Eurasian winter cooling in the warming hiatus of 1998-2012

Abstract

We investigate the relative magnitudes of the contributions of surface temperature trends from different latitude bands to the recent warming hiatus. We confirm from five different global data sets that the global-mean surface temperature trend in the period 1998-2012 is strongly influenced by a pronounced Eurasian winter cooling trend. To understand the drivers of this winter cooling trend, we perform three 20-member ensembles of simulations with different prescribed sea surface temperature and sea ice in the atmospheric model ECHAM6. Our experimental results suggest that the Arctic sea ice loss does not drive systematic changes in the Northern Hemisphere large-scale circulation in the past decades. The observed Eurasian winter cooling trend over 1998-2012 arises essentially from atmospheric internal variability and constitutes an extreme climate event. However, the observed reduction in Arctic sea ice enhances the variability of Eurasian winter climate and thus increases the probability of an extreme Eurasian winter cooling trend. Key Points The recent warming hiatus is strongly influenced by a pronounced Eurasian winter cooling trend The observed Eurasian winter cooling trend over 1998-2012 arises from internal variability The dramatic change in Arctic sea ice enhances the Eurasian winter climate variability