The Arctic has warmed significantly more than global mean surface air temperature over recent decades, as expected from amplification mechanisms. Previous studies have attributed the observed Arctic warming to the combined effect of greenhouse gases and other anthropogenic influences. However, given the sensitivity of the Arctic to external forcing and the intense interest in the effects of aerosols on its climate, it is important to examine and quantify the effects of individual groups of anthropogenic forcing agents.

Recent observed global warming is significantly less than that simulated by climate models. This difference might be explained by some combination of errors in external forcing, model response and internal climate variability.

limate sensitivity models may inaccurately characterize the full Earth system response, as they ignore changes in the carbon cycle, aerosols, land use and land cover.

The polar regions have long been expected to warm strongly as a result of anthropogenic climate change, because of the positive feedbacks associated with melting ice and snow. Several studies have noted a rise in Arctic temperatures over recent decades but have not formally attributed the changes to human influence, owing to sparse observations and large natural variability.