The Recent Emergence of Arctic Amplification

Abstract

Arctic Amplification is robustly seen in climate model simulations of future warming and in the paleoclimate record. Here, we focus on the past century of observations. We show that Arctic Amplification is only a recent phenomenon, and that for much of this period the Arctic cooled while the global-mean temperature rose. To investigate why this occurred, we analyze large ensembles of comprehensive climate model simulations under different forcing scenarios. Our results suggest that the global warming from greenhouse gases was largely offset in the Arctic by regional cooling due to aerosols, with internal climate variability also contributing to Arctic cooling and global warming trends during this period. This suggests that the disruption of Arctic Amplification was due to a combination of factors unique to the 20th century, and that enhanced Arctic warming should be expected to be a consistent feature of climate change over the coming century.

Plain Language Summary

Arctic Amplification is the phenomenon by which the Arctic warms at a faster rate than the global average. Evidence for the occurrence of Arctic Amplification is widely found in climate model simulations as well as in paleo proxy reconstructions of past climate changes. In this study, we investigate the extent to which Arctic Amplification has occurred in observations from the past century. We show that Arctic Amplification is only a recent phenomenon, and that for much of the 20th century, the Arctic cooled while the global-mean temperature rose. We investigate why this happened using a range of climate model simulations, and we find that there were two main causes for these opposing trends. The first is that regional cooling from aerosols counteracted the warming from greenhouse gases in the Arctic. However, this cannot fully explain the observed trends. The second is that natural fluctuations of the climate system manifested in a pattern of Arctic cooling under global warming. This suggests that the disruption of Arctic Amplification was due to a combination of factors unique to the 20th century, implying that enhanced Arctic warming should be expected to be a consistent feature of climate change over the coming century.