彼得森经济研究所-向净零排放过渡的宏观经济影响（英）-2024.3.docx

StephaneHallegatteisseniorclimatechangeadvisoroftheWoridBank.FlorentMcIsaacissenioreconomistattheMacroeconomicModellingUnitoftheMacroeconomics.TradeandInvestmentGlobalPracticeattheWorldBank.HasanDuduisoneconomistftheMiddleEastandCentralAsiaDepartmentoftheInternationalMonetaryFund.CamillaKnudsenisaneconomistattheWorldBank.ChartJoosteisasenioreconomistattheMocroecorxjmicModellingUnitoftheMacroeconomics,TradeandInvestmentGlobalPracticeattheWorldBank.HansAnandBeckistheprogramleaderforTurkeyintheWorldBankEquitableGrowth,FinanceandInstitutionsGroup.d!nEPETERSONINSTITUTEFOR嘴斗1.=IntfpnationalFconomicsWORKINGPAPER24-6MacroeconomicimplicationsofatransitiontonetzeroemissionsApproachesofandlessonsfromWorldBankGroupCountryClimateandDevelopmentReports,withanapplicationtoTurkeyStephaneHallegattezFlorentMcIsaaczHasanDudu,CharlJoostezCam川aKnudsenzandHansBeckMarch2024ABSTRACTIn2022theWorldBankGrouplaunchedanewcorediagnostictool:theCountryClimateandDevelopmentReport(CCDR).Publishedfor42economiessofar,CCDRsuseresilientandlow-emissiondevelopmentscenariostoidentifysynergiesandtradeoffsbetweendevelopmentandclimateobjectives.Thereareseveralmodelingchallengesassociatedwiththeanalysisofthemacroeconomicconsequencesofthesedevelopmentpathways,includingthoserelatedtothenonmarginalnatureoftherequiredtransformation,theroleoftechnologies,andthereplacementoffossilfuel-basedassetswithgreenerones.Toaddresssomeofthesechallenges,severalCCDRshaveusedahybridmodelingapproachthatcombinesasetofsectoralanalyseswithmacroeconomicmodels.Specifically,sectoraltechno-economicmodelsareemployedtoconstructresilientandlow-emissiondevelopmenttrajectoriesinkeysectors.Themacroeconomicimplicationsofthesesectoraltransitionsarethenassessedbylinkingthesectoralmodelswithtwomacroeconomicframeworks:amultisectorgeneralequilibriumframeworkandanaggregatemacrostructuralmodel.Thishybridapproachcombinestheadvantagesofmultipletoolsandcapturesthevariousdimensionsofthetransition,includingtheneedtotacklemultiplemarketfailures,beyondtheemissionsexternality;analyzepriceandnonpricepoliciesandtheirinteractions;representexplicitlythereplacementofassetsandinfrastructure;assessthemacroeconomicfeasibilityofthesectoraltransitionsandtherequiredinvestments.ThispaperusesthecaseofTurkeytodescribethemethodologicalapproachandsummarizestheresultsoftheCCDRsthathavebeenpublishedtodate.Findingssuggestthat,despitelargeinvestmentneeds,thetransitioncan1750MassachusettsAveshington,DC20+1,202.328.9000contributepositivelytoeconomicgrowth,especiallywhenindirectmitigationbenefitsaretakenintoaccountbutonlyifstructuralchallengescanbemanaged,climateanddevelopmentpoliciesarewelldesigned,andnegativeimpactsonsomesectorsorcommunitiesaremitigated.JE1.Codes:E60,Q43,Q54Keywords:Macroeconomicmodeling;climatechange;technologicalchangeAuthor,sNote:ThispaperpreparedforaconferenceonMQCroeCQnOmiCImQlicQtionsOfClimQteAetiononJune5-6,2023,atthePetersonInstituteforInternationalEconomics(PIIE)isanextensionofthemethodologicalpaperfocusedonTurkey,availableasStephaneHallegatte,FlorentMcIsaac,HasanDudu,CharlJooste,CamillaKnudsen,andHansBeck,2023,TheMQeroeConQmiCImQliCQtionsofQTrQnSitiQntoZeroNeiEmissions:AModelingFramework,PolicyResearchWorkingPaper10367,Washington:WorldBankGroup.ThisworkispartoftheanalyticalworkfortheWorldBankCountryClimateandDevelopmentReport(CCDR)forTurkeyandbenefitedfromthecontributionsoftheentireCCDRteam,especiallythemanycolleagueswhodevelopedthesectoralroadmapsonwhichthisworkisbased.TheauthorsthankinparticularthepeerreviewersoftheCCDR,includingdozenofWorldBankstaff,NickSternandAmarBhattacharya,whoprovidedinsightfulcommentsatvariousstageofthiswork.WealsothankEtienneEspagne,JeanPisani-Ferry,DilekSevinc,andMarcNolandfortheirhelpfulcommentsonthismanuscript;IoanaMarinescuandStefanoScarpettafortheirdetailedandconstructivediscussionnotes;andallparticipantsofthePIIEconferenceorganizedbyJeanPisani-FerryandAdamS.Posen.Allremainingerrorsandopinionsareourown.TheauthorsthankthemultidonorClimoteSUQQortFeleiIHYforfundingpartofthiswork.1. IntroductionIn2022theWorldBankGrouplaunchedanewcorediagnostictool:theCountryClimateandDevelopmentReport(CCDR).Todate,38reportscovering42economieshavebeenpublished,withaplantoproducethemforallWorldBankclientcountriesoverthenexttwotofouryears.Seethereportsathttps:/www.worldbank.orv/en/publication/countrv-climate-develoTment-reports.CCDRsaimtohelpcountriesprioritizethemostimpactfulactionstoboostresilienceandadaptationtoclimatechangeandreducegreenhousegas(GHG)emissionswhiledeliveringonbroaderdevelopmentobjectives.MostoftheCCDRsexploreillustrative,ambitiouslow-emissiondevelopmentpathways(figure1).TheapproachesadoptedbyCCDRstoexplorethesepathwaysaretailoredtotheuniquecountrycontexts,includingclimatecommitments,incomelevel,potentialforrenewableenergyorland-basedemissionreductions,anddomesticdevelopmentpriorities.Theyconsiderwhatistechnically,economically,andpoliticallyfeasibleineachcountry.Consequently,theambitionofthescenariosformitigationandadaptationaswellasthetimingofthetransitiondifferfromcountrytocountry.Figure11.ow-emissiondevelopmentscenariosexploredbyCCDRs,selectedcountries,2019-601.ower-middle-income202020252030203520402045205020552060waseqJo98)suoMEUJYearNote:Trajectoriesforgreenhousegasemissionsareshownrelativeto2019emissionlevels.Source：WorldBankGroup(2023).Toimplementtheambitiouslow-emissiondevelopmentstrategies,anonmarginalandsustainedtechnologicaltransformationofeconomicsystemsisrequired,includingchangesinsupply,demand,andproductivitytechnologies,allofwhichhavemultipleandprolongedmicro-andmacroeconomicimplications.1.ow-emissiondevelopmentwouldhaveaparticularlylargenegativeimpactonspecificsectors,potentiallyleadingtoabrupt(financial)assetrevaluationandlossofjobs(Battistonetal.2017;vanderPloegandRezai2020;NGFS2021).Ontheotherhand,sectorswithendproductsandbusinessmodelsthatsupportthetransition,suchasindustriesproducingbatteries,renewableenergy,orinsulationmaterials,couldbenefitfromlow-emissiondevelopment.Inparallel,allsectorscouldbehurtbychangesinrelativepricesorbenefitfromhigherenergyandmaterialefficiency,low-costenergyfromrenewablesources,orhigherlaborproductivitythankstoimprovedairquality.Atthemacroeconomiclevel,thesechangeswillhavesignificantimplications,includingthroughsupplyanddemandshocks,relativeprices,andinternationaltrade.Explorationofthemacroeconomicrisksandopportunitiesofthelow-emissiontransitionrequiresbothsectoralanalyseswithexplicitrepresentationofassetsandproductiontechnologies,and,atthemacroeconomiclevel,ageneralequilibriumframeworktounderstandthespillovereffectsacrosssectorsaswellastheirconsequencesforlaborandcapitalmarkets.Theliteratureshowsuseofvariouseconomicmodels,includingcomputablegeneralequilibrium(CGE)modelsandintegratedassessmentmodels,toshedlightonhowtransitionrisksandopportunitieswillmaterialize.Thesemodelshavebeencentraltoolsintheinternationalclimatepolicydebateformorethanthreedecades,beginningwiththeseminalworkofWilliamNordhaus(1992).Despitesteadyqualitativeandquantitativeimprovements,themodelsarestillsubjecttoseverecriticismsfromtheresearchcommunity,forexamplewithrespecttohowtheytreatuncertainty.ImportantrecentcontributionsincludeKeppoetal.(2021)andStern,Stiglitz,andTayIor(2022).Amongthemostfrequentcriticisms,ithasbeennotedthatthemostcommonclimateeconomicmodelstendtoignore(i)preexistingdistortionsandnonclimate-relatedmarketfailuresthatopenthepossibilityforsynergiesbetweeneconomicgrowthandemissionreductionsFormoreinformation,seeHallegatteetal.