloud feedbacks. While satellite observations have been very useful in augmenting information on clouds, it is mostly related to cloud tops, and there is a lack of information on cloud base height (CBH). In this study, a unique record of CBH information was collected at 706 Automated Surface Observing System (ASOS) ceilometer stations to evaluate the ability of the North American Regional Reanalysis (NARR) model to correctly simulate similar information. It was found that NARR can capture the geographical distribution and the seasonal variation of CBH and cloud base frequency (CBF). On average, the CBF values of NARR were 7% fewer and the CBH values of NARR were 631 m lower than those from observations that span the distance from the surface to 7,600 m. NARR simulates CBH better in arid area in the west of the contiguous United States (CONUS) than in humid areas, where NARR frequently predicted cloud bases too low compared with observations. In the west coast area of the CONUS, the discontinuity between high cloud bases over arid inland areas and low marine cloud layers from the Pacific Ocean over coastal areas produced especially large deviations between the NARR-simulated and ASOS-observed CBHs. © 2019 The Authors. International Journal of Climatology published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"57200926820;57216842449;","The incredible lightness of water vapor",2020,"10.1175/JCLI-D-19-0260.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084940411&doi=10.1175%2fJCLI-D-19-0260.1&partnerID=40&md5=a9b352b07a43895bc890fe06832ade96","The molar mass of water vapor is much less than that of dry air. This makes a moist parcel lighter than a dry parcel of the same temperature and pressure. This effect is referred to as the vapor buoyancy effect and has often been overlooked in climate studies. We propose that the vapor buoyancy effect increases Earth's outgoing longwave radiation (OLR) and that this negative radiative effect increases with warming, stabilizing Earth's climate. We illustrate this mechanism in an idealized tropical atmosphere, where there is no horizontal buoyancy gradient in the free troposphere. Temperature increases toward dry atmosphere columns to compensate the reduced vapor buoyancy, increasing OLR by O(1 W m22) at the reference climate. In warmer climates, the temperature difference between moist and dry columns would increase as a result of increasing atmospheric water vapor, leading to enhanced radiative effect and thereby stabilizing Earth's climate. We estimate that this feedback strength is about O(0.2 W m22 K21) in the idealized atmosphere, which compares to cloud feedback and surface albedo feedback in the current climate. We further show evidence from observations and real-gas radiative transfer calculations for a significant radiative effect of vapor buoyancy in the tropical atmosphere. © 2020 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"7003266014;","Potential problems measuring climate sensitivity from the historical record",2020,"10.1175/JCLI-D-19-0476.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85080039555&doi=10.1175%2fJCLI-D-19-0476.1&partnerID=40&md5=aef1263754524b8fad8303e36de57764","This study investigates potential biases between equilibrium climate sensitivity inferred from warming over the historical period (ECShist) and the climate system’s true ECS (ECStrue). This paper focuses on two factors that could contribute to differences between these quantities. First is the impact of internal variability over the historical period: our historical climate record is just one of an infinity of possible trajectories, and these different trajectories can generate ECShist values 0.3 K below to 0.5 K above (5%–95% confidence interval) the average ECShist. Because this spread is due to unforced variability, I refer to this as the unforced pattern effect. This unforced pattern effect in the model analyzed here is traced to unforced variability in loss of sea ice, which affects the albedo feedback, and to unforced variability in warming of the troposphere, which affects the shortwave cloud feedback. There is also a forced pattern effect that causes ECShist to depart from ECStrue due to differences between today’s transient pattern of warming and the pattern of warming at 23CO2 equilibrium. Changes in the pattern of warming lead to a strengthening low-cloud feedback as equilibrium is approached in regions where surface warming is delayed: the Southern Ocean, eastern Pacific, and North Atlantic near Greenland. This forced pattern effect causes ECShist to be on average 0.2 K lower than ECStrue (;8%). The net effect of these two pattern effects together can produce an estimate of ECShist as much as 0.5 K below ECStrue © 2020 American Meteorological Society."
"56282905200;7003379342;","Radiative effects of daily cycle of cloud frequency in past and future climates",2020,"10.1007/s00382-019-05077-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076605106&doi=10.1007%2fs00382-019-05077-5&partnerID=40&md5=a8288c8aff41c0cc4c7302ab33622d77","The daily cloud cycle or diurnal cloud cycle (DCC) and its response to global warming are critical to the Earth’s energy budget, but their radiative effects have not been systematically quantified. Toward this goal, here we analyze the radiation at the top of the atmosphere and propose a measure of the DCC radiative effect (DCCRE) as the difference between the total radiative fluxes with the full cloud cycle and its uniformly distributed cloud counterpart. When applied to the frequency of cloud occurrence, DCCRE is linked to the covariance between DCC and cloud radiative effects. Satellite observations show that the daily cloud cycle is strongly linked to pacific decadal oscillation (PDO) and climate hiatus, revealing its potential role in controlling climate variability. Climate model outputs show large inter-model spreads of DCCRE, accounting for approximately 20% inter-model spread of the cloud radiative effects. Climate models also suggest that while DCCRE is not sensitive to rising temperatures at the global scale, it can be important in certain regions. Such a framework can be used to conduct a more systematic evaluation of the DCC in climate models and observations with the goal to understand climate variability and reduce uncertainty in climate projections. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature."
"35339026300;57203199846;","Using Late Pleistocene sea surface temperature reconstructions to constrain future greenhouse warming",2020,"10.1016/j.epsl.2019.115911","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075502897&doi=10.1016%2fj.epsl.2019.115911&partnerID=40&md5=e71d9c4ce100b414e93c5c52453e2475","Future greenhouse warming projections conducted with coupled climate models still exhibit a substantial spread in response to a given anthropogenic greenhouse gas concentration scenario. In order to constrain this spread and to provide robust warming projections, our understanding of Earth's global-mean surface temperature response to radiative forcing (referred to as climate sensitivity) needs to be further refined. Here we estimate an averaged glacial/interglacial climate sensitivity using 25 transient Earth system model simulations of the Last Glacial Cycle and a global-mean sea surface temperature (SST) reconstruction derived from 64 globally-distributed paleo-proxies of SST. Our results document that Earth's averaged Late Pleistocene equilibrium climate sensitivity is in the order of ∼4.2 K per CO2 doubling. Using the Representative Concentration Pathway 8.5 for future greenhouse radiative forcing, this value translates into a global-mean surface warming of ∼5.0 K by the year 2100 relative to pre-industrial levels. This estimate is in excellent agreement with the ensemble-mean projection of climate simulations conducted as part of the Coupled Model Intercomparison Project Phase 5 (CMIP5). Our uncertainty analysis reveals further that the lack of robust reconstructions of glacial aerosol forcing is a key contributor to the overall uncertainty of paleo-based estimates of climate sensitivity. © 2019 Elsevier B.V."
"47861021500;56450100300;8696069500;7201504886;","Global variability in radiative-convective equilibrium with a slab ocean under a wide range of CO2 concentrations",2020,"10.1080/16000870.2019.1699387","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85077586059&doi=10.1080%2f16000870.2019.1699387&partnerID=40&md5=3c91f2adf1b8a8f05adab29bcf1341ca","In radiative-convective equilibrium (RCE), radiative cooling of the troposphere is roughly balanced by the vaporization enthalpy set free by precipitating moist convection. Many earlier studies restricted the investigation of RCE to the dynamics of the atmosphere with constant boundary conditions including prescribed surface temperature. We investigate a GCM setup where a slab ocean is coupled to the atmosphere, and we explore a wide range of CO2 concentrations. We obtain reliable statistical quantities from thousand-year-long simulations. For moderate CO2 concentrations, we find unskewed temporal variations of 1–2 K in global mean surface temperature, with an almost constant climate sensitivity of 2 K. At CO2 concentrations beyond four times the preindustrial value, the climate sensitivity decreases to nearly zero as a result of episodic global cooling events as large as 10 K. The dynamics of these cooling events are investigated in detail and shown to be associated with an increase in large-scale low-level stratiform cloudiness in the subsiding region, which is a result of penetrative shallow convection being capped by an inversion and thus not ventilating the lower troposphere. These dynamics depend on the CO2 concentration: both through the effect of temperature on stratification and through the changing spatial scale of organization of the flow, which determines the spatial scale and temporal coherence of the stratiform cloud sheets. © 2020, © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group."
"54893098900;","Reducing Uncertainties in Climate Projections with Emergent Constraints: Concepts, Examples and Prospects",2020,"10.1007/s00376-019-9140-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076403225&doi=10.1007%2fs00376-019-9140-8&partnerID=40&md5=2a3904d0de0c1f2f0f7eb7725ea5e789","Models disagree on a significant number of responses to climate change, such as climate feedback, regional changes, or the strength of equilibrium climate sensitivity. Emergent constraints aim to reduce these uncertainties by finding links between the inter-model spread in an observable predictor and climate projections. In this paper, the concepts underlying this framework are recalled with an emphasis on the statistical inference used for narrowing uncertainties, and a review of emergent constraints found in the last two decades. Potential links between highlighted predictors are explored, especially those targeting uncertainty reductions in climate sensitivity, cloud feedback, and changes of the hydrological cycle. Yet the disagreement across emergent constraints suggests that the spread in climate sensitivity can not be significantly narrowed. This calls for weighting the realism of emergent constraints by quantifying the level of physical understanding explaining the relationship. This would also permit more efficient model evaluation and better targeted model development. In the context of the upcoming CMIP6 model intercomparison a growing number of new predictors and uncertainty reductions is expected, which call for robust statistical inferences that allow cross-validation of more likely estimates. © 2020, Institute of Atmospheric Physics/Chinese Academy of Sciences, and Science Press and Springer-Verlag GmbH Germany, part of Springer Nature."
"57211684836;36720934300;54897465300;57203049177;","Uncertainty in the Evolution of Climate Feedback Traced to the Strength of the Atlantic Meridional Overturning Circulation",2019,"10.1029/2019GL083084","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074814387&doi=10.1029%2f2019GL083084&partnerID=40&md5=cdde8fb667ee93fdaca77ac1eb507675","In most coupled climate models, effective climate sensitivity increases for a few decades following an abrupt CO2 increase. The change in the climate feedback parameter between the first 20 years and the subsequent 130 years is highly model dependent. In this study, we suggest that the intermodel spread of changes in climate feedback can be partially traced to the evolution of the Atlantic Meridional Overturning Circulation. Models with stronger Atlantic Meridional Overturning Circulation recovery tend to project more amplified warming in the Northern Hemisphere a few decades after a quadrupling of CO2. Tropospheric stability then decreases as the Northern Hemisphere gets warmer, which leads to an increase in both the lapse-rate and shortwave cloud feedbacks. Our results suggest that constraining future ocean circulation changes will be necessary for accurate climate sensitivity projections. ©2019. American Geophysical Union. All Rights Reserved."
"56958566100;7007160862;16317635200;57206503877;","The Role of Clouds and Surface Heat Fluxes in the Maintenance of the 2013–2016 Northeast Pacific Marine Heatwave",2019,"10.1029/2019JD030780","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074791357&doi=10.1029%2f2019JD030780&partnerID=40&md5=51b5ec0ec88b0c14a10105989f86e4de","Starting in late 2013, the Northeast (NE) Pacific Ocean experienced anomalously warm sea surface temperatures (SSTs) that persisted for over 2 years. This marine heatwave, known as “the Blob,” produced many devastating ecological impacts with socioeconomic implications for coastal communities. The warm waters observed during the NE Pacific 2013/2016 marine heatwave altered the surface energy balance and disrupted ocean–atmosphere interactions in the region. In principle, ocean–atmosphere interactions following the formation of the marine heatwave could have perpetuated warm SSTs through a positive SST-cloud feedback. The actual situation was more complicated. While reanalysis data show a decrease in boundary layer cloud fraction and an increase in downward shortwave radiative flux at the surface coincident with warm SSTs, this was accompanied by an increase in longwave radiative fluxes at the surface, as well as an increase in sensible and latent heat fluxes out of the ocean mixed layer. The result is a small negative net heat flux anomaly (compared to the anomalies of the individual terms contributing to the net heat flux). This provides new information about the midlatitude ocean–atmosphere system while it was in a perturbed state. More specifically, a mixed layer heat budget reveals that anomalies in both the atmospheric and oceanic processes offset each other such that the anomalously warm SSTs persisted for multiple years. The results show how the atmosphere–ocean system in the NE Pacific is able to maintain itself in an anomalous state for an extended period of time. © 2019. American Geophysical Union. All Rights Reserved."
"56747355700;56593223000;56740520800;56033135100;55199580500;23476421000;","Simulating the climate response to atmospheric oxygen variability in the Phanerozoic: A focus on the Holocene, Cretaceous and Permian",2019,"10.5194/cp-15-1463-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85073896876&doi=10.5194%2fcp-15-1463-2019&partnerID=40&md5=92aa1e57c6a8948dfc0a0d7a137ac03a","The amount of dioxygen (O2) in the atmosphere may have varied from as little as 5% to as much as 35% during the Phanerozoic eon (54 Ma-present). These changes in the amount of O2 are large enough to have led to changes in atmospheric mass, which may alter the radiative budget of the atmosphere, leading to this mechanism being invoked to explain discrepancies between climate model simulations and proxy reconstructions of past climates. Here, we present the first fully 3-D numerical model simulations to investigate the climate impacts of changes in O2 under different climate states using the coupled atmosphere-ocean Hadley Centre Global Environmental Model version 3 (HadGEM3-AO) and Hadley Centre Coupled Model version 3 (HadCM3-BL) models.We show that simulations with an increase in O2 content result in increased global-mean surface air temperature under conditions of a pre-industrial Holocene climate state, in agreement with idealised 1-D and 2-D modelling studies. We demonstrate the mechanism behind the warming is complex and involves a trade-off between a number of factors. Increasing atmospheric O2 leads to a reduction in incident shortwave radiation at the Earth's surface due to Rayleigh scattering, a cooling effect. However, there is a competing warming effect due to an increase in the pressure broadening of greenhouse gas absorption lines and dynamical feedbacks, which alter the meridional heat transport of the ocean, warming polar regions and cooling tropical regions. Case studies from past climates are investigated using HadCM3-BL and show that, in the warmest climate states in the Maastrichtian (72.1-66.0 Ma), increasing oxygen may lead to a temperature decrease, as the equilibrium climate sensitivity is lower. For the Asselian (298.9-295.0 Ma), increasing oxygen content leads to a warmer global-mean surface temperature and reduced carbon storage on land, suggesting that high oxygen content may have been a contributing factor in preventing a ""Snowball Earth"" during this period of the early Permian. These climate model simulations reconcile the surface temperature response to oxygen content changes across the hierarchy of model complexity and highlight the broad range of Earth system feedbacks that need to be accounted for when considering the climate response to changes in atmospheric oxygen content. © 2019 Author(s). This work is distributed under the Creative Commons Attribution 4.0 License."
"26656246100;7102284923;7005978899;","Including the efficacy of land ice changes in deriving climate sensitivity from paleodata",2019,"10.5194/esd-10-333-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067278462&doi=10.5194%2fesd-10-333-2019&partnerID=40&md5=263c9caf12bdd3c24bac186772e1950c","The equilibrium climate sensitivity (ECS) of climate models is calculated as the equilibrium global mean surface air warming resulting from a simulated doubling of the atmospheric CO2 concentration. In these simulations, long-Term processes in the climate system, such as land ice changes, are not incorporated. Hence, climate sensitivity derived from paleodata has to be compensated for these processes, when comparing it to the ECS of climate models. Several recent studies found that the impact these long-Term processes have on global temperature cannot be quantified directly through the global radiative forcing they induce. This renders the prevailing approach of deconvoluting paleotemperatures through a partitioning based on radiative forcings inaccurate. Here, we therefore implement an efficacy factor ""TLIU that relates the impact of land ice changes on global temperature to that of CO2 changes in our calculation of climate sensitivity from paleodata.We apply our refined approach to a proxy-inferred paleoclimate dataset, using ""ϵ [LI] 0:45+0:34-0:20 based on a multi-model assemblage of simulated relative influences of land ice changes on the Last Glacial Maximum temperature anomaly. The implemented ""TLIU is smaller than unity, meaning that per unit of radiative, forcing the impact on global temperature is less strong for land ice changes than for CO2 changes. Consequently, our obtained ECS estimate of 5:8±1:3K, where the uncertainty reflects the implemented range in ""ϵ [LI], is 50% higher than when differences in efficacy are not considered. © Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 License."
"36070123800;57196143493;7402516860;","Estimating Climate Feedbacks Using a Neural Network",2019,"10.1029/2018JD029223","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85063296101&doi=10.1029%2f2018JD029223&partnerID=40&md5=47efc64f878ec89934328db1839be451","A nonlinear method has been developed to estimate climate feedbacks based on the Neural Network (NN) taking advantage of its self-learning skills. The NN model developed here is trained using a reanalysis data set and predicts radiation flux globally from atmospheric and surface variables. The radiative feedbacks of temperature, water vapor, surface albedo, and cloud in the interannual climate variations estimated from the NN method are in agreement with those from a broadly used kernel method. However, the NN method demonstrates significant advantages: (1) it withdraws the linearity assumption of the kernel method and accounts for the nonlinear effects of the feedbacks. In the case of large climate perturbations, such as that in the Arctic caused by sea ice melt, the NN method achieves better radiation closure. (2) The method can directly calculate the radiative feedback of cloud and its components. We find that the high, middle, and low cloud feedback components analyzed from the NN method are linearly additive in the interannual climate variations, although there is a considerable nonlinear effect arising from the interactions between cloud and noncloud variables. ©2019. American Geophysical Union. All Rights Reserved."
"57205587578;7202208382;","Geographical and Seasonal Variability of Cloud-Radiative Feedbacks on Precipitation",2019,"10.1029/2018JD029186","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060597967&doi=10.1029%2f2018JD029186&partnerID=40&md5=438eee26259c5f1fe327079d9dc95e18","We have used observations to study the temporal covariability of precipitation and atmospheric radiative cooling (ARC, defined as positive when the atmosphere is radiatively cooled) on seasonal and longer time scales. Clouds act to decrease the globally averaged ARC, but their radiative effect on the ARC varies with latitude. Clouds decrease the ARC in the tropics, mainly by reducing the outgoing longwave radiation, but they increase the ARC in higher latitudes, primarily by increasing the downwelling longwave radiation at the surface. The temporal correlation of the zonally averaged precipitation rate and the zonally averaged ARC is about −0.7 in the tropics and +0.5 in higher latitudes, and it changes sign almost discontinuously toward the poles at approximately 30°N and 30°S. This suggests that changes in the ARC feed back negatively on precipitating tropical systems and positively on precipitating systems at higher latitudes. ©2019. American Geophysical Union. All Rights Reserved."
"57195672133;56228672600;7103180783;","Influence of Central Siberian Snow-Albedo Feedback on the Spring East Asian Dust Cycle and Connection With the Preceding Winter Arctic Oscillation",2018,"10.1029/2018JD029385","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058469481&doi=10.1029%2f2018JD029385&partnerID=40&md5=6dc7f873f92578828ffe4d75df9d4135","The Asian dust cycle has significant effects on the climate and environment, while its spatiotemporal variability and change mechanisms are not yet completely understood. Reanalysis data from the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA2), data set are used to explore the spatiotemporal distribution of the East Asian dust cycle and possible reasons for the interannual variations. Based on the empirical orthogonal function analysis, the dominant mode of dust emissions from the East Asian deserts in the dust season (spring) shows that the Gobi Desert contributes most of the interannual variance of dust emissions in East Asia. The patterns of the regional circulation, temperature, and radiation are analyzed by regressing these variables against the principal component time series of the first empirical orthogonal function mode. The results show that the enhanced dust emissions are associated with a cyclonic circulation anomaly and cooling in the lower and middle troposphere over Central Siberia. The cooling is attributed to local snow-albedo and cloud-albedo feedbacks. The surface cooling is conducive to maintain the snow cover, whereas the cooling in the middle troposphere is associated with the increase of the relative humidity and cloud cover. The increased snow and cloud cover reflect more shortwave radiation, tending to maintain or amplify the surface cooling. It is also found that the negative phase of the Arctic Oscillation in winter initiates the surface cooling in the next spring and results in positive snow-albedo and cloud feedbacks in Central Siberia, eventually enhancing the East Asian dust cycle. ©2018. American Geophysical Union. All Rights Reserved."
"13405561000;8918407000;35104877900;36655323000;","Changes in Marine Fog Over the North Pacific Under Different Climates in CMIP5 Multimodel Simulations",2018,"10.1029/2018JD028899","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054588037&doi=10.1029%2f2018JD028899&partnerID=40&md5=130308301e50560ff9f997e38f94e067","In this study, the changes in the occurrence of marine fog over the summer North Pacific in warmer sea surface temperature (SST) or increased CO2 climates were investigated based on atmospheric model simulations by using the fifth phase of the Climate Model Intercomparison Project (CMIP5) multimodel data. Initially, the marine fog representation in CMIP5 multimodels was briefly evaluated globally. We found that the simulated marine fog occurrence was represented relatively well in boreal summer but poorly in other seasons. The results indicated that the changes in the North Pacific high-pressure system accompanied by changes in horizontal wind patterns control the changes in marine fog occurrence in the North Pacific. The magnitude of contrasting pair changes in marine fog occurrence in the western and eastern North Pacific are primarily determined by the magnitude of changes in the North Pacific high-pressure system. Global-scale changes in the vertical profiles of the atmosphere (stability changes) can also affect the marine fog changes. These changes in marine fog over the North Pacific were consistent among most CMIP5 models. ©2018. American Geophysical Union. All Rights Reserved."
"6602748142;","Relationships Between Inversion Strength, Lower-Tropospheric Moistening, and Low-Cloud Fraction in the Subtropical Southeast Pacific Derived From Stable Isotopologues of Water Vapor",2018,"10.1029/2018GL078953","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052571228&doi=10.1029%2f2018GL078953&partnerID=40&md5=deb7bf50cea2d58d664cc94f87d962ce","Quantitative, observational constraints on lower-tropospheric mixing are crucial for improved models of low-cloud feedbacks, and analysis of water vapor isotopic composition provides an independent means for generating such constraints. In situ measurements of water vapor isotopic composition from the Chajnantor Plateau, in northern Chile, are merged with sounding data from Antofagasta and satellite measurements of cloud fraction (CF) from the SE Pacific to show an inverse relationship between the estimated inversion strength (EIS) and water vapor export from the marine boundary layer into the free troposphere. When merged with results from the subtropical northern Pacific, the relationship between EIS and water vapor transport is found to be exponential across EIS values ranging from 0 to 15.6 K. The data from Chile are stratified into terciles of EIS with average EIS values of 9, 12.6 and 15.6 K. We show positive relationships between EIS, cloud fraction, and the mixing diagnostic δDv−δDr and negative relationships between EIS and the observed mixing ratios and water vapor δD values at Chajnantor, all of which are consistent with an inverse relationship between inversion strength and water vapor export from the marine boundary layer. Inverse modeling of the isotopic data using a simple process model shows that the average mixing ratios at Chajnantor derived from the marine boundary layer are estimated to be 2.1, 1.15, and 0.84 g/kg, respectively, for the lowest, middle, and highest terciles of EIS. These results can be used to constrain convective parameterizations and models of low-cloud feedbacks. ©2018. American Geophysical Union. All Rights Reserved."
"57201338569;19638935200;56424145700;48661551300;25823927100;7410070663;","Comparison of three ice cloud optical schemes in climate simulations with community atmospheric model version 5",2018,"10.1016/j.atmosres.2018.01.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044357014&doi=10.1016%2fj.atmosres.2018.01.004&partnerID=40&md5=3086c41bbf59a6bce0812a8b4da216aa","A newly implemented Baum-Yang scheme for simulating ice cloud optical properties is compared with existing schemes (Mitchell and Fu schemes) in a standalone radiative transfer model and in the global climate model (GCM) Community Atmospheric Model Version 5 (CAM5). This study systematically analyzes the effect of different ice cloud optical schemes on global radiation and climate by a series of simulations with a simplified standalone radiative transfer model, atmospheric GCM CAM5, and a comprehensive coupled climate model. Results from the standalone radiative model show that Baum-Yang scheme yields generally weaker effects of ice cloud on temperature profiles both in shortwave and longwave spectrum. CAM5 simulations indicate that Baum-Yang scheme in place of Mitchell/Fu scheme tends to cool the upper atmosphere and strengthen the thermodynamic instability in low- and mid-latitudes, which could intensify the Hadley circulation and dehydrate the subtropics. When CAM5 is coupled with a slab ocean model to include simplified air-sea interaction, reduced downward longwave flux to surface in Baum-Yang scheme mitigates ice-albedo feedback in the Arctic as well as water vapor and cloud feedbacks in low- and mid-latitudes, resulting in an overall temperature decrease by 3.0/1.4 °C globally compared with Mitchell/Fu schemes. Radiative effect and climate feedback of the three ice cloud optical schemes documented in this study can be referred for future improvements on ice cloud simulation in CAM5. © 2018 Elsevier B.V."
"55758496500;12785245100;","Objectively combining AR5 instrumental period and paleoclimate climate sensitivity evidence",2018,"10.1007/s00382-017-3744-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021069005&doi=10.1007%2fs00382-017-3744-4&partnerID=40&md5=f3b5e841ff26eedb1cc6818952e84922","Combining instrumental period evidence regarding equilibrium climate sensitivity with largely independent paleoclimate proxy evidence should enable a more constrained sensitivity estimate to be obtained. Previous, subjective Bayesian approaches involved selection of a prior probability distribution reflecting the investigators’ beliefs about climate sensitivity. Here a recently developed approach employing two different statistical methods—objective Bayesian and frequentist likelihood-ratio—is used to combine instrumental period and paleoclimate evidence based on data presented and assessments made in the IPCC Fifth Assessment Report. Probabilistic estimates from each source of evidence are represented by posterior probability density functions (PDFs) of physically-appropriate form that can be uniquely factored into a likelihood function and a noninformative prior distribution. The three-parameter form is shown accurately to fit a wide range of estimated climate sensitivity PDFs. The likelihood functions relating to the probabilistic estimates from the two sources are multiplicatively combined and a prior is derived that is noninformative for inference from the combined evidence. A posterior PDF that incorporates the evidence from both sources is produced using a single-step approach, which avoids the order-dependency that would arise if Bayesian updating were used. Results are compared with an alternative approach using the frequentist signed root likelihood ratio method. Results from these two methods are effectively identical, and provide a 5–95% range for climate sensitivity of 1.1–4.05 K (median 1.87 K). © 2017, Springer-Verlag Berlin Heidelberg."
