Detectable Human Influence on Reduced Day‐to‐Day Temperature Variability in the Cold Season Driven by Arctic Sea‐Ice Loss

ABSTRACT Climate models agree that a reduction of day‐to‐day temperature variability at mid‐to‐high latitudes during the cold season is a robust forced response to anthropogenic global warming. Although recent observations show a similar reduction, how much the observed change is forced and how much is internal variability is uncertain. Here, using large‐ensemble simulations and a Ridge Regression detection tool, we decompose the observed day‐to‐day temperature variability changes since 1950 into contributions of forced and internal components. Our findings show that the observed reduction since the mid‐1970s is dominated by a forced response (about 90%). Observations and models show consistent mechanisms responsible for this reduction in a warming world: the reduction is manifested as cold days warming faster than hot days, driven by Arctic sea‐ice loss and associated reduction in the latitudinal temperature gradient, but not by large‐scale atmospheric circulation changes. Overall, our study detects a robust influence of the Arctic changes on lower latitude day‐to‐day temperature variability, and suggests that this impact will continue in the coming decades.