(2012),OECD(2017),andtheNewClimateEconomy(2018).Oneexceptionistheimpactoffossilfuelsubsidies,whichiswellstudiedbyexistingmodels.;(ii)theroleoftechnologicalchangeswiththepossibilitythatgreenertechnologiesachievehigherproductivitythanalreadymaturetechnologies,asiscurrentlyobservedforrenewableenergyorelectrifiedtransportationSee,forexample,Calietal.(2022)andAmannetal.(2021)onthelinkbetweenenergypricesandproductivity,orAmbecetal.(2013)onthePorterhypothesis.Amoregeneraldebateonhowtoreconcileresultsfromtop-downandtechnology-explicitbottom-upanalysisofclimatetransitionscanbefoundinBohringerandRutherford(2008)andHourcadeetal.(2006).;and(iii)macroeconomicfeedbackandtradeoffsresultingfromthelargeinvestmentsorlabormarkettransitionsneededtoachievethetransition.See,forexample,Guivarchetal.(2011).Whilethefirsttwoarelikelytocontributetooverestimatingthecostofthegreentransition,thelatterlikelycontributestounderestimation.ThispaperusestheTurkeyCCDR(WorldBank2022)todescribethehybridmodelingframeworkusedinmanyCCDRstoaddresssomeofthemodellimitationshighlightedabove.See,forexample,Batailleetal.(2006),Bosettietal.(2006),Kimetal.(2006),andKohleretal.(2006).ItalsosummarizesthemacroeconomicresultsfromotherpublishedCCDRs,buildingonthesummarypaperpublishedatCOP28(WorldBankGroup2023).NotallCCDRshavefollowedtheexactsamemethodologicalapproach:asmentioned,thetoolsandmethodologieshavebeentailoredtothecountrycontextanddifferencesindataavailability.However,theapproachacrossCCDRsissimilarinnature,inthatitaimstocombinegranularinsightfromsector-levelanalysis(e.g.,powersectororhydrologicalmodeling)withtheconsistencyandgeneralequilibriumdimensionsofmacroeconomicmodeling.Conceptually,thehybridmodelingapproachemployedinCCDRsisbasedonfourideas,whichaddressfourkeychallengesintraditionalapproaches:First,constructingasingleintegratedmodelthatcombinesalltherequireddimensionsandmechanismsleadstoincreasingcomplexitythatmakesresultslesstransparentandmoredifficulttointerpret.Toimprovetransparencyandtractability,thehybridapproachusesinsteadasetofconnectedtools,withoutputsofsectoraltechnoeconomicmodelsusedasinputsintomacroeconomicmodels.Suchahybridapproachbenefitsfromtheadvantagesofeachofthesetwotypesofmodels.Specifically,sectoralmodelshaveagranularrepresentationoftechnologiesandthecapitalstock(eg,thebuildingstockorthefleetofvehicles)buttheyhavelittleornorepresentationofeconomicmechanismsandthebehaviorofeconomicagents.Macroeconomicmodels,ontheotherhand,imposemacroeconomicconsistencyandrepresentthebehaviorsofeconomicagents,buthaveasimplifiedrepresentationofsectoralproductionprocessesanddonotrepresentexplicitlythecomplexityandgranularityofthetransitionfrombrowntogreenassets.Second,thereisnoconsensusonwhatconstitutesan“optimal"decarbonizationpathway,whichwillalwaysdependonvaluejudgments.Toavoidthischallenge,CCDRsexploretheimplicationsofplausibleillustrativedecarbonizationscenariosconsistentwitheachcountry,sownclimatetargets(inthecaseofTurkey,thecountryhascommittedtoachievenetzeroemissionsin2053,whichmarksthe130thanniversaryoftherepublic).Thisisamoveawayfromtheusualintertemporalcost-benefitanalysisOfbalancingtransitionandphysicalrisksthroughawell-coordinatedpricemechanism,forwhichthediscountrateSee,forexample,Pindyck(2013).andthecalibrationofthedamagefunctionplayakeyrole.Thelong-termcostsofclimatechangeareexpectedtobesignificant.However,theirestimationisthesubjectofactiveacademicdebate(see,e.g.,IMF2022).Consequently,analysesbasedontheirestimatesaresubjecttohighuncertainty.Third,insteadOfrepresentingclimatepoliciesasanequivalentcarbonpricethepolicythatiseasiesttoincludeinmacroeconomicmodelsCCDRsaimtocapturethecomplexityanddiversityofreal-worldclimatepolicies,whichincludepricingpoliciesbutalso,amongothers,directinvestments,normsandregulations,andsubsidies.Seeacollectionofcasestudiesof25climatepoliciesinWorldBank(2023),highlightingthediversityofapproachesusedinvariouscountries.Inparticular,thecombinationofinsightsfromsectoralandmacromodelsenablesimprovedconsiderationoftheinterplaybetweenpriceandnonpriceinterventions.Itis,forexample,straightforwardinatransportmodeltorepresentnonpricepoliciessuchastheimpactofperformancestandardsorinvestmentininfrastructure.Transportmodelscanalsocapturethefactthatthesamecarbonpricewillyieldalargerreductioninemissionsinthepresenceofinfrastructurethatfacilitatesmodalshift(e.g.,ametrosystem)orelectrification(eg,chargingstations).SeeAvner(2014)foradiscussionofhowthepriceelasticityofCO2emissionsdependsoninfrastructure.Andfinally,insteadoffocusingontheclimateexternalityonly,Weaimatabetterconsiderationofthemanymarketfailuresthatactasbarrierstoanefficientandsmoothdecarbonizationprocessbutalsocreateopportunitiesforshort-termsynergiesbetweenclimateanddevelopmentpolicies.Whilemacroeconomicmodelscaneasilyrepresenttheeffectofdistortivetaxsystems,andhavemadeprogressinrepresentingtheimpactofknowledgespilloversandotherinnovation-relatedmarketfailures,itismorechallengingforthemtocapturetheeffectsofinadequateregulationsormonopolisticbehaviorsthatpreventsomehigh-productivitylower-emissionstechnologiesfromenteringthemarket.Ifnonclimatemarketfailuresareignored,resourcesdirectedtowardthegreentransitionwillalwaysdivertresourcesfromhigher-yieldinvestmentsandreduceeconomicoutputorgenerateinflation(Pisani-Ferry2021).Incontrast,accountingforabroaderrangeofmarketimperfectionsmakesitpossibletoexploreopportunitiesforsynergiesbetweenclimateanddevelopmentobjectives(1.ipseyand1.ancaster1956).TheimpactoftheseSuboptinialitiescanberepresentedexplicitlyinthesectoralmodels,forexamplebyusingasabaselineapowersystemthatdoesnotminimizeelectricityproductioncost.Inpractice,westartfromasetofsector-leveldecarbonizationpathways,describingthechangesinsupplyanddemand,productivecapital,andtechnologies;therequired(publicandprivate)investments;andtheimplicationsforeconomiccostsandbenefits(e.g.,fuelsavings).Theinvestments,costs,andbenefitscanbetriggeredbypriceandnonpricepoliciesorinterventions(whicharenotnecessarilydescribedinthesectoralscenarios).Theinvestments,costs,andbenefitsidentifiedinthesectoralpathwaysarethenenteredintothemacroeconomicmodelstoexplorethefeasibilityofthesectoralscenariosaswellastheiraggregateimplicationsfor(i)growthandothermacroeconomicvariablesand(ii)householdwelfareandemploymentatthesectorallevel.Thefocusofthemacroeconomicanalysesistoensureconsistencyacrossthevarioussectoralscenarios,toidentifypositiveornegativespilloversacrosssectors,andhighlighteconomictradeoffsthatmitigationpoliciesmightentail.InthecaseofTurkey,weanalyzethesepotentialtradeoffsusingtwotypesofmodels:(1)amultisectorCGEmodel,MANAGE(Mitigation,Adaptation,andNewTechnologiesAppliedGeneralEquilibrium),tohighlighttheintrasectoralconsequencesofthetransition,and(2)anaggregatemacrofiscalmodel(MFMod)toaccountforaggregatepriceandwagerigiditieswhendeterminingthefiscalandeconomicconsequencesoftransitioning.Section2presentsthesectoralnetzeropathwaysintheTurkeyCCDR.Sections3and4discusstheintegrationofthesesectoralpathwaysinthetwomacroeconomicmodels,MANAGEandMFMod,respectively.Section5summarizestheresultsofthemacroeconomicanalysisoflow-carbondevelopmentfromallpublishedCCDRs.Section6concludes.2. Bottom-UpApproachtoDefineIllustrativeSectoralRoadmapstoAchieveNetZeroEmissionsThissectionillustratesthehybridapproachbyapplyingittoTurkey.Theleft-handsideoffigure2showsTurkey,sGHGemissionshistoryinwhichtheenergysector(i.e.,power,transportation,buildings,andindustrialsectors)isthelargestcontribut