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1、StephaneHallegatteisseniorclimatechangeadvisoroftheWoridBank.FlorentMcIsaacissenioreconomistattheMacroeconomicModellingUnitoftheMacroeconomics.TradeandInvestmentGlobalPracticeattheWorldBank.HasanDuduisoneconomistftheMiddleEastandCentralAsiaDepartmentoftheInternationalMonetaryFund.CamillaKnudsenisane
2、conomistattheWorldBank.ChartJoosteisasenioreconomistattheMocroecorxjmicModellingUnitoftheMacroeconomics,TradeandInvestmentGlobalPracticeattheWorldBank.HansAnandBeckistheprogramleaderforTurkeyintheWorldBankEquitableGrowth,FinanceandInstitutionsGroup.d!nEPETERSONINSTITUTEFOR嘴斗1.=IntfpnationalFconomics
3、WORKINGPAPER24-6MacroeconomicimplicationsofatransitiontonetzeroemissionsApproachesofandlessonsfromWorldBankGroupCountryClimateandDevelopmentReports,withanapplicationtoTurkeyStephaneHallegattezFlorentMcIsaaczHasanDudu,CharlJoostezCam川aKnudsenzandHansBeckMarch2024ABSTRACTIn2022theWorldBankGrouplaunche
4、danewcorediagnostictool:theCountryClimateandDevelopmentReport(CCDR).Publishedfor42economiessofar,CCDRsuseresilientandlow-emissiondevelopmentscenariostoidentifysynergiesandtradeoffsbetweendevelopmentandclimateobjectives.Thereareseveralmodelingchallengesassociatedwiththeanalysisofthemacroeconomicconse
5、quencesofthesedevelopmentpathways,includingthoserelatedtothenonmarginalnatureoftherequiredtransformation,theroleoftechnologies,andthereplacementoffossilfuel-basedassetswithgreenerones.Toaddresssomeofthesechallenges,severalCCDRshaveusedahybridmodelingapproachthatcombinesasetofsectoralanalyseswithmacr
6、oeconomicmodels.Specifically,sectoraltechno-economicmodelsareemployedtoconstructresilientandlow-emissiondevelopmenttrajectoriesinkeysectors.Themacroeconomicimplicationsofthesesectoraltransitionsarethenassessedbylinkingthesectoralmodelswithtwomacroeconomicframeworks:amultisectorgeneralequilibriumfram
7、eworkandanaggregatemacrostructuralmodel.Thishybridapproachcombinestheadvantagesofmultipletoolsandcapturesthevariousdimensionsofthetransition,includingtheneedtotacklemultiplemarketfailures,beyondtheemissionsexternality;analyzepriceandnonpricepoliciesandtheirinteractions;representexplicitlythereplacem
8、entofassetsandinfrastructure;assessthemacroeconomicfeasibilityofthesectoraltransitionsandtherequiredinvestments.ThispaperusesthecaseofTurkeytodescribethemethodologicalapproachandsummarizestheresultsoftheCCDRsthathavebeenpublishedtodate.Findingssuggestthat,despitelargeinvestmentneeds,thetransitioncan
9、1750MassachusettsAveshington,DC20+1,202.328.9000contributepositivelytoeconomicgrowth,especiallywhenindirectmitigationbenefitsaretakenintoaccountbutonlyifstructuralchallengescanbemanaged,climateanddevelopmentpoliciesarewelldesigned,andnegativeimpactsonsomesectorsorcommunitiesaremitigated.JE1.Codes:E6
10、0,Q43,Q54Keywords:Macroeconomicmodeling;climatechange;technologicalchangeAuthor,sNote:ThispaperpreparedforaconferenceonMQCroeCQnOmiCImQlicQtionsOfClimQteAetiononJune5-6,2023,atthePetersonInstituteforInternationalEconomics(PIIE)isanextensionofthemethodologicalpaperfocusedonTurkey,availableasStephaneH
11、allegatte,FlorentMcIsaac,HasanDudu,CharlJooste,CamillaKnudsen,andHansBeck,2023,TheMQeroeConQmiCImQliCQtionsofQTrQnSitiQntoZeroNeiEmissions:AModelingFramework,PolicyResearchWorkingPaper10367,Washington:WorldBankGroup.ThisworkispartoftheanalyticalworkfortheWorldBankCountryClimateandDevelopmentReport(C
12、CDR)forTurkeyandbenefitedfromthecontributionsoftheentireCCDRteam,especiallythemanycolleagueswhodevelopedthesectoralroadmapsonwhichthisworkisbased.TheauthorsthankinparticularthepeerreviewersoftheCCDR,includingdozenofWorldBankstaff,NickSternandAmarBhattacharya,whoprovidedinsightfulcommentsatvarioussta
