Evaluating Impacts of Recent Arctic Sea Ice Loss on the Northern Hemisphere Winter Climate Change

Understanding the mechanism governing the ongoing global warming is a major challenge facing our society and its sustainable growth. Together with the CO2-forced warming, the concurrent polar sea ice loss might also have contributed to the observed Arctic warming amplification and also to the cooling trends over Eurasia through a dynamical teleconnection. However, previous individual modeling studies suggest widely different findings on the role of sea ice loss in Northern Hemisphere climate change. To help resolve this controversy, we used satellite-derived sea ice and sea-surface temperature to run coordinated hindcast experiments with five different atmospheric general circulation models. The multimodel ensemble-mean results presented in the paper reduce biases of each model and eliminate atmospheric internal unforced variability, and thus provide the best estimate to date of the signal of the polar sea ice loss. The results suggest that the impact of sea ice seems critical for the Arctic surface temperature changes, but the temperature trends elsewhere seem rather due to either sea-surface temperature changes or atmospheric internal variability. They give clear guidance on how to provide society with more accurate climate change attributions. Our work is of interest to stakeholders of countries in the Northern Hemisphere middle and high latitudes