托福阅读材料.doc

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1、ThePlanetEarthThe2000AntarcticOzoneHoleWasLargestEverThe2000AntarcticOzoneHolewasthelargesteverobserved.Earthswetterupperatmospheremaydelayglobalozonerecovery.NASAresearchershavefoundthatanincreaseinwatervaporinthestratosphere,stemmingpartiallyfromgreenhousegases,maydelayozonereco

2、veryandincreasetherateofclimatechange.Tocheckonthelong-termstratosphericcoolingandozonedepletion,NASAputdatafromsatellitesandotherremotesensorsintoitsGISSglobalclimatemodel.Itwasthefirststudytolinkgreenhousegasestoincreasedozonedepletionoverpopulatedareas.Waterandozone.Climatemode

3、lsshowcoolerstratospherictemperatureshappenwhenthereismorewatervaporpresent.Watervaporalsoleadstothebreakdownofozonemolecules.Thestratosphereisthedrylayeroftheatmosphereabovethetroposphere,wheretemperaturesincreasewithheight.Accordingtosatellitedata,upperatmospherictemperaturesaro

4、undtheworld-ataltitudesof20to35mileshigh--havecooledbetween5.4and10.8degreesFahrenheitoverrecentdecades.Drivingforces.NASAfoundtwodrivingforcesbehindthechangeinstratosphericmoisture:Increasedemissionsofthegreenhousegasmethanearetransformedintowaterinthestratosphere,accountingforab

5、outathirdoftheobservedincreaseinmoisturethere.Morewateristransportedfromtheloweratmosphere.Warmerairholdsmorewatervaporthancolderair,sotheamountofwatervaporintheloweratmosphereincreasesasitiswarmedbythegreenhouseeffect.Greenhousegases,suchascarbondioxideandmethane,mayenhancethetra

6、nsportofwaterintothestratosphere.Theincreasedtransportofwatervaportothestratosphereseemslikelytohavebeeninducedbyhumanactivities.Ozonedestruction.Risinggreenhousegasemissionsaccountforallorpartofthewatervaporincrease,whichcausesstratosphericozonedestruction.Whenmorewatervaporworks

7、itswayintothestratosphere,thewatermoleculescanbebrokendown,releasingreactivemoleculesthatcandestroyozone.Ifthetrendofincreasingstratosphericwatervaporcontinues,itcouldincreasefutureglobalwarmingandimpedeozonestratosphericrecovery.Theimpactonglobalwarmingcomesaboutbecausebothwaterv

8、aporandozonearegreenhousegases,wh