"25940064200;10241250100;","The value of knowledge accumulation on climate sensitivity uncertainty: Comparison between perfect information, single stage and act then learn decisions",2018,"10.1007/s11625-018-0528-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047604501&doi=10.1007%2fs11625-018-0528-7&partnerID=40&md5=a493e564f44cea7d0c317f61454b9a36","In COP21 followed by the Paris Agreement, the world is now seriously planning actions to mitigate greenhouse gas emissions toward a “below 2 °C above preindustrial levels” future. Currently, we are still far from identifying the emission pathways to achieve this target because of the various uncertainties in both climate science and the human behavior. As a part of the ICA-RUS project, conducted by Dr. Seita Emori of the National Institute for Environmental Studies we have studied how these uncertainties are eliminated by the accumulation of scientific knowledge and the decision-making processes. We consider the following three questions: first, when and how will the uncertainty range on the global temperature rise be eliminated, second which global emission pathway should be chosen before we get the perfect information, and third how much expenditure is justified in reducing the climate uncertainties. The first question has been investigated by one of the authors. Shiogama et al. (Sci Rep 6:18903, 2016) developed the Allen–Stott–Kettleborough (ASK) method further to estimate how quickly and in what way the uncertainties in future global mean temperature changes can decline when the current observation network of surface air temperature is maintained. Fourteen global climate model results in CMIP5 (CMIP http://cmip-pcmdi.llnl. gov/, 2017) are used as virtual observations of surface air temperature. The purpose of this study is to answer the remaining two questions. Based on the ASK research outcomes, we apply the multi stage decision-making known as Act Then Learn (ATL) process to an integrated assessment model MARIA which includes energy technologies, economic activities, land use changes and a simple climate model block. We reveal how accumulating observations helps to mitigate economic losses by expanding the existing ATL method to deal with the uncertainty eliminating process by ASK. The primary findings are as follows. First, the value of information largely increases as the climate target policy is more stringent. Second, even if the uncertainties in the equilibrium climate sensitivity are not fully resolved, scientific knowledge is still valuable. In other words, the expenditure for scientific researches is rationalized when we really concern the global climate changes. © The Author(s) 2017."
"24402359000;7003591311;7005920812;","Framework for improvement by vertical enhancement: A simple approach to improve representation of low and high-level clouds in large-scale models",2017,"10.1002/2016MS000815","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85017148561&doi=10.1002%2f2016MS000815&partnerID=40&md5=00b96125b23d5e05ed31d7184acda44e","Low and high clouds of shallow extent, especially stratocumulus and even more so for high-level cirrus clouds that reside where vertical resolution is particularly coarse, are poorly represented in large-scale models such as global climate models and weather forecasting models. This adversely affects, among others, estimation of cloud feedbacks for climate prediction and weather forecasts. Here we address vertical resolution as a reason for the failure of these models to adequately represent shallow clouds. We introduce a new methodology, the Framework for Improvement by Vertical Enhancement (FIVE). FIVE computes selected processes on a one-dimensional vertical grid with local high resolution in the boundary layer and near the tropopause. In addition to the host model, variables on the locally high-resolution grid are predicted in parallel so that high-resolution information is retained. By exchanging tendencies with one another, the host model and high-resolution field are always synchronized. The methodology is demonstrated for drizzling stratocumulus capped by a sharp inversion. First, FIVE is applied to a single-column model to identify the cause of biases associated with computing an assigned process at low resolution. Second, a two-dimensional regional model coupled with FIVE is shown to produce results comparable to those performed with high vertical resolution. FIVE is thus expected to represent low clouds more realistically and hence reduce the low-cloud bias in large-scale models. Finally, we propose a number of methods that will be developed and tested to further optimize FIVE. © 2017. The Authors."
"26653789100;57203108896;","A cloud feedback emulator (CFE, version 1.0) for an intermediate complexity model",2017,"10.5194/gmd-10-945-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85014004958&doi=10.5194%2fgmd-10-945-2017&partnerID=40&md5=50acf6667919894955a837b7863bf21e","The dominant source of inter-model differences in comprehensive global climate models (GCMs) are cloud radiative effects on Earth's energy budget. Intermediate complexity models, while able to run more efficiently, often lack cloud feedbacks. Here, we describe and evaluate a method for applying GCM-derived shortwave and longwave cloud feedbacks from 4 × CO2 and Last Glacial Maximum experiments to the University of Victoria Earth System Climate Model. The method generally captures the spread in top-of-the-atmosphere radiative feedbacks between the original GCMs, which impacts the magnitude and spatial distribution of surface temperature changes and climate sensitivity. These results suggest that the method is suitable to incorporate multi-model cloud feedback uncertainties in ensemble simulations with a single intermediate complexity model. © Author(s) 2017."
"7006766881;7003976079;56442691300;","The transformation of Arctic clouds with warming",2016,"10.1007/s10584-016-1772-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84984846221&doi=10.1007%2fs10584-016-1772-4&partnerID=40&md5=98b02a6959a9aa3f3762b31ddc9dde51","The progressive loss of Arctic sea ice leads to increased surface emissions of Dimethyl Sulphide (DMS), which is the dominant local source of sulphate aerosols. We test the hypothesis that cloud condensation nuclei, derived from DMS, will increase cloud-top albedo in an earth-system global climate model. The earth-system model includes fully interactive ocean biology, DMS, atmospheric chemistry, aerosols and cloud microphysics. In an idealised warming scenario, the Arctic Ocean becomes ice-free in summer when atmospheric CO2 is increased by 1 % per year to four times the pre-industrial concentrations. The summer boundary layer near-surface inversion strengthens, increasing stratification with warming, whilst the autumn inversion weakens. We find that the dominant change in cloud albedo arises from the conversion of summer clouds from ice to liquid, reducing the solar flux at the surface by 27 W m−2. Only 1–2 W m−2 of the reduced solar flux is attributed to cloud condensation nuclei associated with sulphate aerosols derived from the 2–5 fold increase in DMS emissions that results from an ice-free ocean. We conclude that aerosol-cloud feedbacks originating from DMS production in the Arctic region are largely mitigated through increased wet deposition of sulphate aerosols by rainfall and as a result are not a significant component of changes in the surface radiation budget in our model. © 2016, Crown Copyright."
"7003719588;6602873978;56030191500;8358602400;24329943700;","On a minimal model for estimating climate sensitivity",2015,"10.1016/j.ecolmodel.2014.10.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84909994296&doi=10.1016%2fj.ecolmodel.2014.10.018&partnerID=40&md5=4f1499f749cfe10c10964925cdf93085","In a recent issue of this journal, Loehle (2014) presents a ""minimal model"" for estimating climate sensitivity, identical to that previously published by Loehle and Scafetta (2011). The novelty in the more recent paper lies in the straightforward calculation of an estimate of transient climate response based on the model and an estimate of equilibrium climate sensitivity derived therefrom, via a flawed methodology. We demonstrate that the Loehle and Scafetta model systematically underestimates the transient climate response, due to a number of unsupportable assumptions regarding the climate system. Once the flaws in Loehle and Scafetta's model are addressed, the estimates of transient climate response and equilibrium climate sensitivity derived from the model are entirely consistent with those obtained from general circulation models, and indeed exclude the possibility of low climate sensitivity, directly contradicting the principal conclusion drawn by Loehle. Further, we present an even more parsimonious model for estimating climate sensitivity. Our model is based on observed changes in radiative forcings, and is therefore constrained by physics, unlike the Loehle model, which is little more than a curve-fitting exercise. © 2014 Elsevier B.V."
"7403508241;","Earth radiation budget, top-of-atmosphere radiation",2014,"10.1007/978-0-387-36699-9_39","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85051548494&doi=10.1007%2f978-0-387-36699-9_39&partnerID=40&md5=398ea3f7ab5a1e4db8dd9fdc8228378b","Satellite measurements of the Earth’s radiation budget have significant influences on the understanding of aerosols, cloud feedbacks, and atmospheric dynamics as well as other major climate physical processes and are critical for validations and improvements of climate models. Continuous, long-term radiation observations from satellite missions would lead to accurate predictions of the future climate. © Springer Science+Business Media New York 2014."
"7006151875;","Model Hierarchy and Simplified Climate Models",2011,"10.1007/978-3-642-00773-6_2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926466016&doi=10.1007%2f978-3-642-00773-6_2&partnerID=40&md5=4234fe73a221714187c2c515fd45f1f7","There is no best climate model! Different models have different advantages which may be due to their complexity or the form of their implemented parameterisations. Table 2.1 gives an (incomplete) overview of the hierarchy of models used for climate simulations. They are ordered according to their spatial dimensions. Only model types are listed but each type may be formulated in different ways. For instance different resolutions are used, different grid structures, parameters and parameterisations are chosen in a different way, etc. There are, for example, more than a dozen different ocean circulation models, all of which basically solve the same conservation equations. For model development and progress the various Modelling Intercomparison Projects provide important insight: AMIP (Atmospheric Modelling Intercomparison Project), OMIP (Ocean …), OCMIP (Ocean Carbon-cycle …), CMIP (Coupled …), PMIP (Paleo …), C4MIP (Coupled Climate-Carbon Cycle Modelling Intercomparison Project), etc. © 2011, Springer-Verlag Berlin Heidelberg."
"56283400100;","Global hydrological changes associated with a perturbation of the climate system: The role of atmospheric feedbacks, their uncertainty and their validation",1999,"10.1016/S0309-1708(99)00016-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033377692&doi=10.1016%2fS0309-1708%2899%2900016-0&partnerID=40&md5=aae1b7e8ebf233ab246be4108614b5fd","The anthropogenic increase of the atmospheric greenhouse effect is expected to bring important perturbations of the climate system during the next century. The models which are used to compute scenarios of this future climate change nevertheless suffer from important uncertainties which make impossible the detailed prediction of regional impacts. Characterizing these uncertainties as precisely as possible constitutes a necessary step to assess a climate risk and realize local impact studies. We describe the manifestation of water vapour and cloud feedbacks in the present models, and show that satellite data, in particular, may constitute an important source of information to constrain more efficiently the models."
"7003869084;7004604556;","The influence of greenhouse warming on the atmospheric component of the hydrological cycle",1996,"10.1002/(SICI)1099-1085(199610)10:10<1317::AID-HYP463>3.0.CO;2-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030265348&doi=10.1002%2f%28SICI%291099-1085%28199610%2910%3a10%3c1317%3a%3aAID-HYP463%3e3.0.CO%3b2-5&partnerID=40&md5=e3f2742a5a7267955cfd1740dce49839","An atmosphere-ocean climate box model is used to examine the influence of cloud feedback on the equilibria of the climate system. The model consists of three non-linear ordinary differential equations, which are simplified forms of the first law of thermodynamics for the atmosphere and ocean and the continuity equation for the atmospheric component of the hydrological cycle. The mass continuity equation expresses the cloud liquid water content as a function of the evaporation rate from the ocean surface and the precipitation rate. Cloud formation releases latent heat. The model clouds also absorb solar energy at a rate consistent with recent findings. The model simulates snow-ice albedo feedback, water vapour feedback and cloud feedback. The global mean precipitation and surface temperature are analysed as they respond to enhanced greenhouse warming. Model results show that cloud feedback can lead to the occurrence of multiple climate equilibria. Some of these are warmer than the present equilibrium, with increased precipitation, while others are colder, with reduced precipitation. If the cloud feedback is weak, enhanced greenhouse forcing leads to a small alteration of the present equilibrium. If the cloud feedback is strong enough, the climate system can be forced into a warmer and wetter equilibrium."
"25031430500;16027966800;55620143100;56463831800;7003406689;7004479957;7004242319;7004198777;57193451125;57189999417;","Simulating Observations of Southern Ocean Clouds and Implications for Climate",2020,"10.1029/2020JD032619","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85095828081&doi=10.1029%2f2020JD032619&partnerID=40&md5=6d3d42054025e5fc79d12bde3aa61e5d","Southern Ocean (S. Ocean) clouds are important for climate prediction. Yet previous global climate models failed to accurately represent cloud phase distributions in this observation-sparse region. In this study, data from the Southern Ocean Clouds, Radiation, Aerosol, Transport Experimental Study (SOCRATES) experiment is compared to constrained simulations from a global climate model (the Community Atmosphere Model, CAM). Nudged versions of CAM are found to reproduce many of the features of detailed in situ observations, such as cloud location, cloud phase, and boundary layer structure. The simulation in CAM6 has improved its representation of S. Ocean clouds with adjustments to the ice nucleation and cloud microphysics schemes that permit more supercooled liquid. Comparisons between modeled and observed hydrometeor size distributions suggest that the modeled hydrometeor size distributions represent the dual peaked shape and form of observed distributions, which is remarkable given the scale difference between model and observations. Comparison to satellite observations of cloud physics is difficult due to model assumptions that do not match retrieval assumptions. Some biases in the model's representation of S. Ocean clouds and aerosols remain, but the detailed cloud physical parameterization provides a basis for process level improvement and direct comparisons to observations. This is crucial because cloud feedbacks and climate sensitivity are sensitive to the representation of S. Ocean clouds. ©2020. American Geophysical Union. All Rights Reserved."
"56379892200;8718425100;57215841277;12242422700;10139397300;57212989384;7006518289;57212515855;7404029779;13402933200;","Quantifying Progress Across Different CMIP Phases With the ESMValTool",2020,"10.1029/2019JD032321","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092353853&doi=10.1029%2f2019JD032321&partnerID=40&md5=f38ff2e5ba1af8f613241ff72b6eaefc","More than 40 model groups worldwide are participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6), providing a new and rich source of information to better understand past, present, and future climate change. Here, we use the Earth System Model Evaluation Tool (ESMValTool) to assess the performance of the CMIP6 ensemble compared to the previous generations CMIP3 and CMIP5. While CMIP5 models did not capture the observed pause in the increase in global mean surface temperature between 1998 and 2013, the historical CMIP6 simulations agree well with the observed recent temperature increase, but some models have difficulties in reproducing the observed global mean surface temperature record of the second half of the twentieth century. While systematic biases in annual mean surface temperature and precipitation remain in the CMIP6 multimodel mean, individual models and high-resolution versions of the models show significant reductions in many long-standing biases. Some improvements are also found in the vertical temperature, water vapor, and zonal wind speed distributions, and root-mean-square errors for selected fields are generally smaller with reduced intermodel spread and higher average skill in the correlation patterns relative to observations. An emerging property of the CMIP6 ensemble is a higher effective climate sensitivity with an increased range between 2.3 and 5.6 K. A possible reason for this increase in some models is improvements in cloud representation resulting in stronger shortwave cloud feedbacks than in their predecessor versions. ©2020. The Authors."
"7004479957;36856321600;","Combining emergent constraints for climate sensitivity",2020,"10.1175/JCLI-D-19-0911.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85090174013&doi=10.1175%2fJCLI-D-19-0911.1&partnerID=40&md5=72576ba08461bc9bf3ffd836d9e41899","A method is proposed for combining information from several emergent constraints into a probabilistic estimate for a climate sensitivity proxy Y such as equilibrium climate sensitivity (ECS). The method is based on fitting a multivariate Gaussian PDF for Y and the emergent constraints using an ensemble of global climate models (GCMs); it can be viewed as a form of multiple linear regression of Y on the constraints. The method accounts for uncertainties in sampling this multidimensional PDF with a small number of models, for observational uncertainties in the constraints, and for overconfidence about the correlation of the constraints with the climate sensitivity. Its general form (Method C) accounts for correlations between the constraints. Method C becomes less robust when some constraints are too strongly related to each other; this can be mitigated using regularization approaches such as ridge regression. An illuminating special case, Method U, neglects any correlations between constraints except through their mutual relationship to the climate proxy; it is more robust to small GCM sample size and is appealingly interpretable. These methods are applied to ECS and the climate feedback parameter using a previously published set of 11 possible emergent constraints derived from climate models in the Coupled Model Intercomparison Project (CMIP). The 62s posterior range of ECS for Method C with no overconfidence adjustment is 4.3 6 0.7 K. For Method U with a large overconfidence adjustment, it is 4.0 6 1.3 K. This study adds confidence to past findings that most constraints predict higher climate sensitivity than the CMIP mean. © 2020 American Meteorological Society."
"57219232158;57219227529;38863214100;","Small Sensitivity of the Simulated Climate of Tidally Locked Aquaplanets to Model Resolution",2020,"10.3847/1538-4357/ab9b83","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091750027&doi=10.3847%2f1538-4357%2fab9b83&partnerID=40&md5=9bf100e7be0424f5f28469af1aa9f26d","Tidally locked terrestrial planets around low-mass stars are the prime targets of finding potentially habitable exoplanets. Several atmospheric general circulation models have been employed to simulate their possible climates; however, model intercomparisons showed that there are large differences in the results of the models even when they are forced with the same boundary conditions. In this paper, we examine whether model resolution contributes to the differences. Using the atmospheric general circulation model ExoCAM coupled to a 50 m slab ocean, we examine three different horizontal resolutions (440 km × 550 km, 210 km × 280 km, and 50 km × 70 km in latitude and longitude) and three different vertical resolutions (26, 51, and 74 levels) under the same dynamical core and the same schemes of radiation, convection, and clouds. Among the experiments, the differences are within 5 K in global-mean surface temperature and within 0.007 in planetary albedo. These differences are from cloud feedback, water vapor feedback, and the decreasing trend of relative humidity with increasing resolution. Relatively small-scale downdrafts between upwelling columns over the substellar region are better resolved and the mixing between dry and wet air parcels and between anvil clouds and their environment are enhanced as the resolution is increased. These reduce atmospheric relative humidity and high-level cloud fraction, causing a lower clear-sky greenhouse effect, a weaker cloud longwave radiation effect, and subsequently a cooler climate with increasing model resolution. Overall, the sensitivity of the simulated climate of tidally locked aquaplanets to model resolution is small. © 2020. The American Astronomical Society. All rights reserved.."
"25823927100;8905764300;57190573387;57200547267;7404438747;55656437900;41362076800;56003637600;56119479900;19638935200;35222779200;57218625456;8713118400;55738957800;56424145700;55491435100;56006950100;57218626608;57218628956;55712637800;57218629236;57217680400;57215902022;57201338569;56263595100;57190225828;57195590505;57218628814;57218629681;7404331975;55838919200;57192093198;57157623300;8684892000;57218479828;","Community Integrated Earth System Model (CIESM): Description and Evaluation",2020,"10.1029/2019MS002036","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089838908&doi=10.1029%2f2019MS002036&partnerID=40&md5=52dad30d3af772ceaaa25ddaaf31d547","A team effort to develop a Community Integrated Earth System Model (CIESM) was initiated in China in 2012. The model was based on NCAR Community Earth System Model (Version 1.2.1) with several novel developments and modifications aimed to overcome some persistent systematic biases, such as the double Intertropical Convergence Zone problem and underestimated marine boundary layer clouds. Aerosols' direct and indirect effects are prescribed using the MACv2-SP approach and data sets. The spin-up of a 500-year preindustrial simulation and three historical simulations are described and evaluated. Prominent improvements include alleviated double Intertropical Convergence Zone problem, increased marine boundary layer clouds, and better El Niño Southern Oscillation amplitude and periods. One deficiency of the model is the significantly underestimated Arctic and Antarctic sea ice in warm seasons. The historical warming is about 0.55 °C greater than observations toward 2014. CIESM has an equilibrium climate sensitivity of 5.67 K, mainly resulted from increased positive shortwave cloud feedback. Our efforts on porting and redesigning CIESM for the heterogeneous Sunway TaihuLight supercomputer are also introduced, including some ongoing developments toward a future version of the model. © 2020 The Authors."
"57202921054;56250119900;7004587644;16425609300;6602926744;57208849962;57217151747;57191172390;57211565887;55796882100;9733409000;35782476600;57213046638;","Evaluation of Southern Ocean cloud in the HadGEM3 general circulation model and MERRA-2 reanalysis using ship-based observations",2020,"10.5194/acp-20-6607-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086464925&doi=10.5194%2facp-20-6607-2020&partnerID=40&md5=3e8b340c588fcb7b5d73d741d934cbd0","Southern Ocean (SO) shortwave (SW) radiation biases are a common problem in contemporary general circulation models (GCMs), with most models exhibiting a tendency to absorb too much incoming SW radiation. These biases have been attributed to deficiencies in the representation of clouds during the austral summer months, either due to cloud cover or cloud albedo being too low. The problem has been the focus of many studies, most of which utilised satellite datasets for model evaluation. We use multi-year ship-based observations and the CERES spaceborne radiation budget measurements to contrast cloud representation and SW radiation in the atmospheric component Global Atmosphere (GA) version 7.1 of the HadGEM3 GCM and the MERRA-2 reanalysis. We find that the prevailing bias is negative in GA7.1 and positive in MERRA-2. GA7.1 performs better than MERRA-2 in terms of absolute SW bias. Significant errors of up to 21Wm-2 (GA7.1) and 39Wm-2 (MERRA-2) are present in both models in the austral summer. Using ship-based ceilometer observations, we find low cloud below 2km to be predominant in the Ross Sea and the Indian Ocean sectors of the SO. Utilising a novel surface lidar simulator developed for this study, derived from an existing Cloud Feedback Model Intercomparison Project (CFMIP) Observation Simulator Package (COSP) - active remote sensing simulator (ACTSIM) spaceborne lidar simulator, we find that GA7.1 and MERRA-2 both underestimate low cloud and fog occurrence relative to the ship observations on average by 4%-9% (GA7.1) and 18% (MERRA-2). Based on radiosonde observations, we also find the low cloud to be strongly linked to boundary layer atmospheric stability and the sea surface temperature. GA7.1 and MERRA-2 do not represent the observed relationship between boundary layer stability and clouds well. We find that MERRA-2 has a much greater proportion of cloud liquid water in the SO in austral summer than GA7.1, a likely key contributor to the difference in the SW radiation bias. Our results suggest that subgrid-scale processes (cloud and boundary layer parameterisations) are responsible for the bias and that in GA7.1 a major part of the SW radiation bias can be explained by cloud cover underestimation, relative to underestimation of cloud albedo. © 2020 Copernicus GmbH. All rights reserved."
"57213753419;7404297096;7005473082;6602859414;35798149500;","A long-term cloud albedo data record since 1980 from UV satellite sensors",2020,"10.3390/rs12121982","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086999308&doi=10.3390%2frs12121982&partnerID=40&md5=fc5f8f1f2111209fb1f0c8650d6e0ba4","Black-sky cloud albedo (BCA) is derived from satellite UV 340 nm observations from NOAA and NASA satellites to infer long-term (1980-2018) shortwave cloud albedo variations induced by volcano eruptions, the El Nino-Southern Oscillation, and decadal warming. While the UV cloud albedo has shown no long-term trend since 1980, there are statistically significant reductions over the North Atlantic and over the marine stratocumulus decks off the coast of California; increases in cloud albedo can be seen over Southeast Asia and over cloud decks off the coast of South America. The derived BCA assumes a C-1 water cloud model with varying cloud optical depths and a Cox-Munk surface BRDF over the ocean, using radiances calibrated over the East Antarctic Plateau and Greenland ice sheets during summer. © 2020 by the authors."
"7005231450;36140403600;7102875574;55875135800;57217343667;","Improved methods for estimating equilibrium climate sensitivity from transient warming simulations",2020,"10.1007/s00382-020-05242-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084075130&doi=10.1007%2fs00382-020-05242-1&partnerID=40&md5=31cee4a64a31b36880bc6bb4a15d9ab2","Equilibrium climate sensitivity (ECS) refers to the total global warming caused by an instantaneous doubling of atmospheric CO2 from the pre-industrial level in a climate system. ECS is commonly used to measure how sensitive a climate system is to CO2 forcing; but it is difficult to estimate for the real world and for fully coupled climate models because of the long response time in such a system. Earlier studies used a slab ocean coupled to an atmospheric general circulation model to estimate ECS, but such a setup is not the same as the fully coupled system. More recent studies used a linear fit between changes in global-mean surface air temperature (ΔT) and top-of-atmosphere net radiation (ΔN) to estimate ECS from relatively short simulations. Here we analyze 1000 years of simulation with abrupt quadrupling (4 × CO2) and another 500-year simulation with doubling (2 × CO2) of pre-industrial CO2 using the CESM1 model, and three other multi-millennium (~5000 year) abrupt 4 × CO2 simulations to show that the linear-fit method considerably underestimates ECS due to the flattening of the −dN/dT slope, as noticed previously. We develop and evaluate three other methods, and propose a new method that makes use of the realized warming near the end of the simulations and applies the −dN/dT slope calculated from a best fit of the ΔT and ΔN data series to a simple two-layer model to estimate the unrealized warming. Using synthetic data and the long model simulations, we show that the new method consistently outperforms the linear-fit method with small biases in the estimated ECS using 4 × CO2 simulations with at least 180 years of simulation. The new method was applied to 4 × CO2 experiments from 20 CMIP5 and 19 CMIP6 models, and the resulting ECS estimates are about 10% higher on average and up to 25% higher for models with medium–high ECS (&gt; 3 K) than those reported in the IPCC AR5. Our new estimates suggest an ECS range of about 1.78–5.45 K with a mean of 3.61 K among the CMIP5 models and about 1.85–6.25 K with a mean of 3.60 K for the CMIP6 models. Furthermore, stable ECS estimates require at least 240 (180) years of simulation for using 2 × CO2 (4 × CO2) experiments, and using shorter simulations may underestimate the ECS substantially. Our results also suggest that it is the forced −dN/dT slope after year 40, not the internally-generated −dN/dT slope, that is crucial for an accurate estimate of the ECS, and this forced slope may be fairly stable. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature."
