title: Recent temperature extremes at high northern latitudes unprecedented in the past 600 years.
abstract: Recently observed extreme temperatures at high northern latitudes are rare by definition, making the longer time span afforded by climate proxies important for assessing how the frequency of such extremes may be changing. Previous reconstructions of past temperature variability have demonstrated that recent warmth is anomalous relative to preceding centuries or millennia, but extreme events can be more thoroughly evaluated using a spatially resolved approach that provides an ensemble of possible temperature histories. Here, using a hierarchical Bayesian analysis of instrumental, tree-ring, ice-core and lake-sediment records, we show that the magnitude and frequency of recent warm temperature extremes at high northern latitudes are unprecedented in the past 600 years. The summers of 2005, 2007, 2010 and 2011 were warmer than those of all prior years back to 1400 (probability P > 0.95), in terms of the spatial average. The summer of 2010 was the warmest in the previous 600 years in western Russia (P > 0.99) and probably the warmest in western Greenland and the Canadian Arctic as well (P > 0.90). These and other recent extremes greatly exceed those expected from a stationary climate, but can be understood as resulting from constant space-time variability about an increased mean temperature.
authors.affiliation: Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, Massachusetts 02138, USA. tingley@fas.harvard.edu
authors.forename: Martin P
authors.initials: MP
authors.lastname: Tingley
authors.forename: Peter
authors.initials: P
authors.lastname: Huybers
mesh_terms: D000704:Analysis of Variance; D001110:Arctic Regions; D001499:Bayes Theorem; D002170:Canada; D055873:Extreme Cold; D055874:Extreme Heat; D062305:Geographic Mapping; D005843:Geography; D057232:Global Warming / Q000266:history* / Q000706:statistics & numerical data*; D006116:Greenland; D049668:History, 15th Century; D049669:History, 16th Century; D049670:History, 17th Century; D049671:History, 18th Century; D049672:History, 19th Century; D049673:History, 20th Century; D049674:History, 21st Century; D012426:Russia; D012621:Seasons; D013997:Time Factors