Climate models underestimate dynamic cloud feedbacks in the tropics

P. G. Hill*, C. E. Holloway, M. P. Byrne, F. H. Lambert, M. J. Webb

*Corresponding author for this work

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Abstract

Cloud feedbacks are the leading cause of uncertainty in climate sensitivity. The complex coupling between clouds and the large-scale circulation in the tropics contributes to this uncertainty. To address this problem, the coupling between clouds and circulation in the latest generation of climate models is compared to observations. Significant biases are identified in the models. The implications of these biases are assessed by combining observations of the present day with future changes predicted by models to calculate observationally constrained feedbacks. For the dynamic cloud feedback (i.e., due to changes in circulation), the observationally constrained values are consistently larger than the model-only values. This is due to models failing to capture a nonlinear minimum in cloud brightness for weakly descending regimes. Consequently, while the models consistently predict that these regimes increase in frequency in association with a weakening tropical circulation, they underestimate the positive cloud feedback associated with this increase.
Original languageEnglish
Article numbere2023GL104573
Number of pages10
JournalGeophysical Research Letters
Volume50
Issue number15
Early online date2 Aug 2023
DOIs
Publication statusPublished - 16 Aug 2023

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