Chick,
look at the instrumental record!  there are huge differences between
different regions - Alaska has warmed substantially while eastern North
America cooled after the 1950s.  locking onto local records, no matter how
beautiful, can lead to serious errors.  If the ice cores are so infallible
why do they give substantially different stories for grip and gisp2 over
the last 1500 years?
the bottom line is that one cannot make a robust case that decadally
hemispheric temperatures over the last 1500 years were  even as warm as the
late 20th century, much less warmer.
Tom
>
>Well said indeed!  This helps me to slowly understand what's being
>done and why.
>
>My nagging problem remains however, and that's that there seem to be
>too many paleo records published that show much larger amplitude
>variations.  Now many can be explained, but some look more robust.
>For example I think most people are wondering about the total
>disagreement between isotope temperatures from GISP II and borehole
>temperatures from GRIP and Dye 3.  Here the usual land use caution
>doesn't apply since I don't think the ice above the boreholes has
>changed much?
>
>And if I understand Tom Crowley's note to me, his reconstruction
>averaged normalized records, thus missing large amplitude variations
>such as the Keigwin Sargasso one, which he used, but which shows a
>large amplitude signal tantalizingly similar to the GRIP/Dye 3
>records. (Tom used GISP II which essentially has no low frequency
>amplitude)
>
>So I read all the papers, and am impressed by the painstakingly
>careful work, but still wonder about a world in which the
>hemispherical low frequency temperature amplitude could be (see Jones
>et al Science this week) only about 0.4°C between 1000 and about
>1950, while parts of the world could have seen amplitudes of up to
>2°C in the same period.  I suppose you could say that, given natural
>forcing only, there can be much larger variance from the mean
>(spatially and temporally) than in the past hundred and fifty years
>when GHG forcing is forcing more uniformity, but does this make sense?
>
>This is why I keep asking questions about the ability of various
>proxies to return low frequency information.
>
>Anything you could say about this would be greatly appreciated.
>
>Finally consider this.  I read recently (don't know the pedigree of
>this number but it WAS published!!) that Milankovitch cooling at this
>point in the Holocene should be about 0.4°C/millenium (other plots
>I've seen would suggest about 2.3 to 1/2 of that).  If that's true,
>then all the cooling since the year 1000 is Milankovitch and there's
>no room for variations in solar activity and multiple volcanic
>eruptions.  Now I'm not saying this is the best way to think about
>such things, but it does remind us that much of the cooling seems to
>have been due to Milankovitch, and, given the small amplitude of the
>proxy records, that is a bit worrisome.  What do people think about
>this?
>
>Regards,
>
>
>Well said Malcolm...
>
>mike
>
>p.s. Chick: You might want to check out the review article by Jones
>et al in the latest Science...
>
>At 01:16 PM 4/26/01 -0700, Malcolm K. Hughes wrote:
>>Dear Chick - some thoughts on a couple of the points you raised,
>>Cheers, Malcolm
>>1.      There is no reference to the ABD in MBH 98 and 99 because
>>the technique
>>was not available at that time - see the dates on Keith's publications that
>>describe it.
>>2.      There are significant regions where the ABD method is not needed,
>>because the trees live much longer than those in the Schweingruber
>>network that
>>Keith has been using, and grow under conditions that make only very
>>conservative
>>standardization necessary. There is a growing body of evidence that these
>>tree-ring records can capture century-to-millennial change accurately (Hughes
>>and Graumlich, 1996 and Hughes and Funkhouser 1998, for example). In
>>fact, the
>>MBH reconstruction before AD 1400 was largely based on these.
>>3.      Keith has pooled information from extremely large regions
>>(presumably to
>>get large enough samples), whereas we (MBH) have been particularly
>>interested in
>>spatial variability, ruling out the use of ABD.
>>4.      The ABD method is new, needs testing, and, I predict, will be
>>modified
>>as it is tested.
>>5.      The benefit of annual resolution is that direct calibration and
>>cross-validation against instrumental records is possible with a
>>high degree of
>>rigor. We are relaxing this condition somewhat in our ongoing analyses,
>>and it
>>will be interesting to see how the uncertainties increase as one includes
>>records with poorer temporal resolution. This is an issue that the
>>advocates of
>>such records do not address, so far as I can see.
>>
>>
>>
>>Professor Malcolm K. Hughes
>>Laboratory of Tree-Ring Research
>>W.Stadium 105
>>University of Arizona
>>Tucson, AZ 85721
>>phone 520-621-6470
>>fax 520-621-8229
>
>_______________________________________________________________________
>                      Professor Michael E. Mann
>           Department of Environmental Sciences, Clark Hall
>                       University of Virginia
>                      Charlottesville, VA 22903
>_______________________________________________________________________
>e-mail: mann@virginia.edu   Phone: (804) 924-7770   FAX: (804) 982-2137
>
>
>Charles. "Chick" F. Keller,
>IGPP.SIO.UCSD - Attn: Chick Keller
>9500 Gilman Drive
>La Jolla, CA 92093-0225
>(858) 822-1510  office
>(858) 534-2902  FAX
>(858) 456-9002  home
>Is the noticeable increase in surfers off Scripps Beach a possible
>indication of global warming?
Thomas J.  Crowley
Dept. of Oceanography
Texas A&M University
College Station, TX  77843-3146
979-845-0795
979-847-8879 (fax)
979-845-6331 (alternate fax)


Hi Mike,
No problem. I am quite happy to work this stuff through in a careful way
and am happy to discuss it all with you. I certainly don't want the work to
be viewed as an attack on previous work such as yours. Unfortunately, this
global change stuff is so politicized by both sides of the issue that it is
difficult to do the science in a dispassionate environment. I ran into the
same problem in the acid rain/forest decline debate that raged in the
1980s. At one point, I was simultaneous accused of being a raving tree
hugger and in the pocket of the coal industry. I have always said that I
don't care what answer is found as long as it is the truth or at least
bloody close to it.
Cheers,
Ed
>Hi Ed,
>
>This is fair enough, and I'm sorry if my spelling out my concerns
>sounded defensive to you. It wasn't meant to be that way.
>
>Lets figure this
>all out based on good, careful
>work and see what the data has to say in the end. We're working towards
>this ourselves, using revised methods and including borehole data, etc.
>and will keep everyone posted on this.
>
>I don't in any way doubt yours and Jan's integrity here.
>
>I'm just a bit concerned that the result is getting used publically, by
>some, before it has gone through the gauntlet of peer review.
>Especially because it is, whether you condone it or not, being used as
>we speak to discredit the work of us, and Phil et al, this is dangerous.
>I think there are some legitimate issues that need to be sorted out
>with regard to the standardization method, and would like to see
>this play out before we jump to conclusions regarding revised estimates
>of the northern hemisphere mean temperature record and the nature of
>the "MWP".
>
>I'd
>be interested to be kept posted on what the status of the manuscript is.
>
>Thanks,
>
>mike
>
>On Wed, 2 May 2001, Edward Cook wrote:
>
>> Hi Mike,
>>
>> >A few quick points Ed,
>> >
>> >These "Wally seminars" are  self-promoting acts on Broecker's part, and I
>> >think the community has to reject them as having any broader significance.
>> >If Broecker had pulled this w/ Ray, Malcolm, Keith, Phil, and Tom around,
>> >he wouldn't get away w/ such a one-sided treatment of the issue. I've been
>> >extremely troubled by what I have heard here.
>>
>> It appears that you are responding in a way that is a bit overly defensive,
>> which I regret. I am not supporting Broecker per se and only explained in a
>> very detailed fashion the origin of the work by Esper and me and how it was
>> presented to refute a very unfair characterization of tree-ring data in
>> Wally's perspective piece. The fact that Esper compared his series with
>> Jones, Briffa, and Mann et al. should not be viewed as an attack on your
>> work. It was never intended to be so, but it is was a clearly legitimate
>> thing to do. As I said, I have no control over Broecker. But it is unfair
>> and indeed incorrect to start out by dismissing the "Special Wally
>> Seminars" as self-promoting acts. To say that is simply wrong. He doesn't
>> bring people in to only express support for his point of view or pet
>> theory, as you are implying. So, I suggest that you cool down a bit on this
>> matter. It detracts from the scientific issues that should properly be
>> debated here. This is the only point on which I will defend Broecker.
>>
>> >I'm also a bit troubled by your comparisons w/ glacial advances, etc. and
>> >how these correlate w/ your reconstruction. Malcolm, Ray, Phil, and others
>> >have been over this stuff time and again, and have pointed out that these
>> >data themselves don't support the notion of globally-synchronoous changes.
>> >You seem to be arguing otherwise? And with regard to association w/
>> >volcanic forcing, Tom has already shown that the major volcanic events are
>> >captured correctly in the existing reconstructions, whether or not the
>> >longer-term trends are correct or not...
>>
>> I am not arguing for "globally-synchronous changes" and never have. To
>> quote what I said about neo-glacial advances, some of the fluctuations in
>> Esper's series "correspond well with known histories of neo-glacial advance
>> in some parts of the NH". Note the use of the word "some" in that quote.
>> That is a fair statement and why shouldn't I say it if it is true,
>> coincidently or not. Whether or not it argues for "globally-synchronous
>> changes" is up to you. I would never argue that everything happening on
>> multi-decadal time scales is phase-locked across the NH. That would be a
>> silly thing to say. But it is perfectly valid to point out the degree to
>> which independent evidence for cold periods based on glacier advances
>> appears to agree with a larger-scale indicator of temperature variablity. I
>> thought this is how science to supposed to proceed. I also don't see your
>> point about volcanic forcing. I mentioned this purely in the spirit of the
>> work of Crowley and others to suggest that the Esper series is probably
>> capturing this kind of signal as well. It has nothing to do with the issue
>> of centennial trends in temperature. You are reading far more into what I
>> wrote than I ever intended or meant.
>>
>> >Re the boreholes. Actually, if  Tom's estimates are correct, and it is also
>> >correct that the boreholes have the low-frequency signal correct over the
>> >past few centuries, we are forced to also accept Tom's result that the
>> >so-called "MWP", at the hemispheric scale, is actually even COOLER relative
>> >to present than our result shows! That was clear in Tom's presentation at
>> >the workshop. So lets be clear about that--Tom's work and the boreholes in
>> >no way support Broecker's conclusion that the MWP was warmer than we have
>> >it--it actually implies the MWP is colder than we have it!
>> >Tom, please speak up if I'm not correct in this regard!
>>
>> I am not saying that Tom's results are wrong. And, I am certainly not
>> saying that Broecker is right. I merely described the results of a new
>> analysis of a somewhat new set of long tree-ring records from the
>> extra-tropics. My statement that the MWP appeared to be comparable to the
>> 20th century does not imply, nor was it meant to imply, that somehow the
>> 20th century temperature is not truly anomalous and being driven by
>> greenhouse gases. To quote from my email, "I would not claim (and nor would
>> Jan) that it exceeded the warmth of the late 20th century. We simply do not
>> have the precision or the proxy replication to say that yet." Note the use
>> of the word "precision". This clearly relates to the issue of error
>> variance and confidence intervals, a point that you clearly emphasize in
>> describing your series. Also note the emphasis on "late 20th century". I
>> think that most researchers in global change research would agree that the
>> emergence of a clear greenhouse forcing signal has really only occurred
>> since after 1970. I am not debating this point, although I do think that
>> there still exists a signficant uncertainty as to the relative
>> contributions of natural and greenhouse forcing to warming during the past
>> 20-30 years at least. Note that I also tried to emphasize the
>> extra-tropical nature of this series, and it may be that the tropics do not
>> show the same strength of warming. But I do argue strongly that we do not
>> have the high-resolution proxy data needed to test for a MWP in the
>> tropics. Please correct me if I am wrong here.
>>
>> >We are in the process of incorporating the borehole data into the
>> >low-frequency component of the reconstruction. The key difference will be
>> >that they are going to be calibrated against the instrumental record and
>> >weighted by the spatial coherence within the borehole data rather than what
>> >Pollack has done. I expect the results will be different, but in any case
>> >quite telling...
>>
>> Fine.
>>
>> >I'll let Malcolm and Keith respond to the issues related to the
>> >standardization of the Esper chronologies, though it immediately sounds to
>> >me quite clear that there is the likelihood of of having contaminated the
>> >century-scales w/ non-climatic info. Having now done some work w/
>> >chronologies in disturbed forests myself now (in collaboration w/ Dave
>> >Stahle), I know how easy it is to get lots of century-scale variability
>> >that has nothing to do w/ climate. I imagine the reviewers of the
>> >manuscript will have to be convinced that this is the case w/ what Esper
>> >has done. I'm very skeptical. I'm also bothered that Broecker has promoted
>> >this work prior to any formal peer review. There are some real issues w/
>> >the standardization approach and there is a real stretch in promoting this
>> >as a hemispheric temperature reconstruction.
>>
>> I appreciate your skepticism and I hope that Jan and I can convince you
>> otherwise. I also encourage you to continue getting your shoulders sore and
>> hands dirty on tree-ring sampling and analysis. Esper's analysis is not
>> perfect. Nor is anyone elses who works in this game. But if Esper's series
>> is wrong on century time scales, then Jones and Briffa are wrong too. If
>> Esper's series is also wrong on inter-decadal time scales, then your series
>> is wrong as well because on that time scale of variablity, his series
>> agrees very well with yours. So, I would be very cautious about declaring
>> that Esper's series is in some sense invalid. Finally, as I have said ad
>> nausem, I have no control over what Broecker thinks or does beyond
>> presenting to him a convincing case for the ability of certain tree-ring
>> series to preserve long-term temperature variability. And again, "I also
>> tried to emphasize the extra-tropical nature of this series." Please give
>> me a break here.
>>
>> >Finally, what is the exact spatial distribution of the sparse data he used.
>> >Scott R. drove home the point regarding the importance of taking into
>> >account spatial sampling in his talk at the workshop. A sparse
>> >extratratropical set of indicators, no matter how
>> >locally-temperature-sensitive they are,  will not, unless you're *very*
>> >lucky w/ the locations, be an accurate indicator of true N. Hem temp. In
>> >general it will overestimate the variance at all timescales. The true N.Hem
>> >temperature (ie, weighted largely by tropical ocean SST) has much less
>> >variance than extratrpoical continents. There may be a large apples and
>> >oranges component to the comparisons you describe.
>>
>> I know your argument and I am sensitive to it, hence my emphasis on
>> "extra-tropical". So, don't look for disagreement on the importance of the
>> tropical SSTs to any estimate of NH temperatures. But let's be honest here.
>> Your reconstruction prior to roughly AD 1600 is dominated by extra-tropical
>> proxies. So, in a way, you are caught in the same dilemma as all other
>> people who have tried to do this.
>>
>> >We've shown that are reconstructions in continental extratropical regions
>> >have lots more variance and variability. It is, as we have all shown, the
>> >averaging over many regions that reduces the amplitude of variability. Our
>> >regional reconstructions show far more significant warm and cold periods.
>> >But they cancel out spatially!
>>
>> Understood, but it is still unclear how this all happens as your
>> reconstruction proceeds back in time with an increasingly limited and
>> spatially-restricted set of proxies. Confidence limits that you place on
>> your series is laudable and I agree, to first order, that the MWP in your
>> series could easily have been cooler than what you show. But it implicitly
>> assumes that the estimates are equally unbiased (or equally biased for that
>> matter) back in time. I don't know if that is an issue here, but I believe
>> that the issue of bias using an increasingly sparse number of predictors
>> scattered irregularly over space has not be investigated. Please correct me
>> if I am wrong here.
>>
>> >If a legitimate argument were to be made that we have significnatly
>> >understiamted, within the context of our uncertainty estimates, the
>> >amplitude of the MWP at the hemispheric scale, I'd be the first to accept
>> >it (note that, as Phil et al pointed out in their recent review article in
>> >Science, we do not dispute that temperatures eearly in the millennium,
>> >within the uncertainty estimates, may have been comparable to early/mid
>> >20th centurys--just not late 20th century temperatures).
>>
>> We are in agreement here. See my earlier comments.
>>
>> >Frankly though Ed, I really don't see it here. We may have to let the
>> >peer-review process decid this, but I think you might benefit from knowing
>> >the  consensus  of the very able group we have assembled in this email
>> >list,  on what Esper/you have done?
>>
>> Of course, I know everyone in this "very able group" and respect their
>> opinions and scientific credentials. The same obviously goes for you. That
>> is not to say that we can't disagree. Afterall, consensus science can
>> impede progress as much as promote understanding.
>>
>> Cheers,
>>
>> Ed
>>
>> >Comments or thoughts?
>> >
>> >cheers,
>> >
>> >mike
>> >
>> >At 10:59 AM 5/2/01 -0400, Edward Cook wrote:
>> >> >Ed,
>> >> >
>> >> >heard some rumor that you are involved in a non-hockey stick
>>reconstruction
>> >> >of northern hemisphere temperatures.  I am very intrigued to learn about
>> >> >this - are these results suggesting the so called Medieval Warm
>>Period may
>> >> >be warmer than the early/mid 20th century?
>> >> >
>> >> >any enlightenment on this would be most appreciated, Tom
>> >> >
>> >> >
>> >> >
>> >> >Thomas J.  Crowley
>> >> >Dept. of Oceanography
>> >> >Texas A&M University
>> >> >College Station, TX  77843-3146
>> >> >979-845-0795
>> >> >979-847-8879 (fax)
>> >> >979-845-6331 (alternate fax)
>> >>
>> >>Hi Tom,
>> >>
>> >>As rumors often are, the one you heard is not entirely accurate. So, I
>>will
>> >>take some time here to explain for you, Mike, and others exactly what was
>> >>done and what the motivation was, in an effort to hopefully avoid any
>> >>misunderstanding. I especially want to avoid any suggestion that this work
>> >>was being done to specifically counter or refute the "hockey stick".
>> >>However, it does suggest (as do other results from your EBM, Peck's work,
>> >>the borehole data, and Briffa and Jones large-scale proxy estimates) that
>> >>there are unresolved (I think) inconsistencies in the low-frequency
>>aspects
>> >>of the hockey stick series compared to other results. So, any comparisons
>> >>with the hockey stick were made with that spirit in mind.
