Abstract
Tropical marine low cloud feedback is key to the uncertainty in climate sensitivity, and it depends on the warming pattern of sea surface temperatures (SSTs). Here, we empirically constrain this feedback in two major low cloud regions, the tropical Pacific and Atlantic, using interannual variability. Low cloud sensitivities to local SST and to remote SST, represented by lower-troposphere temperature, are poorly captured in many models of the latest global climate model ensemble, especially in the less-studied tropical Atlantic. The Atlantic favors large positive cloud feedback that appears difficult to reconcile with the Pacific-we apply a Pareto optimization approach to elucidate trade-offs between the conflicting observational constraints. Examining ~200,000 possible combinations of model subensembles, this multi-objective observational constraint narrows the cloud feedback uncertainty among climate models, nearly eliminates the possibility of a negative tropical shortwave cloud feedback in CO(2)-induced warming, and suggests a 71% increase in the tropical shortwave cloud feedback.