Title: The missing SST pattern effect on central US climate trends
Abstract:
The central US has warmed only moderately since the beginning of the satellite era, but it is unclear whether historical trends are likely to continue in the coming decades. We use ensembles of atmospheric and coupled general circulation models to analyze drivers of historical climate change in the central US from 1979-2014. We find that SST trends play a key role in shaping the distribution of modeled temperature trends. In particular, the observed pattern of SST change, characterized by cooling in the tropical Pacific, causes shifts in large-scale atmospheric circulation which reduce springtime precipitation, decrease surface moisture, and increase sensible heating in the central US. While the resulting "bullseye'' pattern of elevated warming over the central US is robust across AGCMs, the central US has warmed much less quickly in observations. Our simulations suggest that this apparent discrepancy may largely be explained by atmospheric internal variability, of which history resembles an unlikely manifestation, with less drying and weaker warming than expected given observed SSTs. In the future, temperature trajectories may not follow these moderate historical trends. Faithfully representing the processes that govern remote SST patterns and local land-atmosphere interactions—a challenge in the current generation of CMIP6 models—will be crucial for making well-informed projections of future climate in the central US under greenhouse warming.
