Attribution of Arctic temperature change to greenhouse-gas and aerosol influences

The Arctic has warmed significantly more than global mean surface air temperature over recent decades(1), as expected from amplification mechanisms(2,3). Previous studies have attributed the observed Arctic warming to the combined effect of greenhouse gases and other anthropogenic influences(4). However, given the sensitivity of the Arctic to external forcing and the intense interest in the effects of aerosols on its climate(5,6), it is important to examine and quantify the effects of individual groups of anthropogenic forcing agents. Here we quantify the separate contributions to observed Arctic land temperature change from greenhouse gases, other anthropogenic forcing agents (which are dominated by aerosols) and natural forcing agents. We show that although increases in greenhouse-gas concentrations have driven the observed warming over the past century, approximately 60% of the greenhouse-gas-induced warming has been offset by the combined response to other anthropogenic forcings, which is substantially greater than the fraction of global greenhouse-gas-induced warming that has been offset by these forcings(7,8). The climate models considered on average simulate the amplitude of response to anthropogenic forcings well, increasing confidence in their projections of profound future Arctic climate change.