Leveraging CFMIP experiments to evaluate clouds in CESM2

Monday, December 9, 2019 - 11:20
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The Community Earth System Model, Version 2 (CESM2) has a high equilibrium climate sensitivity: estimated at 5.3K based on abrupt quadrupling of carbon dioxide and corroborated with complementary experiments. We review these results and show that much of this sensitivity derives from a strong positive cloud feedback associated with reduced subtropical cloud cover. The suite of Cloud-Feedback Model Intercomparison Project (CFMIP) simulations are used to explore whether this high sensitivity and strong cloud response depend on model configuration and type of forcing. Many of the CFMIP simulations include diagnostics from the satellite simulator package (COSP), allowing comparison with a variety of satellite products. These comparisons with observed clouds provide means for identifying significant model errors in representing clouds. We target a number of cloud regimes in an attempt to determine whether the cloud feedbacks that lead to high climate sensitivity are associated with errors in the baseline climate.

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