>> >>
>> >>What Jan Esper and I are working on (mostly Jan with me as second author)
>> >>is a paper that was in response to Broecker's Science Perspectives
>>piece on
>> >>the Medieval Warm Period. Specifically, we took strong exception to his
>> >>claim that tree rings are incapable of preserving century time scale
>> >>temperature variability. Of course, if Broecker had read the
>>literature, he
>> >>would have known that what he claimed was inaccurate. Be that as it may,
>> >>Jan had been working on a project, as part of his post-doc here, to
>>look at
>> >>large-scale, low-frequency patterns of tree growth and climate in long
>> >>tree-ring records provided to him by Fritz Schweingruber. With the
>>addition
>> >>of a couple of sites from foxtail pine in California, Jan amassed a
>> >>collection of 14 tree-ring sites scattered somewhat uniformly over the
>> >>30-70 degree NH latitude band, with most extending back 1000-1200 years.
>> >>All of the sites are from temperature-sensitive locations (i.e. high
>> >>elevation or high northern latitude. It is, as far as I know, the largest,
>> >>longest, and most spatially representative set of such
>> >>temperature-sensitive tree-ring data yet put together for the NH
>> >>extra-tropics.
>> >>
>> >>In order to preserve maximum low-frequency variance, Jan used the Regional
>> >>Curve Standardization (RCS) method, used previously by Briffa and myself
>> >>with great success. Only here, Jan chose to do things in a somewhat
>>radical
>> >>fashion. Since the replication at each site was generally insufficient to
>> >>produce a robust RCS chronology back to, say, AD 1000, Jan pooled all of
>> >>the original measurement series into 2 classes of growth trends:
>>non-linear
>> >>(~700 ring-width series) and linear (~500 ring-width series). He than
>> >>performed independent RCS on the each of the pooled sets and produced
>>2 RCS
>> >>chronologies with remarkably similar multi-decadal and centennial
>> >>low-frequency characteristics. These chronologies are not good at
>> >>preserving high-frquency climate information because of the scattering of
>> >>sites and the mix of different species, but the low-frequency patterns are
>> >>probably reflecting the same long-term changes in temperature. Jan than
>> >>averaged the 2 RCS chronologies together to produce a single chronology
>> >>extending back to AD 800. It has a very well defined Medieval Warm
>>Period -
>> >>Little Ice Age - 20th Century Warming pattern, punctuated by strong
>>decadal
>> >>fluctuations of inferred cold that correspond well with known histories of
>> >>neo-glacial advance in some parts of the NH. The punctuations also appear,
>> >>in some cases, to be related to known major volcanic eruptions.
>> >>
>> >>Jan originally only wanted to show this NH extra-tropical RCS
>>chronology in
>> >>a form scaled to millimeters of growth to show how forest productivity and
>> >>carbon sequestration may be modified by climate variability and change
>>over
>> >>relatively long time scales. However, I encouraged him to compare his
>> >>series with NH instrumental temperature data and the proxy estimates
>> >>produced by Jones, Briffa, and Mann in order bolster the claim that his
>> >>unorthodox method of pooling the tree-ring data was producing a record
>>that
>> >>was indeed related to temperatures in some sense. This he did by linearly
>> >>rescaling his RCS chronology from mm of growth to temperature
>>anomalies. In
>> >>so doing, Jan demonstrated that his series, on inter-decadal time scales
>> >>only, was well correlated to the annual NH instrumental record. This
>>result
>> >>agreed extremely well with those of Jones and Briffa. Of course, some of
>> >>the same data were used by them, but probably not more than 40 percent
>> >>(Briffa in particular), so the comparison is based on mostly, but not
>> >>fully, independent data. The similarity indicated that Jan's approach was
>> >>valid for producing a useful reconstruction of multi-decadal temperature
>> >>variability (probably weighted towards the warm-season months, but it is
>> >>impossible to know by how much) over a larger region of the NH
>> >>extra-tropics than that produced before by Jones and Briffa. It also
>> >>revealed somewhat more intense cooling in the Little Ice Age that is more
>> >>consistent with what the borehole temperatures indicate back to AD 1600.
>> >>This result also bolsters the argument for a reasonably large-scale
>> >>Medieval Warm Period that may not be as warm as the late 20th century, but
>> >>is of much(?) greater significance than that produced previously.
>> >>
>> >>Of course, Jan also had to compare his record with the hockey stick since
>> >>that is the most prominent and oft-cited record of NH temperatures
>>covering
>> >>the past 1000 years. The results were consistent with the differences
>>shown
>> >>by others, mainly in the century-scale of variability. Again, the Esper
>> >>series shows a very strong, even canonical, Medieval Warm Period - Little
>> >>Ice Age - 20th Century Warming pattern, which is largely missing from the
>> >>hockey stick. Yet the two series agree reasonably well on inter-decadal
>> >>timescales, even though they may not be 1:1 expressions of the same
>> >>temperature window (i.e. annual vs. warm-season weighted). However, the
>> >>tree-ring series used in the hockey stick are warm-season weighted as
>>well,
>> >>so the difference between "annual" and "warm-season weighted" is probably
>> >>not as large as it might seem, especially before the period of
>>instrumental
>> >>data (e.g. pre-1700) in the hockey stick. So, they both share a
>>significant
>> >>degree of common interdecal temperature information (and some, but not
>> >>much, data), but do not co-vary well on century timescales. Again,
>>this has
>> >>all been shown before by others using different temperature
>> >>reconstructions, but Jan's result is probably the most comprehensive
>> >>expression (I believe) of extra-tropical NH temperatures back to AD 800 on
>> >>multi-decadal and century time scales.
>> >>
>> >>Now back to the Broecker perspectives piece. I felt compelled to refute
>> >>Broecker's erroneous claim that tree rings could not preserve long-term
>> >>temperature information. So, I organized a "Special Wally Seminar" in
>>which
>> >>I introduced the topic to him and the packed audience using Samuel
>> >>Johnson's famous "I refute it thus" statement in the form of "Jan
>>Esper and
>> >>I refute Broecker thus". Jan than presented, in a very detailed and well
>> >>espressed fashion, his story and Broecker became an instant convert. In
>> >>other words, Wally now believes that long tree-ring records, when properly
>> >>selected and processed, can preserve low-frequency temperature variability
>> >>on centennial time scales. Others in the audience came away with the same
>> >>understanding, one that we dendrochronologists always knew to be the case.
>> >>This was the entire purpose of Jan's work and the presentation of it to
>> >>Wally and others. Wally had expressed some doubts about the hockey stick
>> >>previously to me and did so again in his perspectives article. So, Jan's
>> >>presentation strongly re-enforced Wally's opinion about the hockey stick,
>> >>which he has expressed to others including several who attended a
>> >>subsequent NOAA meeting at Lamont. I have no control over what Wally says
>> >>and only hope that we can work together to reconcile, in a professional,
>> >>friendly manner, the differences between the hockey stick and other proxy
>> >>temperature records covering the past 1000 years. This I would like to do.
>> >>
>> >>I do think that the Medieval Warm Period was a far more significant event
>> >>than has been recognized previously, as much because the high-resolution
>> >>data to evaluate it had not been available before. That is much less
>>so the
>> >>case now. It is even showing up strongly now in long SH tree-ring series.
>> >>However, there is still the question of how strong this event was in the
>> >>tropics. I maintain that we do not have the proxies to tell us that now.
>> >>The tropical ice core data are very difficult to interpret as temperature
>> >>proxies (far worse than tree rings for sure and maybe even unrelated to
>> >>temperatures in any simple linear sense as is often assumed), so I do not
>> >>believe that they can be used alone as records to test for the
>>existence of
>> >>a Medieval Warm Period in the tropics. That being the case, there are
>> >>really no other high-resolution records from the tropics to use, and the
>> >>teleconnections between long extra-tropical proxies and the tropics are, I
>> >>believe, far too tenuous and probably unstable to use to sort out this
>> >>issue.
>> >>
>> >>So, at this stage I would argue that the Medieval Warm Period was probably
>> >>a global extra-tropical event, at the very least, with warmth that was
>> >>persistent and probably comparable to much of what we have experienced in
>> >>the 20th century. However, I would not claim (and nor would Jan) that it
>> >>exceeded the warmth of the late 20th century. We simply do not have the
>> >>precision or the proxy replication to say that yet. This being said, I do
>> >>find the dismissal of the Medieval Warm Period as a meaningful global
>>event
>> >>to be grossly premature and probably wrong. Kind of like Mark Twain's
>> >>commment that accounts of his death were greatly exaggerated. If, as some
>> >>people believe, a degree of symmetry in climate exists between the
>> >>hemispheres, which would appear to arise from the tropics, then the
>> >>existence of a Medieval Warm Period in the extra-tropics of the NH and SH
>> >>argues for its existence in the tropics as well. Only time and an enlarged
>> >>suite of proxies that extend into the tropics will tell if this is true.
>> >>
>> >>I hope that what I have written clarifies the rumor and expresses my views
>> >>more completely and accurately.
