Model evidence for low‐level cloud feedback driving persistent changes in atmospheric circulation and regional hydroclimate

Recent studies suggest that low clouds in the Pacific play an important role in the observed decadal climate variability and future climate change. In this study, we implement a novel modeling experiment designed to isolate how interactions between local and remote feedbacks associated with low cloud, SSTs, and the large‐scale circulation play a significant role in the observed persistence of tropical Pacific SST and associated North American drought. The modeling approach involves the incorporation of observed patterns of satellite‐derived shortwave cloud radiative effect (SWCRE) into the coupled model framework and is ideally suited for examining the role of local and large‐scale coupled feedbacks and ocean heat transport in Pacific decadal variability. We show that changes in SWCRE forcing in eastern subtropical Pacific alone reproduces much of the observed changes in SST and atmospheric circulation over the past 16 years, including the observed changes in precipitation over much of the Western Hemisphere. Plain Language Summary The role of clouds in climate variability and change remains a major question in the scientific community. Clouds play an important role in the modulation of Earth's climate because they are very effective at reflecting incoming solar radiation and absorbing and emitting Earth's infrared radiation. Unfortunately, the accurate simulation of clouds and their effects on radiation (particularly low clouds that have a net cooling effect on the planet) remains one of the greatest challenges to climate modelers who want to predict climate variations on decadal to centennial timescales. This study examines the influence of low clouds (e.g. marine stratocumulus) located in the eastern Pacific on the global climate system using a novel coupled modeling strategy. Results show that when satellite estimates of low cloud, isolated to the eastern Pacific, are prescribed as an added forcing in the coupled model, much of the recent changes in the Pacific ocean and atmospheric circulation can be reproduced. Of particular interest is the simulation of persistent drought conditions over North America observed during the recent slowdown in global warming. The study examines positive feedbacks between low clouds in the eastern Pacific and the large‐scale ocean and atmospheric circulations that may play a central role in improved climate prediction. Key Points Local and remote feedbacks between low clouds, SST, and large‐scale circulation sustain PDV