13、geofthiswork.WealsothankEtienneEspagne,JeanPisani-Ferry,DilekSevinc,andMarcNolandfortheirhelpfulcommentsonthismanuscript;IoanaMarinescuandStefanoScarpettafortheirdetailedandconstructivediscussionnotes;andallparticipantsofthePIIEconferenceorganizedbyJeanPisani-FerryandAdamS.Posen.Allremainingerrorsan
14、dopinionsareourown.TheauthorsthankthemultidonorClimoteSUQQortFeleiIHYforfundingpartofthiswork.1. IntroductionIn2022theWorldBankGrouplaunchedanewcorediagnostictool:theCountryClimateandDevelopmentReport(CCDR).Todate,38reportscovering42economieshavebeenpublished,withaplantoproducethemforallWorldBankcli
15、entcountriesoverthenexttwotofouryears.Seethereportsathttps:/www.worldbank.orv/en/publication/countrv-climate-develoTment-reports.CCDRsaimtohelpcountriesprioritizethemostimpactfulactionstoboostresilienceandadaptationtoclimatechangeandreducegreenhousegas(GHG)emissionswhiledeliveringonbroaderdevelopmen
16、tobjectives.MostoftheCCDRsexploreillustrative,ambitiouslow-emissiondevelopmentpathways(figure1).TheapproachesadoptedbyCCDRstoexplorethesepathwaysaretailoredtotheuniquecountrycontexts,includingclimatecommitments,incomelevel,potentialforrenewableenergyorland-basedemissionreductions,anddomesticdevelopm
17、entpriorities.Theyconsiderwhatistechnically,economically,andpoliticallyfeasibleineachcountry.Consequently,theambitionofthescenariosformitigationandadaptationaswellasthetimingofthetransitiondifferfromcountrytocountry.Figure11.ow-emissiondevelopmentscenariosexploredbyCCDRs,selectedcountries,2019-601.o
18、wer-middle-income202020252030203520402045205020552060waseqJo98)suoMEUJYearNote:Trajectoriesforgreenhousegasemissionsareshownrelativeto2019emissionlevels.Source：WorldBankGroup(2023).Toimplementtheambitiouslow-emissiondevelopmentstrategies,anonmarginalandsustainedtechnologicaltransformationofeconomics
19、ystemsisrequired,includingchangesinsupply,demand,andproductivitytechnologies,allofwhichhavemultipleandprolongedmicro-andmacroeconomicimplications.1.ow-emissiondevelopmentwouldhaveaparticularlylargenegativeimpactonspecificsectors,potentiallyleadingtoabrupt(financial)assetrevaluationandlossofjobs(Batt
20、istonetal.2017;vanderPloegandRezai2020;NGFS2021).Ontheotherhand,sectorswithendproductsandbusinessmodelsthatsupportthetransition,suchasindustriesproducingbatteries,renewableenergy,orinsulationmaterials,couldbenefitfromlow-emissiondevelopment.Inparallel,allsectorscouldbehurtbychangesinrelativepricesor
21、benefitfromhigherenergyandmaterialefficiency,low-costenergyfromrenewablesources,orhigherlaborproductivitythankstoimprovedairquality.Atthemacroeconomiclevel,thesechangeswillhavesignificantimplications,includingthroughsupplyanddemandshocks,relativeprices,andinternationaltrade.Explorationofthemacroecon
22、omicrisksandopportunitiesofthelow-emissiontransitionrequiresbothsectoralanalyseswithexplicitrepresentationofassetsandproductiontechnologies,and,atthemacroeconomiclevel,ageneralequilibriumframeworktounderstandthespillovereffectsacrosssectorsaswellastheirconsequencesforlaborandcapitalmarkets.Thelitera
23、tureshowsuseofvariouseconomicmodels,includingcomputablegeneralequilibrium(CGE)modelsandintegratedassessmentmodels,toshedlightonhowtransitionrisksandopportunitieswillmaterialize.Thesemodelshavebeencentraltoolsintheinternationalclimatepolicydebateformorethanthreedecades,beginningwiththeseminalworkofWi
24、lliamNordhaus(1992).Despitesteadyqualitativeandquantitativeimprovements,themodelsarestillsubjecttoseverecriticismsfromtheresearchcommunity,forexamplewithrespecttohowtheytreatuncertainty.ImportantrecentcontributionsincludeKeppoetal.(2021)andStern,Stiglitz,andTayIor(2022).Amongthemostfrequentcriticism
25、s,ithasbeennotedthatthemostcommonclimateeconomicmodelstendtoignore(i)preexistingdistortionsandnonclimate-relatedmarketfailuresthatopenthepossibilityforsynergiesbetweeneconomicgrowthandemissionreductionsFormoreinformation,seeHallegatteetal.(2012),OECD(2017),andtheNewClimateEconomy(2018).Oneexceptioni
26、stheimpactoffossilfuelsubsidies,whichiswellstudiedbyexistingmodels.;(ii)theroleoftechnologicalchangeswiththepossibilitythatgreenertechnologiesachievehigherproductivitythanalreadymaturetechnologies,asiscurrentlyobservedforrenewableenergyorelectrifiedtransportationSee,forexample,Calietal.(2022)andAman
27、netal.(2021)onthelinkbetweenenergypricesandproductivity,orAmbecetal.(2013)onthePorterhypothesis.Amoregeneraldebateonhowtoreconcileresultsfromtop-downandtechnology-explicitbottom-upanalysisofclimatetransitionscanbefoundinBohringerandRutherford(2008)andHourcadeetal.(2006).;and(iii)macroeconomicfeedbac
28、kandtradeoffsresultingfromthelargeinvestmentsorlabormarkettransitionsneededtoachievethetransition.See,forexample,Guivarchetal.(2011).Whilethefirsttwoarelikelytocontributetooverestimatingthecostofthegreentransition,thelatterlikelycontributestounderestimation.ThispaperusestheTurkeyCCDR(WorldBank2022)t
29、odescribethehybridmodelingframeworkusedinmanyCCDRstoaddresssomeofthemodellimitationshighlightedabove.See,forexample,Batailleetal.(2006),Bosettietal.(2006),Kimetal.(2006),andKohleretal.(2006).ItalsosummarizesthemacroeconomicresultsfromotherpublishedCCDRs,buildingonthesummarypaperpublishedatCOP28(Worl
30、dBankGroup2023).NotallCCDRshavefollowedtheexactsamemethodologicalapproach:asmentioned,thetoolsandmethodologieshavebeentailoredtothecountrycontextanddifferencesindataavailability.However,theapproachacrossCCDRsissimilarinnature,inthatitaimstocombinegranularinsightfromsector-levelanalysis(e.g.,powersec
31、tororhydrologicalmodeling)withtheconsistencyandgeneralequilibriumdimensionsofmacroeconomicmodeling.Conceptually,thehybridmodelingapproachemployedinCCDRsisbasedonfourideas,whichaddressfourkeychallengesintraditionalapproaches:First,constructingasingleintegratedmodelthatcombinesalltherequireddimensions
32、andmechanismsleadstoincreasingcomplexitythatmakesresultslesstransparentandmoredifficulttointerpret.Toimprovetransparencyandtractability,thehybridapproachusesinsteadasetofconnectedtools,withoutputsofsectoraltechnoeconomicmodelsusedasinputsintomacroeconomicmodels.Suchahybridapproachbenefitsfromtheadva
33、ntagesofeachofthesetwotypesofmodels.Specifically,sectoralmodelshaveagranularrepresentationoftechnologiesandthecapitalstock(eg,thebuildingstockorthefleetofvehicles)buttheyhavelittleornorepresentationofeconomicmechanismsandthebehaviorofeconomicagents.Macroeconomicmodels,ontheotherhand,imposemacroecono
34、micconsistencyandrepresentthebehaviorsofeconomicagents,buthaveasimplifiedrepresentationofsectoralproductionprocessesanddonotrepresentexplicitlythecomplexityandgranularityofthetransitionfrombrowntogreenassets.Second,thereisnoconsensusonwhatconstitutesan“optimaldecarbonizationpathway,whichwillalwaysde
35、pendonvaluejudgments.Toavoidthischallenge,CCDRsexploretheimplicationsofplausibleillustrativedecarbonizationscenariosconsistentwitheachcountry,sownclimatetargets(inthecaseofTurkey,thecountryhascommittedtoachievenetzeroemissionsin2053,whichmarksthe130thanniversaryoftherepublic).Thisisamoveawayfromtheu
36、sualintertemporalcost-benefitanalysisOfbalancingtransitionandphysicalrisksthroughawell-coordinatedpricemechanism,forwhichthediscountrateSee,forexample,Pindyck(2013).andthecalibrationofthedamagefunctionplayakeyrole.Thelong-termcostsofclimatechangeareexpectedtobesignificant.However,theirestimationisth
37、esubjectofactiveacademicdebate(see,e.g.,IMF2022).Consequently,analysesbasedontheirestimatesaresubjecttohighuncertainty.Third,insteadOfrepresentingclimatepoliciesasanequivalentcarbonpricethepolicythatiseasiesttoincludeinmacroeconomicmodelsCCDRsaimtocapturethecomplexityanddiversityofreal-worldclimatep