>> >>
>> >>Cheers,
>> >>
>> >>Ed
>> >>
>> >>==================================
>> >>Dr. Edward R. Cook
>> >>Doherty Senior Scholar
>> >>Tree-Ring Laboratory
>> >>Lamont-Doherty Earth Observatory
>> >>Palisades, New York  10964  USA
>> >>Phone:  1-845-365-8618
>> >>Fax:    1-845-365-8152
>> >>Email:  drdendro@ldeo.columbia.edu
>> >>==================================
>> >
>> >_______________________________________________________________________
>> >                     Professor Michael E. Mann
>> >            Department of Environmental Sciences, Clark Hall
>> >                       University of Virginia
>> >                      Charlottesville, VA 22903
>> >_______________________________________________________________________
>> >e-mail: mann@virginia.edu   Phone: (804) 924-7770   FAX: (804) 982-2137
>> >
>>
>>
>> ==================================
>> Dr. Edward R. Cook
>> Doherty Senior Scholar
>> Tree-Ring Laboratory
>> Lamont-Doherty Earth Observatory
>> Palisades, New York  10964  USA
>> Phone:  1-845-365-8618
>> Fax:    1-845-365-8152
>> Email:  drdendro@ldeo.columbia.edu
>> ==================================
>>
>>
>>
>
>_______________________________________________________________________
>                     Professor Michael E. Mann
>          Department of Environmental Sciences, Clark Hall
>                      University of Virginia
>                     Charlottesville, VA 22903
>_______________________________________________________________________
>e-mail: mann@virginia.edu   Phone: (804) 924-7770   FAX: (804) 982-2137
>
==================================
Dr. Edward R. Cook
Doherty Senior Scholar
Tree-Ring Laboratory
Lamont-Doherty Earth Observatory
Palisades, New York  10964  USA
Phone:  1-845-365-8618
Fax:    1-845-365-8152
Email:  drdendro@ldeo.columbia.edu
==================================


Hi Ed,
On the road, but just had to chime into this debate briefly.
What you say is of course true, but we have to start somewhere. Step #1 is
producing a reconstruction. Without some reasonable estimate of
uncertainty, a reconstruction isn't
very useful in my opinion. Step #2 is producing some reasonable estimate of
uncertainty. In my mind, this is based on looking at the calibration
residuals, seeing if they pass some basic tests for whiteness, normality,
etc., looking at the verification statistics, and seeing if this continues
to hold up in an independent sample. It is important to use the longest
instrumental records we have for independent verification where possible.
Of course, there may be additional biases in the predictors that are
difficult to identify even in a relatively long verification interval
(e.g., ultra low-frequency problems w/ fidelity). Step #3 is trying to
evaluate this as best we can (looking at the frequency domain structure of
the predictors themselves, seeing if there is loss of variance at very long
timescales, looking at the robustness of long-term trends to
standardization issues, etc.), etc...I see this as a successive series of
diagnostics and self-consistency checks that iterate towards getting a
reasonable handle on the uncertainties. This is the approach
that we have taken, and I think it is the most appropriate...
I firmly believe that a reconstruction w/ out some reasonable estimate of
uncertainty is almost useless! If the community wants to use paleodata for
signal detection, model validation, etc. I believe that this is absolutely
essential to do, whether or not we can do a perfect job.
I would be very surprised if Hans would disagree w/ my statement above!
anyways, my two cents on the matter...
mike
At 09:50 AM 5/17/01 -0400, Ed Cook wrote:
>Hi Juerg,
>
>I've done an admittedly quick read of your paper "Extending NAO
>Reconstructions Back to AD 1500" and find it to be fine overall. One slight
>correction on pg. 3 concerning the Cook et al. (1998) recon. The tree-ring
>records used also included some from England, as well as the eastern US and
>northern Fennoscandia. On pg. 10, sentence 8-9 in Conclusions, the wording
>is a little confusing. You say "Including station pressure of Gibraltar and
>Reykjavik as predictors in 1821 lead to a decrease of the confidence
>estimates". This almost sounds like you are doing worse when adding in
>Gibraltar and Reykjavik, when I know you mean the opposite. So, a change in
>wording to something like "... lead to increased confidence in the
>estimates of monthly NAO". Also in Table 1, is the Cullen R4 NAO
>reconstruction the one with instrumental data in it? If so, it has used
>some of the same data as yours. I don't recall if R4 is the one with
>instrumental data. But if it is, you ought to mention that.
>
>
>On a thematic note that doesn't have much direct bearing on the paper as it
>stands now (but which may be of interest to Keith, Phil, and Mike as well),
>I have growing doubts about the validity and use of error estimates that
>are being applied to reconstructions, such as those you have applied in
>Fig. 3. First, as you say at the end of the paper, there is a clear
>frequency dependence in the strength of relationship between the actual and
>proxy-estimated data that is not being considered, i.e. "the SE ... become
>smaller when considering low-pass filtered time series" (pg. 10). The
>assumption of the error estimates as now estimated and applied is that the
>error variance is truly white noise, i.e. equally distributed across all
>frequencies. That is surely not the case. This is different from questions
>about autocorrelated residuals, which tell you nothing about the frequency
>dependence of the quality of the estimates. This is where classic
>regression theory falls down. It is based on the notion that each
>observation is a random sample with no time history or frequency domain
>structure. When we use long time series of observations (climate or proxy)
>to reconstruct some climate variable, we are also using predictors that
>have time series structure and history that cannot vary in a completely
>random fashion even if the data could be completely resampled. This is
>because they represent a series of prior "observations" of
>climatic/environmental conditions. This lack of randomness of the
>observations used for reconstructing past climate again causes me to doubt
>the validity of the error estimates being applied. The degree to which the
>reconstruction can actually vary from year to year within the prescribed
>error limits is itself constrained by the time history of the observations
>themselves used for reconstruction. In contrast, the 2SE limits in your
>Fig. 3 prior to 1821 contain almost all of the estimates. This result could
>be used to claim that there is effectively no useful time history of
>variation in the NAO reconstruction prior to 1821 because each estimate may
>fall with equal probability anywhere in the error envelop. I would regard
>this interpretation as completely wrong. Thus, I would say that the decadal
>period of above-average winter NAO in your reconstruction around AD 1700 is
>real, assuming that the predictors used are providing unbiased estimates,
>even though it is fully enclosed by the 2SE limits that intersect zero.
>This is getting towards the debate with Von Storch over "most probable"
>estimates. I am probably not explaining myself well here and undoubtedly
>need to think more about it. But I really think that error bars, as often
>presented, may potentially distort and unfairly degrade the interpreted
>quality of reconstructions. So, are the error bars better than nothing? I'm
>not so sure.
>
>Cheers,
>
>Ed
>
> >Hello Ed
> >
> >thanks very much for your nice mail. I hope these little
> >comments were useful for you and yes of course
> >we hope too that we can merge the data base sometime
> >later on. This would be great.
> >
> >Do you think that you could send me some comments
> >on our paper by tomorrow?
> >Is your paper for the Orense book?
> >
> >Many greetings and till later
> >
> >Juerg
>
>
>==================================
>Dr. Edward R. Cook
>Doherty Senior Scholar
>Tree-Ring Laboratory
>Lamont-Doherty Earth Observatory
>Palisades, New York 10964  USA
>Email:  drdendro@ldeo.columbia.edu
>Phone:  845-365-8618
>Fax:    845-365-8152
>==================================
_______________________________________________________________________
Professor Michael E. Mann
Department of Environmental Sciences, Clark Hall
University of Virginia
Charlottesville, VA 22903
_______________________________________________________________________
e-mail: mann@virginia.edu   Phone: (804) 924-7770   FAX: (804) 982-2137


John:
For future reference, I think its also important to clarify for you what
the Dahl-Jensen, Clow et al borehole results actually show (see Dahl-Jensen
et al, "Past Temperatures Directly from the Greenland Ice Sheet", Science,
282, October 1998).
In fact, the results show that the amplitude of variability over the past
1000+ years differs by a factor of 2 between the GRIP and Dye 3 borehole
estimates (the latter only 865 km to the south). This is an example of
extreme regional-scale variability, which should give pause to those who
want to draw large-scale inferences.
However, even more importantly, they show in the case of Dye 3, the mid
20th century warm period in the record actually exceeds the Medieval warm
peak! (see Fig 4, lower panel, blue curve). So here we have two temperature
histories less than 1000 km apart in Greenland, which give different
stories regarding the level of Medieval warmth, with at least one of the
histories conforming precisely to the hemispheric trends presented in IPCC
chapter 2 (note that in the chapter, we actually discuss the evidence of
conflicting temperature trends in Greenland, though not specifically
referring to Dahl-Jensen et al).
So do I understand  correctly that you are referring to the results of
Dahl-Jensen et al as conflicting with what we say in the chapter? At the
face of it, this argument has no merit whatsoever. I think we should all
use a better explanation from you, since you seem to be arguing publically
that the Dahl-Jensen et al record undermines what we've said in the chapter.
Thanks in advance,
mike
p.s. I've cc'd in Eric Steig, a collaborator of Clow's and a Greenland &
Antarctic Ice Core expert, to make sure my facts above have been presented
accurately. Perhaps Eric woudl be kind enough to forward my email to Gary
Clow, and Gary can let us know directly if he disagrees with any of my
remarks above.
At 03:30 PM 5/23/01 -0400, Michael E. Mann wrote:
>John,
>
>I appreciate your reply.
>
>However, I don't agree at all w/ your assessment. It was determined early
>on that the ice core borehole results would be discussed in the context of
>the millennial-scale variability section, as they arguably don't have the
>resolution to address the timescales relevant to the past 1000 years. So
>this was in Jean's domain, not mine, and if the cross-references between
>the sections aren't clear enough in that regard, that is indeed our fault.
