翻译实习.docx

翻译实习.docx

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翻译实习

Climatechange

Climatechangeisasignificantandlastingchangeinthestatisticaldistributionofweatherpatternsoverperiodsrangingfromdecadestomillionsofyears.Itmaybeachangeinaverageweatherconditions,orinthedistributionofweatheraroundtheaverageconditions（i.e.,moreorfewerextremeweatherevents）.Climatechangeiscausedbyfactorsthatincludeoceanicprocesses（suchasoceaniccirculation）,variationsinsolarradiationreceivedbyEarth,platetectonicsandvolcaniceruptions,andhuman-inducedalterationsofthenaturalworld;theselattereffectsarecurrentlycausingglobalwarming,and"climatechange"isoftenusedtodescribehuman-specificimpacts.

Scientistsactivelyworktounderstandpastandfutureclimatebyusingobservationsandtheoreticalmodels.Boreholetemperatureprofiles,icecores,floralandfaunalrecords,glacialandperiglacialprocesses,stableisotopeandothersedimentanalyses,andsealevelrecordsservetoprovideaclimaterecordthatspansthegeologicpast.Morerecentdataareprovidedbytheinstrumentalrecord.Physically-basedgeneralcirculationmodelsareoftenusedintheoreticalapproachestomatchpastclimatedata,makefutureprojections,andlinkcausesandeffectsinclimatechange.

1.Terminology

Themostgeneraldefinitionofclimatechangeisachangeinthestatisticalpropertiesoftheclimatesystemwhenconsideredoverlongperiodsoftime,regardlessofcause.Accordingly,fluctuationsoverperiodsshorterthanafewdecades,suchasElNiño,donotrepresentclimatechange.

Thetermsometimesisusedtoreferspecificallytoclimatechangecausedbyhumanactivity,asopposedtochangesinclimatethatmayhaveresultedaspartofEarth'snaturalprocesses.Inthissense,especiallyinthecontextofenvironmentalpolicy,thetermclimatechangehasbecomesynonymouswithanthropogenicglobalwarming.Withinscientificjournals,globalwarmingreferstosurfacetemperatureincreaseswhileclimatechangeincludesglobalwarmingandeverythingelsethatincreasinggreenhousegaslevelswillaffect.

2.Causes

Onthebroadestscale,therateatwhichenergyisreceivedfromthesunandtherateatwhichitislosttospacedeterminetheequilibriumtemperatureandclimateofEarth.Thisenergyisdistributedaroundtheglobebywinds,oceancurrents,andothermechanismstoaffecttheclimatesofdifferentregions.

Factorsthatcanshapeclimatearecalledclimateforcingsor"forcingmechanisms".Theseincludeprocessessuchasvariationsinsolarradiation,deviationsintheEarth'sorbit,mountain-buildingandcontinentaldrift,andchangesingreenhousegasconcentrations.Thereareavarietyofclimatechangefeedbacksthatcaneitheramplifyordiminishtheinitialforcing.Somepartsoftheclimatesystem,suchastheoceansandicecaps,respondslowlyinreactiontoclimateforcings,whileothersrespondmorequickly.

Forcingmechanismscanbeeither"internal"or"external".Internalforcingmechanismsarenaturalprocesseswithintheclimatesystemitself（e.g.,thethermohalinecirculation）.Externalforcingmechanismscanbeeithernatural（e.g.,changesinsolaroutput）oranthropogenic（e.g.,increasedemissionsofgreenhousegases）.

Whethertheinitialforcingmechanismisinternalorexternal,theresponseoftheclimatesystemmightbefast（e.g.,asuddencoolingduetoairbornevolcanicashreflectingsunlight）,slow（e.g.thermalexpansionofwarmingoceanwater）,oracombination（e.g.,suddenlossofalbedointhearcticoceanasseaicemelts,followedbymoregradualthermalexpansionofthewater）.Therefore,theclimatesystemcanrespondabruptly,butthefullresponsetoforcingmechanismsmightnotbefullydevelopedforcenturiesorevenlonger.

2.1Internalforcingmechanisms

Naturalchangesinthecomponentsofearth'sclimatesystemandtheirinteractionsarethecauseofinternalclimatevariability,or"internalforcings."Scientistsgenerallydefinethefivecomponentsofearth'sclimatesystemtoincludeAtmosphere,hydrosphere,cryosphere,lithosphere（restrictedtothesurfacesoils,rocks,andsediments）,andbiosphere.

2.1.1Oceanvariability

Theoceanisafundamentalpartoftheclimatesystem,somechangesinitoccurringatlongertimescalesthanintheatmosphere,massinghundredsoftimesmoreandhavingveryhighthermalinertia（suchastheoceandepthsstilllaggingtodayintemperatureadjustmentfromtheLittleIceAge）.

Short-termfluctuations（yearstoafewdecades）suchastheElNiño-SouthernOscillation,thePacificdecadaloscillation,theNorthAtlanticoscillation,andtheArcticoscillation,representclimatevariabilityratherthanclimatechange.Onlongertimescales,alterationstooceanprocessessuchasthermohalinecirculationplayakeyroleinredistributingheatbycarryingoutaveryslowandextremelydeepmovementofwater,andthelong-termredistributionofheatintheworld'soceans.

