DOI: 10.1126/science.1117368 , 657 (2005); 310Science et al.F. S. Chapin, III,WarmingRole of Land-Surface Changes in Arctic SummerThis copy is for your personal, non-commercial use only.. clicking herecolleagues, clients, or customers by , you can order high-quality copies for yourIf you wish to distribute this article to others. herefollowing the guidelines can be obtained byPermission to republish or repurpose articles or portions of articles (this information is current as of September 30, 2010 ):The following resources related to this article are available online at www.sciencemag.org http://www.sciencemag.org/cgi/content/full/310/5748/657version of this article at: including high-resolution figures, can be found in the onlineUpdated information and services, http://www.sciencemag.org/cgi/content/full/1117368/DC1 can be found at: Supporting Online Materialfound at: can berelated to this articleA list of selected additional articles on the Science Web sites http://www.sciencemag.org/cgi/content/full/310/5748/657#related-content http://www.sciencemag.org/cgi/content/full/310/5748/657#otherarticles, 2 of which can be accessed for free: cites 29 articlesThis article 195 article(s) on the ISI Web of Science. cited byThis article has been http://www.sciencemag.org/cgi/content/full/310/5748/657#otherarticles 7 articles hosted by HighWire Press; see: cited byThis article has been http://www.sciencemag.org/cgi/collection/atmosAtmospheric Science : subject collectionsThis article appears in the following registered trademark of AAAS. is aScience2005 by the American Association for the Advancement of Science; all rights reserved. The title CopyrightAmerican Association for the Advancement of Science, 1200 New York Avenue NW, Washington, DC 20005. (print ISSN 0036-8075; online ISSN 1095-9203) is published weekly, except the last week in December, by theScience on September 30, 2010 www.sciencemag.orgDownloaded from28. D. Lizarralde, J. B. Gaherty, J. A. Collins, G. Hirth, S. D.Kim, Nature 432, 744 (2004).29. L. A. Coogan et al., Chem. Geol. 178, 1 (2001).30. A. Kvassnes, thesis, Woods Hole Oceanographic Institu-tion and Massachusetts Institute of Technology (2004).31. We thank G. Baines and D. Shillington for discussion;B. Ito for support; F. Mazdab and S. Swapp for sam-ple preparation; JAMSTEC, captain, crew, and scienceparty of MODE ‘98 and 2000; and F. Oberli, L. Coogan,and an anonymous reviewer for constructive reviews.This work was supported by NSF grant 0352054 toM.J.C. and B.E.J., NASA Space Grant and W.C. HayesFellowship to J.J.S., and NASA Space Grant to E.A.M.Supporting Online Materialwww.sciencemag.org/cgi/content/full/310/5748/654/DC1Materials and MethodsFigs. S1 to S4Tables S1 to S3References20 June 2005; accepted 23 September 200510.1126/science.1116349Role of Land-Surface Changes inArctic Summer WarmingF. S. Chapin III,1*M. Sturm,5M. C. Serreze,6J. P. McFadden,7J. R. Key,8A. H. Lloyd,9A. D. McGuire,2T. S. Rupp,3A. H. Lynch,10J. P. Schimel,11J. Beringer,10W. L. Chapman,12H. E. Epstein,13E. S. Euskirchen,1L. D. Hinzman,4G. Jia,14C.-L. Ping,15K. D. Tape,1C. D. C. Thompson,1D. A. Walker,1J. M. Welker16A major challenge in predicting Earth’s future climate state is to understandfeedbacks that alter greenhouse-gas forcing. Here we synthesize field datafrom arctic Alaska, showing that terrestrial changes in summer albedo contributesubstantially to recent high-latitude warming trends. Pronounced terrestrialsummer warming in arctic Alaska correlates with a lengthening of the snow-free season that has increased atmospheric heating locally by about 3 watts persquare meter per decade (similar in magnitude to the regional heating expectedover multiple decades from a doubling of atmospheric CO2). The continuationof current trends in shrub and tree expansion could further amplify this atmo-spheric heating by two to seven times.The Arctic provides a test bed to understandand evaluate the consequences of thresholdchanges in regional system dynamics. Over thepast several decades, the Arctic has warmedstrongly in winter (1). However, many Arcticthresholds relate to abrupt physical and eco-logical changes that occur near the freezingpoint of water. Paleoclimate evidence, whichis mostly indicative of summer conditions,shows that the Arctic in summer is nowwarmer than at any time in at least the past400 years (2). This warming should have alarge impact on the rates of water-dependentprocesses. We assembled a wide range ofindependent data sets (surface temperaturerecords, satellite-based estimates of cloud cov-er and energy exchange, ground-based mea-surements of albedo and energy exchange, andfield observations of changes in snow coverand vegetation) to estimate recent and po-tential future changes in atmospheric heat-ing in arctic Alaska. We argue that recentchanges in the length of the snow-free sea-son have triggered a set of interlinked feed-backs that will amplify future rates of summerwarming.Summer warming in arctic Alaska andwestern Canada has accelerated from about0.15- to 0.17-C decade–1(1961–1990 and1966–1995) (1, 3) to about 0.3- to 0.4-Cdecade–1(1961–2004; Fig. 1). There has alsobeen a shift from summer cooling to warm-ing in Greenland and Scandinavia, more pro-nounced warming in Siberia, and continuedsummer warming in the European RussianArctic.The pronounced summer warming in Alas-ka cannot be readily understood from changesin atmospheric circulation, sea ice, or cloudcover. Changes in the North Atlantic Oscil-lation and Arctic Oscillation are linked towinter warming over Eurasia. Variations inthe Pacific North American Teleconnection,Fig. 1. (A) Spatial pattern of high-latitude surface summer (June to August)warming (in -Cover44years,1961to2004)and(B) the temporal airtemperature anomaly (deviation from the long-term mean) in Alaska. Thespatial pattern of temperature increase was estimated from monthlyanomalies of surface air temperature from land and sea stations throughoutthe Northern Hemisphere (42), updated from Chapman and Walsh (3). Thetemporal pattern of temperature is specifically for the Alaskan domain from1930 to 2004.R EPORTSwww.sciencemag.org SCIENCE VOL 310 28 OCTOBER 2005657 on September 30, 2010 www.sciencemag.orgDownloaded fromthe Pacific Decadal Oscillation, and El NiDo–Southern Oscillation have strong impactson Alaskan winter temperatures, but theirinfluences on summer temperatures are com-paratively weak (4–6). There has been