>
>However, there is considerable discussion of the fact that the
>Arctic/North Atlantic regions are inappropriate for inferences into
>hemispheric-scale temperature patterns, and this remains fundamentally
>from any reasonable treatment of the underlying climate dynamics that
>influence that region.
>
>The various hemispheric temperature reconstructions discussed in our
>chapter (the emphasis was on the commonality between them), including Mann
>et al, Jones et al, Briffa et al, Crowley and Lowery, and others, make
>considerable use of just about all of the available reliable low-res and
>high-res paleo data available, and come to a clear concensus regarding the
>relative warmth of the Medieval period at the hemispheric/global scale.
>Crowley's modeling results come to the same conclusion, and it entirely
>independent of
>any empirical paleoclimate reconstructions.
>
>You misrepresent the Mann et al reconstruction--it is not based on "tree
>rings", but uses all high-resolution proxy information commonly available.
>We have shown, in fact, that our reconstruction is robust to the
>inclusion/disclusion of tree ring information. The Crowley and Lowery
>reconstruction, which is discussed in our chapter, makes use of almost no
>tree ring data, and employs lower-resolution proxy indicators, including
>the very records (Keigwin, Lamb's central england temperature record,
>GISP2 o18) that are often used to argue for a warmer MWP, and yet comes to
>the same conclusion. And Tom shows that when averaged across the
>hemisphere, a warmer-than-present-day MWP just doesn't hold up.
>
>Our treatment of this subject in the chapter was far more careful, far
>more inclusive and detailed,  and far more nuanced than you give us credit
>for.  Your comments below remain disturbingly selective and myopic, and we
>have dealt w/ similar comments many times over...
>
>If ABC is looking to do a hatchet job on IPCC so be it (this doesn't
>surprise me--Stossel has an abysmal record in his treatment of
>environmental issues, from what I had heard), but I'll be very disturbed
>if you turn out to have played into this in a way that is unfair to your
>co-authors on chapter 2, and your colleagues in general. This wouldn't
>have surprised me coming from certain individuals, but I honestly expected
>more from you...
>
>Mike
>
>>Date: Wed, 23 May 2001 13:50:49 -0500
>>From: John Christy
>>X-Mailer: Mozilla 4.04 (Macintosh; I; PPC)
>>To: "Michael E. Mann"
>>Subject: Re: IPCC
>>
>>Hi Mike:
>>
>>Here's what happened.  ABC News 20/20 with Stossel wanted me to be part
>>of a segment that will air at the end of June on the climate change
>>issue.  Specifically the piece will be dealing with the alarmist
>>rhetoric that tends to be found in the media.  I am more than happy to
>>talk about that because I've been very disappointed with what has gone
>>on even with respect to some of the IPCC elders and their pronouncements
>>for forthcoming disasters.
>>
>>In one of the pre-interviews they asked about the "Hockey Stick".  I
>>told them of my doubts about the intercentury precision of the record,
>>especially the early part, and that other records suggested the period
>>1000 years ago was warmer.  I remember saying that "you must give the
>>author credit for including the large error bars for that time series in
>>the figure."  I also specifically said that the most precise record of
>>century scale precision, Greenland Borehole temps, was very important to
>>note but that the figure was not in the IPCC.  I then looked quickly at
>>the IPCC reference list and saw the citation of Dahl-Jensen and assumed
>>that it was at least commented on in the 1000 year time series material
>>and told ABC as much.
>>
>>ABC called back a few days later and said they couldn't find a reference
>>to the Greenland stuff in the IPCC discussion of the past 1000 years.
>>So I read the final version, and ABC was right.  I said this was an
>>omission that should not have happened - and that I take part of the
>>blame because I had mentioned it at each of our Lead Author meetings.
>>
>>Last Thursday night, I was one of the guys flown to NY City for the
>>taping of the show.  There was only one question on this particular
>>issue (it was even after Stossel had left the room) and I gave much the
>>same answer as I indicated above (as best as I can remember)- that the
>>"Hockey Stick" (I don't think I used the term "Hockey Stick", and I'm
>>almost positive I did not mention your name at any point) is one
>>realization of temperatures but that other data are not included and
>>that I had thought the "other" data were clearly mentioned in the IPCC,
>>but weren't.  I mentioned the large error bars (as a credit to you) and
>>that I was partly to blame for this omission.  If they use my remark,
>>they could slice and dice it to make it as provocative as possible.
>>
>>Four of us were taped for almost 2 hours, and from this they will select
>>about 8 minutes, so I doubt my remarks will make the show.  When Stossel
>>came back in after all was said and done, he said to me that I might be
>>a good scientist but I didn't have the emotion and passion necessary to
>>excite the audience.  In one way, that is a compliment I suppose.  I
>>think Pat M. will have a good chunk of air time (I don't remember
>>whether he added any comments on the 1000-year time series, but he may
>>have).
>>
>>Whatever is shown, just keep it in context.  There is no way a clear
>>scientific point with all the caveats and uncertainties can come across
>>in such venues.  However, I do agree with Stossel's premise (though I
>>don't know what the piece will actually look like so I may be
>>disappointed) that the dose of climate change disasters that have been
>>dumped on the average citizen is designed to be overly alarmist and
>>could lead us to make some bad policy decisions.  (I've got a good story
>>about the writers of the TIME cover piece a couple of months ago that
>>proves they were not out to discuss the issue but to ignore science and
>>influence government.)
>>
>>It is not bad science to look at arguably the most precise measure of a
>>point temperature (actually two boreholes) when that point shows a 600+
>>year period of greater warmth than today.  On that time scale, the
>>equivalent spatial scale is much larger than any of the regional
>>oscillations we now identify.  But, there are several other (admittedly
>>less robust) measures that suggest greater warmth 1000 years ago that
>>are outside the N. Atlantic area.  I just don't think tree rings, if
>>averaged over a century, can tell us which century was warmest.  We've
>>never had two complete, independent centuries of global instrumental
>>data (separated by more than one century) to even test this idea.  (By
>>the way, I came to my own conclusions long before Broekers piece
>>appeared.)  This is an area of further work that I promoted to the NRC
>>about 2 months ago (more funding for Paleo work to assess intercentury
>>precision of all proxy records.)
>>
>>Regarding the IPCC.  The IPCC TAR is good, but it is not perfect nor
>>sacred and is open to criticism as any document should be.  In some
>>cases it is already outdated. Some of the story lines used to generate
>>high temperature changes are simply ridiculous.  The IPCC is us.  We are
>>under no gag rule to keep our thoughts to ourselves.  I thought our
>>chapter turned out pretty good overall, and I attribute that to the
>>open, working relationship we all had (some other chapter groups did not
>>experience this) and to the tireless efforts of our convening lead
>>authors.
>>
>>Good to hear from you.
>>
>>John C.
>>
>>
>>--
>>************************************************************
>>John R. Christy
>>Director, Earth System Science Center   voice: 256-961-7763
>>Professor, Atmospheric Science          fax:  256-961-7751
>>Alabama State Climatologist
>>University of Alabama in Huntsville
>>
>>
>>Mail:  University of Alabama in Huntsville, Huntsville AL 35899
>>Express:   NSSTC/ESSC 320 Sparkman Dr., Huntsville AL 35805
>
>_______________________________________________________________________
>                      Professor Michael E. Mann
>           Department of Environmental Sciences, Clark Hall
>                       University of Virginia
>                      Charlottesville, VA 22903
>_______________________________________________________________________
>e-mail: mann@virginia.edu   Phone: (804) 924-7770   FAX: (804) 982-2137
>
>
_______________________________________________________________________
Professor Michael E. Mann
Department of Environmental Sciences, Clark Hall
University of Virginia
Charlottesville, VA 22903
_______________________________________________________________________
e-mail: mann@virginia.edu   Phone: (804) 924-7770   FAX: (804) 982-2137


Mike:
You are right: this is a disinformation campaign.
Some remarks
1)  On the Christy et al grl paper, I sent the following to John following
the IPCC Shanghai mtg.:
Date: Mon, 22 Jan 2001 15:39:20 -0700 (MST)
From: Kevin Trenberth
To: John Christy
Subject: your grl paper
John:
Just back from IPCC.  One surprise was the strong Saudi delegation
distributed your recent grl paper and wanted it inserted into the SPM!  In
spite of the fact that you are a lead author on Chapter 2 , the paper is
referenced, etc.  In fact Simon Brown was there.
Chris Folland made a comment about his hypothesis for this: related to
changes/growth in ships.  My hypothesis focusses on the buoy data.
See our recent paper submitted to jgr:
  also

This shows that during and following El Nino there is an anomalous flux of
heat out of ocean into atmosphere in the east Pacific of order 50 W m-2 over
many months: so ocean T warms relative to air.  During La Lina flux goes
other way.  i.e. air warms relative to ocean.
So your results must be affected by 1997-98 event at end of series and that
may explain trend differential.
Hope this helps
Regards
Kevin
i.e. the result is not as advertized.
=====================
2) wrt Lindzen's paper
Here is the text from my recent Senate testimony
The determination of the climatic response to the changes in heating and
cooling is complicated by feedbacks.  Some of these can amplify the original
warming (positive feedback) while others serve to reduce it (negative
feedback).  If, for instance, the amount of carbon dioxide in the atmosphere
were suddenly doubled, but with other things remaining the same, the outgoing
long-wave radiation would be reduced and instead trapped in the atmosphere.
