亚洲发展中国家的脱碳途径：来自建模情景的证据-亚开行（英）

DECARBONIZATIONPATHWAYSINDEVELOPINGASIAEVIDENCEFROMMODELINGSCENARIOSManishaPradhananga,DavidA.Raitzer,IvaSebastian-Samaniego,andDaryllNavalADBECONOMICSNO.711WORKINGPAPERSERIESDecember2023ASIANDEVELOPMENTBANKADBEconomicsWorkingPaperSeriesDecarbonizationPathwaysinDevelopingAsia:EvidencefromModelingScenariosManishaPradhananga,DavidA.Raitzer,IvaSebastian-Samaniego,andDaryllNavalManishaPradhananga(mpradhananga@)andDavidA.Raitzer(draitzer@)areeconomists,IvaSebastian-Samaniego(isebastian@)isasenioreconomicsofficer,andDaryllNaval(dnaval.consultant@)isaconsultantattheEconomicResearchandDevelopmentImpactDepartment,AsianDevelopmentBank.No.711|December2023TheADBEconomicsWorkingPaperSeriespresentsresearchinprogresstoelicitcommentsandencouragedebateondevelopmentissuesinAsiaandthePacific.TheviewsexpressedarethoseoftheauthorsanddonotnecessarilyreflecttheviewsandpoliciesofADBoritsBoardofGovernorsorthegovernmentstheyrepresent.ASIANDEVELOPMENTBANKꢀCreativeCommonsAttribution3.0IGOlicense(CCBY3.0IGO)©2023AsianDevelopmentBank6ADBAvenue,MandaluyongCity,1550MetroManila,PhilippinesTel+63286324444;Fax+63286362444Somerightsreserved.Publishedin2023.ISSN2313-6537(print),2313-6545(electronic)PublicationStockNo.WPS230593-2DOI:/10.22617/WPS230593-2TheviewsexpressedinthispublicationarethoseoftheauthorsanddonotnecessarilyreflecttheviewsandpoliciesofꢀtheAsianDevelopmentBank(ADB)oritsBoardofGovernorsorthegovernmentstheyrepresent.ADBdoesnotguaranteetheaccuracyofthedataincludedinthispublicationandacceptsnoresponsibilityforanyconsequenceoftheiruse.ThementionofspecificcompaniesorproductsofmanufacturersdoesnotimplythattheyareendorsedorrecommendedbyADBinpreferencetoothersofasimilarnaturethatarenotmentioned.Bymakinganydesignationoforreferencetoaparticularterritoryorgeographicarea,orbyusingtheterm“country”inꢀthispublication,ADBdoesnotintendtomakeanyjudgmentsastothelegalorotherstatusofanyterritoryorarea.ThispublicationisavailableundertheCreativeCommonsAttribution3.0IGOlicense(CCBY3.0IGO)/licenses/by/3.0/igo/.Byusingthecontentofthispublication,youagreetobeboundbyꢀtheꢀtermsofthislicense.Forattribution,translations,adaptations,andpermissions,pleasereadtheprovisionsandꢀtermsofuseat/terms-use#openaccess.ThisCClicensedoesnotapplytonon-ADBcopyrightmaterialsinthispublication.Ifthematerialisattributedtoꢀanothersource,pleasecontactthecopyrightownerorpublisherofthatsourceforpermissiontoreproduceit.ADBcannotbeheldliableforanyclaimsthatariseasaresultofyouruseofthematerial.Pleasecontactpubsmarketing@ifyouhavequestionsorcommentswithrespecttocontent,orifyouwishtoꢀobtaincopyrightpermissionforyourintendedusethatdoesnotfallwithintheseterms,orforpermissiontousetheꢀADBlogo.CorrigendatoADBpublicationsmaybefoundat/publications/corrigenda.Note:Inthispublication,“$”referstoUnitedStatesdollars.ABSTRACTUnlessdevelopingAsiadecarbonizesitsdevelopment,globalwarmingisunlikelytostaybelowtheinternationallyagreedlimitof2°Cabovepreindustriallevels.Integratedassessmentmodelingoffersinsightsintohowalowcarbontransitioncanbeachieved.TheSixthAssessmentReportoftheIntergovernmentalPanelonClimateChangeincorporatedanambitiousmodelintercomparisoneffortthatcompiledthousandsofmodel-scenariocombinationstoconsiderlowcarbondevelopmentpathways.ThispaperexplorestheevidencewithinthatdatabasetoconsiderdecarbonizationpathwaysfordevelopingAsia.Overall,acomparisonofthemajormodelsfindsstrongconsistencyinthetransformationoftheenergysectorrequiredtoachieveParisAgreementgoals.Thisincludesarapiddeclineintheshareofcoal—amainstayofthepowersectorindevelopingAsia—andasubstantialriseinrenewableenergy.Thecostofthetransitioncanberelativelylowifmitigationeffortsareefficient,asassumedinthemodels.Keywords:

climatechange,integratedassessmentmodel,mitigation,energy,ParisAgreement,NDCsJELcodes:

C61,D58,Q4,Q541.IntroductionDevelopingAsiahasaspecialstakeintheglobalclimatecrisis,astheregionisbothhighlyvulnerabletoclimatechangeandaccountsforagrowingshareoftheworld’sgreenhousegas(GHG)emissions.Asof2019,developingAsiaishometosomeofthebiggestemittersandaccountsforabout44%ofglobalGHGemissions.Althoughpercapitaemissionsfromtheregionarewellbelowadvancedeconomies,theyarerapidlyincreasing(WorldResourcesInstituten.d.).Ifregionalemissionstrendscontinue,nomatterwhetherotherregionsrapidlyreduceemissions,achievingtheParisAgreementgoaloflimitingglobalmeantemperaturerisetowellbelow2°Cwillnotbepossible(Emmerlinget.al.2023).Asthelargestsourceofemissions,theenergysectorwillneedtoundergoatransformationtoachievetheregion’sclimategoals.Thisisparticularlyimportant,giventhatenergyconsumptionintheregionisexpectedtoriserapidlyfromlowlevels.Inthelast2decades,developingAsiamaderapidprogressinexpandingaccesstoelectricity.However,112.5millionpeopleintheregionstilldonothaveaccesstoelectricity,while1.3billiondonothaveaccesstocleancookingtechnologies(WorldBankn.d.).AchievingthistransformationoftheenergysystemtomeetdevelopmentandclimategoalswillposearangeofchallengesaswellasopportunitiesfordevelopingAsia.Inrecentyears,integratedassessmentmodelinghasmadeadvancesintheabilitytoconsiderlowcarbondevelopmentpathways.Moreintegratedassessmentmodelsnowendogenizetechnicalchange,andtheyhaveagrowingrangeofenergytechnologiesreflected(Wilsonetal.2021).Toagreaterdegree,modelershavealsoworkedtogetherinintercomparisoneffortstounderstandlargerpatternsinscenarioresults(O’Neilletal.2020).TheSixthAssessmentReportoftheIntergovernmentalPanelonClimateChange(IPCC)incorporatedanambitiousmodelintercomparisoneffortthatcompiledthousandsofsubmittedmodel-scenariocombinations,eachofwhichhadthousandsofoutputs,inanintegratedscenario2database(Byersetal.2022).ThispaperexplorestheevidencewithinthatdatabasetoconsiderdecarbonizationpathwaysindevelopingAsiaundercurrentpoliciesandcommitmentsandpledgesunderParisAgreement.2.ContextHistorically,GHGemissionsfromdevelopingAsiawererelativelylow.In1990,theregionaccountedforaboutaquarterofglobalGHGemissionsand54%oftheglobalpopulation.However,followingrapidgrowthinmajoreconomiesintheregion,emissionsfromtheregionincreasedtoabout44%oftheglobalsharein2019.TheregionisnowhometosomeofthebiggestemittersintheworldincludingIndia,Indonesia,andthePeople’sRepublicofChina(PRC)(Figure1).Together,thesethreeeconomiesaccountforaboutathirdofglobalGHGemissions.Figure1:GlobalAnnualGreenhouseGasEmissionsGtCO2e=billiontonsofcarbondioxideequivalent.Note:Emissionsfromland-usechangeandforestry,whichcanbepositiveornegative,areincluded.RestofdevelopingAsiaincludesallremainingAsianDevelopmentBankdevelopingmembereconomies,exceptforHongKong,ChinaandTaipei,Chinaforlackofdata.Source:WorldResourcesInstitute.ClimateWatch(accessed10January2023).Percapitaemissionsfromtheregionremainbelowadvancedeconomiesbutarerapidlyincreasing(Figure2).TheincreasehasbeenparticularlysharpforthePRC,wherepercapitaGHGemissionsincreasedmorethanthreefoldfrom2.5tonsin1991to8.6tonsin2019.3Meanwhile,GHGemissionsinadvancedeconomiesstartedtodeclineinthelate2010sbutremainabovetheglobalaverage.Figure2:GreenhouseGasPerCapitaEmissions,1990–2019GtCO2e=billiontonsofcarbondioxideequivalent;PRC=People’sRepublicofChina.Note:Greenhousegasemissionsincludelanduse,land-usechange,andforestry.“RestofDevelopingAsia”includesall46AsianDevelopmentBankmembereconomies,excludingIndia,Indonesia,andthePRC.“Advancedeconomies”include35economies.Source:WorldResourcesInstitute.ClimateWatch(accessedFebruary2023).Theenergysectoraccountsforthree-fourthsofglobalGHGemissionsandnearlyaslargeashareindevelopingAsia.Withintheenergysector,electricityandheatproductionarethebiggestcontributors,accountingforabout40%ofemissionsfromdevelopingAsiain2019(Figure3).Electricityandheatproductionwerethefastest-growingsourcesofGHGemissionsintheregionfrom1991to2019inbothrelativeandabsoluteterms.Apartfromelectricityandheatproduction,othermajorsourcesofGHGemissionsincludemanufacturing(18%),agriculture,andland-usechangeandforestry(14%),transportation(9%),andindustrialprocesses(8%).Atthesametime,thesourcesofemissionsvaryamongtheeconomies.Forinstance,closetohalfofGHGemissionsinIndonesiacomefromlanduse,includingfromdeforestationofpeatswampscontainingthousandsoftonsofcarbonperhectare.Meanwhile,agricultureremainsamajorsourceofGHGemissionsinSouthAsiancountriesthatincludeNepal(54%)andPakistan(44%).4Figure3:GreenhouseGasEmissions,bySector,2019Note:Greenhousegasemissionsfromland-usechangeandforestry,whichcanbepositiveornegative,areincluded.“DevelopingAsia”includesallAsianDevelopmentBankmembereconomiesexcludingHongKong,ChinaandTaipei,Chinaforlackofdata.Source:WorldResourcesInstitute.ClimateWatch(accessedFebruary2023).MuchoftheincreaseinGHGemissionsintheregionduringthelast3decadeswasdrivenbyasharpriseincarbondioxideemissions.In2019,carbondioxideemissionsaccountedfor78%ofthetotalGHGemissions,markinganotablerisefrom60%in1990(Figure4).Meanwhile,emissionsfromothersources,althoughincreasinginvolume,havebeendeclininginshares.Anexceptiontothistrendisfluorinatedgases,recognizedasapotentGHGandcommonlyemployedassubstitutesforozone-depletingsubstances.From1991to2019,theshareoffluorinatedgaseshasslightlyincreasedfrom0.1%to2.2%.5Figure4:GreenhouseGasEmissionsinDevelopingAsia,byGasType,1990–2019Note:“DevelopingAsia”includesallAsianDevelopmentBankmembereconomiesexcludingHongKong,ChinaandTaipei,Chinaforlackofdata.Source:WorldResourcesInstitute.ClimateWatch(accessedFebruary2023).DevelopingAsia’sprimaryenergysupplyincreasedby218%from1,820milliontonsofoilequivalent(Mtoe)in1991to5,800Mtoein2020(Figure5),whichisfarabovethe15%growthintherestoftheworld.1TheincreaseisdrivenmainlybythePRC,whoseprimaryenergysupplyincreasedfour-foldsfrom848Mtoe(accountingfor46.8%ofdevelopingAsia’sthermalenergystorage[TES])to3,470Mtoe(59.9%).Thesurgeinenergydemand,drivenbyrapideconomicgrowthandpopulationexpansion,hasprimarilybeenmetthroughtheextensiveuseofcoalasanenergysource.Coalaccountedfor48.7%oftotalprimaryenergyin2020,followedbycrudeoilat23.7%,andnaturalgasat11.6%.Incontrast,coalprovidedonly11.3%ofprimaryenergyintherestoftheworld.1Primaryenergysupplyisthetotalamountofprimaryenergythataneconomyhasatitsdisposal,whichincludesimportedenergy,exportedenergy(subtractedoff),andenergyextractedfromnaturalresources(energyproduction).6Figure5:PrimaryEnergySupply,1991–2020(a)DevelopingAsia(b)RestoftheWorldNGL=naturalgasliquids.Note:“DevelopingAsia”includesall46developingmembersoftheAsianDevelopmentBankwithavailabledata.Source:Enerdata.GlobalEnergyandCO2

Data(accessed20September2022).7TotalelectricitysupplyindevelopingAsiaincreasedfrom1,691terawatt-hours(TWh)in1991to11,932TWhin2020.Coal,themostcarbonintensivemajorsourceofelectricity,remainstheprimarysourceofpowerintheregion,althoughitssharestartedtodeclineinthelastdecade(Figure6).Coal’ssharesinthegenerationmixincreasedfrom52.5%in1991toanall-timehighof66.3%in2011,thereafterstartingaperiodofdecline,reaching59.5%in2020.Figure6:ElectricityGenerationinDevelopingAsia,1991–2020Source:Enerdata.GlobalEnergyandCO2

Data(accessed20September2022).EnergyintensityindevelopingAsiaisfarabovethatofadvancedeconomies,whichimplieseconomicgrowthhasmorepotentialtoincreaseenergydemand.ThisisespeciallysointhePRCandinCentralAsia.Atthesametime,energyintensityhasfallenovertime.Thisisinpartduetoincreasingefficiencywithtechnicalchangeandinpartduetoastructuralshiftoftheeconomytowardservices(Figure7).2Between2004and2019,globalenergyintensitydeclined2Energyintensityreferstothephysicalenergyrequiredtogenerateeachunitofgrossdomesticproduct.TheInternationalEnergyAgencyusesenergyintensityastheindicatorusedtotrackprogressonglobalenergyefficiency.8by21.7%toreach4.7megajoules(MJ)per2017UnitedStatesdollar($)purchasingpowerparity(PPP).TheSustainableDevelopmentGoal(SDG)targetof3.4MJper2017$PPPby2030willrequireanannualreductionof2.6%until2030.Theworld,however,hasfailedtodeliveronthis,withreductionsrangingfrom0.8%to2.2%during2016–2019(IEA2022).Energyintensitystillvarieswidelyacrosstheregion,althoughmosteconomiesremainwellabovetheSDG,andtheregionremainsabovetheworldaverage(Figure8).Figure7:TrendsinEnergyIntensity,2004–2020(megajouleper2015$PPP)PRC=People’sRepublicofChina,PPP=purchasingpowerparity.Note:“Advancedeconomies”include36economies.Source:Enerdata.GlobalEnergyandCO2

