UNIT-5-The-Villain-in-the-Atmosphere课文翻译大学英语二

UNIT5TheVillainintheAtmosphereThereisonegaspresentintheairwebreathethatisessentialtolife.Unfortunately,onecanhavetoomuchofagoodthingandthegrowthincarbondioxidethreatenstowarmupourplanettoadangerousextent.IsaacAsimovintroducesustothisvillainintheatmosphere,explaininghowitworksandwhatcanbedoneaboutit.Thevillainintheatmosphereiscarbondioxide.Itdoesnotseemtobeavillain.Itisnotverypoisonousanditispresentintheatmosphereinsosmallaquantity—only0.034percent—thatitdoesusnoharm.What’smore,thatsmallquantityofcarbondioxideintheairisessentialtolife.Plantsabsorbcarbondioxideandconvertitintotheirowntissue,whichserveasthebasicfoodsupplyforallofanimallife(includinghumanbeings,ofcourse).Intheprocesstheyliberateoxygen,whichisalsonecessaryforallanimallife.Buthereiswhatthisapparentlyharmlessandcertainlyessentialgasisdoingtous:Thesealevelisrisingveryslowlyfromyeartoyear.Inalllikelihood,itwillcontinuetoriseanddosoatagreaterrateinthecourseofthenexthundredyears.Wheretherearelow-lyingcoastalareas(wherealargefractionoftheworld’spopulationlives)thewaterwilladvancesteadily,forcingpeopletoretreatinland.Eventuallytheseawillreachtwohundredfeetaboveitspresentlevel,andwillbesplashingagainstthewindowsalongthetwentiethfloorsofManhattan’sskyscrapers.Floridawilldisappearbeneaththewaves,aswillmuchoftheBritishIsles,thecrowdedNilevalley,andthelow-lyingareasofChina,India,andRussia.Notonlywillmanycitiesbedrowned,butmuchofthemostproductivefarmingareasoftheworldwillbelost.Asthefoodsupplydrops,starvationwillbewidespreadandthestructureofsocietymaycollapseunderthepressure.Andallbecauseofcarbondioxide.Buthowdoesthatcomeabout?Whatistheconnection?Itbeginswithsunlight,towhichthevariousgasesoftheatmosphere(includingcarbondioxide)aretransparent.Sunlight,strikingthetopoftheatmosphere,travelsrightthroughmilesofittowarmtheEarth’ssurface.Atnight,theEarthcoolsbyradiatingheatintospaceintheformofinfraredradiation.However,theatmosphereisnotquiteastransparenttoinfraredradiationasitistovisiblelight.Carbondioxideinparticulartendstoblocksuchradiation.Lessheatislostatnight,forthatreason,thanwouldbelostifcarbondioxidewerenotpresentintheatmosphere.Withoutthesmallquantityofthatgaspresent,theEarthwouldbedistinctlycooler,perhapsuncomfortablycool.Wecanbethankfulthatcarbondioxideiskeepinguscomfortablywarm,buttheconcentrationofcarbondioxideintheatmosphereisgoingupsteadilyandthatiswherethevillainycomesin.In1958,carbondioxidemadeuponly0.0316percentoftheatmosphere.Eachyearsince,theconcentrationhascreptupwardanditnowstandsat0.0340percent.Itisestimatedthatby2020theconcentrationwillbenearlytwicewhatitisnow.Thismeansthatinthecomingdecades,Earth’saveragetemperaturewillgoupslightly.Asaresult,thepolaricecapswillbegintomelt.Somethinglike90percentoftheiceintheworldistobefoundinthehugeAntarcticaicecap,andanother8percentisintheGreenlandicecap.Iftheseicecapsbegintomelt,thesealevelwillrise,withtheresultthatIhavealreadydescribed.Butwhyistheconcentrationofcarbondioxideintheatmospheresteadilyrising?Toblamearetwofactors.Firstofall,inthelastfewcenturies,firstcoal,thenoilandnaturalgas,havebeenburnedforenergyatarapidlyincreasingrate.Thecarboncontainedinthesefuels,whichhasbeensafelyburiedundergroundformanymillionsofyears,isnowbeingburnedtocarbondioxideandpouredintotheatmosphereatarateofmanytonsperday.Tomakemattersworse,Earth’sforestshavebeendisappearing,slowlyatfirst,butinthelastcoupleofcenturiesquiterapidly.Rightnowitisdisappearingattherateofsixty-fouracresperminute.Whateverreplacestheforest—grasslandorfarmsorscrub—producesplantsthatdonotconsumecarbondioxideatanequalrate.Thus,notonlyismorecarbondioxidebeingaddedtotheatmospherethroughburningoffuel,butastheforestsdisappear,lesscarbondioxideisbeingremovedfromtheatmospherebyplants.Butthisgivesusanewperspectiveonthematter.Thecarbondioxideisnotrisingbyitself.Itispeoplewhoareburningthecoal,oil,andgas.Itispeoplewhoarecuttingdowntheforests.Itispeople,then,whoarethevillains.Whatistobedone?First,wemustsaveourforests,andevenreplantthem.Second,wemusthavenewsourcesoffuelthatdonotinvolvetheproductionofcarbondioxide.Nuclearpowerisoneofthem,butifthatisthoughttoodangerous,thereareotheralternatives.Thereistheenergyofwaves,tides,wind,andtheEarth’sinteriorheat.Mostofall,thereisthedirectuseofsolarenergy.Allofthiswilltaketime,work,andmoney,tobetrue,butnationsspendmoretime,work,andmoneyinordertosupportcompetingmilitarymachinesthatcanonlydestroyusall.Shouldweobjecttospendinglesstime,work,andmoneyinordertosaveusall?在我们呼吸的空气中，有一种气体对生命是必不可少的。遗憾的是，一样好东西我们可能会拥有得太多，而二氧化碳的增长威胁着我们，使地球变暖到一种危险的程度。艾萨克•阿西莫夫向我们介绍了大气层中的这个坏蛋，向我们解释了它是怎样活动的以及对付它的办法。大气层中的恶棍艾萨克•阿西莫夫大气层中的恶棍乃是二氧化碳。二氧化碳看上去不像一个恶棍。它毒性不大，在大气层中的含量极小——只占0.034％——不会对我们造成任何伤害。再者，空气中的那一点点二氧化碳对生命至关重要。植物吸收二氧化碳并将其转化成它们自己的组织，充当所有动物（当然也包括人类）的基本食物供给。在这一过程中，植物释放氧气，而氧气又是所有动物生命所不可缺少的。然而，这一看上去无害而且无疑又必不可少的气体却正在对我们产生影响。年复一年，海平面正在慢慢上升。它很可能继续上升，而在今后数百年间，会以更快的速度上升。在那些低洼的沿海地区（在这些地区居住着世界上很大一部分人口），海水会稳步向前推进，迫使人们向内陆退居。最后，海水将会高出目前海平面两百英尺，一阵阵海浪将会拍打曼哈顿摩天大楼二十层楼的窗户。佛罗里达将会沉没在海浪之下，英伦三岛的大部分，人口稠密的尼罗河流域，还有中国、印度和俄罗斯的低洼地区也都将遭到同样的命运。不仅许多城市将被淹没，而且世界上大部分盛产粮食的地区也将会失去。由于食品供应下降，到