To restore the radiative balance, the atmosphere must warm up and, in the
absence of other changes, the warming at the surface and throughout the
troposphere would be about 1.2\dg C.  In reality, many other factors will
change, and various feedbacks come into play, so that the best IPCC estimate
of the average global warming for doubled carbon dioxide is 2.5\dg C.  In
other words, the net effect of the feedbacks is positive and roughly doubles
the response otherwise expected.  The main positive feedback comes from
increases in water vapor with warming.
In 2001, the IPCC gave special attention to this topic. The many issues with
water vapor and clouds were addressed at some length in Chapter 7 (of which I
was a lead author, along with Professor Richard Lindzen (M.I.T.), and
others).  Recent possibilities that might nullify global warming (Lindzen
2001) were considered but not accepted because they run counter to the
prevailing evidence, and the IPCC (Stocker et al., 2001) concluded that ``the
balance of evidence favours a positive clear sky water vapour feedback of the
magnitude comparable to that found in the simulations."
===
Here is a more complete rebuttal, written March 23 to MacCracken.
Subject: Re: Recent Lindzen paper
Kevin Trenberth
1) The paper is based on very simple conceptual ideas that do not mesh with
reality. Fig. 2 is simply not correct.  For a more correct view of the
overturning see:
Trenberth, K. E., D. P. Stepaniak and J. M. Caron, 2000: The global monsoon
as seen through the  divergent atmospheric circulation. {J. Climate},
13, 3969--3993.
This paper also shows that the flow in the tropics is dominated by transients
(and thus mixing) of all kinds.  The mean overturning is only about a third
of the daily mean variance for a month and much less if the intra diurnal
variations and interannual variations are included.
2) The "observations" analysis makes absolutely no sense to me at all.  There
is a totally inadequate description of what is done and no way to decipher
what a dot in Fig 5 or Fig 6 is.  Given 20 months, and daily values (how
was that done?) why are there only about 330 points?  Why isn't Fig 6 part
of Fig. 5?
In any event the results are totally at odds with other evidence.  Here I
refer to the Goes Precipitation Index which uses 3 hourly data on OLR, and
thus on high cloud, as an index of rainfall, and it is clear from many
studies that OLR generally decreases (convection and high cloud increase)
with SST, the reverse of the relationship in Fig. 5.
Moreover the whole conceptual basis for anything here is surely flawed.  As
stated, on short time scales SST is not changing.  But clouds are NOT caused
by local SST, rather they arise from either transients, like the MJO, or for
the ITCZ and SPCZ (which are major operators in this region), they come from
moisture convergence (P>>E) and so it is the patterns of SST (gradients) as
well as where the warmest water is that determines where the convergence and
clouds occur.  Now in the warm pool, the convergence is focussed more on the
edges, as that is where the pressure gradients are greater, and so the
convergence is not where SST is necessarily highest.
In any case, moisture is not equal to cloudy air. Many analyses show that
moisture is much more extensive, see for example
Trenberth, K. E., and C. J. Guillemot, 1998: Evaluation of the atmospheric
moisture and hydrological cycle in the NCEP/NCAR reanalyses. {Climate
Dyn.}, {14}, 213--231.
Even with such results, other factors need to be considered.
One process might be
High SST => convergence => rainfall and cloud
OR
Less cloud => more solar radiation => higher SST
Those give opposite relations and both operate.  The latter is more important
in the Indian Ocean where subsidence (from the Pacific) dominates.
However, it also operates over the oceans in the region in question in
northern summer, because that is the monsoon season, and the main convection
is over land, meaning subsidence over the ocean.
None of this is sorted out in any way in this paper.
In fact it is so bad in this regard I do not know how it got published.
In Fig 5 etc, no correlations are given, nor are their significance levels.
My rough estimate is that the correlation is about 0.2 to 0.3 and that is
significant if the 330 or so points are independent.  But why should I have
to guess at that.
Again I would question the editorial and review process.
3) Finally, I refer you to chapter 7 of IPCC which is a more balanced
assessment.  Lindzen was a coauthor of that with me and others.  Lindzen
wrote 7.2.1 and the same figure 1 in the BAMS article was included as 7.1 in
chapter 7 along with similar ones from models, showing that these things are
fully simulated in good models, although better with higher resolution.
Anyway, his arguments were fully considered in chapter 7 and you can read it
to see the result.  The whole of 7.2.1, including 7.2.1.1. 7.2.1.2 and
7.2.1.3 was put together originally by Lindzen, Pierrehumbert and Le Treut,
but basically the final version was rewritten by me to provide better
balance.  Pierrehumbert is an agnostic of sorts: disbelieves everything
including models but seems to have faith in simple theories.  Le Treut was
sound on the modeling. I did not change the substance of what they prepared,
I did reshape it and polish and it ended up in a form they accepted.
Note at the end it clearly states:
"the balance of evidence favours a positive clear sky water vapour feedback of
the magnitude comparable to that found in the simulations."
The 4 subsections together are quite long and throughly air the issue, much
moreso than any previous IPCC report.  For those of you who do not have it:
7.2.1 "Physics of the water vapour and cloud feedbacks" (draft written by
Lindzen) is 1.3 pages, 7.2.1.1 (I think Pierrehumbert) "Water vapour
feedback", is 1 page, 7.2.1.2 "Representation of watre vapour in models" is
1.5 pages (Le Treut) and 7.2.1.3 "Summary on water vapour feedbacks" is half
a page or so.
---------------
Kevin E. Trenberth			     e-mail: trenbert@ucar.edu
Climate Analysis Section, NCAR, ML           www.cgd.ucar.edu/cas/
P. O. Box 3000,	[1850 Table Mesa Drive]      (303) 497 1318
Boulder, CO 80307  [80305]		     (303) 497 1333 (fax)
*******************************
On Thu, 24 May 2001, Michael E. Mann wrote:
> FYI. I received this from a colleague. This gives you some idea of who is
> behind this latest disinformation push.
>
> A note to all regarding the Broecker piece, which has been heavily referred
> to in this and other similar recent pieces (though it is an opinion piece,
> and not peer-reviewed).
> A response by Bradley, Briffa, Crowley, Hughes, Jones, and Mann appears in
> tomorrows issue of "Science". This response simply points out that old
> fallacies that are simply reiterated in Broecker's piece...
>
> mike
>
>
>
>
>
> >                                   COMPETITIVE ENTERPRISE INSTITUTE
> >
> >
> >                            Advancing the principles of free enterprise and
> >                             limited government
> >
> >
> >                                    5/16/01
> >
> >                      Latest Global Warming Report Already Obsolete
> >
> >                             By Paul J. Georgia
> >
> >
> >
> >               The United Nations Intergovernmental Panel on Climate Change
> >(IPCC) is
> >               conducting a campaign of fear to convince us that energy
> >suppression is
> >               our only salvation.  The "Summary for Policymakers" of the
> >group's latest
> >               report ? the report itself has not been officially released ?
> >paints a horrific
> >               picture of a climate system gone mad.
> >
> >               The new report, known as the "Third Assessment Report" (TAR),
> >is
> >               expected to be the focal point for policymakers for the next
> >five years as
> >               they decide what to do about global warming, just as the 1995
> >Second
> >               Assessment Report has guided policymakers for the last five
> >years.
> >               Indeed, the bureaucrats driving the global warming process
> >are using the
> >               IPCC to justify their anti-energy policies.  Klaus Toepfer,
> >executive
> >               director of the United Nations Environment Programme, said,
> >"The
> >               scientific consensus presented in this comprehensive report
> >about
> >               human induced climate change should sound alarm bells in
> >every
> >               national capital and in every local community."[1]
> >
> >               In the midst of this campaign, however, the science continues
> >to move
> >               apace, leaving many of the IPCC's underlying assumptions and
> >               subsequent conclusions in shambles.  A sampling of scientific
> >studies
> >               published after the completion of the final drafts of the TAR
> >is presented
> >               here to give the reader a taste of the constant flux of
> >scientific inquiry and
> >               our rapidly changing understanding of the climate system.
> >Indeed, if
> >               recent studies are correct there would be little
> >justification for Kyoto-style
> >               policies that would ultimately impede humanity's ability to
> >provide itself
> >               with the wealth- and health-enhancing benefits of modern
> >civilization.
> >
> >               Water Vapor Feedback.  The biggest uncertainty in climate
> >science
> >               remains "feedback" effects on the climate.  The conventional
> >explanation
> >               by proponents of global warming theory always assumes that
> >               human-induced increases in atmospheric concentrations of
> >greenhouse
> >               gases, primarily carbon dioxide, could lead to catastrophic
> >warming of
> >               the planet.  Man-made greenhouse gas emissions, however, are
> >only an
> >               indirect cause of the forecasted warming.  A doubling of
> >carbon dioxide
> >               concentrations alone would lead to slight warming of about
> >one degree
> >               Celsius (1.8 degrees Fahrenheit) over the next 100 years.
> >This small
> >               amount of warming, according to standard global warming
> >theory, speeds
> >               up evaporation, thereby increasing the amount of water vapor
> >(a major
> >               greenhouse gas) in the atmosphere.  This "positive water
> >vapor feedback"
> >               effect is where most of the predicted warming comes from.