"57216885260;6603728352;57208850489;26535307200;57212235065;6603858896;57216872504;57216879288;55840004000;7006117817;57216873113;7404574877;14632189100;49664027700;7004027377;","Assessing the performance of climate change simulation results from BESM-OA2.5 compared with a CMIP5 model ensemble",2020,"10.5194/gmd-13-2277-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085091950&doi=10.5194%2fgmd-13-2277-2020&partnerID=40&md5=6d07ec7b497f8175bae584d8b9827f9f","The main features of climate change patterns, as simulated by the coupled ocean-atmosphere version 2.5 of the Brazilian Earth System Model (BESM), are compared with those of 25 other CMIP5 models, focusing on temperature, precipitation, atmospheric circulation, and radiative feedbacks. The climate sensitivity to quadrupling the atmospheric CO2 concentration was investigated via two methods: linear regression <span classCombining double low line""cit"" idCombining double low line""xref_paren.1"">(<a hrefCombining double low line""#bib1.bibx34"">Gregory et al.</a>, <a hrefCombining double low line""#bib1.bibx34"">2004</a>) and radiative kernels <span classCombining double low line""cit"" idCombining double low line""xref_paren.2"">(<a hrefCombining double low line""#bib1.bibx73"">Soden and Held</a>, <a hrefCombining double low line""#bib1.bibx73"">2006</a>; <a hrefCombining double low line""#bib1.bibx75"">Soden et al.</a>, <a hrefCombining double low line""#bib1.bibx75"">2008</a>). Radiative kernels from both the National Center for Atmospheric Research (NCAR) and the Geophysical Fluid Dynamics Laboratory (GFDL) were used to decompose the climate feedback responses of the CMIP5 models and BESM into different processes. By applying the linear regression method for equilibrium climate sensitivity (ECS) estimation, we obtained a BESM value close to the ensemble mean value. This study reveals that the BESM simulations yield zonally average feedbacks, as estimated from radiative kernels, that lie within the ensemble standard deviation. Exceptions were found in the high latitudes of the Northern Hemisphere and over the ocean near Antarctica, where BESM showed values for lapse rate, humidity feedback, and albedo that were marginally outside the standard deviation of the values from the CMIP5 multi-model ensemble. For those areas, BESM also featured a strong positive cloud feedback that appeared as an outlier compared with all analyzed models. However, BESM showed physically consistent changes in the temperature, precipitation, and atmospheric circulation patterns relative to the CMIP5 ensemble mean. © 2019 Lippincott Williams and Wilkins. All rights reserved."
"7003420726;35580303100;","Bayesian deconstruction of climate sensitivity estimates using simple models: Implicit priors and the confusion of the inverse",2020,"10.5194/esd-11-347-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083899171&doi=10.5194%2fesd-11-347-2020&partnerID=40&md5=0becc9cf99f6509507bb292d70bc53f3","Observational constraints on the equilibrium climate sensitivity have been generated in a variety of ways, but a number of results have been calculated which appear to be based on somewhat informal heuristics. In this paper we demonstrate that many of these estimates can be reinterpreted within the standard subjective Bayesian framework in which a prior over the uncertain parameters is updated through a likelihood arising from observational evidence. We consider cases drawn from paleoclimate research, analyses of the historical warming record, and feedback analysis based on the regression of annual radiation balance observations for temperature. In each of these cases, the prior which was (under this new interpretation) implicitly used exhibits some unconventional and possibly undesirable properties. We present alternative calculations which use the same observational information to update a range of explicitly presented priors. Our calculations suggest that heuristic methods often generate reasonable results in that they agree fairly well with the explicitly Bayesian approach using a reasonable prior. However, we also find some significant differences and argue that the explicitly Bayesian approach is preferred, as it both clarifies the role of the prior and allows researchers to transparently test the sensitivity of their results to it. © Author(s) 2020."
"35509639400;57204833386;49664027700;7201504886;","Sugar, Gravel, Fish, and Flowers: Dependence of Mesoscale Patterns of Trade-Wind Clouds on Environmental Conditions",2020,"10.1029/2019GL085988","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083484048&doi=10.1029%2f2019GL085988&partnerID=40&md5=ff264d32716d7a34346cadf0bb8893dc","Trade-wind clouds exhibit a large diversity of spatial organizations at the mesoscale. Over the tropical western Atlantic, a recent study has visually identified four prominent mesoscale patterns of shallow convection, referred to as flowers, fish, gravel, and sugar. We show that these four patterns can be identified objectively from satellite observations by analyzing the spatial distribution of infrared brightness temperatures. By applying this analysis to 19 years of data, we examine relationships between cloud patterns and large-scale environmental conditions. This investigation reveals that on daily and interannual timescales, the near-surface wind speed and the strength of the lower-tropospheric stability discriminate the occurrence of the different organization patterns. These results, combined with the tight relationship between cloud patterns, low-level cloud amount, and cloud-radiative effects, suggest that the mesoscale organization of shallow clouds might change under global warming. The role of shallow convective organization in determining low-cloud feedback should thus be investigated. ©2020. The Authors."
"55537426400;57204914522;7201485519;24329376600;","Fixed anvil temperature feedback: Positive, zero, or negative?",2020,"10.1175/JCLI-D-19-0108.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091673748&doi=10.1175%2fJCLI-D-19-0108.1&partnerID=40&md5=74a67425c0c82340e6c793d03f81d3c8","The fixed anvil temperature (FAT) theory describes a mechanism for how tropical anvil clouds respond to global warming and has been used to argue for a robust positive longwave cloud feedback. A constant cloud anvil temperature, due to increased anvil altitude, has been argued to lead to a ''zero cloud emission change'' feedback, which can be considered positive relative to the negative feedback associated with cloud anvil warming when cloud altitude is unchanged. Here, partial radiative perturbation (PRP) analysis is used to quantify the radiative feedback caused by clouds that follow the FAT theory (FAT-cloud feedback) and to set this in the context of other feedback components in two atmospheric general circulation models. The FAT-cloud feedback is positive in the PRP framework due to increasing anvil altitude, but because the cloud emission does not change, this positive feedback is cancelled by an equal and opposite component of the temperature feedback due to increasing emission from the cloud. To incorporate this cancellation, the thermal radiative damping with fixed relative humidity and anvil temperature (T-FRAT) decomposition framework is proposed for longwave feedbacks, in which temperature, fixed relative humidity, and FAT-cloud feedbacks are combined. In T-FRAT, the cloud feedback under the FAT constraint is zero, while that under the proportionately higher anvil temperature (PHAT) constraint is negative. The change in the observable cloud radiative effect with FAT-cloud response is also evaluated and shown to be negative due to so-called cloud masking effects. It is shown that ''cloud masking'' is a misleading term in this context, and these effects are interpreted more generally as ''cloud climatology effects''. © 2020 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"57212781009;36889113900;","Understanding the links between climate feedbacks, variability and change using a two-layer energy balance model",2020,"10.1007/s00382-020-05189-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081637760&doi=10.1007%2fs00382-020-05189-3&partnerID=40&md5=4cb031e2b67e0a85ef5d1216322bb60a","A simple, two-layer energy balance model (EBM) is used to investigate climate variability in Coupled Model Intercomparison Project Phase 5 (CMIP5) models and examine possible links between variability and climate sensitivity, and the roles of stochastic variability, radiative feedbacks and ocean mixing. The EBM represents global variability that, while somewhat stronger than the CMIP5 models, simulates reasonable ratios between shorter and longer timescales. Variability in the EBM to the range of parameters from the Global Climate Models is found to be particularly sensitive to stochastic variability, especially on interannual time-scales. Radiative feedbacks and ocean mixing parameters are also important, particularly for decadal timescales. A modest amount of the model-to-model spread in the variance of global temperature in the CMIP5 models is explained by the EBM. The EBM exhibits a stronger link between equilibrium climate sensitivity and the magnitude of the variability than it does for transient climate response, especially on decadal and longer timescales. The EBM results suggests that spread in stochastic forcing across the CMIP5 models is the single greatest factor degrading the correlation between variability and climate sensitivity, although model to model differences in radiative forcing and mixing into the deep ocean are also important. The findings suggest that from a theoretical point of view investigating constraints from variability may be a fruitful exercise. However, they also suggest that normalizing variability in general circulation models by stochastic forcing, uptake into the deep ocean and radiative forcing are all important first steps to reduce factors that will otherwise confound the correlations. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature."
"57200083124;14051038900;24080132800;57194003391;57194275819;","The Role of Climate Sensitivity in Upper-Tail Sea Level Rise Projections",2020,"10.1029/2019GL085792","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082509451&doi=10.1029%2f2019GL085792&partnerID=40&md5=23c9a89999f254c652cf22a7b2536d56","The current uncertainty surrounding the Earth's equilibrium climate sensitivity is an important driver for climate hazard projections. While the implications for projected global temperature changes have been extensively studied, the impacts on sea level projections have been relatively unexplored. Here we analyze the relationship between the climate sensitivity and sea level projections, with a particular focus on the high-impact upper tail. We utilize a Bayesian calibration of key climate and sea level parameters using historical observations and the reduced-complexity Earth system model, Hector-BRICK. This methodology allows us to focus on plausible realizations of the climate system in a probabilistic framework. We analyze the effects of high-end climate sensitivity (above 5 K) on projections and spatial patterns of sea level change. The sea level projections hinge critically on the upper tail of the climate sensitivity, especially for the highly decision-relevant upper tail. Results have important implications for timing of threshold exceedances and regional variability. ©2020. American Geophysical Union. All Rights Reserved."
"57112070700;23012746800;","Equilibrium- And transient-state dependencies of climate sensitivity: Are they important for climate projections?",2020,"10.1175/JCLI-D-19-0248.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85080121770&doi=10.1175%2fJCLI-D-19-0248.1&partnerID=40&md5=f013ccf26d39ed3d03e4636a7046b80f","The effective equilibrium climate sensitivity is generally assumed to be constant in climate change studies, whereas it may vary due to different mechanisms. This study assesses the importance of the different types of state dependencies of the radiative feedbacks for constraining climate projections from the historical record. In transition, the radiative feedbacks may vary with the changes in the warming pattern due to inhomogeneous ocean heat uptake. They may also vary in equilibrium due to their dependence on both temperature and CO2 concentration. A two-layer energy balance model (EBM) that accounts for these effects is shown to improve the representation of any CO2 pathway for the CMIP5 ensemble. Neglecting the nonlinear effects in constraint studies of climate projections from the historical record may induce errors in the estimated future warming. TheEBMframework is used to study these errors for three characteristicCO2 pathways. The results show that the pattern effect of ocean heat uptake is not of major importance by inducing a median error of roughly 22% for a high-emission scenario. In contrast, assuming a log-linear CO2-ERF relationship and neglecting the equilibrium-state dependencies induce a larger median error of roughly 210%. This median error is likely due to the non-log-linear dependency of the instantaneous (nonadjusted) forcing, suggesting that the equilibrium-state dependencies do not induce any systematic error. However, they contribute to increasing uncertainties in future warming estimation. © 2020 American Meteorological Society."
"24528897900;23486734100;7003802133;57208462871;55286185400;7103206141;","Revisiting the Impact of Sea Salt on Climate Sensitivity",2020,"10.1029/2019GL085601","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079574921&doi=10.1029%2f2019GL085601&partnerID=40&md5=22e5408ef066d5be77f85c24d3feb363","Recent laboratory and field studies point to an increase of sea salt aerosol (SSA) emissions with temperature, suggesting that SSA may lower climate sensitivity. We assess the impact of a strong (4.2% K -1) and weak (0.7% K -1) temperature response of SSA emissions on the climate sensitivity of the coupled climate model CM4. We find that the stronger temperature dependence improves the simulation of marine aerosol optical depth sensitivity to temperature and lowers CM4 Transient Climate Response (-0.125 K), and Equilibrium Climate Sensitivity (-0.5 K). At CO2 doubling, the higher SSA emission sensitivity causes a negative radiative feedback (-0.125 W m−2 K−1), which can only be partly explained by changes in the radiative effect of SSA (-0.08 W m−2 K−1). Stronger radiative feedbacks are dominated by more negative low-level cloud feedbacks in the Northern Hemisphere, which are partly offset by more positive feedbacks in the Southern Hemisphere associated with a weaker Atlantic Meridional Overturning Circulation. Published 2020. This article is a U.S. Government work and is in the public domain in the USA."
"7402645443;7006729790;7004325649;7003854810;7404150761;11240723300;","Monetizing the Value of Measurements of Equilibrium Climate Sensitivity Using the Social Cost of Carbon",2020,"10.1007/s10666-019-09662-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064259199&doi=10.1007%2fs10666-019-09662-0&partnerID=40&md5=17c0eea1c70757f86f44ae77558ab9cf","There has been much work on the value of learning about climate and the value of information regarding the climatic system. The present research moves beyond an abstract hypothesis about future learning and considers concrete Earth Observing Systems that could enhance knowledge of the climatic system and better inform decision makers. This study shows how real options theory in combination with the social cost of carbon may help to calculate the value of information regarding equilibrium climate sensitivity and estimate the relative advantages of two different Earth Observing Systems (EOSs) for learning about ECS. One system aims to improve measurements of decadal global temperature increase and another targets measurements of decadal change of global cloud radiative effect. The paper concludes that a new EOS that substantially reduces the uncertainty in cloud radiative effect would be expected to have more value than improving estimations of the global surface temperature alone. © 2019, Springer Nature Switzerland AG."
"36052878000;7201472576;6603341831;","A simulator for the CLARA-A2 cloud climate data record and its application to assess EC-Earth polar cloudiness",2020,"10.5194/gmd-13-297-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078894032&doi=10.5194%2fgmd-13-297-2020&partnerID=40&md5=3af9784330e778fa4054dbaabc893dc1","This paper describes a new satellite simulator for the CLARA-A2 climate data record (CDR). This simulator takes into account the variable skill in cloud detection in the CLARA-A2 CDR by using a different approach to other similar satellite simulators to emulate the ability to detect clouds. In particular, the paper describes three methods to filter out clouds from climate models undetectable by observations. The first method is comparable to the current simulators in the Cloud Feedback Model Intercomparison Project (CFMIP) Observation Simulator Package (COSP), since it relies on a single visible cloud optical depth at 550 nm (τc) threshold applied globally to delineate cloudy and cloud-free conditions. Methods two and three apply long/lat-gridded values separated by daytime and nighttime conditions. Method two uses gridded varying τc as opposed to method one, which uses just a τc threshold, and method three uses a cloud probability of detection (POD) depending on the model τc. The gridded POD values are from the CLARA-A2 validation study by Karlsson and Håkansson (2018). Methods two and three replicate the relative ease or difficulty for cloud retrievals depending on the region and illumination. They increase the cloud sensitivity where the cloud retrievals are relatively straightforward, such as over midlatitude oceans, and they decrease the sensitivity where cloud retrievals are notoriously tricky, such as where thick clouds may be inseparable from cold snow-covered surfaces, as well as in areas with an abundance of broken and small-scale cumulus clouds such as the atmospheric subsidence regions over the ocean. The simulator, together with the International Satellite Cloud Climatology Project (ISCCP) simulator of the COSP, is used to assess Arctic clouds in the EC-Earth climate model compared to the CLARA-A2 and ISCCP H-Series (ISCCPH) CDRs. Compared to CLARA-A2, EC-Earth generally underestimates cloudiness in the Arctic. However, compared to ISCCP and its simulator, the opposite conclusion is reached. Based on EC-Earth, this paper shows that the simulated cloud mask of CLARA-A2, using method three, is more representative of the CDR than method one used for the ISCCP simulator. The simulator substantially improves the simulation of the CLARA-A2-detected clouds, especially in the polar regions, by accounting for the variable cloud detection skill over the year. The approach to cloud simulation based on the POD of clouds depending on their τc, location, and illumination is the preferred one as it reduces cloudiness over a range of cloud optical depths. Climate model comparisons with satellite-derived information can be significantly improved by this approach, mainly by reducing the risk of misinterpreting problems with satellite retrievals as cloudiness features. Since previous studies found that the CLARA-A2 CDR performs well in the Arctic during the summer months, and that method three is more representative than method one, the conclusion is that EC-Earth likely underestimates clouds in the Arctic summer. © Author(s) 2020."
"57194590834;7402739568;55924208000;","The Impact of a Stochastic Parameterization Scheme on Climate Sensitivity in EC-Earth",2019,"10.1029/2019JD030732","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076357138&doi=10.1029%2f2019JD030732&partnerID=40&md5=128b3a5f8fb4ecae980472d27b16d0c7","Stochastic schemes, designed to represent unresolved subgrid-scale variability, are frequently used in short and medium-range weather forecasts, where they are found to improve several aspects of the model. In recent years, the impact of stochastic physics has also been found to be beneficial for the model's long-term climate. In this paper, we demonstrate for the first time that the inclusion of a stochastic physics scheme can notably affect a model's projection of global warming, as well as its historical climatological global temperature. Specifically, we find that when including the “stochastically perturbed parametrization tendencies” (SPPT) scheme in the fully coupled climate model EC-Earth v3.1, the predicted level of global warming between 1850 and 2100 is reduced by 10% under an RCP8.5 forcing scenario. We link this reduction in climate sensitivity to a change in the cloud feedbacks with SPPT. In particular, the scheme appears to reduce the positive low cloud cover feedback and increase the negative cloud optical feedback. A key role is played by a robust, rapid increase in cloud liquid water with SPPT, which we speculate is due to the scheme's nonlinear interaction with condensation. ©2019. The Authors."
"30667558200;57193132723;6603925960;","The Cumulus and Stratocumulus CloudSat-CALIPSO Dataset (CASCCAD)",2019,"10.5194/essd-11-1745-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075728960&doi=10.5194%2fessd-11-1745-2019&partnerID=40&md5=34519406e6b18e16c6eb6d535d9dc0a6","Low clouds continue to contribute greatly to the uncertainty in cloud feedback estimates. Depending on whether a region is dominated by cumulus (Cu) or stratocumulus (Sc) clouds, the interannual low-cloud feedback is somewhat different in both spaceborne and large-eddy simulation studies. Therefore, simulating the correct amount and variation of the Cu and Sc cloud distributions could be crucial to predict future cloud feedbacks. Here we document spatial distributions and profiles of Sc and Cu clouds derived from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and CloudSat measurements. For this purpose, we create a new dataset called the Cumulus And Stratocumulus CloudSat-CALIPSO Dataset (CASCCAD), which identifies Sc, broken Sc, Cu under Sc, Cu with stratiform outflow and Cu. To separate the Cu from Sc, we design an original method based on the cloud height, horizontal extent, vertical variability and horizontal continuity, which is separately applied to both CALIPSO and combined CloudSat-CALIPSO observations. First, the choice of parameters used in the discrimination algorithm is investigated and validated in selected Cu, Sc and Sc-Cu transition case studies. Then, the global statistics are compared against those from existing passive- and active-sensor satellite observations. Our results indicate that the cloud optical thickness - as used in passive-sensor observations - is not a sufficient parameter to discriminate Cu from Sc clouds, in agreement with previous literature. Using clustering-derived datasets shows better results although one cannot completely separate cloud types with such an approach. On the contrary, classifying Cu and Sc clouds and the transition between them based on their geometrical shape and spatial heterogeneity leads to spatial distributions consistent with prior knowledge of these clouds, from ground-based, ship-based and field campaigns. Furthermore, we show that our method improves existing Sc-Cu classifications by using additional information on cloud height and vertical cloud fraction variation. Finally, the CASCCAD datasets provide a basis to evaluate shallow convection and stratocumulus clouds on a global scale in climate models and potentially improve our understanding of low-level cloud feedbacks. The CASCCAD dataset (Cesana, 2019, <a hrefCombining double low line""https://doi.org/10.5281/zenodo.2667637"">https://doi.org/10.5281/zenodo.2667637</a>) is available on the Goddard Institute for Space Studies (GISS) website at <span classCombining double low line""uri"">https://data.giss.nasa.gov/clouds/casccad/</span> (last access: 5 November 2019) and on the zenodo website at <span classCombining double low line""uri"">https://zenodo.org/record/2667637</span> (last access: 5 November 2019). © 2015 Royal Society of Chemistry. All rights reserved."
"55704590100;7005902717;","Quantifying the Cloud Particle-Size Feedback in an Earth System Model",2019,"10.1029/2019GL083829","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074194066&doi=10.1029%2f2019GL083829&partnerID=40&md5=65b778e1a6e4fb4464ba3e3e586de066","Physical process-based two-moment cloud microphysical parameterizations, in which effective cloud particle size evolves prognostically with climate change, have recently been incorporated into global climate models. The impacts of cloud particle-size change on the cloud feedback, however, have never been explicitly quantified. Here we develop a partial radiative perturbation-based method to estimate the cloud feedback associated with particle-size changes in the Community Earth System Model. We find an increase of cloud particle size in the upper troposphere in response to an instantaneous doubling of atmospheric CO2. The associated net, shortwave, and longwave cloud feedbacks are estimated to be 0.18, 0.33, and −0.15 Wm−2 K−1, respectively. The cloud particle-size feedback is dominated by its shortwave component with a maximum greater than 1.0 Wm−2 K−1 in the tropics and the Southern Ocean. We suggest that the cloud particle-size feedback is an underappreciated contributor to the spread of cloud feedback and climate sensitivity among current models. ©2019. American Geophysical Union. All Rights Reserved."
"56502199700;8067118800;10243650000;55355176000;","Incorporation of inline warm rain diagnostics into the COSP2 satellite simulator for process-oriented model evaluation",2019,"10.5194/gmd-12-4297-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85073230501&doi=10.5194%2fgmd-12-4297-2019&partnerID=40&md5=d2d9d54b5df88c1df62866200d848eac","The Cloud Feedback Model Intercomparison Project Observational Simulator Package (COSP) is used to diagnose model performance and physical processes via an apple-to-apple comparison to satellite measurements. Although the COSP provides useful information about clouds and their climatic impact, outputs that have a subcolumn dimension require large amounts of data. This can cause a bottleneck when conducting sets of sensitivity experiments or multiple model intercomparisons. Here, we incorporate two diagnostics for warm rain microphysical processes into the latest version of the simulator (COSP2). The first one is the occurrence frequency of warm rain regimes (i.e., non-precipitating, drizzling, and precipitating) classified according to CloudSat radar reflectivity, putting the warm rain process diagnostics into the context of the geographical distributions of precipitation. The second diagnostic is the probability density function of radar reflectivity profiles normalized by the in-cloud optical depth, the so-called contoured frequency by optical depth diagram (CFODD), which illustrates how the warm rain processes occur in the vertical dimension using statistics constructed from CloudSat and MODIS simulators. The new diagnostics are designed to produce statistics online along with subcolumn information during the COSP execution, eliminating the need to output subcolumn variables. Users can also readily conduct regional analysis tailored to their particular research interest (e.g., land-ocean differences) using an auxiliary post-process package after the COSP calculation. The inline diagnostics are applied to the MIROC6 general circulation model (GCM) to demonstrate how known biases common among multiple GCMs relative to satellite observations are revealed. The inline multi-sensor diagnostics are intended to serve as a tool that facilitates process-oriented model evaluations in a manner that reduces the burden on modelers for their diagnostics effort. © 2019 Geoscientific Model Development. All rights reserved."
"56276584900;10042470700;","Efficacy of black carbon aerosols: The role of shortwave cloud feedback",2019,"10.1088/1748-9326/ab21e7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85072711403&doi=10.1088%2f1748-9326%2fab21e7&partnerID=40&md5=dab35964525ab0f8d5b3201553626f6f","Using idealized climate model simulations, we investigate the effectiveness of black carbon (BC) aerosols in warming the planet relative to CO2 forcing. We find that a 60-fold increase in the BC aerosol mixing ratio from the present-day levels leads to the same equilibrium global mean surface warming (∼4.1 K) as for a doubling of atmospheric CO2 concentration. However, the radiative forcing is larger (∼5.5 Wm-2) in the BC case relative to the doubled CO2 case (∼3.8 Wm-2) for the same surface warming indicating the efficacy (a metric for measuring the effectiveness) of BC aerosols to be less than CO2. The lower efficacy of BC aerosols is related to the differences in the shortwave (SW) cloud feedback: negative in the BC case but positive in the CO2 case. In the BC case, the negative SW cloud feedback is related to an increase in the tropical low clouds which is associated with a northward shift (∼7) of the Intertropical Convergence Zone (ITCZ). Further, we show that in the BC case fast precipitation suppression offsets the surface temperature mediated precipitation response and causes ∼8% net decline in the global mean precipitation. Our study suggests that a feedback between the location of ITCZ and the interhemispheric temperature could exist, and the consequent SW cloud feedback could be contributing to the lower efficacy of BC aerosols. Therefore, an improved representation of low clouds in climate models is likely the key to understand the global climate sensitivity to BC aerosols. © 2019 The Author(s). Published by IOP Publishing Ltd."
"57210173382;56655654500;","Is Arctic Amplification Dominated by Regional Radiative Forcing and Feedbacks: Perspectives From the World-Avoided Scenario",2019,"10.1029/2019GL082320","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85069793020&doi=10.1029%2f2019GL082320&partnerID=40&md5=1fb34e3e60aaf0bf94e682f0c25d3028","Arctic amplification (AA) is typically associated with Planck, lapse rate, and ice albedo feedbacks. However, the relative importance of poleward energy transport on AA remains uncertain. Here, we analyze integrations from a Chemistry Climate Model to investigate the impact of the Montreal Protocol on forcing, feedback, and transport contributions to AA. Two ensembles of future integrations are considered—one projecting decreasing ozone-depleting substance concentrations and stratospheric ozone recovery and another assuming that ozone-depleting substances are not regulated (the “World Avoided”). We find similar degrees of AA in both ensembles, despite a negative radiative forcing over the Arctic in the “World Avoided” from massive ozone loss. That negative radiative forcing is primarily balanced from positive atmospheric energy flux convergence and long-wave cloud feedbacks. Our results highlight the impact of inhomogeneous radiative forcing on regional differences in forcing and feedback strength and the importance of radiative forcing meridional structure on poleward energy transport. ©2019. American Geophysical Union. All Rights Reserved."
