{{B}}pAssAgE two{{/B}}

ClimAtiC ConDitions ArE DEliCAtEly ADjustED to thE Composition oF thEEArth’s AtmosphErE. iF thErE wErE A ChAngE in thE AtmosphErE For ExAmplE, in thE rElAtivE proportions oF AtmosphErE gAsEs thE ClimAtE woulD proBABly ChAngE Also.A、slight inCrEAsE in wAtEr vApor, For instAnCE, woulD inCrEAsE thE hEAt-rEtAining CApACity oF thE AtmosphErE AnD woulD lEAD to A risE in gloBAl tEmpErAturEs. in ContrAst, A lArgE inCrEAsE in wAtEr vApor woulD inCrEAsE thE thiCknEss AnD ExtEnt oF thE ClouD lAyEr, rEDuCing thE Amount oF solAr EnErgy rEAChing thEEArth’s surFACE. thE lEvEl oF CArBon DioxiDE,Co2, in thE AtmosphErE hAs An importAnt EFFECt on ClimAtiC ChAngE. most oF thEEArth’s inComing EnErgy is short wAvElEngth rADiAtion, whiCh tEnDs to pAss through AtmosphEriCCo2 EAsily. thEEArth, howEvEr, rErADiAtEs muCh oF thE rECEivED EnErgy As A long wAvElEngth rADiAtion, whiChCo2 ABsorBs AnD thEn rEmits towArD thEEArth. this phEnomEnon, known As thE grEEnhousE EFFECt, CAn rEsult in An inCrEAsE in thE surFACE tEmpErAturE oF A plAnEt.An ExtrEmE ExAmplE oF thE EFFECt is shown By thE vEnus, A plAnEt CovErED By hEAvy ClouDs ComposED mostly oFCo2, whosE surFACE tEmpErAturEs hAvE BEEn mEAsurED At 430℃. iF thECo2 ContEnt oF thE AtmosphErE is rEDuCED, thE tEmpErAturE FAlls.ACCorDing to onE rEspECtABlE thEory, iF thE AtmosphEriCCo2 ConCEntrAtion wErE hAlvED, thEEArth woulD BEComE ComplEtEly CovErED with iCE.AnothEr EquAlly rEspECtABlE thEory, howEvEr, stAtEs thAt A hAlving oF thECo2 ConCEntrAtion woulD lEAD only to A rEDuCtion in gloBAl tEmpErAturEs oF 3℃. iF, BECAusE oF An inCrEAsE in ForEst FirEs or volCAniC ACtivitiEs, thECo2 ContEnt oF thE AtmosphErE inCrEAsED, A wArmEr ClimAtE woulD BE proDuCED、 plAnt growth, whiCh rEliEs on Both thE wArmth AnD thE AvAilABility oFCo2, woulD proBABly inCrEAsE.As A ConsEquEnCE, plAnts woulD usE morE AnD morECo2.EvEntuAllyCo2 lEvEls woulD Diminish AnD thE ClimAtE, in turn, woulD BEComE CoolEr. with rEDuCED tEmpErAturEs mAny plAnts woulD DiE;Co2 woulD thErEBy BE rEturnED to thE AtmosphErE AnD grADuAlly thE tEmpErAturEs woulD risE AgAin. thus, iF this proCEss oCCurrED, thErE might BE A long-tErm osCillAtion in thE Amount oFCo2 prEsEnt in thE AtmosphErE, with rEgulAr tEmpErAturE inCrEAsEs AnD DECrEAsEs oF A sEt mAgnituDE. somE ClimAtologists ArguE thAt thE Burning oF Fossil FuEls hAs rAisED thE lEvEl oFCo2 in thE AtmosphErE AnD hAs CAusED A gloBAl tEmpErAturE risE oF At lEAst 1℃.But A supposED gloBAl tEmpErAturE risE oF 1℃ mAy in rEAlity BE only sEvErAl rEgionAl tEmpErAturE inCrEAsEs, rEstriCtED to ArEAs whErE thErE ArE mAny mEtEorologiCAl stAtions AnD CAusED simply By shiFts in thE pAttErn oF AtmosphEriC CirCulAtion. othEr ArEAs, For ExAmplE, thE southErn hEmisphErE oCEAniC zonE, mAy BE ExpEriEnCing An EquivAlEnt tEmpErAturE DECrEAsE thAt is unrECognizED BECAusE oF thE shortAgE oF mEtEorologiCAl rECorDing stAtions.

whiCh oF thE Following quEstions DoEs thE pAssAgE supply inFormAtion For AnswEringA．why ArE projECtions oF thE EFFECts oF ChAngEs in wAtEr vApor lEvEls on thE ClimAtE so inACCurAtE
B．whAt ArE thE stEps in thE proCEss thAt tAkEs plACE AsCo₂ ABsorBs long wAvElEngth rADiAtion
C．how might our unDErstAnDing oF thE grEEnhousE EFFECt BE improvED iF thE Burning oF Fossil FuEls wErE DECrEAsED
D．whAt might CAusE A sEriEs oF rEgulAr inCrEAsEs AnD DECrEAsEs in thE Amount oFCo₂ in thE AtmosphErE