> >This
> >               assumption has never been tested.
> >
> >               A recent study in the Bulletin of the American Meteorological
> >Society
> >               suggests that the reverse is true.[2]  The authors find a
> >negative water
> >               vapor feedback effect that is powerful enough to offset all
> >other positive
> >               feedbacks.  Using detailed daily observations of cloud cover
> >from
> >               satellites in the tropics and comparing them to sea surface
> >temperatures,
> >               the researchers found that there is an "iris effect" in which
> >higher
> >               temperatures reduce the warming effect of clouds.
> >
> >               According to a NASA statement about the study, "Clouds play a
> >critical
> >               and complicated role in regulating the temperature of the
> >Earth. Thick,
> >               bright, watery clouds like cumulus shield the atmosphere from
> >incoming
> >               solar radiation by reflecting much of it back into space.
> >Thin, icy cirrus
> >               clouds are poor sunshields but very efficient insulators that
> >trap energy
> >               rising from the Earth's warmed surface. A decrease in cirrus
> >cloud area
> >               would have a cooling effect by allowing more heat energy, or
> >infrared
> >               radiation, to leave the planet."[3]
> >
> >               The researchers found that a one degree Celsius rise in ocean
> >surface
> >               temperature decreased the ratio of cirrus cloud area to
> >cumulus cloud
> >               area by 17 to 27 percent, allowing more heat to escape.
> >
> >               In an interview, lead author Dr. Richard S. Lindzen said the
> >climate
> >               models used in the IPCC have the cloud physics wrong.  "We
> >found that
> >               there were terrible errors about clouds in all the models,
> >and that that will
> >               make it impossible to predict the climate sensitivity because
> >the
> >               sensitivity of the models depends primarily on water vapor
> >and clouds.
> >               Moreover, if clouds are wrong, there's no way you can get
> >water vapor
> >               right. They're both intimately tied to each other."  Lindzen
> >argues that
> >               due to this new finding he doesn't expect "much more than a
> >degree
> >               warming and probably a lot less by 2100."[4]
> >
> >               The study is the best empirical confirmation to date of the
> >negative
> >               feedback hypothesis proposed by Lindzen early on in the
> >global warming
> >               debate.  It builds on earlier empirical work by Drs. Roy
> >Spencer of NASA
> >               and William Braswell of Nichols Research Corporation.  Their
> >1997 study
> >               also cast doubt on the assumption of a positive water vapor
> >feedback
> >               effect.[5]  They found that the tropical troposphere, the
> >layer of air
> >               between 25,000 and 50,000 feet, is much dryer than climate
> >modelers
> >               previously thought.  Further empirical work will no doubt
> >confirm whether
> >               this phenomenon is common throughout the tropics, which act
> >as the
> >               Earth's exhaust vents for escaping heat.
> >
> >
> >               Black Carbon.  In 1995, the IPCC had to explain in its Second
> >               Assessment Report why its previous predictions of global
> >temperature
> >               change were nearly three times larger than observed in the
> >actual
> >               temperature record.  The SAR concluded that emissions of
> >sulfate
> >               aerosols from burning coal were offsetting the warming that
> >should be
> >               caused by carbon dioxide levels in the atmosphere.  Sulfate
> >aerosols,
> >               according to this explanation, reflect incoming solar
> >radiation back to
> >               space, thereby cooling the planet.
> >
> >
> >               The TAR takes the sulfate aerosol idea even further.  The SAR
> >had
> >               predicted a temperature rise of 1 to 3.5 degrees C (1.8 to
> >6.3 degrees F)
> >               over the next 100 years.  The TAR goes even further,
> >anticipating a 1.4 to
> >               5.8 degrees C (2.52 to 10.44 degrees F) rise in temperature.
> >The
> >               extreme case scenario of a 5.8 degrees C of warming, for
> >instance, is
> >               based partly on assumptions that the whole world will raise
> >its level of
> >               economic activity to that of the U.S., will equal U.S. per
> >capita energy
> >               use, and energy use will be carbon intensive.  The primary
> >assumption
> >               behind the new scenario, however, is that sulfate aerosol
> >emissions will
> >               be eliminated by government regulation, giving carbon dioxide
> >free
> >               reign.[6]
> >
> >               Sulfate aerosols, then, are a key component of catastrophic
> >global
> >               warming scenarios.  Without them, the IPCC cannot explain why
> >the
> >               earth is not warming according to their forecasts, nor can
> >they
> >               reasonably claim that global warming will lead to
> >catastrophes of biblical
> >               proportions.
> >
> >               A new study in Nature eliminates sulfate aerosols as a
> >corrective for the
> >               models. [7]  The author, Mark Jacobson, a professor with the
> >Department
> >               of Civil & Environmental Engineering at Stanford University,
> >examines
> >               how black carbon aerosols affect the Earth's climate.  Unlike
> >other
> >               aerosols that reflect solar radiation back into space, black
> >carbon (soot)
> >               absorbs solar radiation, thereby raising atmospheric
> >temperatures.
> >
> >               Until now the warming influence of black carbon was thought
> >to be minor,
> >               leading researchers to ignore it.  James Hansen, with the
> >Goddard
> >               Institute for Space Studies, in a paper published in August
> >2000, first
> >               suggested that black carbon plays an important role in global
> >               warming.[8]  Jacobson found "a higher positive forcing from
> >black carbon
> >               than previously thought, suggesting that the warming effect
> >from black
> >               carbon may nearly balance the net cooling effect of other
> >anthropogenic
> >               aerosol constituents."
> >
> >               There you have it.  Soot offsets the cooling effect of other
> >aerosols,
> >               meaning we are back at square one.  Scientists still do not
> >have a
> >               plausible explanation for why the Earth has failed to warm in
> >line with
> >               climate model results.  Indeed, all the prognostications of
> >the IPCC are
> >               wrong if the Nature study is right.
> >
> >
> >               Natural Cycles.  The main propaganda device of the TAR is the
> >"hockey
> >               stick graph."  The graph is a temperature record derived from
> >tree rings
> >               dating back to 1000 AD and running through 1900, with the
> >20th century
> >               thermometer-based temperature data attached at the end.[9]
> >It claims to
> >               show that global temperatures have remained steady or even
> >decreased
> >               during the last millennium until the industrial age, when
> >there was an
> >               anomalous warming represented by the blade of the hockey
> >stick.  The
> >               hockey stick is largely bogus, however.  The margin of error
> >is so large
> >               that nearly any temperature trend could be drawn to fit
> >within it.
> >
> >
> >
> >               The hockey stick features prominently in all of IPCC Chairman
> >Robert
> >               Watson's speeches, and to the uninitiated it is very
> >persuasive.  Senator
> >               John McCain (R-AZ), for example, expressed alarm when he saw
> >the
> >               graph at Commerce Committee hearings last May.
> >
> >
> >               Watson uses the hockey stick to claim that current warming is
> >greater
> >               than at any other time in the last 1,000 years.  The Medieval
> >Warm
> >               Period (MWP) and the Little Ice Age (LIA) were two naturally
> >occurring
> >               events during the last millennium where the range of global
> >temperature
> >               change exceeded that of the 20th century.  During the MWP,
> >global
> >               temperatures were higher than they are today.  The MWP,
> >however, does
> >               not show up in the hockey stick graph.
> >
> >               The hockey stick has effectively been dismantled in a recent
> >study in
> >               Science, however.[10]  Wallace Broecker, of the
> >Lamont-Doherty Earth
> >               Observatory, argues that the MWP and the LIA were indeed
> >global
> >               phenomena.  Referring to the hockey stick, Broecker notes, "A
> >recent,
> >               widely cited reconstruction leaves the impression that the
> >20th century
> >               warming was unique during the last millennium.  It shows no
> >hint of the
> >               Medieval Warm Period (from around 800 to 1200 A.D.) during
> >which the
> >               Vikings colonized Greenland, suggesting that this warm event
> >was
> >               regional rather than global. It also remains unclear why just
> >at the dawn
> >               of the Industrial Revolution and before the emission of
> >substantial
> >               amounts of anthropogenic [manmade] greenhouse gases, Earth's
> >               temperature began to rise steeply."
> >
> >
> >               Broecker reviewed several scientific studies which
> >reconstruct the Earth's
> >               temperature history into the distant past using various
> >proxies.  He
> >               concludes, "The post-1860 natural warming was the most recent
> >in a
> >               series of similar warmings spaced at roughly 1500-year
> >intervals
> >               throughout the present interglacial, the Holocene."[11]  In
> >other words,
> >               the current warm period may just be attributable to natural
> >cycles.
> >
> >
> >               Flawed Temperature Data.  The National Oceanic and
> >Atmospheric
> >               Administration (NOAA) claimed that the year 2000 was the
> >sixth
> >               warmest since 1880.  Other temperature records find less
> >warming.[12]
> >               Last year was only the 14th warmest, or 9th coolest, year
> >since 1979
> >               according to the satellite temperature record,[13] and only
> >the 9th
> >               warmest, according to records that include only measurements
> >from
> >               meteorological stations.[14]
> >
> >               The NOAA data, which is cited by government officials and the
> >news
> >               media, may be the least accurate, according to a study that
> >recently
> >               appeared in Geophysical Research Letters.[15]  The NOAA
> >datasets "are
> >               a mixture of near-surface air temperatures over land and sea
> >water
> >               temperatures over oceans," according to lead author Dr. John
> >Christy,
> >               professor of atmospheric science and director of the Earth
> >System
> >               Science Center at the University of Alabama in Huntsville.