Data(accessed20September2022).Itishoweveronlyanimperfectproxytoenergyefficiencyindicatorasitcanbeaffectedbyseveralfactorsnotnecessarilylinkedtopureefficiencysuchasclimate.9Figure8:EnergyIntensity,1991and2020(megajouleper2015$PPP)LaoPDR=LaoPeople’sDemocraticRepublic,PRC=People’sRepublicofChina,PPP=purchasingpowerparity.Notes:ADBplacedonholditsregularassistanceinAfghanistaneffective15August2021.Effective1February2021,ADBplacedatemporaryholdonsovereignprojectdisbursementsandnewcontractsinMyanmar.Source:Enerdata.GlobalEnergyandCO2

Data(accessed20September2022).10ThehighenergyintensityindevelopingAsia,suppliedbyacarbonintensiveenergysystem,meansthatfutureeconomicgrowthcangreatlyincreasegreenhousegasemissions.Comparedwiththerestoftheworld,growthingrossdomesticproductindevelopingAsiaisexpectedtobemuchmorerapid.Projectionsagreedbytheinternationalmodellingcommunityforthe“middleoftheroad”scenarioofthesharedsocioeconomicpathways(SSP2)showtheregiongrowingmorethantwiceasfastastherestoftheworldinthecomingdecades,withcertainlargeeconomies,suchasIndiaandIndonesia,growingevenfaster(Figure9).Unlessthatgrowthismuchgreenerthanthepatternstodate,achievingthegoalsoftheParisAgreementwillnotbepossible.Figure9:ProjectedGrowthofGrossDomesticProductunderthe“MiddleoftheRoad”ScenarioGDP=grossdomesticproduct,PRC=People’sRepublicofChina.Note:ValuesreflectanaverageofresultsfrommodelsintheSharedSocioeconomicPathwayScenarioDatabase.Source:Riahi,Keywan,DetlefP.vanVuuren,ElmarKriegler,JaeEdmonds,BrianC.O’Neill,etal.2016.“TheSharedSocioeconomicPathwaysandtheirEnergy,LandUse,andGreenhouseGasEmissionsImplications:AnOverview.”GlobalEnvironmentalChange42,153–68.WithindevelopingAsia,thereisrecognitionoftheimportanceofchangingcourse.AlloftheeligibleeconomiesintheregionhaveagreedtotheParisAgreement,whichseekstolimitglobalwarmingtowellbelow2°Candpursueeffortsto1.5°Ccomparedtopreindustriallevels.AllParisAgreementpartiesintheregionhavesubmittednationallydeterminedcontributions(NDCs),11mostofwhichcontaincommitmentstoreduceemissionsby2030.Goingbeyondtheseshort-termcommitments,19developingAsianeconomies,accountingforabout80%oftheregion’s2019totalGHGemissions,havemadepledgestoachievecarbonneutrality(ornetzero)withinthe21stcentury.However,thosepledgesarenonbindingandlargelyremaintobereflectedinspecificplansandpolicies.3.ObjectivesWithrapidlygrowingeconomiesandnearlyhalfofglobalGHGemissions,thedevelopmenttrajectoryofAsiaiscriticaltoachievingthegoalsoftheParisAgreement.OnlyifAsiachangescoursedramaticallyintermsofenergyandlandusecanglobalwarmingbekeptcontained.Thequestionthen,ishowAsiawouldneedtotransformtoachievethegoalsoftheParisAgreement.Thisstudyattemptstoanswerthefollowingquestions,drawingonaninternationaldatabaseofresultsfromleadingclimate-energy-economymodels.