Revisiting Causal Links Between the Arctic and Midlatitudes

The question of the rapidly-warming Arctic’s influence on midlatitude atmospheric dynamics and weather has been of great interest to the atmospheric science community. As the Arctic has warmed faster than anywhere else on the globe, the question of its influence on lower latitudes is important but not fully understood. While some studies have stated that the Arctic is expected to strongly influence the middle latitudes, and in some cases is already doing so; others have expressed less certainty and pointed to the large internal variability of the midlatitude atmospheric dynamics. Here, we use employ a technique from causal theory, namely Granger causality, to revisit the hypothesis that Arctic amplification causes changes in the midlatitude atmospheric circulation and to re-examine the influence of Arctic warming in the context of midlatitude internal variability. With this approach we quantify the extent to which Arctic temperatures provide additional information for forecasting midlatitude weather and climate and compare this Arctic influence to the influence of other drivers/predictors of the midlatitude circulation.