"57207486814;12645767500;57203722524;7101959253;57203030873;","When Will Spaceborne Cloud Radar Detect Upward Shifts in Cloud Heights?",2019,"10.1029/2018JD030242","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068682942&doi=10.1029%2f2018JD030242&partnerID=40&md5=c2ee56b46219485a0843e01dba8d49d0","Cloud feedbacks remain the largest source of uncertainty in future climate predictions. Simulations robustly project an increase in cloud height, which is supported by some observational evidence. However, how much of this increasing trend is due to climate warming and how much is due to multiyear natural variability still remains unclear because of the brevity of existing observational records. Here we estimate when the signal will become detectable at 95% confidence by existing radar technology. We use output from a Representative Concentration Pathway 8.5 Community Earth System Model version 1 simulation in a Monte Carlo analysis to determine (1) what is the first year at which changes in the altitude of high cloud can be confidently estimated if we continue to fly W-band cloud radar, (2) what radar sensitivity is required to detect those changes, and (3) at what latitude will we first detect these changes? In Community Earth System Model version 1 a cloud radar record would be able to confidently detect upward shifts in cloud height over 20–60°N before 2030 for a radar with a sensitivity of −15 dBZ and stable calibration errors of ±0.25 dBZ. Furthermore, vertical resolution could be degraded to 1.6 km with little effect on detection year. Results are more sensitive to the magnitude of calibration errors than to the minimum detectable echo. Our earlier midlatitude detection contrasts with a previous lidar-based analysis, which may be due to radar detecting different parts of the clouds and our use of simulations that account for changing geographical patterns of forced warming through time. ©2019. American Geophysical Union. All Rights Reserved."
"57193576596;7005187754;","On the future role of the most parsimonious climate module in integrated assessment",2019,"10.5194/esd-10-135-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062988669&doi=10.5194%2fesd-10-135-2019&partnerID=40&md5=0746760bf000386d802e0ce153456d7f","In the following, we test the validity of a one-box climate model as an emulator for atmosphere-ocean general circulation models (AOGCMs). The one-box climate model is currently employed in the integrated assessment models FUND, MIND, and PAGE, widely used in policy making. Our findings are twofold. Firstly, when directly prescribing AOGCMs' respective equilibrium climate sensitivities (ECSs) and transient climate responses (TCRs) to the one-box model, global mean temperature (GMT) projections are generically too high by 0.5 K at peak temperature for peak-and-decline forcing scenarios, resulting in a maximum global warming of approximately 2 K. Accordingly, corresponding integrated assessment studies might tend to overestimate mitigation needs and costs. We semi-analytically explain this discrepancy as resulting from the information loss resulting from the reduction of complexity. Secondly, the one-box model offers a good emulator of these AOGCMs (accurate to within 0.1&thinsp;K for Representative Concentration Pathways, RCPs, namely RCP2.6, RCP4.5, and RCP6.0), provided the AOGCM's ECS and TCR values are universally mapped onto effective one-box counterparts and a certain time horizon (on the order of the time to peak radiative forcing) is not exceeded. Results that are based on the one-box model and have already been published are still just as informative as intended by their respective authors; however, they should be reinterpreted as being influenced by a larger climate response to forcing than intended. © 2019 Author(s)."
"6603888947;","On the reliability of computer-based climate models",2019,"10.4408/IJEGE.2019-01.O-05","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85072686501&doi=10.4408%2fIJEGE.2019-01.O-05&partnerID=40&md5=b5f1acdff636b57d8789a7f23425963c","Since 1850 the global surface temperature of the Earth has warmed by about 0.9°C. The computer climate models adopted by the Intergovernmental Panel on Climate Change (IPCC), such as the General Circulation Models of the Coupled Model Intercomparison Project Phase 5 (CMIP5), projected that the global surface temperature could rise more than 1.5°C by 2030 and more than 4-5°C by 2100 relative to the pre-industrial period (1850-1900) because of anthropogenic greenhouse gas emissions. These computer projections are being used to justify expensive mitigation policies to drastically reduce CO2 emissions due to the use of fossil fuel. However, these models must be validated before their interpretation of climate change could be considered reliable. Herein, I summarize recent scientific research pointing out that these GCMs fail to properly reconstruct the natural variability of the climate throughout the entire Holocene and at multiple time scales such as: (1) the Holocene Climatic Optimum (9000-6000 years ago) with the subsequent cooling from 5000 years ago to now; (2) the large millennial oscillations observed throughout the Holocene that were responsible, for example, for the Medieval Warm Period; (3) several shorter climatic oscillations with periods of about 9.1, 10.4, 20, 60 years; (4) the climate change trend after 2000 to date, which the models greatly overestimate; and many other patterns. These different pieces of evidence imply two main facts: (1) the models' equilibrium climate sensitivity (ECS) to radiative forcing, such as to an atmospheric CO2 doubling, is overestimated at least by a factor of 2, which implies a more realistic ECS between 1°C and 2°C; (2) there are a number of solar and astronomical forcings that are still missing in the models or are poorly understood yet. Consequently, these GCMs are not physically reliable for properly interpreting past and future climatic changes. Alternatively, semi-empirical climatic models should be used. Data analysis found that the climatic natural variability is made of several oscillations from the decadal to the millennial scales (e.g. periods of about 9.1, 10.4, 20, 60, 115, 1000 years) and others. These oscillations are coherent with solar, lunar and astronomical oscillations. A semi-empirical climate model that makes use of these oscillations plus a reduced ECS reconstructs with great accuracy the climate variability observed since 1850 and projects a very moderate warming until 2040 and a warming lower than 2°C from 2000 to 2100 using the same anthropogenic emission scenarios used for the 21st-century climate simulations of the CMIP5 models. This result suggests that climatic adaptation policies, which are far less expensive than the mitigation ones, could be sufficient to address the consequences of climatic changes that could occur during the 21st century. © Sapienza Università Editrice."
"56492516000;7006151875;","The realized warming fraction: A multi-model sensitivity study",2018,"10.1088/1748-9326/aaebae","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060144180&doi=10.1088%2f1748-9326%2faaebae&partnerID=40&md5=c8107c780f0f0dbcaf533716ce044873","The degree of physical-biogeochemical equilibration of the climate system determines for how long global warming will continue after anthropogenic CO 2 emissions have ceased. The physical part of this equilibration process is quantified by the realized warming fraction (RWF), but RWF estimates differ strongly between different climate models. Here we analyze the RWF spread and its physical causes in three model ensembles: 1. an ensemble of comprehensive climate models, 2. an ensemble of reduced-complexity models, and 3. an observationally constrained parameter ensemble of the Bern3D-LPX reduced-complexity model. We show that RWF is generally lower in models with higher equilibrium climate sensitivity. The RWF uncertainty from applying different extrapolation methods for climate sensitivity is substantial, but smaller than the inter-model spread in the three ensembles. We decompose the inter-model spread of RWF using a diagnostic global energy balance model, to compare the spread contribution by the climate sensitivity to contributions by other physical quantities: the efficiency and efficacy of ocean heat uptake, and the effective radiative forcing. In the ensembles of the comprehensive climate models and the Bern3D-LPX model, the spread of the RWF is mostly determined by the spread of the climate sensitivity; for the reduced-complexity models, the spread contribution by the ocean heat uptake efficiency is dominant. Compared to the comprehensive models, the reduced-complexity models have a lower range of climate sensitivities and lower, more unitary ocean heat uptake efficacies, resulting in higher RWF. However, by tuning such models to higher climate sensitivities, they can also achieve RWF values in the lower range of comprehensive models, as demonstrated for Bern3D-LPX. This suggests that reduced-complexity models remain useful tools for future climate change projections, but should employ a range of climate sensitivity tunings to account for the uncertainty in both the long-term warming and the RWF. © 2018 The Author(s). Published by IOP Publishing Ltd."
"7402645443;7004325649;","Probabilistic reasoning about measurements of equilibrium climate sensitivity: combining disparate lines of evidence",2018,"10.1007/s10584-018-2315-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056170030&doi=10.1007%2fs10584-018-2315-y&partnerID=40&md5=175c790d326f7bf96a740512ee248865","Where policy and science intersect, there are always issues of ambiguous and conflicting lines of evidence. Combining disparate information sources is mathematically complex; common heuristics based on simple statistical models easily lead us astray. Here, we use Bayesian Nets (BNs) to illustrate the complexity in reasoning under uncertainty. Data from joint research at Resources for the Future and NASA Langley are used to populate a BN for predicting equilibrium climate sensitivity (ECS). The information sources consist of measuring the rate of decadal temperature rise (DTR) and measuring the rate of percentage change in cloud radiative forcing (CRF), with both the existing configuration of satellites and with a proposed enhanced measuring system. The goal of all measurements is to reduce uncertainty in equilibrium climate sensitivity. Subtle aspects of probabilistic reasoning with concordant and discordant measurements are illustrated. Relative to the current prior distribution on ECS, we show that after 30 years of observing with the current systems, the 2σ uncertainty band for ECS would be shrunk on average to 73% of its current value. With the enhanced systems over the same time, it would be shrunk to 32% of its current value. The actual shrinkage depends on the values actually observed. These results are based on models recommended by the Social Cost of Carbon methodology and assume a Business as Usual emissions path. © 2018, The Author(s)."
"56524474400;","Sharing of climate risks across world regions",2018,"10.1142/S2010007818500070","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85049954397&doi=10.1142%2fS2010007818500070&partnerID=40&md5=af90714a3194bf97a62f4817b4474114","Climate change impacts are stochastic and highly uncertain and moreover heterogeneous across regions. That is, there is a potential to sharing this risk ex-ante across regions and hence to reduce the welfare-economic costs of these risks. We analyze how climate risks could be reduced via an insurance scheme at the global scale across regions and quantify the potential welfare gains. We introduce risk sharing of global climate risk represented by the equilibrium climate sensitivity, and introduce an asset-based insurance scheme to allow for risk sharing across regions. We estimate that such risk sharing scheme could lead to welfare gains reducing the global costs of climate change by up to 15%. Such a scheme implies transfers of about USD 200 billion per year and faces important implementation challenges. The results provide a motivation for the loss and damage mechanism related negotiations about sharing risks of climate change at the global level. © 2018 World Scientific Publishing Company."
"57201027668;","On the influence of solar cycle lengths and carbon dioxide on global temperatures",2018,"10.1016/j.jastp.2018.01.026","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042927181&doi=10.1016%2fj.jastp.2018.01.026&partnerID=40&md5=83d324ae69f957ff667755de90373a6d","By combining Solar Cycle Lengths (SCL) and CO2 this paper predicts a global average surface temperature (GAST) anomaly of 1.5K in the year 2100 compared to 0.42K in 1996–2006. This assumes a continuing CO2 increase of 2 ppm per year and our derived form of Transient Climate Response (TCR), whose value 1.93 ± 0.26 K (K) per CO2 doubling would be 1.23 times higher if the Sun were ignored. After the CO2 effect has been subtracted out, the SCL explains a healthy 55% of the remaining variance. It also estimates that 37% of the recent warming from 1980 to 2001 was due to solar effects. We then compare with models created from Scafetta (2010, 2013) (the first of which has the best fit of all) and from radiative forcings estimated by Myhre et al. (2001) and Skeie et al. (2011). The latter confirms the solar contribution to 1980–2001 warming as 33%, in contrast to the negligible value given by Benestad &amp; Schmidt (2009). It also gives a TCR of 1.3K if only CO2 continues to rise, and 2.0K if CH4 and NO2 also rise proportionately. Likewise this model estimates the ratio between the sensitivities of forcings from the Sun and greenhouse gases as 2.9 (versus 1.0 for Benestad &amp; Schmidt (2009)). We develop a negative exponential model for post-forced warming to derive a ratio between Equilibrium Climate Sensitivity (ECS) and TCR, estimated to be 1.15. Two statistical novelties of the paper are the computation of the exact left tail probability of the Durbin-Watson statistic, and the demonstration of an approximate relationship between the Akaike Information Criterion and the tail probability of the F-statistic. © 2018 Elsevier Ltd"
"35098801000;9635016300;6603375472;","Towards Bayesian hierarchical inference of equilibrium climate sensitivity from a combination of CMIP5 climate models and observational data",2018,"10.1007/s10584-018-2232-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85049571001&doi=10.1007%2fs10584-018-2232-0&partnerID=40&md5=18006c12884c46d1de8f531629834d6c","Despite decades of research, large multi-model uncertainty remains about the Earth’s equilibrium climate sensitivity to carbon dioxide forcing as inferred from state-of-the-art Earth system models (ESMs). Statistical treatments of multi-model uncertainties are often limited to simple ESM averaging approaches. Sometimes models are weighted by how well they reproduce historical climate observations. Here, we propose a novel approach to multi-model combination and uncertainty quantification. Rather than averaging a discrete set of models, our approach samples from a continuous distribution over a reduced space of simple model parameters. We fit the free parameters of a reduced-order climate model to the output of each member of the multi-model ensemble. The reduced-order parameter estimates are then combined using a hierarchical Bayesian statistical model. The result is a multi-model distribution of reduced-model parameters, including climate sensitivity. In effect, the multi-model uncertainty problem within an ensemble of ESMs is converted to a parametric uncertainty problem within a reduced model. The multi-model distribution can then be updated with observational data, combining two independent lines of evidence. We apply this approach to 24 model simulations of global surface temperature and net top-of-atmosphere radiation response to abrupt quadrupling of carbon dioxide, and four historical temperature data sets. Our reduced order model is a 2-layer energy balance model. We present probability distributions of climate sensitivity based on (1) the multi-model ensemble alone and (2) the multi-model ensemble and observations. © 2018, The Author(s)."
"56598005900;6602239759;6603328138;57194386514;","An improved method to estimate reference cloud-free images for the visible band of geostationary satellites",2017,"10.1080/01431161.2017.1372859","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064127806&doi=10.1080%2f01431161.2017.1372859&partnerID=40&md5=69de985262455c81525b0e8a733744d2","Geostationary images have been used frequently in the past 50 years to derive geophysical information. As a complement to all-sky observations, clear-sky counterparts play an important role in the derivation of cloud properties. We investigated ways to improve estimates of top-of-atmosphere (TOA) visible clear-sky images, over the full spatial and temporal resolution of Meteosat First Generation (MFG) satellites. Estimation was based on TOA measurements in MFG’s visible channel, collected for a specific time of the day over the span of several days. In addition, a cloud climatology aided estimation. Parameter optimization and the introduction of a spatial filter over ocean resulted in a bias of −1.0 to −2.0 digital counts (DC) and a root mean square error (RMSE) of 2.0–3.0 DC when averaged over the complete field of view. This excludes the Spring period which has up to −3.5 DC bias and up to 5.5 DC RMSE. Reasons for these exceptional differences were found in rapid greenness change, affecting reflectances over vegetated surfaces, and dust storms, with an effect over tropical land and ocean surfaces. Similarly, sea ice and snow affected polar regions seasonally. Applied to 24 years of MFG imagery, we successfully used improved clear-sky estimates to stably detect clouds. Additionally, these clear-sky estimates may prove useful for characterization of instrument degradation as well as cloud feedback studies. © 2017 Informa UK Limited, trading as Taylor & Francis Group."
"57194834755;","Correcting problems with the conventional basic calculation of climate sensitivity",2016,"10.1016/B978-0-12-804588-6.00020-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85023184213&doi=10.1016%2fB978-0-12-804588-6.00020-3&partnerID=40&md5=8a50d60c413821207a22ffa2cda0af1f","The conventional basic climate model applies basic physics to climate, estimating sensitivity to CO2. However, it has two serious architectural errors. It only allows feedbacks in response to surface warming, so it omits the driver-specific feedbacks. It treats extra-absorbed sunlight, which heats the surface and increases outgoing long-wave radiation (OLR), the same as extra CO2, which reduces OLR from carbon dioxide in the upper atmosphere but does not increase the total OLR. The rerouting feedback is proposed. An increasing CO2 concentration warms the upper troposphere, heating the water vapor emissions layer and some cloud tops, which emit more OLR and descend to lower and warmer altitudes. This feedback resolves the nonobservation of the hotspot. An alternative model is developed, whose architecture fixes the errors. By summing the (surface) warmings due to climate drivers, rather than their forcings, it allows driver-specific forcings and allows a separate CO2 response (the conventional model applies the same response, the solar response, to all forcings). It also applies a radiation balance, estimating OLR from properties of the emission layers. Fitting the climate data to the alternative model, we find that the equilibrium climate sensitivity is most likely less than 0.5C, increasing CO2 most likely caused less than 20% of the global warming from the 1970s, and the CO2 response is less than one-third as strong as the solar response. The conventional model overestimates the potency of CO2 because it applies the strong solar response instead of the weak CO2 response to the CO2 forcing. © 2016 Elsevier Inc. All rights reserved."
"37027011900;6603925960;7102410621;57207507108;30667558200;35203328900;6507495053;8669401600;","An EarthCARE/ATLID simulator to evaluate cloud description in climate models",2015,"10.1002/2015JD023919.","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029233955&doi=10.1002%2f2015JD023919.&partnerID=40&md5=a841e2f926210712fe99bf7f708280df","Clouds still remain the largest source of uncertainty in model-based predictions of future climate; thus, the description of the clouds in climate models needs to be evaluated. In particular, the cloud detailed vertical distribution that impacts directly the cloud radiative effect needs to be evaluated. Active satellite sensors directly measure the cloud vertical distribution with high accuracy; their observations should be used for model evaluation together with a satellite simulator in order to allow fair comparison between models and observations. The next cloud lidar in space, EarthCARE/ATmospheric LIDar (ATLID), is planned for launch in 2018, while the current spaceborne cloud lidar CALIPSO/CALIOP is expected to stop collecting data within the next coming years. Here we describe the characteristics of the ATLID on board the EarthCARE satellite (spatial resolution, signal-to-noise ratio, wavelength, field of view, pulse repetition frequency, orbit, and high-spectral resolution lidar) that need to be taken into account to build a Cloud Feedback Model Intercomparison Project Observation Simulator Package (COSP)/ATLID simulator. We then present the COSP/ATLID simulator, and the low-, middle-, high-level cloud covers it produces, as well as the zonal mean cloud fraction profiles and the height-intensity histograms that are simulated by COSP/ATLID when overflying an atmosphere predicted by LMDZ5 global circulation model. Finally, we compare the clouds simulated by COSP/ATLID with those simulated by COSP/CALIPSO when overflying the same atmosphere. As the main differences between ATLID and CALIOP are taken into account in the simulators, the differences between COSP/ATLID and COSP/CALIPSO cloud covers are less than 1% in nighttime conditions. © 2015. American Geophysical Union."
"16245558300;7101610644;15065751600;7202010300;35957510700;7402475964;","The rainfall sensitivity of tropical net primary production in CMIP5 Twentieth- and Twenty-First-Century simulations",2015,"10.1175/JCLI-D-14-00675.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950150160&doi=10.1175%2fJCLI-D-14-00675.1&partnerID=40&md5=1154af3200b1f7dca4b3236c737a7765","Recent efforts to narrow the spread in equilibrium climate sensitivity (ECS) across global climate models have focused on identifying observationally based constraints, which are rooted in empirical correlations between ECS and biases in the models' present-day climate. This study reexamines one such constraint identified from CMIP3 models: the linkage between ECS and net top-of-the-atmosphere radiation biases in the Southern Hemisphere (SH). As previously documented, the intermodel spread in the ECS of CMIP3 models is linked to present-day cloud and net radiation biases over the midlatitude Southern Ocean, where higher cloud fraction in the present-day climate is associated with larger values of ECS. However, in this study, no physical explanation is found to support this relationship. Furthermore, it is shown here that this relationship disappears in CMIP5 models and is unique to a subset of CMIP models characterized by unrealistically bright present-day clouds in the SH subtropics. In view of this evidence, Southern Ocean cloud and net radiation biases appear inappropriate for providing observationally based constraints on ECS. Instead of the Southern Ocean, this study points to the stratocumulus-to-cumulus transition regions of the SH subtropical oceans as key to explaining the intermodel spread in the ECS of both CMIP3 and CMIP5 models. In these regions, ECS is linked to present-day cloud and net radiation biases with a plausible physical mechanism: models with brighter subtropical clouds in the present-day climate show greater ECS because 1) subtropical clouds dissipate with increasing CO2 concentrations in many models and 2) the dissipation of brighter clouds contributes to greater solar warming of the surface. © 2015 American Meteorological Society."
"57202076497;57212803688;55697757300;","Forty-year (1971–2010) semiquantitative observations of visibilitycloud-precipitation in Korea and its implication for aerosol effects on regional climate",2015,"10.1080/10962247.2015.1016633","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944055964&doi=10.1080%2f10962247.2015.1016633&partnerID=40&md5=91286e3c019da7805f7a87952f77f0f0","Forty-year (1971–2010) observations of cloud cover and types have been analyzed, and implications on the effects of aerosol–cloud feedback were explored. Cloud cover and types have been observed over Korea on the basis of visible (human-eye) attributes without any change in official observing instructions. Visibility has been used as an ongoing proxy measure of aerosol concentrations, and observed meteorological variables such as sunshine duration and precipitation have been employed to analyze aerosol causes and implications for urban and regional climate. The analysis revealed persistent decade-long patterns in Korea: steadily reduced visibility (–0.37 km/yr), consistently decreasing sunshine duration (–0.06 %/hr), and declining occurrence of light precipitation. Spatial distributions of sunshine duration and visibility exhibited more localized variations in the early period (1971–1990), and tended to be more uniform throughout Korea over more recent years (1991–2010), implying the recent regional-scale impact of cloud change over northeast Asia. Cloud analysis results showed that the five most common types were stratocumulus (Sc), cirrus (Ci), altostratus (As), stratus (St), and nimbostratus (Ns), with occurrences of 33%, 17%, 17%, 9%, and 8%, respectively. Occurrence of rarely precipitating or nonprecipitating low-level Sc clouds showed an increasing (+0.34%/yr), but no (or only minor) effects of aerosols on heavy precipitation such as cumulus cloud types were found. Cloud cover in the range of 6/10 to 8/10 units has increased by 31.5 ± 6.5%, and occurrences of both cloud-free (~2/10 units) and overcast (~8/10 units) conditions have decreased. © 2015 A&WMA."
"22939192200;56224155200;36118090300;","Examinations of cloud variability and future change in the coupled model intercomparison project phase 3 simulations",2014,"10.1007/s13143-014-0038-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957441921&doi=10.1007%2fs13143-014-0038-1&partnerID=40&md5=bb1cea51be0798503f9df0e463992d32","Low-level cloud variability is critical to the radiation balance of Earth due to its wide spatial coverage. Using the adjusted International Satellite Cloud Climatology Project (ISCCP) observations of Clement et al. (2009), and the Coupled Model Intercomparison Project Phase 3 (CMIP3) model simulations, this study examines the observed and the simulated low-cloud variations and their relationships with large-scale environmental variables. From the observational analysis, significant correlations are found between low clouds and those of sea surface temperature (SST), lower tropospheric stability (LTS), and sea level pressure (SLP) over tropical marine areas of low cloud prevailing regions during most of the year. Increase of SST coincides with the reduction of LTS and increased vertical motion, which tends to reduce low-level clouds in subtropical oceans. Among the 14 models investigated, CGCM3 and HadGEM1 exhibit more realistic representation of the observed relationship between low-level clouds and large-scale environments. In future climate projection, these two models show a good agreement in the reduction of low-cloud throughout much of the global oceans in response to greenhouse gas forcing, suggesting a positive low-cloud feedback in a climate change context. © 2014, Korean Meteorological Society and Springer Science+Business Media Dordrecht."
"7201737956;48361871200;55712637800;7404147955;55628525997;","Equilibrium climate sensitivity",2014,"10.3724/sp.j.1248.2013.069","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900027731&doi=10.3724%2fsp.j.1248.2013.069&partnerID=40&md5=98d858fbec39499309b1d7b09440b3b8",[No abstract available]
"13403754000;7006614696;7007021059;7004379124;","Analysis of cloud properties associated with tropical convection in climate models and satellite data",2012,"10.2151/jmsj.2012-504","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870478967&doi=10.2151%2fjmsj.2012-504&partnerID=40&md5=573b1ea6a3eb37fd97902247ae44d23d","Cloud properties associated with tropical convection are analyzed for 11 models participating in Cloud Feedback Model Intercomparison Project Phase 1 (CFMIP1) in comparison with International Satellite Cloud Climatology Project (ISCCP) and other satellite observations and reanalysis datasets. Cloud properties are analyzed for different regimes of large-scale circulation field sorted by monthly mean of pressure coordinated vertical velocity at 500 hPa as an index of large-scale circulation. The present analysis is focused on warm oceanic regions with sea surface temperatures above 27°C where convection is active. The warm oceanic regions cover the vertical motion regimes ranging from strong ascent to weak descent. The ISCCP simulator outputs are used to evaluate cloud properties in the models. Cloud amount of optically thick high-clouds with optical thicknesses (τ) ≧ 3.6 and cloud-top pressure (CTP) ≦ 440 hPa is overestimated in the strong ascent regime while that of optically thin high-clouds with τ < 3.6 is underestimated for all the regimes. Cloud amount of optically thick low-clouds with CTP ≧ 680 hPa is overestimated in the weak vertical motion regime as well in some models. The relevance of cloud amount bias to cloud radiative effect bias is discussed. Observations show that optically thick clouds in the strong ascent regime often have tops around 180-310 hPa. In many models, the cloud top often reaches higher altitude compared to the observations. The tendency can especially be seen in the models adopting the moisture accumulation type scheme presumably due to excessively deep convection. Comparison of upward motion strength among the models and reanalyses suggests that cumulus parameterization performs better when entrainment rate is varied with large-scale environmental fields to reduce the convection deepness where necessary. © 2012, Meteorological Society of Japan."
