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1、Unit8FocusonGlobalWarmingJohnWeierTwenty-fiveyearsagoifyoumadeatriptothelocallibraryandperusedtheperiodicalsectionforarticlesonglobalwarming,you’dprobablyhavecomeupwithonlyafewabstractsfromhardcoresciencejournalsormaybeablurbinsomeesotericgeopoliticalmagazine.AsanInternet
2、searchonglobalwarmingnowattests,thesubjecthasbecomeasrootedinourpublicconsciousnessasMadonna2ormicrowavecooking.1Perhapsallthisattentionisdeserved.Withthepossibleexceptionofanotherworldwar,giantasteroid,oranincurableplague,globalwarmingmaybethesinglelargestthreattoourplan
3、et.2Fordecadeshumanfactoriesandcarshavespewedbillionsoftonsofgreenhousegasesintotheatmosphere,andtheclimatehasbeguntoshowsomesignsofwarming.Manyseethisasaharbingerofwhatistocome.3Ifwedon’tcurbourgreenhousegasemissions,thenlow-lyingnationscouldbeawashinseawater,rainanddrou
4、ghtpatternsacrosstheworldcouldchange,hurricanescouldbecomemorefrequent,andElNinoscouldbecomemoreintense.OurWarmingPlanetWhathasworriedmanypeoplenowisthatoverthepast250yearshumanshavebeenartificiallyraisingtheconcentrationofgreenhousegasesintheatmosphere.Ourfactories,power
5、plants,andcarsburncoalandgasolineandspitoutaseeminglyendlessstreamofcarbondioxide.Weproducemillionsofpoundsofmethanebyallowingourtrashtodecomposeinlandfillsandbybreedinglargeherdsofmethane-belchingcattle.Nitrogen-basedfertilizers,whichweuseonnearlyallourcrops,releaseunnat
6、uralamountsofnitrogenoxideintotheatmosphere.Oncethesecarbon-basedgreenhousegasesgetintotheatmosphere,theystaytherefordecadesorlonger.AccordingtotheIntergovernmentalPanelonClimateChange(IPCC)sincetheindustrialrevolution,carbondioxidelevelshaveincreased31percentandmethanele
7、velshaveincreased151percent.Paleoclimatereadingstakenfromfossilrecordsshowthatthesegases,twoofthemostabundantgreenhousegases,areattheirhighestlevelsinthepast420,000years.Manyscientistsfearthattheincreasedconcentrationsofgreenhousegaseshavepreventedadditionalthermalradiati
8、onfromleavingtheEarth.Inessence,thesegasesaretrappingexcessheatintheEarth’satmosphereinmuchthesa
