The Shortwave Cloud-SST Feedback Amplifies Multi-Decadal Pacific Sea Surface Temperature Trends: Implications for Observed Cooling
Abstract
Climate models struggle to produce sea surface temperature (SST) gradient trends in the tropical Pacific comparable to those seen recently in nature. Here, we investigate whether models systematically underestimate internally-generated SST trends by underestimating cloud feedbacks on SST gradients. A heat-budget analysis reveals coupling between cloud-radiative effects, circulation, and SST gradients in driving multi-decadal variability in the Eastern Pacific and suggests that biases in cloud feedbacks may be causing models to underestimate internal SST variability. We find that the magnitude of the cloud-SST feedback in the subtropical Southeast Pacific is correlated across models with the magnitude of Eastern Pacific multi-decadal SST variability. Using this relationship and observed feedback estimates, we estimate that internal Eastern Pacific SST variability is under-predicted in most models. Adjusting for model bias increases the likelihood of generating a cooling trend at least as large as observations in preindustrial control simulations by between ~10% and ~58%.