简介：WesternChinaexperiencedanextremehotsummerin2015,breakinganumberoftemperaturerecords.Thesummermeansurfaceairtemperature(SAT)anomalywastwicetheinterannualvariability.Thehottestdaytimetemperature(TXx)andwarmestnight-timetemperature(TNx)werethehighestinChinasince1964.Thisextremehotsummeroccurredinthecontextofsteadilyincreasingtemperaturesinrecentdecades.Wecarriedoutasetofexperimentstoevaluatetheextenttowhichthechangesinseasurfacetemperature(SST)/seaiceextent(SIE)andanthropogenicforcingdrovetheseverityoftheextremesummerof2015inwesternChina.Ourresultsindicatethatabout65%-72%oftheobservedchangesintheseasonalmeanSATandthedailymaximum(Tmax)anddailyminimum(Tmin)temperaturesoverwesternChinaresultedfromchangesinboundaryforcings,includingtheSST/SIEandanthropogenicforcing.Fortherelativeroleofindividualforcing,thedirectimpactofchangesinanthropogenicforcingexplainabout42%oftheSATwarmingand60%(40%)oftheincreaseinTNxandTmin(TXxandTmax)inthemodelresponse.ThechangesinSST/SIEcontributedtotheremainingsurfacewarmingandtheincreaseinhotextremes,whicharemainlytheresultofchangesintheSSToverthePacificOcean,whereasuperElNi?oeventoccurred.OurstudyindicatesaprominentroleforthedirectimpactofanthropogenicforcingintheseverityoftheextremehotsummerinwesternChinain2015,althoughthechangesinSST/SIE,aswellastheinternalvariabilityoftheatmosphere,alsomadeacontribution.