The Crucial Role of Sea Surface Temperature Warming Patterns in Future Projections of Extreme Weather, Climate, and Hydrological Sensitivity

Recent studies indicate that virtually all global climate models (GCMs) have difficulty simulating historical sea surface temperature (SST) warming patterns over the past four decades. GCMs tend to produce enhanced warming in the eastern equatorial Pacific and the Southern Ocean warming while the observations show intensified warming in the Indo-Pacific Warm Pool and slight cooling in the eastern equatorial Pacific and Southern Ocean. The cause of this model-observation difference is still unclear and under debate. Using Geophysical Fluid Dynamics Laboratory's latest higher resolution global atmospheric model AM4 and the seasonal to decadal prediction system SPEAR, we show that this model-observation difference in SST change patterns is significant even considering modeled internal variability , and could have a profound implications for near-term projections of extreme weather such as the frequency of atmospheric rivers (AR), tropical storms (TS) and mesoscale convection systems (MCS), as well as climate feedbacks that strongly affect modeled climate sensitivity. If the future SST warming pattern continues to resemble the observed pattern from the past few decades rather than the simulated/predicted patterns by climate models, our results suggest 1) a drastically different future prediction of extreme weather and associated hydroclimate changes over the Western Hemisphere, 2) substantially less global mean warming due to stronger negative feedback and lower climate sensitivity, and 3) a stronger global hydrological sensitivity to warming. Therefore, it is imperative to understand the causes of model biases in multidecadal SST warming patterns before more confident projections of future climate can be made.