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1、Focusonglobalwarming Twenty-fiveyearsagoifyoumadeatriptothelocallibraryandperusedtheperiodicalsectionforarticlesonglobalwarming,you'dprobablyhavecomeupwithonlyafewabstractsfromhardcoresciencejournalsormaybeablurbinsomeesotericgeopoliticalmagazine.AsanInternetsearchong
2、lobalwarmingnowattests,thesubjecthasbecomeasrootedinourpublicconsciousnessasMadonnaormicrowavecooking. Perhapsallthisattentionisdeserved.Withthepossibleexceptionofanotherworldwar,agiantasteroid,oranincurableplague,globalwarmingmaybethesinglelargestthreattoourplanet.Fo
3、rdecadeshumanfactoriesandcarshavespewedbillionsoftonsofgreenhousegasesintotheatmosphere,andtheclimatehasbeguntoshowsomesignsofwarming.Manyseethisasaharbingerofwhatistocome.Ifwedon'tcurbourgreenhousegasemissions,thenlow-lyingnationscouldbeawashinseawater,rainanddroughtp
4、atternsacrosstheworldcouldchange,hurricanescouldbecomemorefrequent,andElNinoscouldbecomemoreintense.OurWarmingPlanet Whathasworriedmanypeoplenowisthatoverthepast250yearshumanshavebeenartificiallyraisingtheconcentrationofgreenhousegasesintheatmosphere.Ourfactories,po
5、werplants,andcarsburncoalandgasolineandspitoutaseeminglyendlessstreamofcarbondioxide.Weproducemillionsofpoundsofmethanebyallowingourtrashtodecomposeinlandfillsandbybreedinglargeherdsofmethane-belchingcattle.Nitrogen-basedfertilizers,whichweuseonnearlyallourcrops,releas
6、eunnaturalamountsofnitrogenoxideintotheatmosphere. Oncethesecarbon-basedgreenhousegasesgetintotheatmosphere,theystaytherefordecadesorlonger.AccordingtotheIntergovernmentalPanelonClimateChange(IPCC),sincetheindustrialrevolution,carbondioxidelevelshaveincreased31percent
7、andmethanelevelshaveincreased151percent.Paleoclimatereadingstakenfromfossilrecordsshowthatthesegases,twoofthemostabundantgreenhousegases,areattheirhighestlevelsinthepast420,000years.Manyscientistsfearthattheincreasedconcentrationsofgreenhousegaseshavepreventedadditiona
8、lthermalradiationfromleavingtheEarth.Inessence,thesegasesaretrappingexcessheatintheEarth'satmosphereinmuchthesamewayt
