title: Arctic warming aloft is data set dependent.
abstract: Arctic sea ice and snow on land have retreated polewards at an alarming pace in the past few decades. Such retreat locally amplifies surface warming through a positive feedback, which causes the Arctic surface to warm faster than the rest of the globe. In contrast, ice and snow retreat causes little warming in the atmosphere above when the stable winter atmosphere inhibits vertical heat exchange. We therefore find surprising the recent report by Graversen et al. in which they claim that recent Arctic atmospheric warming extends far deeper into the atmosphere than expected, and can even exceed the surface warming during the polar night. Using a different data set, we show that there is much less warming aloft in winter, consistent with the recent retreat of ice and snow, as well as recent changes in atmospheric heat transport.
authors.affiliation: Atmospheric Science Department, 408 Atmospheric Sciences and Geophysics Hall, University of Washington, Seattle, Washington 98195, USA. bitz@atmos.washington.edu
authors.forename: Cecilia M
authors.initials: CM
authors.lastname: Bitz
authors.forename: Qiang
authors.initials: Q
authors.lastname: Fu