> >
> >               Since actual air temperature data over many large ocean areas
> >are
> >               nonexistent, the NOAA uses sea surface temperatures as a
> >"proxy,"
> >               assuming that sea surface temperatures and air temperatures
> >move in
> >               lock step.  This is not the case, according to the data
> >compiled by
> >               Christy and his colleagues at the Hadley Centre of the United
> >Kingdom's
> >               Meteorological Office, who worked on the study.  The
> >researchers used
> >               buoy data in the tropical Pacific Ocean to compare "long-term
> >(8-20 year)
> >               trends for temperatures recorded one meter below the sea
> >surface and
> >               three meters above it."
> >
> >               What they found was a significant discrepancy.  "For each
> >buoy in the
> >               Eastern Pacific, the air temperatures measured at the three
> >meter height
> >               showed less of a warming trend than did the same buoy's water
> >               temperatures at one meter depth," the study said.  The
> >difference is a
> >               near-surface seawater warming trend of 0.37 degrees C per
> >decade and
> >               an air temperature trend of only 0.25 degrees C per decade
> >during the
> >               20-year period tested.  Replacing the sea surface
> >temperatures with the
> >               air temperature data reduces the Earth's global warming trend
> >by a third,
> >               from 0.19 to 0.13 degree C per decade.
> >
> >               This is significant due to difficulties with reconciling the
> >various global
> >               temperature data sets, particularly the discrepancy between
> >tropospheric
> >               temperatures measured by satellites that show little to no
> >warming, and
> >               the surface-based temperature data that show slightly more
> >warming.
> >               Last year, the National Research Council stated that both
> >temperature
> >               records are correct and speculated about an explanation.[16]
> >
> >               This brings up another problem, however.  The standard
> >explanation of
> >               the greenhouse effect suggests warming occurs first five
> >kilometers
> >               above the earth's surface in the atmospheric layer known as
> >the
> >               troposphere.  How events at the surface are connected to what
> >happens
> >               high in the atmosphere is not clear, but it is believed that
> >surface
> >               warming would follow tropospheric warming through climatic
> >processes
> >               such as air circulation.[17]  If both temperature records are
> >correct, then
> >               this explanation of the greenhouse effect is wrong.  Christy
> >et al. brings
> >               the surface temperature data into closer agreement with the
> >satellite
> >               data, suggesting that a better explanation for the
> >discrepancy is flawed
> >               surface data.
> >
> >               Progressive Science.  At a press conference at the National
> >Press
> >               Club on April 18, Mr. Jan Pronk, chairman of the Sixth
> >Conference of the
> >               Parties of the United Nations Framework Convention on Climate
> >Change
> >               said most issues were still on the table in the ongoing Kyoto
> >negotiations
> >               but the scientific basis of catastrophic global warming could
> >not be
> >               questioned.  That would be like going back ten years, he
> >said.  This is a
> >               myopic and erroneous view of science.  Science is not static
> >but
> >               dynamic.  It reaches tentative conclusions at best, and those
> >               conclusions constantly give way to new data.  The IPCC is a
> >static
> >               process, however.  The Third Assessment Report is already
> >obsolete and
> >               it has not even been released yet.  With these four recent
> >studies, it may
> >               be time to bid catastrophic global warming theory a warm
> >farewell.
> >
> >
> >
> >
> >
> >         [1] "Evidence of Rapid Global Warming Accepted by 99 Nations,"
> >Environment News Service, January 22,
> >         2001.
> >         [2] Richard S. Lindzen, Ming-Dah Chou, and Arthur Y. Hou, "Does the
> >Earth Have an Adaptive Infrared Iris?,
> >         Bulletin of the American Meteorological Society, 82:417-32, March
> >2001.
> >         [3] ftp://www.gsfc.nasa.gov/pub/PAO/Releases/2001/01-18.htm
> >         [4] "Is Globe Warming?  Sure, But Far Less than Alarmists Say,"
> >Tech Central Station
> >         ( March 5,
> >2001.
> >         [5] Roy W. Spencer and William D. Braswell, "How Dry is the
> >Tropical Free Troposphere? Implications for
> >         Global Warming Theory," Bulletin of the American Meteorological
> >Society, 78:1097-1106.
> >         [6] In correspondence with Nature magazine, one of the IPCC's
> >coordinating lead authors, Thomas Stocker of
> >         the Physics Institute at the University of Bern in Switzerland,
> >wrote, "First, although climate modeling has
> >         advanced during the past five years, this is not the main reason
> >for the revised range of temperature
> >         projections.  The higher estimates of maximum warming by the year
> >2100 stem from a more realistic view of
> >         sulphate aerosol emissions.  The new scenarios assume emissions
> >will be reduced substantially in the coming
> >         decades, as this becomes technically and economically feasible, to
> >avoid acid rain.  Sulphate emissions have
> >         a cooling effect, so reducing them leads to higher estimates of
> >warming."  See "Climate panel looked at all
> >         the evidence," Nature, 410: 299, March 15, 2001.
> >         [7] Mark Z. Jacobson, "Strong radiative heating due to the mixing
> >state of black carbon in atmospheric
> >         aerosols," Nature, 409: 695-72, February 8, 2001.
> >         [8] James D. Hansen, Makiko Sato, Reto Ruedy, Andrew Lacis, and
> >Valdir Oinas, "Global Warming in the
> >         twenty-first century: An alternative scenario," Proceedings of the
> >National Academy of Sciences,
> >         97:9875-9880.
> >         [9] The tree ring data originated with Michael E. Mann, Raymond S.
> >Bradley and Malcolm K. Hughes,
> >         "Northern Hemisphere Temperatures During the Past Millennium:
> >Inferences, Uncertainties, and Limitations,"
> >         Geophysical Research Letters, 26: 759, March 15, 1999.
> >         [10] Wallace S. Broecker, "Was the Medieval Warm Period Global?"
> >Science, 291: 1497-99, February 23,
> >         2001.
> >         [11] Also see H.H. Lamb, Climate History and the Modern World, (New
> >York: Routledge, 1985), and Brian
> >         Fagan, The Little Ice Age: How Climate Made History, 1300-1850,
> >(New York: Basic Books, 2000).
> >         [12]
> >         [13]
> >         [14] #Phil
> >         [15] John R. Christy, David E. Parker, Simon J. Brown, Ian Macadam,
> >Martin Stendal, and William B. Norris,
> >         "Differential Trends in Tropical Sea Surface and Atmospheric
> >Temperatures since 1979," Geophysical
> >         Research Letters, 28:183.
> >         [16] Reconciling Observations of Global Temperature Change,
> >National Academy Press: Washington, D.C.,
> >         2000.
> >         [17] Richard S. Lindzen, "Climate Forecasting: When Models are
> >Qualitatively Wrong," George C. Marshall
> >         Institute, Washington, D.C., 2000.
> >
> >
> >
> >             ©5/16/01 Competitive Enterprise Institute
>
> _______________________________________________________________________
>                      Professor Michael E. Mann
>             Department of Environmental Sciences, Clark Hall
>                        University of Virginia
>                       Charlottesville, VA 22903
> _______________________________________________________________________
> e-mail: mann@virginia.edu   Phone: (804) 924-7770   FAX: (804) 982-2137
>
>
>


Stepan
it is just pressure of work. I am afraid the final report did not go to INTAS . I will do
it this week! I still expect we will get the money outstanding - just late . Sorry.
Keith
At 02:22 PM 5/31/01 +0600, you wrote:
Dear Keith,
Thank you for the print of collaborative article published in the J.
of Geophysical Research I have received some days ago. The article is
very interesting and, I think, these reconstructions will be used by
many researchers of different disciplines.
At the end of the last year Janet asked me to send the account of the
bank to transfer the rest money of the INTAS project (737 Euros). I have
sent you the necessary form to transfer the money for my name, but
the Ekaterinburg Branch of Bank for Foreing Trade did not receive the
money until now. Do you know the reason?
This summer I am very busy. Along with Fritz Schweingruber and his team
(four persons)we will visit many sites (using helicopter) on the North of
European and Siberian Arctic and Subarctic (from the Lower of Pechora
river in the west to the Lover of Khatanga river in the East). We will
try to find a new sources of subfossil wood material between the Yamal
Peninsula and Taimyr Peninsula, on the one hand, and between the Yamal
Peninsula and Kola Peninsula, on the other hand. The second aim is to
collect samples from living trees of different ages for estimating
biomas changes.
After this trip I and my post-graduate student will be working in the
Polar Urals (large-scale mapping of forest-tundra ecosystems over the
forest-tundra ecotone for three time intervals: the beginning of the
XXth century, the 1960ties and the 2000ties.
At the end of September I intend to be in Davos.
Best Regards,
Stepan
stepan@ipae.uran.ru
--
Dr. Keith Briffa, Climatic Research Unit, University of East Anglia,
Norwich, NR4 7TJ, United Kingdom
Phone: +44-1603-593909    Fax: +44-1603-507784