Arctic warming driven by change in the tropics

Greenland and northeastern Canada experienced some of the most rapid warming of the late twentieth and early twenty-first centuries, with human-induced climate change usually assumed to be in play. Qinghua Ding et al. show that about half of the observed warming can be attributed to changes in sea surface temperature in the equatorial Pacific Ocean which in turn influence the large-scale atmospheric circulation that moves warm air from the tropics to Greenland and northeastern Canada. Further research will be needed to establish whether or not the Pacific changes themselves are a response to the effects of human activity on the climate system.