Quantifying Cloud Feedbacks for Climate Sensitivity
A new study,[8] however, has succeeded at quantifying these cloud feedbacks at 0.43 ± 0.35 W/m^2/K. This means that for every 1 C warming, we can expect an additional 0.43 W/m^2, amplifying warming. Given these results, there is just a 2.5% chance that the net cloud feedback has a negative sign. These findings also help constrain values for ECS. The study estimates ECS to be 3.2 C, and argues that the chance that ECS is less than 2 C is about 0.5%. “Considering changes in just these two factors, we are able to constrain global cloud feedback to 0.43 ± 0.35 W⋅m−2⋅K−1 (90% confidence), implying a robustly amplifying effect of clouds on global warming and only a 0.5% chance of ECS below 2 K.” The paper is currently behind a paywall, but you can read a summary of it on CarbonBrief.[9]
References:
[1] Dessler, A. E. (2010), A determination of the cloud feedback from climate variations over the past decade, Science, 330, 1523– 1527, doi:10.1126/science.1192546.
[2] Dessler, A. E., and Loeb, N. G. (2013), Impact of dataset choice on calculations of the short‐term cloud feedback, J. Geophys. Res. Atmos., 118, 2821– 2826, doi:10.1002/jgrd.50199.
[3] Zhou, C., M. D. Zelinka, A. E. Dessler, and P. Yang, 2013: An Analysis of the Short-Term Cloud Feedback Using MODIS Data. J. Climate, 26, 4803–4815, https://doi.org/10.1175/JCLI-D-12-00547.1.
[4] Zelinka, M. D., Myers, T. A., McCoy, D. T., Po-Chedley, S., Caldwell, P. M., Ceppi, P., et al. (2020). Causes of higher climate sensitivity in CMIP6 models. Geophysical Research Letters, 47, e2019GL085782. https://doi.org/10.1029/2019GL085782
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL085782
[5] Myers, T.A., Scott, R.C., Zelinka, M.D. et al. Observational constraints on low cloud feedback reduce uncertainty of climate sensitivity. Nat. Clim. Chang. 11, 501–507 (2021). https://doi.org/10.1038/s41558-021-01039-0
[6] Mülmenstädt, J., Salzmann, M., Kay, J.E. et al. An underestimated negative cloud feedback from cloud lifetime changes. Nat. Clim. Chang. 11, 508–513 (2021). https://doi.org/10.1038/s41558-021-01038-1
[7] Stephens, G.L. The cooling of light rains in a warming world. Nat. Clim. Chang. 11, 468–470 (2021). https://doi.org/10.1038/s41558-021-01056-z
[8] Paulo Ceppi, Peer Nowack. Observational evidence that cloud feedback amplifies global warming. Proceedings of the National Academy of Sciences Jul 2021, 118 (30) e2026290118; DOI: 10.1073/pnas.2026290118 https://www.pnas.org/content/118/30/e2026290118
[9] Ayesha Tandon.Clouds study finds that low climate sensitivity is ‘extremely unlikely.’ CarbonBrief. July 21 2021. https://www.carbonbrief.org/clouds-study-finds-that-low-climate-sensitivity-is-extremely-unlikely?fbclid=IwAR225L6aKkDv4IVx-U6-t1qQeHJ01yEkF5NwAMULkJM_N51qugi9clbplSc
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