英语高级视听-听力原文-Unit-5-The-global-warning

Unit5TheglobalwarningTheNorthPolehasbeenfrozenfor100,000years.Butaccordingtoscientists,thatwon'tbetruebytheendofthiscentury.Thetopoftheworldismelting.There'sbeenadebateburningforyearsaboutthecausesofglobalwarming.Butthescientistsyou'reabouttomeetsaythedebateisover.Newevidenceshowsmaniscontributingtothewarmingoftheplanet,pumpingoutgreenhousegasesthattrapsolarheat.MuchofthisnewevidencewascompiledbyAmericanscientistBobCorell,wholedastudycalledtheArcticClimateImpactAssessment.It'sanawkwardname—butconsiderthefindings:theseasarerising,hurricaneswillbemorepowerful,likeKatrina,andpolarbearsmaybeheadedtowardextinction.Whatdoesthemeltingarcticlooklike?CorrespondentScottPelleywentnorthtoseewhatBobCorellcallsaglobalwarning.Towersoficetheheightof10-storybuildingsriseonthecoastofGreenland.It'sthebiggesticesheetintheNorthernHemisphere,measuringsome700,000squaremiles.Buttemperaturesinthearcticarerisingtwiceasfastastherestoftheworld,soalotofGreenland'siceisrunningtothesea.Rightnowtheentireplanetisoutofbalance,saysBobCorell,whoisamongtheworld'stopauthoritiesonclimatechange.Heled300scientistsfromeightnationsintheArcticClimateImpactAssessment.Corellbelieveshehasseenthefuture.Thisisabellwether,abarometer.Somepeoplecallitthecanaryinthemine.Thewarningthatthingsarecoming,hesays.In10yearshereinthearctic,weseewhattherestoftheplanetwillseein25or35yearsfromnow.Overthelastfewdecades,theNorthPolehasbeendramaticallyreducedinsizeandCorellsaystheglacierstherehavebeenrecedingforthelast50years.Backin1987,PresidentReaganaskedCorelltolookintoclimatechange.He'sbeenatiteversince.InIceland,heshowed60Minutesglaciersthatweregrowinguntilthe1990sandarenowmelting.Infact,98percentoftheworld'smountainglaciersaremelting.Corellsaysallthatwaterwillpushsealevelsthreefeethigherallaroundtheworldin100years.YouandIsithere,anotherfoot.Yourchildren,anotherfoot.Yourgrandchildren,anotherfoot.Anditwon'ttakelongforsealeveltoinundate,saysCorell.Sealevelwillbeinundatingthelowlandsofvirtuallyeverycountryoftheworld,oursincluded,Corellpredicts.Tofindthesightsandsoundsofthearcticmelting,therearefewplacesbetterthanafjordinGreenland,withaglacierjustashortdistanceaway.Pelleystoodonahugeblockoficethathadsplitofffromtheglacierandhaddroppedintothesea—abigiceberg.ThispartofGreenlandismeltingfasterthanjustaboutanyother.Togetasenseoftheenormityofwhat'shappening,considerthis:TheicethatismeltinghereistheequivalentofalltheiceintheAlps,Pelleyexplained,standingatoptheiceberg.That'smorethan105millionacresofmeltedicein15years.JustfourminutesafterPelleyclearedoffthisberg,partoftheicecavedin.60Minutesgotabird's-eyeviewofhowunstabletheiceisbecomingonaflightwithglaciologistCarlBoggild.Boggildanchored10researchstationstotheice.Buteverytimehecomestovisit,theiceandhisstationshavemoved.Flyingovertheice,Pelleynoticedlotsoffissuresandcrevicesbreakingthroughtheice.Askedwhatcausesthis,Boggildexplained,Thisisactuallytheiceflow,whereyouhavesomuchtensionintheicethatitcannotsticktogether.Anditbreaksandopensacrevicewhichgoesabout150,200feetdown.Theiceisalsomeltingonthesides,Boggildsays.Highoverhead,Pelleyremarkedthatonecouldhearthewaterrunning.It'slikeasmallriver,Boggildsaid.Aleadingtheorysaysthoselittleriverslubricatethebottomoftheicesheet,helpingitmoveoffthebedrockandouttosea.Andtheremaybenostoppingit.Arcticwarmingisaccelerating.It'sachainreaction.Assnowandicemelttheyrevealdarklandandwaterthatabsorbsolarheat.Thatmeltsmoresnowandice,andarounditgoes.There'slongbeenadebateabouthowmuchofthisisearth'snaturallychangingclimateandhowmuchisman'sdoing.PaulMayewski,attheUniversityofMaine,saystheanswertothatquestionisfrozeninsideanicecorefromGreenland.WithfundingfromtheNationalScienceFoundation,Mayewskihasled35expeditionscollectingdeepicecoresfromglaciers.Theicecaptureseverythingintheair,layingdownarecordcoveringhalfamillionyears.Wecangotoanysectionoftheicecore,totell,basically,whatthegreenhousegaslevelswere;wecantellwhetherornotitwasstormy,whatthetemperatureswerelike,Mayewskiexplains.60MinutesbroughtMayewskibacktoGreenland,wherehesayshisresearchhasproventhattheiceandtheatmospherehaveman'sfingerprintsalloverthem.Mayewskisayswehaven'tseenatemperaturerisetothislevelgoingbackatleast2,000years,andarguablyseveralthousandyears.Asforcarbondioxide(CO2)levels,Mayewskisays,wehaven'tseenCO2levelslikethisinhundredsofthousandsofyears,ifnotmillionsofyears.Whatdoesthattellhim?Itallpointstosomethingthathaschangedandsomethingthathasimpactedthesystemwhichwasn'tdoingitmorethan100yearsago.Andweknowexactlywhatitis.It'shumanactivity,hesays.It'sactivitylikeburningfossilfuels,releasingcarbondioxideandothergreenhousegases.TheU.S.isbyfarthelargestpolluter.Corellsaysthere'ssomuchgreenhousegasintheairalreadythatmoretemperatureriseisinevitable.Evenifwestoppedusingeverycar,truck,andpowerplant—stoppingallgreenhousegasemissions—Mayewskisaystheplanetwouldcontinuetowarmanyway.Wouldcontinuetowarmforanother,aboutanotherdegree,hesays.That'senoughtomelttheArctic—andifgreenhousegasescontinuetoincrease,thetemperaturewillriseevenmore.Theicethat'smeltingal