"57212024136;57193844239;57212021393;57212019537;","Model Analysis of the Anthropogenic Aerosol Effect on Clouds over East Asia",2012,"10.1080/16742834.2012.11446968","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050557180&doi=10.1080%2f16742834.2012.11446968&partnerID=40&md5=b3006087fb57c23ec219183a90bc46f6","A coupled meteorology and aerosol/chemistry model WRF-Chem (Weather Research and Forecast model coupled with Chemistry) was used to conduct a pair of simulations with present-day (PD) and preindustrial (PI) emissions over East Asia to examine the aerosol indirect effect on clouds. As a result of an increase in aerosols in January, the cloud droplet number increased by 650 cm–3 over the ocean and East China, 400 cm–3 over Central and Southwest China, and less than 200 cm–3 over North China. The cloud liquid water path (LWP) increased by 40–60 g m–2 over the ocean and Southeast China and 30 g m–2 over Central China; the LWP increased less than 5 g m–2 or decreased by 5 g m–2 over North China. The effective radius (Re) decreased by more than 4 µm over Southwest, Central, and Southeast China and 2 µm over North China. In July, variations in cloud properties were more uniform; the cloud droplet number increased by approximately 250–400 cm–3, the LWP increased by approximately 30–50 g m–2, and Re decreased by approximately 3 µm over most regions of China. In response to cloud property changes from PI to PD, shortwave (SW) cloud radiative forcing strengthened by 30 W m–2 over the ocean and 10 W m–2 over Southeast China, and it weakened slightly by approximately 2–10 W m–2 over Central and Southwest China in January. In July, SW cloud radiative forcing strengthened by 15 W m–2 over Southeast and North China and weakened by 10 W m–2 over Central China. The different responses of SW cloud radiative forcing in different regions was related to cloud feedbacks and natural variability. © 2012, © Institute of Atmospheric Physics, Chinese Academy of Sciences."
"23103883900;","A parameterised carbon feedback model for the calculation of global warming from attainable fossil fuel emissions",2011,"10.1260/0958-305X.22.7.859","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80055017421&doi=10.1260%2f0958-305X.22.7.859&partnerID=40&md5=b2e20932a7c24e1da4e532f438a4aea7","This paper evaluates the IPCC SRES scenarios against fossil fuel depletion models and proposes attainable carbon emissions trajectories. The contemporary carbon feedback cycle is then evaluated in light of recent studies and attainable carbon emissions. In light of deficiencies in the contemporary carbon feedback cycle, a parametric carbon feedback model is constructed that is consistent with empirical evidence. A radiative feedback model, that overestimates transient response when used in conjunction with equilibrium climate sensitivity, is then used in sensitivity studies to calculate the range of plausible global warming responses. The model predicts a maximum atmospheric concentration of CO2 in the range of 500-560ppm and a maximum global mean surface temperature increase of 1.5-2°C relative to year 2000."
"7403180902;7005070958;","A procedure for evaluating feedback mechanisms in coupled atmosphere/ocean climate models",2004,"10.1029/2004GL019876","https://www.scopus.com/inward/record.uri?eid=2-s2.0-6044253668&doi=10.1029%2f2004GL019876&partnerID=40&md5=4006454bbde9063cbaa55811c66662f8","To understand inter-model differences in long-term simulations of climate change, as exist between coupled atmosphere/ocean general circulation models, it is necessary to first understand climate feedback mechanisms that operate within each of the various models. With this goal in mind, we have employed an 1870 to 1989 simulation, with prescribed increases in greenhouse gases, that was performed using the National Center for Atmospheric Research Community Climate System Model Version 1, as a vehicle for determining two feedback processes operating within that model. These are cloud feedback and snow/ice albedo feedback. A prerequisite to evaluating feedback mechanisms is to first evaluate the direct radiative forcing, caused by the increasing greenhouse gases, which produces global warming by the model, and a procedure for doing this is presented. Cloud feedback is then evaluated by referencing the model's change in global-mean cloud-radiative forcing to the direct greenhouse-gas induced radiative forcing, and a comparable procedure is employed to determine snow/ice albedo feedback. This model produces a moderately strong negative cloud feedback and a modest positive snow/ice albedo feedback. But the main purpose of this study is to provide a reasonably simple procedure for determining both cloud feedback and snow/ice albedo feedback within coupled atmosphere/ocean GCMs. Copyright 2004 by the American Geophysical Union."
"7004547261;7101609607;7004327151;7003668116;7003945443;","Comparison of satellite and ground-based measurements of cloud liquid water in several climate zones",2001,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035574230&partnerID=40&md5=f3ec2589dd09b090766c6c3e011ff2b6","An overview is given on some of the issues and considerations required to understand remotely sensed cloud liquid water. It is emphasized that the ultimate use of the data must be considered, i.e. the spatial and temporal scales required."
"56157800800;","Correction to: “Early Earth's climate: Cloud feedback from reduced land fraction and ozone concentrations”",1995,"10.1029/95GL02193","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85005697456&doi=10.1029%2f95GL02193&partnerID=40&md5=9df30c96723c70fcf869d0622a4e3710",[No abstract available]
"57202997809;12782225200;35147687500;57217352376;","Characterization of raindrop size distributions and its response to cloud microphysical properties",2021,"10.1016/j.atmosres.2020.105292","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092020194&doi=10.1016%2fj.atmosres.2020.105292&partnerID=40&md5=82d2e5a1d83f542476f24dbbcc4dcb51","Cloud feedbacks continue to alter with climate change, which remains the largest source of uncertainty in global climate. Raindrop size distribution (DSD) is a fundamental characteristic of cloud microphysical and dynamical processes. This study characterizes the DSD and its response to cloud microphysical properties during the Indian Summer Monsoon season (June-October 2013–2015). The derived rain rate varied from 0.50 to 395.4 mm/h, which was segregated into stratiform rain (mean and standard deviation of 2.12 ± 1.24 mm/h) and convective rain (13.10 ± 14.45 mm/h). We found that as the convective DSD mode diameter gradually shifts to a larger drop size with increasing rain rate, the number concentration of small-sized rain drops decreased by about three orders of magnitude. While the mass-weighted mean diameter and normalized DSD scaling parameter were significantly higher for convective rain than stratiform rain, the normalized DSD scaling parameter was lowest for both convective and stratiform rain compared to previous studies over this region. The stratiform DSD was more skewed towards large raindrop size at a high cloud effective radius compared to a low cloud effective radius. However, the opposite response of the DSD for convective rain suggests the predominance of small-sized cloud/ice hydrometeors. This finding was further corroborated by the presence of narrower DSD at high cloud droplet number concentration compared to a low cloud droplet number concentration for the convective rain. The low wind shear and high convective available potential energy for convective rain further substantiated the persistent convective cores during monsoon accompanied by the formation of large size raindrops in the convective systems. Such a distinct response of DSD to different rain regimes could help in the short-term prediction of extreme rainfall events. © 2020 Elsevier B.V."
"56457851700;7103016965;13402835300;25924878400;26645289600;","A regime-oriented approach to observationally constraining extratropical shortwave cloud Feedbacks",2020,"10.1175/JCLI-D-19-0987.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85094879042&doi=10.1175%2fJCLI-D-19-0987.1&partnerID=40&md5=4290b9e8dfd49aab0ef98f795ab5e02f","The extratropical shortwave (SW) cloud feedback is primarily due to increases in extratropical liquid cloud extent and optical depth. Here, we examine the response of extratropical (358–758) marine cloud liquid water path (LWP) to a uniform 4-K increase in sea surface temperature (SST) in global climate models (GCMs) from phase 5 of the Coupled Model Intercomparison Project (CMIP5) and variants of the HadGEM3-GC3.1 GCM. Compositing is used to partition data into periods inside and out of cyclones. The response of extratropical LWP to a uniform SST increase and associated atmospheric response varies substantially among GCMs, but the sensitivity of LWP to cloud controlling factors (CCFs) is qualitatively similar. When all other predictors are held constant, increasing moisture flux drives an increase in LWP. Increasing SST, holding all other predictors fixed, leads to a decrease in LWP. The combinations of these changes lead to LWP, and by extension reflected SW, increasing with warming in both hemispheres. Observations predict an increase in reflected SW over oceans of 0.8–1.6 W m22 per kelvin SST increase (358–758N) and 1.2–1.9 W m22 per kelvin SST increase (358–758S). This increase in reflected SW is mainly due to increased moisture convergence into cyclones because of increasing available moisture. The efficiency at which converging moisture is converted into precipitation determines the amount of liquid cloud. Thus, cyclone precipitation processes are critical to constraining extratropical cloud feedbacks. © 2020 American Meteorological Society."
"26654147000;55767074400;","Could crop albedo modification reduce regional warming over Australia?",2020,"10.1016/j.wace.2020.100282","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091224397&doi=10.1016%2fj.wace.2020.100282&partnerID=40&md5=010871b2387ddcc60b7d471426e58c3a","Climate observations and projections for Australia show an increase in warm temperature extremes, including the frequency, duration and intensity of heatwaves. Recent global scale studies have suggested that agricultural land-use management options, such as increasing crop albedo, could reducing local warming. Australia has approximately 3,727,210 km2 of cropland agricultural land-use, the majority of which is in southwest Western Australia and southeast Australia. This presents a potential opportunity to reduce regional warming via crop albedo enhancement. We use a regional climate model at 10 km resolution, to show that crop albedo enhancement of up to 0.1 could reduce monthly mean daily maximum temperatures by −1.0 °C to −1.2 °C, and monthly highest maximum temperatures by up to −1.4 °C to −1.6 °C during the cropping season. This cooling is approximately 3 times higher over Australia than global climate models predict. We highlight stronger cooling over southwest Western Australia as compared to southeast Australia, the opposite to global model studies which poorly resolve southwestern agricultural regions. The regional cooling was driven by a reduction in surface net shortwave radiation leading to a decrease in both sensible and latent heat flux of up to 50 W m−2 and 20 W m−2 respectively, when albedo is increased by up to 0.1. There were no cloud feedbacks or effects on precipitation. Our results highlight the importance of using regional climate models at a sufficiently high spatial resolution when investigating agricultural land-use management to reduce regional warming. © 2020 The Authors"
"7004500706;12759949700;6603535726;36655728800;7102856414;36655855100;7404303923;55199710600;6603196127;54279670400;7005978899;55053409600;57218794688;56706919700;55578889300;7004828383;36627331700;13410099900;55292805500;7006798407;35346106500;57196452651;36701462300;7102886537;8401913500;6701853567;56044817200;26643043700;8315173400;56403375500;8068419200;","The Pliocene Model Intercomparison Project Phase 2: Large-scale climate features and climate sensitivity",2020,"10.5194/cp-16-2095-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85095815894&doi=10.5194%2fcp-16-2095-2020&partnerID=40&md5=d0f6fc204fbf6a7bd3c1edbc59190dd1","The Pliocene epoch has great potential to improve our understanding of the long-term climatic and environmental consequences of an atmospheric CO2 concentration near ~ 400 parts per million by volume. Here we present the large-scale features of Pliocene climate as simulated by a new ensemble of climate models of varying complexity and spatial resolution based on new reconstructions of boundary conditions (the Pliocene Model Intercomparison Project Phase 2; PlioMIP2). As a global annual average, modelled surface air temperatures increase by between 1.7 and 5.2 °C relative to the pre-industrial era with a multi-model mean value of 3.2 °C. Annual mean total precipitation rates increase by 7 % (range: 2 %-13 %). On average, surface air temperature (SAT) increases by 4.3 °C over land and 2.8 ° C over the oceans. There is a clear pattern of polar amplification with warming polewards of 60° N and 60° S exceeding the global mean warming by a factor of 2.3. In the Atlantic and Pacific oceans, meridional temperature gradients are reduced, while tropical zonal gradients remain largely unchanged. There is a statistically significant relationship between a model's climate response associated with a doubling in CO2 (equilibrium climate sensitivity; ECS) and its simulated Pliocene surface temperature response. The mean ensemble Earth system response to a doubling of CO2 (including ice sheet feedbacks) is 67 % greater than ECS; this is larger than the increase of 47 % obtained from the PlioMIP1 ensemble. Proxy-derived estimates of Pliocene sea surface temperatures are used to assess model estimates of ECS and give an ECS range of 2.6-4.8 °C. This result is in general accord with the ECS range presented by previous Intergovernmental Panel on Climate Change (IPCC) Assessment Reports. © Author(s) 2020."
"6701431208;36876405100;8866821900;25031430500;7102696626;6508048114;57210230785;34771961800;57210350827;57202754759;7101816869;6701853567;","CO2 Increase Experiments Using the CESM: Relationship to Climate Sensitivity and Comparison of CESM1 to CESM2",2020,"10.1029/2020MS002120","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85096477917&doi=10.1029%2f2020MS002120&partnerID=40&md5=1ec036c8a348a72ab850ecde7048a8c3","We examine the response of the Community Earth System Model Versions 1 and 2 (CESM1 and CESM2) to abrupt quadrupling of atmospheric CO2 concentrations (4xCO2) and to 1% annually increasing CO2 concentrations (1%CO2). Different estimates of equilibrium climate sensitivity (ECS) for CESM1 and CESM2 are presented. All estimates show that the sensitivity of CESM2 has increased by 1.5 K or more over that of CESM1. At the same time the transient climate response (TCR) of CESM1 and CESM2 derived from 1%CO2 experiments has not changed significantly—2.1 K in CESM1 and 2.0 K in CESM2. Increased initial forcing as well as stronger shortwave radiation feedbacks are responsible for the increase in ECS seen in CESM2. A decomposition of regional radiation feedbacks and their contribution to global feedbacks shows that the Southern Ocean plays a key role in the overall behavior of 4xCO2 experiments, accounting for about 50% of the total shortwave feedback in both CESM1 and CESM2. The Southern Ocean is also responsible for around half of the increase in shortwave feedback between CESM1 and CESM2, with a comparable contribution arising over tropical ocean. Experiments using a thermodynamic slab-ocean model (SOM) yield estimates of ECS that are in remarkable agreement with those from fully coupled Earth system model (ESM) experiments for the same level of CO2 increase. Finally, we show that the similarity of TCR in CESM1 and CESM2 masks significant regional differences in warming that occur in the 1%CO2 experiments for each model. ©2020. The Authors."
"57219598490;13403622000;36600036800;57219597614;","Equilibrium climate sensitivity above 5 °C plausible due to state-dependent cloud feedback",2020,"10.1038/s41561-020-00649-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85094101567&doi=10.1038%2fs41561-020-00649-1&partnerID=40&md5=e8329588dc2b5610de476a314fed4001","The equilibrium climate sensitivity of Earth is defined as the global mean surface air temperature increase that follows a doubling of atmospheric carbon dioxide. For decades, global climate models have predicted it as between approximately 2 and 4.5 °C. However, a large subset of models participating in the 6th Coupled Model Intercomparison Project predict values exceeding 5 °C. The difference has been attributed to the radiative effects of clouds, which are better captured in these models, but the underlying physical mechanism and thus how realistic such high climate sensitivities are remain unclear. Here we analyse Community Earth System Model simulations and find that, as the climate warms, the progressive reduction of ice content in clouds relative to liquid leads to increased reflectivity and a negative feedback that restrains climate warming, in particular over the Southern Ocean. However, once the clouds are predominantly liquid, this negative feedback vanishes. Thereafter, other positive cloud feedback mechanisms dominate, leading to a transition to a high-sensitivity climate state. Although the exact timing and magnitude of the transition may be model dependent, our findings suggest that the state dependence of the cloud-phase feedbacks is a crucial factor in the evolution of Earth’s climate sensitivity with warming. © 2020, The Author(s), under exclusive licence to Springer Nature Limited."
"22982141200;8284622100;57208585760;6602164207;57218843163;7006206130;55731174900;36017879100;7405682849;30267501800;","Elevation dependent warming over the Tibetan Plateau: Patterns, mechanisms and perspectives",2020,"10.1016/j.earscirev.2020.103349","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85090420032&doi=10.1016%2fj.earscirev.2020.103349&partnerID=40&md5=c6f273b687308c7604c1d34265f6b2ef","The Tibetan Plateau (TP) is also known as the “Third Pole”. Elevation dependent warming (EDW), the phenomenon that warming rate changes systematically with elevation, is of high significance for realistically estimating warming rates and their impacts over the TP. This review summarizes studies of characteristics and mechanisms behind EDW over the TP based on multiple observed datasets and model simulations. Spatial expression of EDW and explanatory mechanisms are still largely unknown because of the lack of suitable data over the TP. The focus is on the roles played by known mechanisms such as snow/ice-albedo feedback, cloud feedback, atmospheric water vapor feedback, aerosol feedback, and changes in land use, ozone and vegetation. At present, there is limited consensus on the main mechanisms controlling EDW. Finally, new perspectives and unresolved issues are outlined, including quantification of EDW in climate model simulations, explanation of the long-term EDW reconstructed from proxies, interaction between the Asian summer monsoon and EDW, importance of EDW for future environmental changes and water resources, and current gaps in understanding EDW over extremely high elevations. Further progress requires a more comprehensive ground observation network, greater use of remote sensing data, and high-resolution climate modeling with better representation of both atmospheric and cryospheric processes. © 2020 Elsevier B.V."
"56022904600;55199580500;8920681600;57191645976;57153303400;7403211753;7202671706;8068419200;55623265200;57200562152;22235860400;26424843400;9234991600;57219702937;57214860424;19933461800;7006624548;34876910600;35273009200;","Global mean surface temperature and climate sensitivity of the early Eocene Climatic Optimum (EECO), Paleocene-Eocene Thermal Maximum (PETM), and latest Paleocene",2020,"10.5194/cp-16-1953-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85094842119&doi=10.5194%2fcp-16-1953-2020&partnerID=40&md5=cc93986d242501760425e68cb2f0b516","Accurate estimates of past global mean surface temperature (GMST) help to contextualise future climate change and are required to estimate the sensitivity of the climate system to CO2 forcing through Earth s history. Previous GMST estimates for the latest Paleocene and early Eocene (57 to 48 million years ago) span a wide range (9 to 23 C higher than pre-industrial) and prevent an accurate assessment of climate sensitivity during this extreme greenhouse climate interval. Using the most recent data compilations, we employ a multi-method experimental framework to calculate GMST during the three DeepMIP target intervals: (1) the latest Paleocene (57 Ma), (2) the Paleocene Eocene Thermal Maximum (PETM; 56 Ma), and (3) the early Eocene Climatic Optimum (EECO; 53.3 to 49.1 Ma). Using six different methodologies, we find that the average GMST estimate (66% confidence) during the latest Paleocene, PETM, and EECO was 26.3 C (22.3 to 28.3 C), 31.6 C (27.2 to 34.5 C), and 27.0 C (23.2 to 29.7 C), respectively. GMST estimates from the EECO are 10 to 16 C warmer than pre-industrial, higher than the estimate given by the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (9 to 14 C higher than pre-industrial). Leveraging the large ""signal"" associated with these extreme warm climates, we combine estimates of GMST and CO2 from the latest Paleocene, PETM, and EECO to calculate gross estimates of the average climate sensitivity between the early Paleogene and today. We demonstrate that ""bulk"" equilibrium climate sensitivity (ECS; 66% confidence) during the latest Paleocene, PETM, and EECO is 4.5 C (2.4 to 6.8 C), 3.6 C (2.3 to 4.7 C), and 3.1 C (1.8 to 4.4 C) per doubling of CO2. These values are generally similar to those assessed by the IPCC (1.5 to 4.5 C per doubling CO2) but appear incompatible with low ECS values (1:5 per doubling CO2). © 2020 American Institute of Physics Inc.. All rights reserved."
"36553486200;57196143493;55656837900;","Robust Acceleration of Stratospheric Moistening and Its Radiative Feedback Under Greenhouse Warming",2020,"10.1029/2020JD033090","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092581453&doi=10.1029%2f2020JD033090&partnerID=40&md5=6bd2deb2260b79dd0cfbfc57f314cbd9","Stratospheric water vapor (SWV) changes, in response to increasing CO2, as a feedback component may play an important role in the Earth's energy budget. It has drawn extensive studies in the past decade. Here, we calculate the SWV climate feedback using the 150-year CO2 forcing (1pctCO2) simulations in the CMIP6 ensemble of models. All models robustly show a moistening of the stratosphere, causing a positive radiative feedback to surface warming. We find that the stratospheric moistening rate and the SWV feedback both increase with surface warming. The moistening occurs at a rate of 0.9 ± 0.1 ppmv K−1 and its radiative feedback measured by the fixed dynamical heating method is 0.11 ± 0.02 W m−2 K−1 in the first 50 model years; the moistening rate increases to 1.2 ± 0.2 ppmv K−1 and the feedback increases to 0.16 ± 0.03 W m−2 K−1 in the last 50 model years when the global-mean surface temperature is 3.3 K warmer. These increases are found to be caused by an amplified rate of tropical tropopause warming with respect to surface warming, which is 0.6 and 1.1 K K−1 for the two 50-year periods, respectively. We conclude that the SWV feedback is strengthening with surface warming, which can contribute to increasing climate sensitivity in the future under global warming. ©2020. American Geophysical Union. All Rights Reserved."
"56450100300;16644246500;","Understanding the Extreme Spread in Climate Sensitivity within the Radiative-Convective Equilibrium Model Intercomparison Project",2020,"10.1029/2020MS002165","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85094143709&doi=10.1029%2f2020MS002165&partnerID=40&md5=9bc687eb94c47d2dd40a221d53ea105b","The Radiative-Convective Equilibrium Model Intercomparison Project (RCEMIP) consists of simulations at three fixed sea-surface temperatures (SSTs: 295, 300, and 305 K) and thus allows for a calculation of the climate feedback parameter based on the change of the top-of-atmosphere radiation imbalance. Climate feedback parameters range widely across RCEMIP, roughly from −6 to 3 W m−2 K−1, particularly across general-circulation models (GCMs) as well as global and large-domain cloud-resolving models (CRMs). Small-domain CRMs and large-eddy simulations have a smaller range of climate feedback parameters due to the absence of convective self-aggregation. More than 70–80% of the intermodel spread in the climate feedback parameter can be explained by the combined temperature dependencies of convective aggregation and shallow cloud fraction. Low climate sensitivities are associated with an increase of shallow cloud fraction (increasing the planetary albedo) and/or an increase in convective aggregation with warming. An increase in aggregation is associated with an increase in outgoing longwave radiation, caused primarily by mid-tropospheric drying, and secondarily by an expansion of subsidence regions. Climate sensitivity is neither dependent on the average amount of aggregation nor on changes in deep/anvil cloud fraction. GCMs have a lower overall climate sensitivity than CRMs because in most GCMs convective aggregation increases with warming, whereas in CRMs, convective aggregation shows no consistent temperature trend. ©2020. The Authors."
"55704590100;7005902717;","On the Increase of Climate Sensitivity and Cloud Feedback With Warming in the Community Atmosphere Models",2020,"10.1029/2020GL089143","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091478288&doi=10.1029%2f2020GL089143&partnerID=40&md5=b4b156c54f554a2df524b8f5cc72a045","Modeling and paleoclimate proxy-based studies suggest that equilibrium climate sensitivity (ECS) depends on the background climate state, though the reason is not thoroughly understood. Here we study the state dependence of ECS over a large range of global mean surface temperature (GMST) in the Community Atmosphere Model (CAM) Versions 4, 5, and 6 by varying atmospheric CO2 concentrations. We find a robust increase of ECS with GMST in all three models, albeit at different rates, which is primarily attributed to strengthening of the shortwave cloud feedback (λcld) at both high and low latitudes. Over high latitudes, increasing GMST leads to a reduction in the cloud ice fraction, weakening the (negative) cloud-phase feedback due to the phase transition of cloud ice to liquid and thereby strengthening λcld. Over low-latitude regions, increasing GMST strengthens λcld likely through the nonlinear increase in water vapor, which causes low-cloud thinning through thermodynamic and radiative processes. ©2020. American Geophysical Union. All Rights Reserved."
"56230211700;55894937000;7401776640;26645289600;7402064802;7403180902;6603546080;","Observed sensitivity of low-cloud radiative effects to meteorological perturbations over the global oceans",2020,"10.1175/JCLI-D-19-1028.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85090437695&doi=10.1175%2fJCLI-D-19-1028.1&partnerID=40&md5=86e6dc1455af4da0db68615bebdd6fc9","Understanding how marine low clouds and their radiative effects respond to changing meteorological conditions is crucial to constrain low-cloud feedbacks to greenhouse warming and internal climate variability. In this study, we use observations to quantify the low-cloud radiative response to meteorological perturbations over the global oceans to shed light on physical processes governing low-cloud and planetary radiation budget variability in different climate regimes. We assess the independent effect of perturbations in sea surface temperature, estimated inversion strength, horizontal surface temperature advection, 700-hPa relative humidity, 700-hPa vertical velocity, and near-surface wind speed. Stronger inversions and stronger cold advection greatly enhance low-level cloudiness and planetary albedo in eastern ocean stratocumulus and midlatitude regimes. Warming of the sea surface drives pronounced reductions of eastern ocean stratocumulus cloud amount and optical depth, and hence reflectivity, but has a weaker and more variable impact on low clouds in the tropics and middle latitudes. By reducing entrainment drying, higher free-tropospheric relative humidity enhances low-level cloudiness. At low latitudes, where cold advection destabilizes the boundary layer, stronger winds enhance low-level cloudiness; by contrast, wind speed variations have weak influence at midlatitudes where warm advection frequently stabilizes the marine boundary layer, thus inhibiting vertical mixing. These observational constraints provide a framework for understanding and evaluating marine low-cloud feedbacks and their simulation by models. Ó 2020 American Meteorological Society."