38、olicies,whichincludepricingpoliciesbutalso,amongothers,directinvestments,normsandregulations,andsubsidies.Seeacollectionofcasestudiesof25climatepoliciesinWorldBank(2023),highlightingthediversityofapproachesusedinvariouscountries.Inparticular,thecombinationofinsightsfromsectoralandmacromodelsenablesi
39、mprovedconsiderationoftheinterplaybetweenpriceandnonpriceinterventions.Itis,forexample,straightforwardinatransportmodeltorepresentnonpricepoliciessuchastheimpactofperformancestandardsorinvestmentininfrastructure.Transportmodelscanalsocapturethefactthatthesamecarbonpricewillyieldalargerreductioninemi
40、ssionsinthepresenceofinfrastructurethatfacilitatesmodalshift(e.g.,ametrosystem)orelectrification(eg,chargingstations).SeeAvner(2014)foradiscussionofhowthepriceelasticityofCO2emissionsdependsoninfrastructure.Andfinally,insteadoffocusingontheclimateexternalityonly,Weaimatabetterconsiderationofthemanym
41、arketfailuresthatactasbarrierstoanefficientandsmoothdecarbonizationprocessbutalsocreateopportunitiesforshort-termsynergiesbetweenclimateanddevelopmentpolicies.Whilemacroeconomicmodelscaneasilyrepresenttheeffectofdistortivetaxsystems,andhavemadeprogressinrepresentingtheimpactofknowledgespilloversando
42、therinnovation-relatedmarketfailures,itismorechallengingforthemtocapturetheeffectsofinadequateregulationsormonopolisticbehaviorsthatpreventsomehigh-productivitylower-emissionstechnologiesfromenteringthemarket.Ifnonclimatemarketfailuresareignored,resourcesdirectedtowardthegreentransitionwillalwaysdiv
43、ertresourcesfromhigher-yieldinvestmentsandreduceeconomicoutputorgenerateinflation(Pisani-Ferry2021).Incontrast,accountingforabroaderrangeofmarketimperfectionsmakesitpossibletoexploreopportunitiesforsynergiesbetweenclimateanddevelopmentobjectives(1.ipseyand1.ancaster1956).TheimpactoftheseSuboptiniali
44、tiescanberepresentedexplicitlyinthesectoralmodels,forexamplebyusingasabaselineapowersystemthatdoesnotminimizeelectricityproductioncost.Inpractice,westartfromasetofsector-leveldecarbonizationpathways,describingthechangesinsupplyanddemand,productivecapital,andtechnologies;therequired(publicandprivate)
45、investments;andtheimplicationsforeconomiccostsandbenefits(e.g.,fuelsavings).Theinvestments,costs,andbenefitscanbetriggeredbypriceandnonpricepoliciesorinterventions(whicharenotnecessarilydescribedinthesectoralscenarios).Theinvestments,costs,andbenefitsidentifiedinthesectoralpathwaysarethenenteredinto
46、themacroeconomicmodelstoexplorethefeasibilityofthesectoralscenariosaswellastheiraggregateimplicationsfor(i)growthandothermacroeconomicvariablesand(ii)householdwelfareandemploymentatthesectorallevel.Thefocusofthemacroeconomicanalysesistoensureconsistencyacrossthevarioussectoralscenarios,toidentifypos
47、itiveornegativespilloversacrosssectors,andhighlighteconomictradeoffsthatmitigationpoliciesmightentail.InthecaseofTurkey,weanalyzethesepotentialtradeoffsusingtwotypesofmodels:(1)amultisectorCGEmodel,MANAGE(Mitigation,Adaptation,andNewTechnologiesAppliedGeneralEquilibrium),tohighlighttheintrasectoralc
48、onsequencesofthetransition,and(2)anaggregatemacrofiscalmodel(MFMod)toaccountforaggregatepriceandwagerigiditieswhendeterminingthefiscalandeconomicconsequencesoftransitioning.Section2presentsthesectoralnetzeropathwaysintheTurkeyCCDR.Sections3and4discusstheintegrationofthesesectoralpathwaysinthetwomacr
49、oeconomicmodels,MANAGEandMFMod,respectively.Section5summarizestheresultsofthemacroeconomicanalysisoflow-carbondevelopmentfromallpublishedCCDRs.Section6concludes.2. Bottom-UpApproachtoDefineIllustrativeSectoralRoadmapstoAchieveNetZeroEmissionsThissectionillustratesthehybridapproachbyapplyingittoTurkey.Theleft-handsideoffigure2showsTurkey,sGHGemissionshistoryinwhichtheenergysector(i.e.,power,transportation,buildings,andindustrialsectors)isthelargestcontribut
