The Radiative Forcing Model Intercomparison Project (RFMIP) is a World Climate Research Programme endorsed community model intercomparison project (MIP) that seeks to evaluate why state-of-the-art climate models respond the way they do to different human and natural climate influences such as greenhouse gases, air pollutants, land use change, solar variability and volcanic eruptions.
In the last round of coordinated Earth System model experiments (CMIP6), RFMIP provided critical information on the energetic influence of different climate forcers over the historical period and their potential future effects. The diversity of model responses to the same aerosol emissions (figure below) can be used to train emulators such as fair to infer information about the Earth’s climate sensitivity (Smith et al., 2021).
For the next round of climate model experiments, I am co-chairing RFMIP with Ryan Kramer (NOAA GFDL) and Tim Andrews (UK Met Office).
References
2021
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Energy Budget Constraints on the Time History of Aerosol Forcing and Climate Sensitivity
C. J. Smith, G. R. Harris, M. D. Palmer, N. Bellouin, W. Collins, G. Myhre, M. Schulz, J. C. Golaz, M. Ringer, T. Storelvmo, and P. M. Forster
Journal of Geophysical Research: Atmospheres, Jun 2021
An observationally constrained time series of historical aerosol effective radiative forcing (ERF) from 1750 to 2019 is developed in this study. We find that the time history of aerosol ERFs diagnosed in CMIP6 models exhibits considerable variation and explore how the time history of aerosol forcing influences the probability distributions of present-day aerosol forcing and emergent metrics such as climate sensitivity. Using a simple energy balance model, trained on CMIP6 climate models and constrained by observed near-surface warming and ocean heat uptake, we derive estimates for the historical aerosol forcing. We find 2005–2014 mean aerosol ERF to be −1.1 (−1.8 to −0.5) W m−2 relative to 1750. Assuming recently published historical emissions from fossil fuel and industrial sectors and biomass burning emissions from SSP2-4.5, aerosol ERF in 2019 is −0.9 (−1.5 to −0.4) W m−2. There is a modest recovery in aerosol forcing (+0.025 W m−2 decade−1) between 1980 and 2014. This analysis also gives a 5%–95% range of equilibrium climate sensitivity of 1.8°C –5.1°C (best estimate 3.1°C) with a transient climate response of 1.2°C –2.6°C (best estimate 1.8°C).