"57204710873;36809017200;26645289600;55014468500;7003971889;55332348600;24329376600;","Intermodel spread in the pattern effect and its contribution to climate sensitivity in CMIP5 and CMIP6 models",2020,"10.1175/JCLI-D-19-1011.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85090435070&doi=10.1175%2fJCLI-D-19-1011.1&partnerID=40&md5=07abba46818fc5fb147c04351ee39238","Radiative feedbacks depend on the spatial patterns of sea surface temperature (SST) and thus can change over time as SST patterns evolve—the so-called pattern effect. This study investigates intermodel differences in the magnitude of the pattern effect and how these differences contribute to the spread in effective equilibrium climate sensitivity (ECS) within CMIP5 and CMIP6 models. Effective ECS in CMIP5 estimated from 150-yr-long abrupt43CO2 simulations is on average 10% higher than that estimated from the early portion (first 50 years) of those simulations, which serves as an analog for historical warming; this difference is reduced to 7% on average in CMIP6. The (negative) net radiative feedback weakens over the course of the abrupt43CO2 simulations in the vast majority of CMIP5 and CMIP6 models, but this weakening is less dramatic on average in CMIP6. For both ensembles, the total variance in the effective ECS is found to be dominated by the spread in radiative response on fast time scales, rather than the spread in feedback changes. Using Green’s functions derived from two AGCMs shows that the spread in feedbacks on fast time scales may be primarily due to differences in atmospheric model physics, whereas the spread in feedback evolution is primarily governed by differences in SST patterns. Intermodel spread in feedback evolution is well explained by differences in the relative warming in the west Pacific warm-pool regions for the CMIP5 models, but this relation fails to explain differences across the CMIP6 models, suggesting that a stronger sensitivity of extratropical clouds to surface warming may also contribute to feedback changes in CMIP6. Ó 2020 American Meteorological Society."
"57219241546;57219246674;57219244004;55241800100;57219244690;55342815900;57196452651;7005978899;7003625897;56628141500;57112884200;35346106500;8696069500;","A Bayesian framework for emergent constraints: Case studies of climate sensitivity with PMIP",2020,"10.5194/cp-16-1715-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091823923&doi=10.5194%2fcp-16-1715-2020&partnerID=40&md5=951a8940c962f97d6bd006f93b5ae130","In this paper we introduce a Bayesian framework, which is explicit about prior assumptions, for using model ensembles and observations together to constrain future climate change. The emergent constraint approach has seen broad application in recent years, including studies constraining the equilibrium climate sensitivity (ECS) using the Last Glacial Maximum (LGM) and the mid-Pliocene Warm Period (mPWP). Most of these studies were based on ordinary least squares (OLS) fits between a variable of the climate state, such as tropical temperature, and climate sensitivity. Using our Bayesian method, and considering the LGM and mPWP separately, we obtain values of ECS of 2.7K (0.6-5.2, 5th-95th percentiles) using the PMIP2, PMIP3, and PMIP4 datasets for the LGM and 2.3K (0.5-4.4) with the PlioMIP1 and PlioMIP2 datasets for the mPWP. Restricting the ensembles to include only the most recent version of each model, we obtain 2.7K (0.7-5.2) using the LGM and 2.3K (0.4-4.5) using the mPWP. An advantage of the Bayesian framework is that it is possible to combine the two periods assuming they are independent, whereby we obtain a tighter constraint of 2.5K (0.8-4.0) using the restricted ensemble. We have explored the sensitivity to our assumptions in the method, including considering structural uncertainty, and in the choice of models, and this leads to 95% probability of climate sensitivity mostly below 5K and only exceeding 6K in a single and most uncertain case assuming a large structural uncertainty. The approach is compared with other approaches based on OLS, a Kalman filter method, and an alternative Bayesian method. An interesting implication of this work is that OLS-based emergent constraints on ECS generate tighter uncertainty estimates, in particular at the lower end, an artefact due to a flatter regression line in the case of lack of correlation. Although some fundamental challenges related to the use of emergent constraints remain, this paper provides a step towards a better foundation for their potential use in future probabilistic estimations of climate sensitivity. © 2020 Author(s)."
"6506286471;7103030382;56816985200;36504013400;56618728500;57202534407;26221127400;57219201801;57207750305;55764106200;6507684871;12767129100;57051593900;36342537900;","Simulations for CMIP6 With the AWI Climate Model AWI-CM-1-1",2020,"10.1029/2019MS002009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091676050&doi=10.1029%2f2019MS002009&partnerID=40&md5=e5d5947fa6925a65eea56aa0f8ff7b0b","The Alfred Wegener Institute Climate Model (AWI-CM) participates for the first time in the Coupled Model Intercomparison Project (CMIP), CMIP6. The sea ice-ocean component, FESOM, runs on an unstructured mesh with horizontal resolutions ranging from 8 to 80 km. FESOM is coupled to the Max Planck Institute atmospheric model ECHAM 6.3 at a horizontal resolution of about 100 km. Using objective performance indices, it is shown that AWI-CM performs better than the average of CMIP5 models. AWI-CM shows an equilibrium climate sensitivity of 3.2°C, which is similar to the CMIP5 average, and a transient climate response of 2.1°C which is slightly higher than the CMIP5 average. The negative trend of Arctic sea-ice extent in September over the past 30 years is 20–30% weaker in our simulations compared to observations. With the strongest emission scenario, the AMOC decreases by 25% until the end of the century which is less than the CMIP5 average of 40%. Patterns and even magnitude of simulated temperature and precipitation changes at the end of this century compared to present-day climate under the strong emission scenario SSP585 are similar to the multi-model CMIP5 mean. The simulations show a 11°C warming north of the Barents Sea and around 2°C to 3°C over most parts of the ocean as well as a wetting of the Arctic, subpolar, tropical, and Southern Ocean. Furthermore, in the northern middle latitudes in boreal summer and autumn as well as in the southern middle latitudes, a more zonal atmospheric flow is projected throughout the year. ©2020. The Authors."
"7201485519;7005056279;","Testing a Physical Hypothesis for the Relationship Between Climate Sensitivity and Double-ITCZ Bias in Climate Models",2020,"10.1029/2019MS001999","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091666221&doi=10.1029%2f2019MS001999&partnerID=40&md5=6c87f170594c86e088af9055e293277b","Tian (2015, https://doi.org/10.1002/2015GL064119) found that Coupled Model Intercomparison Project Phases 3 and 5 (CMIP3 and CMIP5) climate models with too much precipitation in a region of the Southeast Pacific (due to a double-Intertropical Convergence Zone [ITCZ] bias) tend to have lower climate sensitivities and suggested that this might form the basis of an “emergent constraint,” which could rule out lower values of climate sensitivity. However, no physical mechanism has been proposed to explain this relationship. Here we advance the hypothesis that deep convection encroaching into regions that should be dominated by shallow clouds hampers the formation of shallow clouds in the present climate and reduces the magnitude of positive low-level cloud feedbacks, resulting in smaller values of climate sensitivity. We test this hypothesis first by performing sensitivity tests with the HadGEM2-A aquaplanet model subject to a uniform +4 K sea surface temperature (SST) perturbation, in which we vary the degree to which deep convection associated with the single/double ITCZ extends toward subtropical low-cloud regions. Experiments with more precipitation encroaching into the subtropics have weaker subtropical cloud radiative effects in the present-day simulations and less positive subtropical cloud feedbacks, consistent with our hypothesis. We test this hypothesis further by looking for the predicted relationships across multimodel ensembles of SST forced Atmospheric Model Intercomparison Project (AMIP) experiments subject to a uniform +4 K SST increase. Relationships of the expected sign are found in the CMIP5 AMIP+4K experiments, but not all are statistically significant at the 5% level. We find no statistically significant support for our hypothesis in the currently available CMIP6 AMIP+4K experiments. ©2020. The Authors."
"6603036806;7007034953;","Pervasive Warming Bias in CMIP6 Tropospheric Layers",2020,"10.1029/2020EA001281","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091536176&doi=10.1029%2f2020EA001281&partnerID=40&md5=87162ddfd24b27644347e65add574895","The tendency of climate models to overstate warming in the tropical troposphere has long been noted. Here we examine individual runs from 38 newly released Coupled Model Intercomparison Project Version 6 (CMIP6) models and show that the warm bias is now observable globally as well. We compare CMIP6 runs against observational series drawn from satellites, weather balloons, and reanalysis products. We focus on the 1979–2014 interval, the maximum span for which all observational products are available and for which models were run using historically observed forcings. For lower-troposphere and midtroposphere layers both globally and in the tropics, all 38 models overpredict warming in every target observational analog, in most cases significantly so, and the average differences between models and observations are statistically significant. We present evidence that consistency with observed warming would require lower model Equilibrium Climate Sensitivity (ECS) values. © 2020. The Authors."
"57218515789;55796506900;55673982300;57217487135;57218442044;","Analysis of Short-term Cloud Feedback in East Asia Using Cloud Radiative Kernels",2020,"10.1007/s00376-020-9281-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089382748&doi=10.1007%2fs00376-020-9281-9&partnerID=40&md5=7233b5269f1e0cf12ec32c6b791c87df","Cloud radiative kernels were built by BCC_RAD (Beijing Climate Center radiative transfer model) radiative transfer code. Then, short-term cloud feedback and its mechanisms in East Asia (0.5°S–60.5°N, 69.5°–150.5°E) were analyzed quantitatively using the kernels combined with MODIS satellite data from July 2002 to June 2018. According to the surface and monsoon types, four subregions in East Asia—the Tibetan Plateau, northwest, temperate monsoon (TM), and subtropical monsoon (SM)—were selected. The average longwave, shortwave, and net cloud feedbacks in East Asia are −0.68 ± 1.20, 1.34 ± 1.08, and 0.66 ± 0.40 W m−2 K−1 (±2σ), respectively, among which the net feedback is dominated by the positive shortwave feedback. Positive feedback in SM is the strongest of all subregions, mainly due to the contributions of nimbostratus and stratus. In East Asia, short-term feedback in spring is primarily caused by marine stratus in SM, in summer is primarily driven by deep convective cloud in TM, in autumn is mainly caused by land nimbostratus in SM, and in winter is mainly driven by land stratus in SM. Cloud feedback in East Asia is chiefly driven by decreases in mid-level and low cloud fraction owing to the changes in relative humidity, and a decrease in low cloud optical thickness due to the changes in cloud water content. © 2020, Institute of Atmospheric Physics/Chinese Academy of Sciences, and Science Press and Springer-Verlag GmbH Germany, part of Springer Nature."
"8083646600;57203030873;35490828000;","Improved clouds over Southern Ocean amplify Antarctic precipitation response to ozone depletion in an earth system model",2020,"10.1007/s00382-020-05346-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087737293&doi=10.1007%2fs00382-020-05346-8&partnerID=40&md5=1f4d555cb96dc157659c0c74156d74ed","Increasing precipitation on the Antarctic Ice Sheet (AIS) in a warming climate has the potential to partially mitigate Antarctica’s contribution to sea level rise. We show that a simple, physically motivated change to the shallow convective cloud phase in the Community Earth System Model (CESM)—improving a long-standing bias in shortwave cloud forcing over the Southern Ocean—leads to an enhanced response of precipitation when the model is forced with realistic stratospheric ozone depletion, with other radiative forcing remaining constant. We analyze two ozone-forced ensemble experiments with the CESM version 1.1: one using the standard version of the model and the other using the cloud-modified version. The standard version exhibits a precipitation increase on the AIS of 34 gigatons year−1; the cloud-modified version shows an increase of 109 Gt year−1. The cloud-modified version shows a more robust, year-round poleward shift in the westerly jet and storm tracks, which brings more precipitation to the AIS, compared to the standard version. Greater surface warming and larger-amplitude stationary waves further increase the Antarctic precipitation response. The enhanced warming in the cloud-modified version is explained by larger positive shortwave cloud feedbacks, while the enhanced poleward jet shift is associated with a stronger meridional temperature gradient in the upper troposphere—lower stratosphere. These results illustrate (1) the sensitivity of forced changes in Antarctic precipitation to the mean state of a climate model and (2) the strong role of atmospheric dynamics in driving that forced precipitation response. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature."
"57203874129;36809017200;7003971889;35728460100;56179222300;6602558284;","Antarctic Elevation Drives Hemispheric Asymmetry in Polar Lapse Rate Climatology and Feedback",2020,"10.1029/2020GL088965","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089907491&doi=10.1029%2f2020GL088965&partnerID=40&md5=dd5e0946245b4a8979d332dedc5e6b83","The lapse rate feedback is the dominant driver of stronger warming in the Arctic than the Antarctic in simulations with increased CO2. While Antarctic surface elevation has been implicated in promoting a weaker Antarctic lapse rate feedback, the mechanisms in which elevation impacts the lapse rate feedback are still unclear. Here we suggest that weaker Antarctic warming under CO2 forcing stems from shallower, less intense climatological inversions due to limited atmospheric heat transport above the ice sheet elevation and elevation-induced katabatic winds. In slab ocean model experiments with flattened Antarctic topography, stronger climatological inversions support a stronger lapse rate feedback and annual mean Antarctic warming comparable to the Arctic under CO2 doubling. Unlike the Arctic, seasonality in warming over flat Antarctica is mainly driven by a negative shortwave cloud feedback, which exclusively dampens summer warming, with a smaller contribution from the winter-enhanced lapse rate feedback. ©2020. American Geophysical Union. All Rights Reserved."
"57190858567;57203030873;57218515581;55803016100;","Quantifying the Influence of Cloud Radiative Feedbacks on Arctic Surface Warming Using Cloud Locking in an Earth System Model",2020,"10.1029/2020GL089207","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089398074&doi=10.1029%2f2020GL089207&partnerID=40&md5=03c90a44824898cb9a6f728fe83895f2","Understanding the influence of clouds on amplified Arctic surface warming remains an important unsolved research problem. Here, this cloud influence is directly quantified by disabling cloud radiative feedbacks or “cloud locking” within a state-of-the-art and well-documented model. Through comparison of idealized greenhouse warming experiments with and without cloud locking, the influence of Arctic and global cloud feedbacks is assessed. Global cloud feedbacks increase both global and Arctic warming by around 25%. In contrast, disabling Arctic cloud feedbacks has a negligible influence on both Arctic and global surface warming. Interestingly, the sum of noncloud radiative feedbacks does not change with either global or Arctic-only cloud locking. Notably, the influence of Arctic cloud feedbacks is likely underestimated, because, like many models, the model used here underestimates high-latitude supercooled cloud liquid. More broadly, this work demonstrates the value of regional and global cloud locking in a well-characterized model. © 2020. American Geophysical Union. All Rights Reserved."
"7003420726;35580303100;8696069500;7201504886;","What could we learn about climate sensitivity from variability in the surface temperature record?",2020,"10.5194/esd-11-709-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089608989&doi=10.5194%2fesd-11-709-2020&partnerID=40&md5=67873287022496ca36dba8fc398b66f4","We examine what can be learnt about climate sensitivity from variability in the surface air temperature record over the instrumental period, from around 1880 to the present. While many previous studies have used trends in observational time series to constrain equilibrium climate sensitivity, it has also been argued that temporal variability may also be a powerful constraint. We explore this question in the context of a simple widely used energy balance model of the climate system. We consider two recently proposed summary measures of variability and also show how the full information content can be optimally used in this idealised scenario. We find that the constraint provided by variability is inherently skewed, and its power is inversely related to the sensitivity itself, discriminating most strongly between low sensitivity values and weakening substantially for higher values. It is only when the sensitivity is very low that the variability can provide a tight constraint. Our investigations take the form of ""perfect model"" experiments, in which we make the optimistic assumption that the model is structurally perfect and all uncertainties (including the true parameter values and nature of internal variability noise) are correctly characterised. Therefore the results might be interpreted as a best-case scenario for what we can learn from variability, rather than a realistic estimate of this. In these experiments, we find that for a moderate sensitivity of 2.5 °C, a 150-year time series of pure internal variability will typically support an estimate with a 5 %-95% range of around 5 °C (e.g. 1.9-6.8 °C). Total variability including that due to the forced response, as inferred from the detrended observational record, can provide a stronger constraint with an equivalent 5 %-95 % posterior range of around 4 °C (e.g. 1.8-6.0 °C) even when uncertainty in aerosol forcing is considered. Using a statistical summary of variability based on autocorrelation and the magnitude of residuals after detrending proves somewhat less powerful as a constraint than the full time series in both situations. Our results support the analysis of variability as a potentially useful tool in helping to constrain equilibrium climate sensitivity but suggest caution in the interpretation of precise results. © 2020 SPIE. All rights reserved."
"12767369600;57131609600;57211853843;55460998900;","Climate Sensitivity and Feedbacks of BCC-CSM to Idealized CO2 Forcing from CMIP5 to CMIP6",2020,"10.1007/s13351-020-9204-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85090089572&doi=10.1007%2fs13351-020-9204-9&partnerID=40&md5=68cc4477c27b352744581a48e5339728","Climate sensitivity represents the response of climate system to doubled CO2 concentration relative to the preindustrial level, which is one of the sources of uncertainty in climate projections. It is unclear how the climate sensitivity and feedbacks will change as a model system is upgraded from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to CMIP6. In this paper, we address this issue by comparing two versions of the Beijing Climate Center Climate System Model (BCC-CSM) participating in CMIP6 and CMIP5, i.e., BCC-CSM2-MR and BCC-CSM1.1m, which have the same horizontal resolution but different physical parameterizations. The results show that the equilibrium climate sensitivity (ECS) of BCC-CSM slightly increases from CMIP5 (2.94 K) to CMIP6 (3.04 K). The small changes in the ECS result from compensation between decreased effective radiative forcing (ERF) and the increased net feedback. In contrast, the transient climate response (TCR) evidently decreases from 2.19 to 1.40 K, nearly the lower bound of the CMIP6 multimodel spread. The low TCR in BCC-CSM2-MR is mainly caused by the small ERF overly even though the ocean heat uptake (OHU) efficiency is substantially improved from that in BCC-CSM1.1m. Cloud shortwave feedback (λSWCL) is found to be the major cause of the increased net feedback in BCC-CSM2-MR, mainly over the Southern Ocean. The strong positive λSWCL in BCC-CSM2-MR is coincidently related to the weakened sea ice-albedo feedback in the same region. This result is caused by reduced sea ice coverage simulated during the preindustrial cold season, which leads to reduced melting per 1-K global warming. As a result, in BCC-CSM2-MR, reduced surface heat flux and strengthened static stability of the planetary boundary layer cause a decrease in low-level clouds and an increase in incident shortwave radiation. This study reveals the important compensation between λSWCL and sea ice-albedo feedback in the Southern Ocean. © 2020, The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg."
"56480734000;35509639400;7004714030;","Observational Evidence for a Stability Iris Effect in the Tropics",2020,"10.1029/2020GL089059","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088588112&doi=10.1029%2f2020GL089059&partnerID=40&md5=cbd4b15307ed3baf3a0ab4447e003abc","Anvil clouds cover extensive areas of the tropics, and their response to global warming can affect cloud feedbacks and climate sensitivity. A growing number of models and theories suggest that when the tropical atmosphere warms, anvil clouds rise and their coverage decreases, but observational support for this behavior remains limited. Here we use 10 years of measurements from the space-borne CALIPSO lidar to analyze the vertical distribution of clouds and isolate the behavior of anvil clouds. On the interannual time scale, we find a strong evidence for anvil rise and coverage decrease in response to tropical warming. Using meteorological reanalyses, we show that this is associated with an increase in static stability and with a reduction in clear-sky radiatively driven mass convergence at the anvil height. These relationships hold over a large range of spatial scales. This is consistent with the stability Iris mechanism suggested by theory and modeling studies. ©2020. The Authors."
"55795535700;57203164459;25031430500;","Using a-train observations to evaluate east pacific cloud occurrence and radiative effects in the community atmosphere model",2020,"10.1175/JCLI-D-19-0870.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85093068904&doi=10.1175%2fJCLI-D-19-0870.1&partnerID=40&md5=e4ecc393ee5609609b8e06ba3ddc01c4","Using information from the A-Train satellites, the properties and radiative effects of eastern Pacific Ocean boundary layer clouds are evaluated in the Community Atmosphere Model, version 5 (CAM5), from the summer of 2007 and 2008. The cloud microphysical properties are inferred using measurements from CloudSat and CALIPSO (CC) that are then used to calculate the broadband radiative flux profiles. Accounting appropriately for sampling differences between the measurements and the simulation, evidence of the ''too few, too bright'' low cloud bias is found in CAM5. Single-layer low clouds have a frequency of occurrence of 42% from CC, as compared with just 29% in CAM5, and the averaged cloud radiative kernel (CRK) for the model shows stronger cooling. For stratocumulus in particular, the cooling in the model CRK is larger by a factor of 2 relative to the observations, implying an overly sensitive tropical low cloud feedback. Differences in the day/night occurrence of stratocumulus help to explain some of the difference in the CRK. The cloud-type microphysics for liquid clouds is represented reasonably well by the model, with a tendency for smaller water paths and smaller effective radii. Overall, the occurrence and CRK have partially compensating errors such that the net cooling at the top of the atmosphere for eastern Pacific low clouds is 243 W m22 in CAM5, as compared with 232 W m22 from CC. The cooling effect in the model is accomplished by fewer low clouds with a narrower range of properties, as compared with more clouds with a broader range of properties in the observation-based dataset. © 2020 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"57218243832;57218242945;57218243859;","Anthropocene climate bifurcation",2020,"10.5194/npg-27-391-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088413683&doi=10.5194%2fnpg-27-391-2020&partnerID=40&md5=791d0f2e143089c8f1be2596c72aeb83","This article presents the results of a bifurcation analysis of a simple energy balance model (EBM) for the future climate of the Earth. The main focus is on the following question: can the nonlinear processes intrinsic to atmospheric physics, including natural positive feedback mechanisms, cause a mathematical bifurcation of the climate state, as a consequence of continued anthropogenic forcing by rising greenhouse gas emissions? Our analysis shows that such a bifurcation could cause an abrupt change to a drastically different climate state in the EBM, which is warmer and more equable than any climate existing on Earth since the Pliocene epoch. In previous papers, with this EBM adapted to paleoclimate conditions, it was shown to exhibit saddle-node and cusp bifurcations, as well as hysteresis. The EBM was validated by the agreement of its predicted bifurcations with the abrupt climate changes that are known to have occurred in the paleoclimate record, in the Antarctic at the Eocene-Oligocene transition (EOT) and in the Arctic at the Pliocene-Paleocene transition (PPT). In this paper, the EBM is adapted to fit Anthropocene climate conditions, with emphasis on the Arctic and Antarctic climates. The four Representative Concentration Pathways (RCP) considered by the IPCC (Intergovernmental Panel on Climate Change) are used to model future <span classCombining double low line""inline-formula"">CO2</span> concentrations, corresponding to different scenarios of anthropogenic activity. In addition, the EBM investigates four naturally occurring nonlinear feedback processes which magnify the warming that would be caused by anthropogenic <span classCombining double low line""inline-formula"">CO2</span> emissions alone. These four feedback mechanisms are ice-albedo feedback, water vapour feedback, ocean heat transport feedback, and atmospheric heat transport feedback. The EBM predicts that a bifurcation resulting in a catastrophic climate change, to a pre-Pliocene-like climate state, will occur in coming centuries for an RCP with unabated anthropogenic forcing, amplified by these positive feedbacks. However, the EBM also predicts that appropriate reductions in carbon emissions may limit climate change to a more tolerable continuation of what is observed today. The globally averaged version of this EBM has an equilibrium climate sensitivity (ECS) of 4.34 K, near the high end of the likely range reported by the IPCC. © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License."
"55542116900;7102604282;","Radiative forcing of anthropogenic aerosols on cirrus clouds using a hybrid ice nucleation scheme",2020,"10.5194/acp-20-7801-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088410166&doi=10.5194%2facp-20-7801-2020&partnerID=40&md5=3098bcf483ca23a4ec40e503774cdec8","Anthropogenic aerosols impact cirrus clouds through ice nucleation, thereby changing the Earth's radiation budget. However, the magnitude and sign of anthropogenic forcing in cirrus clouds is still very uncertain depending on the treatments for ice-nucleating particles (INPs), the treatments for haze particle freezing, and the ice nucleation scheme. In this study, a new ice nucleation scheme (hereafter the HYBRID scheme) is developed to combine the best features of two previous ice nucleation schemes, so that global models are able to calculate the ice number concentration in both updrafts and downdrafts associated with gravity waves, and it has a robust sensitivity to the change of aerosol number. The scheme is applied in a box model, and the ice number concentrations (9:52 ± 2:08 L-1) are somewhat overestimated but are in reasonable agreement with those from an adiabatic parcel model (9:40±2:31 L-1). Then, the forcing and cloud changes associated with changes in aircraft soot, sulfur emission, and all anthropogenic emissions between the preindustrial (PI) period and the present day (PD) are examined using the CESM/IMPACT global model with the HYBRID scheme. Aircraft soot emissions decrease the global average ice number concentration (Ni) by-1:0 ± 2:4 × 107 m-2 (-1 %) (over the entire column) due to the inhibition of homogeneous nucleation and lead to a radiative forcing of-0:14 ± 0:07 W m-2, while the increase in sulfur emissions increases the global average Ni by 7:3 ± 2:9 × 107 m-2 (5 %) due to the increase in homogeneous nucleation and leads to a radiative forcing of-0:02 ± 0:06 W m-2. The possible effects of aerosol and cloud feedbacks to the meteorological state in remote regions partly contribute to reduce the forcing and the change in Ni due to anthropogenic emissions. The radiative forcing due to all increased anthropogenic emissions from PI to PD is estimated to be-0:20 ± 0:05 W m-2. If newly formed secondary organic aerosols (SOAs) act as INPs and inhibit homogeneous nucleation, the Ni formed from heterogeneous nucleation is increased. As a result, the inclusion of INPs from SOA increases the change in Ni to 12:0±2:3×107 m-2 (9 %) and increases (makes less negative) the anthropogenic forcing on cirrus clouds to-0:04 ± 0:08 W m-2 from PI to PD. © Author(s) 2020."