Aschematicofmodernthermohalinecirculation.Tensofmillionsofyearsago,continentalplatemovementformedaland-freegaparoundAntarctica,allowingformationoftheACCwhichkeepswarmwatersawayfromAntarctica.

2.2Externalforcingmechanisms

IncreaseinatmosphericCO2levels

Milankovitchcyclesfrom800,000yearsagointhepastto800,000yearsinthefuture.

VariationsinCO2,temperatureanddustfromtheVostokicecoreoverthelast450,000years

2.2.1Orbitalvariations

Mainarticle:

Milankovitchcycles

SlightvariationsinEarth'sorbitleadtochangesintheseasonaldistributionofsunlightreachingtheEarth'ssurfaceandhowitisdistributedacrosstheglobe.Thereisverylittlechangetothearea-averagedannuallyaveragedsunshine;buttherecanbestrongchangesinthegeographicalandseasonaldistribution.ThethreetypesoforbitalvariationsarevariationsinEarth'seccentricity,changesinthetiltangleofEarth'saxisofrotation,andprecessionofEarth'saxis.Combinedtogether,theseproduceMilankovitchcycleswhichhavealargeimpactonclimateandarenotablefortheircorrelationtoglacialandinterglacialperiods,[7]theircorrelationwiththeadvanceandretreatoftheSahara,[7]andfortheirappearanceinthestratigraphicrecord.[8]

TheIPCCnotesthatMilankovitchcyclesdrovetheiceagecycles;CO2followedtemperaturechange"withalagofsomehundredsofyears";andthatasafeedbackamplifiedtemperaturechange.[9]Thedepthsoftheoceanhavealagtimeinchangingtemperature（thermalinertiaonsuchscale）.Uponseawatertemperaturechange,thesolubilityofCO2intheoceanschanged,aswellasotherfactorsimpactingair-seaCO2exchange.

2.2.2Solaroutput

Mainarticle:

Solarvariation

Variationsinsolaractivityduringthelastseveralcenturiesbasedonobservationsofsunspotsandberylliumisotopes.Theperiodofextraordinarilyfewsunspotsinthelate17thcenturywastheMaunderMinimum.

ThesunisthepredominantsourceforenergyinputtotheEarth.Bothlong-andshort-termvariationsinsolarintensityareknowntoaffectglobalclimate.

Threetofourbillionyearsagothesunemittedonly70%asmuchpowerasitdoestoday.Iftheatmosphericcompositionhadbeenthesameastoday,liquidwatershouldnothaveexistedonEarth.However,thereisevidenceforthepresenceofwaterontheearlyEarth,intheHadean[11][12]andArchean[13][11]eons,leadingtowhatisknownasthefaintyoungSunparadox.[14]Hypothesizedsolutionstothisparadoxincludeavastlydifferentatmosphere,withmuchhigherconcentrationsofgreenhousegasesthancurrentlyexist.[15]Overthefollowingapproximately4billionyears,theenergyoutputofthesunincreasedandatmosphericcompositionchanged.TheGreatOxygenationEvent–oxygenationoftheatmospherearound2.4billionyearsago–wasthemostnotablealteration.Overthenextfivebillionyearsthesun'sultimatedeathasitbecomesaredgiantandthenawhitedwarfwillhavelargeeffectsonclimate,withtheredgiantphasepossiblyendinganylifeonEarththatsurvivesuntilthattime.

Solaroutputalsovariesonshortertimescales,includingthe11-yearsolarcycle[16]andlonger-termmodulations.[17]SolarintensityvariationsareconsideredtohavebeeninfluentialintriggeringtheLittleIceAge,[18]andsomeofthewarmingobservedfrom1900to1950.Thecyclicalnatureofthesun'senergyoutputisnotyetfullyunderstood;itdiffersfromtheveryslowchangethatishappeningwithinthesunasitagesandevolves.ResearchindicatesthatsolarvariabilityhashadeffectsincludingtheMaunderMinimumfrom1645to1715A.D.,partoftheLittleIceAgefrom1550to1850A.D.whichwasmarkedbyrelativecoolingandgreaterglacierextentthanthecenturiesbeforeandafterward.[19][20]Somestudiespointtowardsolarradiationincreasesfromcyclicalsunspotactivityaffectingglobalwarming,andclimatemaybeinfluencedbythesumofalleffects（solarvariation,anthropogenicradiativeforcings,etc.）.

Interestingly,a2010study[23]suggests,“thattheeffectsofsolarvariabilityontemperaturethroughouttheatmospheremaybecontrarytocurrentexpectations.”

InanAug2011PressRelease,[24]CERNannouncedthepublicationintheNaturejournaltheinitialresultsfromitsCLOUDexperiment.Theresultsindicatethationisationfromcosmicrayssignificantlyenhancesaerosolformationinthepresenceofsulphuricacidandwater,butintheloweratmospherewhereammoniaisalsorequired,thisisinsufficienttoaccountforaerosolformationandadditionaltracevapoursmustbeinvolved.Thenextstepistofindmoreaboutthesetracevapours,includingwhethertheyareofnaturalorhumanorigin.

2.2.3Volcanism

Inatmospherictemperaturefrom1979to2010,determinedbyMSUNASAsa