Sources of contrasting temperature extreme behavior during the recent global warming hiatus

Although the recent global warming hiatus has featured a pause in the annual, global mean surface air temperature (SAT) trend, both global mean and extreme SAT trends have exhibited pronounced seasonal variability. In particular, summertime land SAT hot extremes have increased steadily, whereas wintertime land SAT cold extremes also have increased, though slightly, during the hiatus. Recent studies suggest that both the annual and seasonal variability of the global mean SAT trend during the hiatus may take root in tropical Pacific sea surface temperature (SST) variability. In this study we examine the degree to which contrasting trends in SAT extremes during the hiatus also may be linked to tropical Pacific SST variability, in addition to other sources of internal climate variability and radiative forcing. For this purpose, we analyze SAT extremes data in observational and reanalysis datasets and two 10-member ensembles of a global coupled climate model (GFDL CM2.1), one that is free-running with historical radiative forcings and the other that is free-running except for the restoration of tropical eastern Pacific SSTs to observed values. Preliminary results suggest that contrasting behavior in extreme SAT trends may be attributed, in part, to tropical Pacific variability over some regions, although other sources of internal climate variability also are important.