"35857960400;7004940109;7003375121;35240660700;","Modelling the present global terrestrial climatic response due to a chicxulub-type asteroid impact",2020,"10.3390/atmos11070747","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088088769&doi=10.3390%2fatmos11070747&partnerID=40&md5=e667e5daa5c79fe9a04e2ea16918c2ae","A Chicxulub-like asteroid event occurs, on average, approximately every ~27 to 200 million years. Therefore, such an event could happen presently. Here, we simulate the climatic anomalies it may cause with respect to the current conditions, assuming the same target geology of carbonates and evaporates and a 1 Gt release of sulphate gases. We used a thermodynamic model, including water vapor, cloudiness (by greenhouse and albedo effects), and cryosphere feedback to calculate aerosol cooling. We found that it took nearly 4.5 years for solar radiation to recover its preimpact value-during the first year practically no solar radiation reached the surface. Recovery of the temperature took more than 45 years. The lowest temperatures occurred between 1.5 and 5 years after the impact, being the coldest at-14 °C below the preimpact temperature. July surface temperature anomalies occurred 1.5 years after the impact, becoming one of the largest, compared to preimpact temperatures. Most continents showed temperature anomalies of-45 °C. The least cold places were the polar regions with temperature anomalies between approximately-5 and 0 °C. As for the most remarkable climatic effect, we found that, for ~6 years, the ice extended over almost all the ocean surface and, after ~25 years, it covered nearly half of the surface, remaining so for beyond 45 years. The continental ice remained without reduction beyond 45 years. Sixty years after the impact, the surface oceanic and continental fractions covered by ice were 0.52 and 0.98, respectively. We also modeled the effect of smaller quantities of sulfur released after asteroid impacts, concluding that an instantaneous, large climatic perturbation attributed to a loading range may lead to a semi-permanent shift in the climate system. © 2020 by the authors."
"36657850900;55688930000;55087038900;7006705919;","Assessing Global and Local Radiative Feedbacks Based on AGCM Simulations for 1980–2014/2017",2020,"10.1029/2020GL088063","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086800660&doi=10.1029%2f2020GL088063&partnerID=40&md5=2591b8373425d207c0eae448f7089ab1","We examine radiative feedbacks based on short-term climate variability by analyzing atmospheric general circulation model (AGCM) simulations, including Atmospheric Model Intercomparison Project within CMIP phase 6 (AMIP6) with known effective radiative forcing (ERF) for 1980–2014 and one with zero ERF for 1980–2017. We first verify the Kernel-Gregory feedback calculation by showing that both clear-sky radiative fluxes and all-sky radiative feedbacks from the kernel method agree with model simulations. We find that global-mean net feedback for 1980–2017/2014 is −2 W m−2 K−1, about twice the feedback estimated for long-term warming (4 × CO2) experiments. This difference is mainly caused by a near-zero global-mean net cloud feedback for 1980–2017/2014. We show that the lapse rate feedback for 1980–2017/2014 is the largest contributor to the amplified temperature change over the three poles (Arctic, Antarctic, and Tibetan Plateau), followed by surface albedo feedback and Planck feedback deviation from its global mean. Except for a higher surface albedo feedback in Antarctic, other feedbacks are similar between Arctic and Antarctic. ©2020. The Authors."
"55293560600;7101959253;35587189700;","The Influence of Sea Surface Temperature Reemergence on Marine Stratiform Cloud",2020,"10.1029/2020GL086957","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084508767&doi=10.1029%2f2020GL086957&partnerID=40&md5=aafe9b2b809f9aa684530a1da4e6d18a","The global distribution of winter to winter sea surface temperature (SST) reemergence is analyzed using a novel metric based on an autoregressive 1 model, and the global impact of SST on cloud amount and cloud type are examined using satellite data. A region in the northeastern Pacific Ocean is identified where wintertime SSTs are correlated with the occurrence of marine stratiform cloud the following winter. This correlation is likely a manifestation of SST reemergence. We hypothesize that through this reemergence mechanism marine stratus cloud amount, and thus shortwave cloud radiative effect, in the northeastern Pacific exhibits memory on inter-seasonal and even multi-year time scales and that exploration of this relationship may provide insight into the SST—low cloud feedbacks. ©2020. American Geophysical Union. All Rights Reserved."
"8696069500;7003979342;","Tuning the MPI-ESM1.2 Global Climate Model to Improve the Match With Instrumental Record Warming by Lowering Its Climate Sensitivity",2020,"10.1029/2019MS002037","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085389793&doi=10.1029%2f2019MS002037&partnerID=40&md5=70b8d342484537369452f514b44109fc","A climate model's ability to reproduce observed historical warming is sometimes viewed as a measure of quality. Yet, for practical reasons it cannot be considered a purely empirical result of the modeling efforts because the desired result is known in advance and so is a potential target of tuning. Here we report how the latest edition of the Max Planck Institute for Meteorology Earth System Models (MPI-ESM1.2) atmospheric component (ECHAM6.3) had its sensitivity systematically tuned in order to improve the modeled match with the instrumental record. In practice, this was done by targeting an equilibrium climate sensitivity of about 3 K, slightly lower than in the previous model generation (MPI-ESM), which warmed more than observed, and in particular by addressing a climate sensitivity of about 7 K in an intermediate version of the model. In the process we identified several controls on cloud feedback, some of which confirm recently proposed hypotheses. We find the model exhibits excellent fidelity with the observed centennial global warming. We further find that an alternative approach with high climate sensitivity compensated by strong aerosol cooling instead would yield colder than observed results in the second half of the twentieth century. ©2020. The Authors."
"55582587700;7103180783;14036209800;7402401574;53880473700;","Processes shaping the spatial pattern and seasonality of the surface air temperature response to anthropogenic forcing",2020,"10.1007/s00382-020-05211-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083372536&doi=10.1007%2fs00382-020-05211-8&partnerID=40&md5=5e9d7e085f4d92b5e3db39b8942c5a39","In the period 1960–2010, the land surface air temperature (SAT) warmed more rapidly over some regions relative to the global mean. Using a set of time-slice experiments, we highlight how different physical processes shape the regional pattern of SAT warming. The results indicate an essential role of anthropogenic forcing in regional SAT changes from the 1970s to 2000s, and show that both surface–atmosphere interactions and large-scale atmospheric circulation changes can shape regional responses to forcing. Single forcing experiments show that an increase in greenhouse gases can lead to regional changes in land surface warming in winter (DJF) due to snow-albedo feedbacks, and in summer (JJA) due to soil-moisture and cloud feedbacks. Changes in anthropogenic aerosol and precursor (AA) emissions induce large spatial variations in SAT, characterized by warming over western Europe, Eurasia, and Alaska. In western Europe, SAT warming is stronger in JJA than in DJF due to substantial increases in clear sky shortwave radiation over Europe, associated with decreases in local AA emissions since the 1980s. In Alaska, the amplified SAT warming in DJF is due to increased downward longwave radiation, which is related to increased water vapor and cloud cover. In this case, although the model was able to capture the regional pattern of SAT change, and the associated local processes, it did not simulate all processes and anomalies correctly. For the Alaskan warming, the model is seen to achieve the correct regional response in the context of a wider North Pacific anomaly that is not consistent with observations. This demonstrates the importance of model evaluation that goes beyond the target variable in detection and attribution studies. © 2020, The Author(s)."
"55831437900;6603982006;","Polar Amplification as an Inherent Response of a Circulating Atmosphere: Results From the TRACMIP Aquaplanets",2020,"10.1029/2019GL086771","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082530054&doi=10.1029%2f2019GL086771&partnerID=40&md5=9db2d917ddac86b9a42eaa2bbb77ac2f","In the Tropical Rain belts with an Annual cycle and Continent Model Intercomparison Project (TRACMIP) ensemble of aquaplanet climate model experiments, CO2-induced warming is amplified in the poles in 10 out of 12 models, despite the lack of sea ice. We attribute causes of this amplification by perturbing individual radiative forcing and feedback components in a moist energy balance model. We find a strikingly linear pattern of tropical versus polar warming contributions across models and processes, implying that polar amplification is an inherent consequence of diffusion of moist static energy by the atmosphere. The largest contributor to polar amplification is the instantaneous CO2 forcing, followed by the water vapor feedback and, for some models, cloud feedbacks. Extratropical feedbacks affect polar amplification more strongly, but even feedbacks confined to the tropics can cause polar amplification. Our results contradict studies inferring warming contributions directly from the meridional gradient of radiative perturbations, highlighting the importance of interactions between feedbacks and moisture transport for polar amplification. ©2020. American Geophysical Union. All Rights Reserved."
"7404657786;57215902022;19638935200;55712637800;","Evaluation on the Vertical Distribution of Liquid and Ice Phase Cloud Fraction in Community Atmosphere Model Version 5.3 using Spaceborne Lidar Observations",2020,"10.1029/2019EA001029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082313128&doi=10.1029%2f2019EA001029&partnerID=40&md5=0cb5735b872e993e20e89122cf197f4d","Cloud partition between liquid and ice phases and their vertical distributions are crucial to energy budget and global climate. Liquid and ice cloud fractions simulated by Community Atmosphere Model version 5.3 and Cloud Feedback Model Intercomparison Project Observational Simulator Package version 1.4 are evaluated by comparing to satellite retrieval data from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation. Model underestimates liquid cloud by 3.3%, 5.5%, and 3.1% and overestimates ice cloud by 1.5%, 6.3%, and 4.6% in high, medium, and low levels, respectively. The misclassification of liquid cloud to ice cloud occurs in all model levels, leading to an overall underestimation of supercooled liquid fraction (SLF) globally and a shift of 50% SLF line from about −20°C in observation to −5°C in model. Specifically, model produces excessive ice cloud in extratropics and insufficient liquid cloud in tropics at mixed-phase levels with temperature between 0 and −40°C. ©2020. The Authors."
"57215530945;57197840302;56909903600;57193952922;14036628000;","Evaporative Resistance is of Equal Importance as Surface Albedo in High-Latitude Surface Temperatures Due to Cloud Feedbacks",2020,"10.1029/2019GL085663","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081072205&doi=10.1029%2f2019GL085663&partnerID=40&md5=6085ef30a7a918110f9fbd7708b66bcf","Arctic vegetation is known to influence Arctic surface temperatures through albedo. However, it is less clear how plant evaporative resistance and albedo independently influence surface climate at high latitudes. We use surface properties derived from two common Arctic tree types to simulate the climate response to a change in land surface albedo and evaporative resistance in factorial combinations. We find that lower evaporative resistances lead to an increase of low clouds. The reflection of light due to the difference in albedos between vegetation types is similar to the loss of incident sunlight due to increased cloud cover resulting from lower evaporative resistance from vegetation change. Our results demonstrate that realistic changes in evaporative resistance can have an equal impact on surface temperature to changes in albedo and that cloud feedbacks play a first-order role in determining the surface climate response to changes in Arctic land cover. ©2020. American Geophysical Union. All Rights Reserved."
"57203927213;36731553900;","Optimising Production through Intelligent Manufacturing",2020,"10.1051/e3sconf/202015203012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079764858&doi=10.1051%2fe3sconf%2f202015203012&partnerID=40&md5=02d35a93b40006080f295ff8073c1be1","Intelligent manufacturing system (IMS) has been the focus of most industries since Industry 4.0 revolution. IMS is being implemented through the integration of Internet of Things, (IoT), Cyber-Physical Systems (CPS), digital twin and big data analytics to optimize production through smart manufacturing. This research presents a conceptual approach of an adaptive clustering algorithm (ACA) for advanced manufacturing decision-making for smart machining manufacturing. The work considers product monitoring and assessment, machine health and operating parameters monitoring, as an important factor for intelligent decision making on a machining production line through the developed cyber twin of the machine tool for production optimisation. Cyber twin of the machine tool is developed which runs on a realtime sequence with the physical asset fussed with smart sensors and controllers enabled with cloud computing, IoT and data analytics. The ACA enables resources monitoring, production monitoring, machine condition monitoring, cloud feedback notification, product monitoring, and assessment, for intelligent decision-making from a cluster of similar machines using ANN clustering tool for self-aware, self-predict and self-reconfiguration in a smart machining production line to detect a cutting tool chipping of less than 0.25mm size. The method is proposed to optimise production by increasing productivity through intelligent decision and prediction for tool change, tool failure, maintenance, adjustment of operating parameters. © 2020 The Authors, published by EDP Sciences."
"13611521400;57200211699;35742922300;57215055994;","Decomposing East-Asian winter temperature and monsoonal circulation changes using timeslice experiments",2020,"10.1007/s00382-019-05114-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078256240&doi=10.1007%2fs00382-019-05114-3&partnerID=40&md5=824fffed4f24f81aaaa0b643d6951bb5","Based on a set of pilot atmosphere-only experiments from the Cloud Feedback Model Intercomparison Project Phase 3 (CFMIP-3), in this study, the winter surface air temperature (SAT) and monsoonal circulation changes in East Asia as a response to the 4 × CO2 forcing in coupled model are decomposed into the four parts in terms of the responses to the uniform SST warming, 4 × CO2 radiative effect, SST pattern changes, and plant physiological effect. The uniform SST warming presents the most significant influence on the increase of SAT change, which strengthens the East Asian winter monsoon (EAWM) circulation. The CO2 radiative effect can also induce the SAT increase over East Asia but with a magnitude smaller compared to the uniform SST warming, in which more warming is in land than ocean and the EAWM circulation could be weakened consequently due to the decreased land–sea thermal contrast in response to the CO2 radiative effect. The SAT changes in response to the SST pattern change show inconsistencies over the eastern and southern parts of East Asia between the two models, associated with the large difference for EAWM circulation changes, indicating that the SST pattern change could be the primary source of inter-model uncertainties in the East-Asian SAT change. As for the influence of plant physiological effect, it could generate a SAT rise in many highly vegetated regions. Further analyses for different areas show that both the uniform SST warming and CO2 radiative effects could induce more intense SAT increase in northern East Asia, while the plant physiological effect has a more significant influence on that in southern/eastern part of East Asia. © 2020, The Author(s)."
"7006329926;7401945370;8067118800;","Precipitation efficiency and its role in cloud-radiative feedbacks to climate variability",2020,"10.2151/jmsj.2020-024","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084213887&doi=10.2151%2fjmsj.2020-024&partnerID=40&md5=04ee5eb077c55db563dacddd47361aec","Precipitation efficiency (PE) is a useful concept for estimating precipitation under a given environmental con-dition. PE is used in various situations in meteorology such as to evaluate severe precipitation associated with a single storm event, as a parameter of cumulus convective parameterization, and to separate clouds and precipitation in climate projection studies. PE has been defined in several ways. In this review, we first introduce defini-tions of PE from microscopic and macroscopic perspectives, and provide estimates of PE based on observational and modeling approaches. Then, we review PE in shallow and organized deep convective systems that provide either a conceptual framework or physical constraints on representations of convection in models. Specifically, we focus on the roles of PE in cloud-radiative feedbacks to climate variability. Finally, we argue the usefulness of PE for investigating cloud and precipitation changes in climate projection studies. © The Author(s) 2020."
"43961612000;","Determining the Social Cost of Carbon: Under Damage and Climate Sensitivity Uncertainty",2020,"10.1007/s10640-019-00389-w","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076129262&doi=10.1007%2fs10640-019-00389-w&partnerID=40&md5=f0353e28385f39106b5830a10b771788","This article quantifies the impact on optimal climate policy, of both damage elasticity and equilibrium climate sensitivity uncertainty, under separable preferences for risk and intergenerational inequality. The primary findings are as follows. (1) Such preferences can depress the social cost of carbon (SCC) when calibration aims at matching actual economic outcomes, countering the prevailing view that the SCC is greater with separable than with conventional entangled preferences. (2) Damage elasticity uncertainty has larger effects on climate policy than equilibrium climate sensitivity uncertainty, even under high impact tail risk of the latter. (3) Risk aversion decisively strengthens optimal climate policy under joint damage and climate sensitivity uncertainty, than with a single source of uncertainty alone. Indeed, failing to account for the interaction between damage and climate sensitivity uncertainty underestimates the cost of climate change by more than US dollars 1 trillion. © 2019, Springer Nature B.V."
"57194201247;7004479957;","Understanding Negative Subtropical Shallow Cumulus Cloud Feedbacks in a Near-Global Aquaplanet Model Using Limited Area Cloud-Resolving Simulations",2019,"10.1029/2018MS001572","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067358941&doi=10.1029%2f2018MS001572&partnerID=40&md5=0fa0cef327b84d3e7b8b73b7e4eb4ea0","Limited area cloud-resolving model (CRM) simulations called LASAM are used to reproduce and understand negative subtropical shallow cumulus cloud feedbacks in a near-global aquaplanet CRM (NGAqua) with 4-K sea surface temperature (SST) warming. NGAqua spans a large tropical channel domain, with 4-km horizontal resolution, zonally symmetric equatorially peaked SST, and no cumulus parameterization. Prior work showed that its coarsely resolved shallow cumulus increases with warming. It was suggested that with warmer SST, the moister boundary layer is destabilized by more clear-sky radiative cooling, driving more cumulus convection. A small doubly periodic version of the same CRM is configured to analyze this low cloud increase in a simpler context. It is driven by steady thermodynamic and advective forcing profiles averaged over the driest subtropical column humidity quartile of NGAqua. Sensitivity studies separate effects of radiative cooling and free tropospheric relative humidity changes from other aspects of NGAqua's warmer climate. Enhanced clear-sky radiative cooling explains most of the cloud increase due to SST warming, regardless of CRM model resolution and advection scheme. A boundary layer energy budget shows that the downward entrainment heat flux strengthens to balance enhanced radiative cooling, carried by a stronger updraft cloud mass flux from a larger cumulus cloud fraction. In deeper trade cumulus layers, the enhanced radiative cooling in a warming climate may be balanced by increased precipitation warming, leaving the cloud coverage area almost unchanged. With larger domain sizes, shallow cumulus self-aggregates, especially with higher SST, marginally increasing domain-mean cloud fraction, but this is a secondary contributor to the cloud feedback. ©2019. The Authors."
"23094149200;7404829395;","Net cloud thinning, low-level cloud diminishment, and hadley circulation weakening of precipitating clouds with tropicalwest Pacific SST using MISR and other satellite and reanalysis data",2019,"10.3390/rs11101250","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85066761544&doi=10.3390%2frs11101250&partnerID=40&md5=326a5b79e05b4a91507fbab43e384319","Daily gridded Multi-Angle Imaging Spectroradiometer (MISR) satellite data are used in conjunction with CERES, TRMM, and ERA-Interim reanalysis data to investigate horizontal and vertical high cloud structure, top-of-atmosphere (TOA) net cloud forcing and albedo, and dynamics relationships against local SST and precipitation as a function of the mean TropicalWest Pacific (TWP; 120°E to 155°W 30°S-30°N) SST. As the TWP warms, the SST mode (~29.5 °C) is constant, but the area of the mode grows, indicating increased kurtosis of SSTs and decreased SST gradients overall. This is associated with weaker low-level convergence and mid-tropospheric ascent (!500) over the highest SSTs as the TWP warms, but also a broader area of weak ascent away from the deepest convection, albeit stronger when compared to when the mean TWP is cooler. These associated dynamics changes are collocated with less anvil and thick cloud cover over the highest SSTs and similar thin cold cloud fraction when the TWP is warmer, but broadly more anvil and cirrus clouds over lower local SSTs (SST &lt; 27 °C). For all TWP SST quintiles, anvil cloud fraction, defined as clouds with tops &gt; 9 km and TOA albedos between 0.3-0.6, is closely associated with rain rate, making it an excellent proxy for precipitation; but for a given heavier rain rate, cirrus clouds are more abundant with increasing domain-mean TWP SST. Clouds locally over SSTs between 29-30 °C have a much less negative net cloud forcing, up to 25 W m-2 greater, when the TWP is warm versus cool. When the local rain rate increases, while the net cloud fraction with tops &lt; 9 km decreases, mid-level clouds (4 km &lt; Ztop &lt; 9 km) modestly increase. In contrast, combined low-level and mid-level clouds decrease as the domain-wide SST increases (-10% deg-1). More cirrus clouds for heavily precipitating systems exert a stronger positive TOA effect when the TWP is warmer, and anvil clouds over a higher TWP SST are less reflective and have a weaker cooling effect. For all precipitating systems, total high cloud cover increases modestly with higher TWP SST quintiles, and anvil + cirrus clouds are more expansive, suggesting more detrainment when TWP SSTs are higher. Total-domain anvil cloud fraction scales mostly with domain-mean w500, but cirrus clouds mostly increase with domain-mean SST, invoking an explanation other than circulation. The overall thinning and greater top-heaviness of clouds over the TWP with warming are possible TWP positive feedbacks not previously identified. © 2019 by the authors."
"55264269400;7404240633;40660999000;6603195572;","Evaluation of Summer Monsoon Clouds over the Tibetan Plateau Simulated in the ACCESS Model Using Satellite Products",2019,"10.1007/s00376-018-7301-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060137321&doi=10.1007%2fs00376-018-7301-9&partnerID=40&md5=68b25fc3b90b1bdc8691e30cbfa366ea","Cloud distribution characteristics over the Tibetan Plateau in the summer monsoon period simulated by the Australian Community Climate and Earth System Simulator (ACCESS) model are evaluated using COSP [the CFMIP (Cloud Feedback Model Intercomparison Project) Observation Simulator Package]. The results show that the ACCESS model simulates less cumulus cloud at atmospheric middle levels when compared with observations from CALIPSO and CloudSat, but more ice cloud at high levels and drizzle drops at low levels. The model also has seasonal biases after the onset of the summer monsoon in May. While observations show that the prevalent high cloud at 9–10 km in spring shifts downward to 7–9 km, the modeled maximum cloud fractions move upward to 12–15 km. The reason for this model deficiency is investigated by comparing model dynamical and thermodynamical fields with those of ERA-Interim. It is found that the lifting effect of the Tibetan Plateau in the ACCESS model is stronger than in ERA-Interim, which means that the vertical velocity in the ACCESS model is stronger and more water vapor is transported to the upper levels of the atmosphere, resulting in more high-level ice clouds and less middle-level cumulus cloud over the Tibetan Plateau. The modeled radiation fields and precipitation are also evaluated against the relevant satellite observations. © 2019, Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag GmbH Germany, part of Springer Nature."
"57212781009;36717393600;8877858700;57191914668;56413849700;26645289600;","Evaluating Cloud Feedbacks and Rapid Responses in the ACCESS Model",2019,"10.1029/2018JD029189","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060127574&doi=10.1029%2f2018JD029189&partnerID=40&md5=31e77929b228026ebbecbc83f8e7a30f","A cloud feedback diagnostic package is implemented in the Australian Community Climate and Earth-System Simulator General Circulation Model, based on the methodology of “cloud radiative kernels.” Using separate increased sea surface temperature and CO 2 experiments, both the “rapid response” cloud contribution to forcing and temperature-mediated cloud feedbacks are analyzed. Under increased temperature and CO 2 changes, temperature-mediated cloud radiative feedback dominates over the rapid response in the final radiative response. Cloud feedback is positive in both long and short wave, with short wave dominating global values. Contributing most to this are low to mid-level clouds, of medium-to-high optical thickness. As a means of illustration of the methodology, a number of key parameters related to clouds, precipitation, and convection that are typically used in “tuning” in the model are modified. These changes result in substantial impacts on the model's current climate, but only modest changes to rapid response and feedbacks occur globally, regionally, and as a function of cloud optical thickness and height. This limited set of experiments shows that cloud adjustments and feedbacks in this model are robust under these changes, lending confidence that both model climate change projections and the conclusions of attribution studies are not overly sensitive to such parameterization tuning. Of course, a considerably larger set of experiments would be needed to demonstrate that feedbacks and rapid response are robust under the wider set of tuning adjustments commonly undertaken. ©2018 Australian Bureau of Meteorology, Commonwealth of Australia."
"56336403300;7405753162;55880176800;","Persistence of Summer Sea Surface Temperature Anomalies in the Midlatitude North Pacific and Its Interdecadal Variability",2018,"10.1007/s00376-017-7184-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048065132&doi=10.1007%2fs00376-017-7184-1&partnerID=40&md5=6bf6b6350ed4c0de913622001d36d112","The present study investigates the persistence of summer sea surface temperature anomalies (SSTAs) in the midlatitude North Pacific and its interdecadal variability. Summer SSTAs can persist for a long time (approximately 8–14 months) around the Kuroshio Extension (KE) region. This long persistence may be strongly related to atmospheric forcing because the mixed layer is too shallow in the summer to be influenced by the anomalies at depths in the ocean. Changes in atmospheric circulation, latent heat flux, and longwave radiation flux all contribute to the long persistence of summer SSTAs. Among these factors, the longwave radiation flux has a dominant influence. The effects of sensible heat flux and shortwave radiation flux anomalies are not significant. The persistence of summer SSTAs displays pronounced interdecadal variability around the KE region, and the variability is very weak during 1950–82 but becomes stronger during 1983–2016. The changes in atmospheric circulation, latent heat flux, and longwave radiation flux are also responsible for this interdecadal variability because their forcings on the summer SSTAs are sustained for much longer after 1982. © 2018, Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag GmbH Germany, part of Springer Nature."
