英语 Unit 4 Global warming课件 新人教版选修6 课件VIP免费

Unit4GlobalwarmingRecordhighreadingsofCO2raiseconcern据测定，大气的二氧化碳浓度日均值于今年5月初达到了400ppm，这是人类历史上的最高纪录。OnThursday，May9th,2013，scientistsreportedthatworldwidelevelsofCO2，themainreasonbehindglobalwarminghadreached400partspermillion，amilestone(里程碑)neverreachedbyhumansbefore.AccordingtoPieterTans，aresearcherattheNationalOceanicandAtmosphericAdministration，thelasttimetheearthreachedthishighalevelofCO2wasabout2millionyearsago.Duringthistimetheearthwasmuchwarmer.Greenlandwasactuallygreen，consistingofforestinsteadoficeandthesealevelswereatleast33－66feethigher.Sohowimportantisthisnumberwhichhappenstobeadailyfigure？Itsimportanceistowarnusthatunlesssomethingextremeisdonesoontochangethistrend，thingscanonlygetworse.Thegoodnewsisthatthetrendcanbechanged，becausetheincreaseinCO2whichisthebyproductoftheburningoffossilfuelslikecoalforelectricityandoilforpetrol，isadirectresultofhumanactivity.Accordingtoexperts，in2011wemanagedtoaddanaverageof2.4millionpoundsofCO2intotheaireverysecond.What’sconcerningscientistsmorethanthisunprecedented(空前的)milestoneof400partspermillion，istherapidpaceatwhichthegreenhousegasisincreasing.Theybelievethatplantsandanimalscanadapt(适应)whenclimatechangesoccurslowlyoverthousandsofyears，butnotifthechangescomewithinashortperiodoftime，whichiswhatishappeningnow.Whatisevenmorealarmingisthatiftheoceanswerenotabsorbingsomeofthegas，thelevelswouldbeevenhigher！Hopefully，theworldwilltrytochangethisrapidlyworseningsituation.谢谢观看！