Extratropical shortwave cloud feedbacks in the context of the global circulation and hydrological cycle | CU Experts

Shortwave (SW) cloud feedback (SWFB) is the primary driver of; uncertainty in the effective climate sensitivity (ECS) predicted by; global climate models (GCMs). ECS for several GCMs in the Sixth Coupled; Model Intercomparison Project (CMIP6) exceed 5K, above the fifth; assessment report (AR5) ‘likely’ maximum (4.5K) due to extratropical; SWFB’s that are more positive than those simulated in previous; generation CMIP5 GCMs. Here we show that across 57 GCMs Southern Ocean; SW_FB; can be predicted from the sensitivity of column-integrated; liquid water mass (LWP) to moisture convergence and to surface; temperature. The response of LWP to moisture convergence and the; response of albedo to LWP anti-correlate across GCMs. This is because; GCMs that simulate a larger response of LWP to moisture convergence tend; to have higher mean-state LWPs, which reduces the impact of additional; LWP on albedo. Observational constraints suggest a modestly negative; Southern Ocean SWFB— inconsistent with extreme ECS.

McCoy DT; Field PR; Frazer M; Zelinka MD; Elsaesser G; Mülmenstädt J; Tan I; Myers TA; Lebo ZJ

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