"56193650100;56931957400;20435752700;7003591311;","Feedback mechanisms of shallow convective clouds in a warmer climate as demonstrated by changes in buoyancy",2018,"10.1088/1748-9326/aac178","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048066462&doi=10.1088%2f1748-9326%2faac178&partnerID=40&md5=5028847a74a2eaf5932cb601945673db","Cloud feedbacks could influence significantly the overall response of the climate system to global warming. Here we study the response of warm convective clouds to a uniform temperature change under constant relative humidity (RH) conditions. We show that an increase in temperature drives competing effects at the cloud scale: a reduction in the thermal buoyancy term and an increase in the humidity buoyancy term. Both effects are driven by the increased contrast in the water vapor content between the cloud and its environment, under warming with constant RH. The increase in the moisture content contrast between the cloud and its environment enhances the evaporation at the cloud margins, increases the entrainment, and acts to cool the cloud. Hence, there is a reduction in the thermal buoyancy term, despite the fact that theoretically this term should increase. © 2018 The Author(s). Published by IOP Publishing Ltd."
"56555458900;7408519295;","Can CFMIP2 models reproduce the leading modes of cloud vertical structure in the CALIPSO-GOCCP observations?",2018,"10.1007/s00704-017-2051-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85012293312&doi=10.1007%2fs00704-017-2051-7&partnerID=40&md5=fc6a2e64c7f034be0f340a15295d33ba","Using principal component (PC) analysis, three leading modes of cloud vertical structure (CVS) are revealed by the GCM-Oriented CALIPSO Cloud Product (GOCCP), i.e. tropical high, subtropical anticyclonic and extratropical cyclonic cloud modes (THCM, SACM and ECCM, respectively). THCM mainly reflect the contrast between tropical high clouds and clouds in middle/high latitudes. SACM is closely associated with middle-high clouds in tropical convective cores, few-cloud regimes in subtropical anticyclonic clouds and stratocumulus over subtropical eastern oceans. ECCM mainly corresponds to clouds along extratropical cyclonic regions. Models of phase 2 of Cloud Feedback Model Intercomparison Project (CFMIP2) well reproduce the THCM, but SACM and ECCM are generally poorly simulated compared to GOCCP. Standardized PCs corresponding to CVS modes are generally captured, whereas original PCs (OPCs) are consistently underestimated (overestimated) for THCM (SACM and ECCM) by CFMIP2 models. The effects of CVS modes on relative cloud radiative forcing (RSCRF/RLCRF) (RSCRF being calculated at the surface while RLCRF at the top of atmosphere) are studied in terms of principal component regression method. Results show that CFMIP2 models tend to overestimate (underestimated or simulate the opposite sign) RSCRF/RLCRF radiative effects (REs) of ECCM (THCM and SACM) in unit global mean OPC compared to observations. These RE biases may be attributed to two factors, one of which is underestimation (overestimation) of low/middle clouds (high clouds) (also known as stronger (weaker) REs in unit low/middle (high) clouds) in simulated global mean cloud profiles, the other is eigenvector biases in CVS modes (especially for SACM and ECCM). It is suggested that much more attention should be paid on improvement of CVS, especially cloud parameterization associated with particular physical processes (e.g. downwelling regimes with the Hadley circulation, extratropical storm tracks and others), which may be crucial to reduce the CRF biases in current climate models. © 2017, The Author(s)."
"6602122304;","Introduction",2018,"10.1016/B978-0-12-810549-8.00001-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041232824&doi=10.1016%2fB978-0-12-810549-8.00001-5&partnerID=40&md5=736d4df30bf67352d9ed277344275603","This chapter gives a short overview of the book's content. The volume overall presents recent research on observational and modeling aspects of mixed-phase clouds. Observations of mixed-phase clouds are illustrated using passive and active remote sensing, from ground-based, aircraft, and satellite instruments. Studies based on airborne measurements are shown for Arctic clouds and convectively forced mixed-phase clouds at mid-latitudes. For the modeling aspects, large eddy simulations (LES) are used to analyze in detail several cases of Arctic mixed-phase clouds. One chapter illustrates a new approach for sub-grid parameterization of mixed-phase clouds used in general circulation models (GCM). Finally, two studies use GCMs and satellite observations to address mixed-phase cloud feedback in the climate system, and the impact of phase partitioning of mixed-phase clouds on the equilibrium climate sensitivity. © 2018 Elsevier Inc. All rights reserved."
"55683910600;13403622000;26645289600;","The Climatic Impact of Thermodynamic Phase Partitioning in Mixed-Phase Clouds",2018,"10.1016/B978-0-12-810549-8.00010-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041184570&doi=10.1016%2fB978-0-12-810549-8.00010-6&partnerID=40&md5=799d2f554334533b5cd17cfabff86f9b","This chapter presents an extension of previous work on the impact of the supercooled liquid fraction (SLF) of mixed-phase clouds on equilibrium climate sensitivity (ECS) using a series of coupled climate simulations constrained by satellite observations. Simulations with vastly differing values of SLF were run with both present-day and doubled CO2 concentrations. The ECS values were shown to increase monotonically with increasing SLF, and the increases in ECS were attributed to a progressive weakening of the cloud phase feedback. This study presents non-cloud feedbacks (Planck, water vapor, lapse rate, albedo) and cloud feedbacks computed using two different methods. In the global mean, the Planck feedback is the strongest non-cloud feedback followed by the water vapor feedback. Additional simulations run to gauge the influence of the model tuning required to avoid climate drift in the coupled simulations suggest that the results of previous work are robust to retuning. © 2018 Elsevier Inc. All rights reserved."
[No author id available],"Erratum to: Researching climate change and community in neoliberal contexts: an emerging critical approach: Researching climate change and community in neoliberal contexts (Wiley Interdisciplinary Reviews: Climate Change, (2017), 8, 4, (e463), 10.1002/wcc.463)",2017,"10.1002/wcc.487","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027572100&doi=10.1002%2fwcc.487&partnerID=40&md5=f4d62062f260cd4127b5aa120d036142","The following errors were published in the 4th Issue of Wiley Interdisciplinary Reviews: Climate Change (WCC), DOI: 10.1002/wcc.v8.4. We apologize for these errors. In the article cited below, the name of the Domain Editor indicated in the “Edited by” line should be “Dr. Gwen Blue” instead of “Mike Hulme”. Researching climate change and community in neoliberal contexts: an emerging critical approach [Article in WIREs Clim Change 2017, 8:e463. doi: 10.1002/wcc.463] The correct text is shown below: Edited by Gwen Blue, Domain Editor, and Mike Hulme, Editor-in-Chief In the articles cited below, the name of the Editor, Mike Hulme, was inadvertently deleted in the “Edited by” line. Cloud feedback mechanisms and their representation in global climate models [Article in WIREs Clim Change 2017, 8:e465. doi: 10.1002/wcc.465] The correct text is shown below: Edited by Eduardo Zorita, Domain Editor, and Mike Hulme, Editor-in-Chief Contributions and perspectives from geography to the study of climate [Article in WIREs Clim Change 2017, 8:e466. doi: 10.1002/wcc.466] The correct text is shown below: Edited by Matthias Heymann, Domain Editor, and Mike Hulme, Editor-in-Chief Adaptive capacity: exploring the research frontier [Article in WIREs Clim Change 2017, 8:e467. doi: 10.1002/wcc.467] The correct text is shown below: Edited by Maria Carmen Lemos, Domain Editor, and Mike Hulme, Editor-in-Chief Heat, health, and humidity in Australia’s monsoon tropics: a critical review of the problematization of ‘heat’ in a changing climate [Article in WIREs Clim Change 2017, 8:e468. doi: 10.1002/wcc.468] The correct text is shown below: Edited by Irene Lorenzoni, Domain Editor, and Mike Hulme, Editor-in-Chief. © 2017 Wiley Periodicals, Inc."
"22939192200;36118090300;57203012560;56224155200;","Cloud radiative effects and changes simulated by the Coupled Model Intercomparison Project Phase 5 models",2017,"10.1007/s00376-017-6089-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020420925&doi=10.1007%2fs00376-017-6089-3&partnerID=40&md5=59d5b31d0171e62e17d5381c8183833b","Using 32 CMIP5 (Coupled Model Intercomparison Project Phase 5) models, this study examines the veracity in the simulation of cloud amount and their radiative effects (CREs) in the historical run driven by observed external radiative forcing for 1850–2005, and their future changes in the RCP (Representative Concentration Pathway) 4.5 scenario runs for 2006–2100. Validation metrics for the historical run are designed to examine the accuracy in the representation of spatial patterns for climatological mean, and annual and interannual variations of clouds and CREs. The models show large spread in the simulation of cloud amounts, specifically in the low cloud amount. The observed relationship between cloud amount and the controlling large-scale environment are also reproduced diversely by various models. Based on the validation metrics, four models—ACCESS1.0, ACCESS1.3, HadGEM2-CC, and HadGEM2-ES—are selected as best models, and the average of the four models performs more skillfully than the multimodel ensemble average. All models project global-mean SST warming at the increase of the greenhouse gases, but the magnitude varies across the simulations between 1 and 2 K, which is largely attributable to the difference in the change of cloud amount and distribution. The models that simulate more SST warming show a greater increase in the net CRE due to reduced low cloud and increased incoming shortwave radiation, particularly over the regions of marine boundary layer in the subtropics. Selected best-performing models project a significant reduction in global-mean cloud amount of about −0.99% K−1 and net radiative warming of 0.46 W m−2 K−1, suggesting a role of positive feedback to global warming. © 2017, Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag GmbH Germany."
"55087038900;","Hadley cell widening in warming climate and implication to expansion of world dry lands",2017,"10.1142/9789814723541_0005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059499429&doi=10.1142%2f9789814723541_0005&partnerID=40&md5=8161a2651ecdf481266904603c922988","Observational analyses show that the Hadley cell has expanded by 2-5° latitudes over the past three decades. This expansion is also a robust feature of general circulation model (GCM) simulated climate changes in response to the increase of greenhouse gases but with a much slower rate. The Hadley cell widening has important implications for shifts in precipitation patterns that lead to the expansion of world dry land, and for the cloud feedback to the climate system. Reconciling the discrepancy in Hadley cell widening between the GCM simulations and observations and understanding the mechanisms responsible for this aspect of global climate change represent new challenges in climate research. © 2017 by World Scientific Publishing Co. Pte. Ltd. All Rights Reserved."
"55087038900;","Hadley cell widening in warming climate and implication to expansion of world dry lands",2017,"10.1142/9789814723541_0005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020238623&doi=10.1142%2f9789814723541_0005&partnerID=40&md5=878e0e82fbaf6158f4723ee004ec5c83","Observational analyses show that the Hadley cell has expanded by 2-5° latitudes over the past three decades. This expansion is also a robust feature of general circulation model (GCM) simulated climate changes in response to the increase of greenhouse gases but with a much slower rate. The Hadley cell widening has important implications for shifts in precipitation patterns that lead to the expansion of world dry land, and for the cloud feedback to the climate system. Reconciling the discrepancy in Hadley cell widening between the GCM simulations and observations and understanding the mechanisms responsible for this aspect of global climate change represent new challenges in climate research. © 2017 World Scientific Publishing Co. Pte. Ltd."
"16645334100;9638541400;","Vibration analysis, control and genetic algorithm optimization of a piezoelectric elements bonded rotating spacecraft composite beam",2016,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-85016467358&partnerID=40&md5=9fe782778c31355f66d87b9264b1511c","The paper reviews the outstanding problems focused on Contrails and Cirrus Cloud, its assessment, consequences and solution synthesis, and identify future directions that could be followed. The Rationale for assessing Clouds, Aerosols and their interactions is associated with the representation of cloud processes in climate models which has been recognized as a dominant source of uncertainty in our understanding of changes in the climate system. Clouds respond to climate forcing mechanisms in multiple ways, and intermodel differences in cloud feedbacks constitute by far the primary source of spread of both equilibrium and transient climate responses simulated by climate models despite the fact that most models agree that the feedback is positive. Thus confidence in climate projections requires a thorough assessment of how cloud processes have been accounted for a radiative forcing (RF) of climate change through their interaction with radiation, and also as a result of their interaction with clouds. Estimate of Effective Radiative Forcing from Combined Aerosol-Radiation and Aerosol-Cloud Interactions is also relevant. There are a large number of satellite surface sensors recently launched or shortly to be launched. Recent satellite instruments such as CHRIS, MERIS, MODIS and ASTER, are essential in obtaining relevant data to that end. Theory, model studies and observations suggest that some Solar Radiation Management Methods (SRM methods) may be able to counteract a portion of global warming effects (on temperature, sea ice and precipitation) due to high concentrations of anthropogenic Green House Gases (GHGs). A new coordinated earth observation, aviation and environment program should be able to bring in at minimal cost the aircraft and ground-based measurement community, the satellite analysis community, the chemistry and climate modeling communities, along with the international research community to participate in specific projects, to deliver realistic outcomes. These initiatives may incorporate Models and Measurements, which in this case describes a critical, objective evaluation of the models used to predict aviation impacts, a unified global data set for contrails and cirrus, with well characterized accuracy and within reach using existing satellite observations, in a coordinated effort within Earth Observation initiatives."
"7003521825;35234249500;57206487279;7003875226;","Erratum: Equilibrium climate sensitivity in light of observations over the warming hiatus (Nature Climate Change (2015) 5 (449-453))",2015,"10.1038/nclimate2710","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84932162850&doi=10.1038%2fnclimate2710&partnerID=40&md5=ab6998bfafb16d7057ec23334ba79ab2",[No abstract available]
"57131609600;55913183200;7402989545;","Climate Sensitivity of the Flexible Global Ocean-Atmosphere-Land System Model",2014,"10.1007/978-3-642-41801-3_26","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027972702&doi=10.1007%2f978-3-642-41801-3_26&partnerID=40&md5=c0fa1dd2dff9969ec5f10279a664f0ee","Projections of future climate change by climate system models depend on the sensitivities of models to specified greenhouse gases. To reveal and understand the different climate sensitivities of version 2 of the grid-point and spectral Flexible Global Ocean-Atmosphere-Land System Model, FGOALS-g2 and FGOALS-s2, respectively, which were developed by the National Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics (LASG/IAP), global mean surface air temperature responses to idealized CO2 forcing are investigated by using the output of abruptly quadrupling CO2 experiments. The globally averaged near-surface air temperature is characterized by a fast response to CO2 forcing during the first 20 years and a slow response afterward. The climate sensitivity, defined as the equilibrium temperature under doubled CO2 forcing, estimated by Gregory regression method, is approximately 3.7 K in FGOALS-g2 and 4.5 K in FGOALS-s2. The larger sensitivity of FGOALS-s2 is mainly attributed to a weaker negative long wave clear-sky feedback and stronger positive shortwave clear-sky feedback at the fast-response stage, as evidenced by the more rapid response of water vapor increase and sea-ice decrease in FGOALS-s2 than that in FGOALS-g2. At the slow-response stage in FGOALSs2, larger responses of increasing total cloud fraction and condensed water path result in a stronger negative shortwave cloud feedback, which tends to reduce the sensitivity of the model. © Springer-Verlag Berlin Heidelberg 2014."
"36445544500;","Impact of aerosols on climate sensitivity of CO2 as implemented in climate models",2013,"10.1260/0958-305X.24.3-4.421","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880300695&doi=10.1260%2f0958-305X.24.3-4.421&partnerID=40&md5=9917a06f71fbf831c45319342f26847c","There are indications that the cooling effect of anthropogenic aerosols is overestimated. This has fundamental consequences for estimates of the climate sensitivity of CO2 and thus for temperature forecasts. Current climate models reflect this uncertainty by a wide range of "" projections"". Apart from cloud feedback, the largest uncertainty in these models is the effect of anthropogenic aerosols. The way current climate models implement the effect of different forcings is analyzed. This analysis is qualitative only, as there are major uncertainties in the quantity and effect of aerosol emissions and for confounding factors, such as ocean currents, which influence global heat distribution."
[No author id available],"Information from paleoclimate archives - Executive summary",2013,"10.5169/seals-391143","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027973380&doi=10.5169%2fseals-391143&partnerID=40&md5=f6b75ee732db85e90414a914725b223a","An Executive Summary extracted from Chapter 5: Information from Paleoclimate Archives - Final Draft Underlying Scientific-Technical Assessment. IPCC Fifth Assessment Report, Climate Change 2013: The Physical Science Basis, is discussed. With very high confidence, the current rates of CO2, CH4 and N2O rise in atmospheric concentrations and the associated radiative forcing are unprecedented with respect to the highest resolution ice core records of the last 22,000 years. New estimates of the equilibrium climate sensitivity based on reconstructions and simulations of the Last Glacial Maximum show that values below 1 °C as well as above 6 °C for a doubling of atmospheric CO2 concentration are very unlikely. There is high confidence that global mean sea level was above present during some warm intervals of the mid-Pliocene (3.3 to 3.0 million years ago), implying reduced volume of polar ice sheets. New temperature reconstructions and simulations of the warmest millennia of the last interglacial period (129,000 to 116,000 years ago) show with medium confidence that global mean annual surface temperatures were never more than 2 °C higher than pre-industrial. There is high confidence that minima in Northern Hemisphere extratropical glacier extent between 8,000 and 6,000 years ago were primarily due to high summer insolation."
"6701652286;","The role of low clouds in determining climate sensitivity in response to a doubling of CO2 as obtained from 16 mixed-layer models",2011,"10.1007/s10584-011-0047-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81555203531&doi=10.1007%2fs10584-011-0047-3&partnerID=40&md5=9005caf8e8e2228781c3e54879c9d8fb","The effects that low clouds in sub-tropical to tropical latitudes have in determining a given model's climate sensitivity is investigated by analyzing the cloud data produced by 16 ""slab"" or mixed-layer models submitted to the PCMDI and CFMIP archives and their respective response to a doubling of CO2. It is found that, within the context of the 16 models analyzed, changes of these low clouds appear to play a major role in determining model sensitivity but with changes of middle cloud also contributing especially from middle to higher latitudes. It is noted that the models with the smallest overall cloud change produce the smallest climate sensitivities and vice versa although the overall signs of the respective cloud feedbacks are positive. It is also found that the amounts of low cloud as simulated by the respective control runs have very little correlation with their respective climate sensitivities. In general, the overall latitude-height patterns of cloud change as derived from these more recent experiments agree quite well with those obtained from much earlier studies which include increases of the highest cloud, decreases of cloud lower down in the middle and lower tropospheric and small increases of low clouds. Finally, other mitigating factors are mentioned which could also affect the spread of the resulting climate sensitivities. © 2011 U.S. Government."
[No author id available],"Proceedings of the 5th WSEAS International Conference on Remote Sensing, REMOTE '09",2009,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-78149342497&partnerID=40&md5=c581f9cfda4e0a8b252c06eb422e94cd","The proceedings contain 11 papers. The topics discussed include: real time mobile object tracking based on chromatic information; global atmospheric heat distributions observed from space; air-borne photogrammetric systems used in topographic and cadastral works in Romania; GIS applications in the field of the Maramures subterranean mining exploitations; remote sensing imagery for soil characterization: a wavelet neural data fusion approach; exploration of Misrsat-1 data in different change detection applications; ocean, land and meteorology studies using space-based lidar measurements; forest biomass estimation using ALOS satellite images; use of CERES cloud and radiation data for model evaluation and cloud feedback studies; momentum fluxes estimation within the marine atmospheric boundary layer; and estimation of virtual dimensionality of hyperspectral data by principle component analysis and higher order statistical method."
"7403282069;8891521600;7801693068;","Use of CERES cloud and radiation data for model evaluation and cloud feedback studies",2009,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-78149342130&partnerID=40&md5=a16300f5a92e46dd2d82048261f7578a","The availability of enormous amounts of satellite remote sensing data provides a golden opportunity to improve the capability of climate models for projecting future climate change. In this study, we will present recent progress in using CERES (Clouds and the Earth's Radiant Energy System) satellite data to evaluate model performance with regards to the vertical structures of radiative fluxes and cloud radiative effects and to provide an unambiguous estimate of the magnitude of low cloud feedbacks."
"35509639400;57212781009;6603639908;7201443624;7004479957;7004714030;7403288995;23392612400;57205885015;7004169476;7202208382;7003543851;6603422104;7201485519;","How well do we understand climate change feedbacks?",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845363449&partnerID=40&md5=c6137fbebc2248665bd362e8cd2a457b","By reviewing recent observational, numerical, and theoretical studies, progress in understanding the physics of climate change feedbacks is achieved as well as some of the reasons for the intermodel differences. Intermodel differences in cloud feedbacks have been confirmed as the primary source of climate-sensitivity uncertainty, and recent studies suggest that these differences stem primarily from the response of low-level clouds. New methodologies of model-data comparison and of decomposition of the global cloud feedbacks into dynamical and thermodynamical components should help to determine which of the model cloud feedbacks seem more reliable."
"7402933297;","Water vapor and cloud feedback mechanisms: Inferences from satellite observations and numerical modeling",1997,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030720441&partnerID=40&md5=76a604ce8b7864f98f86765c287f8307","The sensitivity of water vapor and cloud forcings to ocean temperature changes and their relationship with large scale circulation regimes (LSCR) were studied using satellite outgoing longwave radiation, sea surface temperature (SST) and LSCR data. On interannual time scales, LSCR changes contribute substantially to anomalies in the water vapor and cloud forcing observed during major climate events such as the El Nino. Experiments show that over 75% of the observed apparent sensitivity are due to changes in the LSCR, with direct radiative feedback accounting for less that 20% of the observed changes. Possible pitfalls in data interpretation are indicated when adjustments are made for changes in the LSCR since runaway greenhouse warming does not exists."
[No author id available],"Proceedings of the 1997 IEEE International Geoscience and Remote Sensing Symposium, IGARSS'97. Part 3 (of 4)",1997,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030709513&partnerID=40&md5=8b1ec4a3f1e50a3fdfba1cbd46a5812e","The proceedings contains 218 papers from the 1997 IEEE International Geoscience and Remote Sensing Symposium. Topics discussed include: global ocean-atmosphere exchanges; water vapor and cloud feedback mechanisms; satellite-based coastal monitoring; cloud macrostructure and radiation; global atmospheric aerosol and cloud monitoring and retrieval; light precipitation Doppler spectrum; rain patterns evolution tracking; NASA DC-8 airborne cloud radar; microwave imaging radar systems; buried object detection; area-based stereo matching algorithm; satellite derived time-series datasets visualization; weather satellite imagery; land surface parameterization; radar ocean remote sensing; tropical forest monitoring; and interferometric synthetic aperture radar."
"6701324864;","Mesoscale processes of cloud formation, cloud radiation interaction, and their modelling with explicit cloud microphysics",1994,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041146056&partnerID=40&md5=7a3e1227a860863f39f9d869c6dde9e5","An analysis is made of a global distribution of clouds and the main processes of cloud formation. Mesostructure and microstructure of different types of clouds are described. Methods for the calculation of the optical and radiative properties of clouds are discussed with emphasis on the cloud microstructure and the phase state. Effects of longwave and solar radiation on the evolution of different cloud types are reviewed on the basis of mesoscale modelling and some observational data. A scheme of cloud feedback processes in the climatic system and recommendations for the construction of a global semi-empirical cloud-radiation model are presented. -Author"
"6508302632;","Potential role of oceanic mixed layer dynamics on the model climate sensitivity",1991,"10.1016/0924-7963(91)90030-X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026006761&doi=10.1016%2f0924-7963%2891%2990030-X&partnerID=40&md5=20044d805ca82a2731eba59264dd0897","A seasonal resolution, multi-box energy balance model has been developed to simulate the climate changes arising as a result of natural or anthropogenous influences. The model divides the global climatic system into 12 interactive domains according to the real geographical structure. The domains are separated by a surface (ocean-, land- or cryosphere-type) and an atmospheric block. The ocean-type surface block is based on a one dimensional Hoffert-type ocean submodel, but the depth of the oceanic mixed layer can vary in connection with the surface processes. The climatic variables of the domains are the surfaces and air temperatures and-in the case of the oceanic type surfaces-the mixed layer depth. The calculations show that the dynamics of the mixed layer can be attributed to the essential deviation, with respect to the constant mixed layer depth in the basic climate experiments. The equilibrium climate sensitivity has been analyzed in two cases. The modelled warming for a doubling in CO2 is 2.2° C for a constant mixed layer depth and 1.3° C for a variable mixed layer thickness. The global temperature response to a 1% change in the solar constant is a change in temperature of 1.5° C for a ""frozen"" mixed layer depth and 0.9° C for a dynamically mixed layer. These experiments reveal that the mixed layer dynamics can play an enhanced role in the behaviour of the modelled climate system. © 1991."
"7403029589;7007140056;","Parameterizations of cloud feedback in a radiative-convective model",1985,"10.1007/BF00877457","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022170382&doi=10.1007%2fBF00877457&partnerID=40&md5=975e6dd6ff73d08a029bf7c1cef9c2a3","The effect of cloud feedback on the response of a radiative-convective model to a change in cloud model parameters, atmospheric CO2 concentration, and solar constant has been studied using two different parameterization schemes. The method for simulating the vertical distribution of both cloud cover and cloud optical thickness, which depends on the relative humidity and on the saturation mixing ratio of water vapor, respectively, is the same in both approaches, but the schemes differ with respect to modeling the water vapor profile. In scheme I atmospheric water vapor is coupled to surface parameters, while in scheme II an explicit balance equation for water vapor in the individual atmospheric layers is used. For both models the combined effect of feedbacks due to variations in lapse rate, cloud cover, and cloud optical thickness results in different relationships between changes in surface temperature, planetary temperature, and cloud cover. Specifically, for a CO2 doubling and a 2% increase in solar constant, in both models the surface warming is reduced by cloud feedback, in contrast to no feedback, with the greater reduction in scheme I as compared to that of scheme II. © 1985 Birkhäuser Verlag."
"8707123200;","Earth radiation budget observations, old and new.",1984,"10.1007/978-94-009-6421-1_12","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021568958&doi=10.1007%2f978-94-009-6421-1_12&partnerID=40&md5=434269b6851394d551e0dd248effea4c","A brief review of the climatology of radiation budget observations from satellites is presented, emphasizing the possibility of making estimates of energy transport. Then as an example of new data, calculations of the cloud feedback estimated from the new Nimbus-7 ERB observations are discussed. -Author"