Mark C. Serreze

TL;DR: In this paper, the authors present asynthesis of these observations, and conclude that roughly half of the pronounced recent rise in Northern Hemispherewinter temperatures reflects shifts in atmosphericcirculation. But, such changes are not consistent with anthropogenic forcing and include generally positive phases of the North Atlantic and ArcticOscillations and extratropical responses to the El-NinoSouthern Oscillation.

TL;DR: The past decade has seen substantial advances in understanding Arctic amplification, that trends and variability in surface air temperature tend to be larger in the Arctic region than for the Northern Hemisphere or globe as a whole as discussed by the authors.

TL;DR: In this paper, a multi-model ensemble mean time series provides a true representation of forced change by greenhouse gas (GHG) loading, 33-38% of the observed September trend from 1953-2006 is externally forced, growing to 47-57% from 1979-2006.

TL;DR: The sequence of extreme September sea ice extent minima over the past decade suggests acceleration in the response of the Arctic sea ice cover to external forcing, hastening the ongoing transition towards a seasonally open Arctic Ocean.

TL;DR: It is shown that terrestrial changes in summer albedo contribute substantially to recent high-latitude warming trends and the continuation of current trends in shrub and tree expansion could further amplify this atmospheric heating by two to seven times.