FaIR calibration data

This dataset contains the full data, input scripts and produced output data for the AR6-consistent calibration of FaIRv2.1.1.

The zipfile contains everything, allowing you perform your own analysis. The GitHub version contains enough for "bare bones" reproducibility, including downloading of external datasets and generation of intermediate files. 

The CSV file is the output most people will probably care about, containing the constrained, calibrated parameter set.

FaIR v2.1.1

Obtainable from https://pypi.org/project/fair/

From the command line:

pip install fair==2.1.1

Calibration v1.2

Along with fixing a few minor things, the biggest two changes are (1) the constraints are updated to much more recent history (2022 where available) and (2) future warming from SSPs has been dropped as a constraint, typically making projected uncertainties a little wider than IPCC (though medians are still quite close).

In the calibrated_constrained_parameters.csv file, the column names have been prefixed by the component of FaIR that they relate to (done in order to reduce namespace ambiguities). clim=climate, cc=carbon cycle, ari=aerosol-radiation interactions, aci=aerosol-cloud interactions, o3=ozone, fscale=forcing scaling.

• 1.5 million prior ensemble
• Climate response calibrated on 49 abrupt-4xCO2 experiments from CMIP6 and sampled using correlated kernel density estimates
• Methane lifetime calibrated on 4 AerChemMIP experiments for 1850 and 2014 (Thornhill et al. 2021a, 2021b). Unlike other variables which are sampled around some prior uncertainty, only the best estimate historical calibration is used. The base (1750) lifetime has been fixed and consistently used across projections.
• Carbon cycle uses the parameters from Leach et al. 2021 calibrated for FaIR 2.0.0 using 11 C4MIP models.
• Aerosol cloud interactions depend on SO2, BC and OC, using new calibrations from 13 RFMIP and AerChemMIP models, with the APRP code fixed by Mark Zelinka (Zelinka et al. 2023). Prior of -2 to 0 W/m2.
• Aerosol radiation interactions use prior values from AR6 Ch6, with a factor of two uncertainty for each species and a prior in the range of -0.6 to 0.0.
• Ozone uses the same methodology as AR6 (Smith et al. 2021b).
• NOx emissions are updated from RCMIP to fix a unit conversion issue, where biomass burning emissions from GFED are in units of NO and everything else (from CEDS) is in NO2. FaIR uses NO2 units consistently. In RCMIP v5.1.0 (Nicholls and Lewis 2021), the conversion was not done. When using this calibration for future scenarios, it is important that this is carefully considered.
• Effective radaitive forcing uncertainty follows the distributions in AR6, with asymmetric distributions switched to skew-normal.
• Volcanic forcing time series updated to 2022 (from IGCC).

AR6_updated (v1.2.0)

• 1001-member posterior (deliberately chosen).
• Emissions and concentrations from RCMIP (i.e. based on CMIP6), but with NOx updated as above. ssp245 chosen for post-2014.
• Temperature from IGCC (Forster et al. 2023) (1850-2022, mean of 4 datasets).
• Warming 2003-2022 relative to 1850-1900 range from IGCC.
• CO2 concentrations constrained to IGCC estimate for 2022.
• Ocean heat content from IGCC (1971-2020), linear.
• two step constraining procedure used: first RMSE of less than 0.17K (up from 0.16), then 8-variable distribution fitting.
• Aerosol ERF, ERFari and ERFaci as in AR6 WG1
• No future warming constraints.

Performance relative to AR6 assessed ranges

Note 1: TCRE and AF are very poor constraints, taken only from model evidence, so we should not put too much weight on them.

Note 2: No future warming constraint is used: these are for sense-checking only.

Note 3: present-day CO2 concentration, ERFari and ERFaci are not constraints used by AR6.

References

• Forster et al. 2023: https://doi.org/10.5194/essd-15-2295-2023
• Leach et al. 2021: https://doi.org/10.5194/gmd-14-3007-2021
• Nicholls and Lewis 2021: https://doi.org/10.5281/zenodo.4589756
• Smith et al. 2021a: https://doi.org/10.1029/2020JD033622
• Smith et al. 2021b: https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_FGD_Chapter07_SM.pdf
• Thornhill et al. 2021a: https://doi.org/10.5194/acp-21-853-2021
• Thornhill et al. 2021b: https://doi.org/10.5194/acp-21-1105-2021
• Zelinka et al. 2023: https://doi.org/10.5194/acp-23-8879-2023