(i)HowwouldAsia’semissionsevolveundercurrentpolicies,comparedwithNDCs,andaworldthatmeetstheParisAgreementgoalofahighprobabilityofkeepingwarmingwellbelow2°C?(ii)HowwouldAsia’senergymixevolveundercurrentpolicies,comparedwithNDCsandunderawellbelow2°Cscenario?(iii)Whatwouldbetheimplicationsforinvestmentandeconomicgrowthofpursuitofthedecarbonizationscenarios?124.MethodsIntegratedassessmentmodels(IAMs)combinedifferentstrandsofknowledgetoprovideinsightsonhowtheglobaleconomy,alongwithenergy,land,andagriculturesystems,interactswiththeenvironment.IAMsprovidethebulkofevidencereliedonbytheIPCCforinsightsintoalternativemitigationstrategiesandtheirfeedbacksandtradeoffs.AspartoftheIPCC’sSixthAssessment(AR6)Report,authorsoftheWorkingGroupIIIonMitigationofClimateChangeundertookacomprehensiveexercisetocollectandassessquantitative,model-basedscenarios.Thecompilationandassessmentofthescenarios,collectivelyreferredtoastheAR6scenarioexploreranddatabase,ishostedbytheInternationalInstituteforAppliedSystemsAnalysis(IIASA).Thedatabasecontains3,131scenariorunsfrom188models,withdataon1,775variablesonsocioeconomicdevelopment,GHGemissions,andsectoraltransformationsacrossenergy,landuse,transportation,andindustry.Thesubmittedscenariorunsrepresentthelatestscientificunderstandingofthepathwaysofevolutionofglobalenergysystemsandassociatedemissions,aswellasimplicationsforeconomiesinmajorworldregions.ThispaperharnessesthisunderstandingfromtheAR6ScenarioDatabasetounderstandpatternsinmodeledresultsofdifferentclimatepolicyscenariosfordevelopingAsia.Byusingadatabasereflectingarangeofmodelsforanalyzedscenarios,thepaperavoidsthebiasesthatmaybeembeddedinonespecificmodelandreliesonlargerpatternsoffindingsrepresentingarangeofmodelstructuresandperspectives.Toencapsulatearangeofclimatepolicyfutures,theanalysisselectedIAMsandscenariorunsfromtheAR6databasethatcorrespondtofourclimatepolicyscenarios:(i)Currentpoliciesassumenoadditionaleffortonclimatechangemitigationbeyondthatisalreadyincludedincurrentenergyandclimatepolicies.(ii)NDCeffortassumesimplementationofNDCsuntil2030,withgradualstrengtheningthereafter.13(iii)2°CassumeseconomiesfollowtheirNDCsuntil2030andacoordinatedeffortthereaftertostaywithinthecarbonbudgetconsistentwiththewellbelow2°CgoaloftheParisAgreement.Afterreachingthebudget,emissionsneedtostayatorclosetozeroandnotrelyonnegativeemissionstotakecareofan“overshoot”ofthecarbonbudget.(iv)2°CearlyactionassumeseconomiestakeearlyactionandfollowanacceleratedpathtomeetParisAgreementgoalsoflimitingwarmingtowellbelow2°C,withoutovershoot.TheanalysisexcludesscenariorunsthatdidnotpasshistoricalandfuturevettingbytheIPCC,asindicatedinthedatabase.Intermsofsharedsocioeconomicpathways(SSPs)thatdeterminepopulationandgrowthprojections,itonlyincludesscenariosthatareconsistentwiththeSSP2‘middleoftheroad’category.Thescenariorunsarethenfilteredbasedonthepolicycategoryname.Forthe2°Cscenarios,additionalfilteringiscarriedouttoensureacarbonbudgetthatisconsistentwithwellbelow2°Cwarming.3Thisalsoexcludesscenariorunsthatallowforovershootofthecarbonbudgettoberemediedthroughnegativeemissions.DetailsofthefilteringmethodologyaresummarizedinTable1.Table1:SelectionCriteriaforScenariosfromtheAR6DatabaseScenarioPolicyCategoryNameCarbonBudget(GtCO2,2020-2100)CurrentPoliciesNDCEffort2°CP1b:currentpoliciesP1c:NDCP3b:NDC+delayedglobalactionP2a:Immediateglobalactionwithouttransfers--1035to12651035to12652°CearlyactionAR6=SixthAnnualReportoftheIntergovernmentalPanelonClimateChange,GtCO2=billiontonsofcarbondioxide,NDC=nationallydeterminedcontributions.Source:Authors.3Wellbelow2°Cisinterpretedasahigherthan67%probabilityofstayingbelow2°Cpeaktemperatureincrease.ThisisbasedonclimatecategoryC3oftheIPCCAR6WorkingGroupIIIreport(IPCC2022).Thepeaktemperatureisreachedin2080inthenetzeroscenarios.14TheremainingAR6scenariorunsacrossthe4climatescenariosarefrom11commonIAMs.Afterdroppingolderversionsofthemodels,thescreeningleftjust9models.Figure10showsthattheselected9IAMsareamongthetop10modelsthatcontributedthemostscenariostoIPCCAR6WorkingGroupIIIreport.Figure10:NumberofScenarioRunsfromtheTop10ModelFamiliesAIM=Asia-PacificIntegratedModeling;COFFEE=ComputableIntegratedFrameworkforEnergyandtheEnvironment;GCAM=GlobalChangeAnalysisModel;GEME-3=GeneralEquilibriumModelforEconomy-Energy-Environment;IMAGE=IntegratedModeltoAssesstheGlobalEnvironment;MESSAGE=ModelforEnergySupplyStrategyAlternativesandtheirGeneralEnvironmentalImpact;POLES=ProspectiveOutlookonLong-termEnergySystems;REMIND=REgionalModelofINvestmentandDevelopment;TIAM=TIMESIntegratedAssessmentModel;WITCH=WorldInducedTechnicalChangeHybrid.Source:IntergovernmentalPanelonClimateChange.2022.ClimateChange2022:MitigationofClimateChange.ContributionofWorkingGroupIIItotheSixthAssessmentReportoftheIntergovernmentalPanelonClimateChange.CambridgeandNewYork:CambridgeUniversityPress.Table2liststhescenariorunsthatwereincludedintheanalysis.Inthecaseofmultiplescenariosofthesamemodel,resultsareaveragedacrossthescenarios.TheAppendixprovidesmoredetailsontheIAMs.15Table2:ScenarioRunsandModelsIncludedintheAnalysisModelsAIM/CGE2.2CurrentPoliciesEN_NPi2100NDCEffortEN_INDCi21002°C2°CearlyactionEN_INDCi2030_1200--COFFEE1.1EN_NPi2100CO_CurPolEN_INDCi2100_COV_NDCpEN_INDCi2030_1200EN_INDCi2030_1000--CO_NDCplusEN_INDCi2100_COV_NDCpEN_INDCi2100CO_NDCplusGEM-E3_V2021IMAGE3.0EN_NPi2100CO_CurPolEN_NPi2100_COVEN_INDCi2030_1400EN_INDCi2030_1200EN_NPi2020_1400EN_NPi2020_1200MESSAGEEN_NPi2100_COEN_INDCi2100_COV_NDCpEN_INDCi2030_1400_COV_NDCpEN_NPi2020_1400_COVix-VGLOBIOM_1.1NGFS2_CurrentPoliciesNGFS2_NDCsPOLESENGAGEEN_NPi2100_COVEN_INDCi2100_COV_NDCpEN_INDCi2030_1200EN_INDCi2030_1000_COV_NDCpEN_NPi2020_1000_COVEN_NPi2020_1200REMIND-MAgPIE2.1-4.2EN_NPi2100_COVNGFS2_CurrentPoliciesEN_INDCi2100_COV_NDCpNGFS2_NDCsSusDev_SSP2-NDCEN_INDCi2030_1200EN_NPi2020_1200CEMICS_SSP2-NpiSusDev_SSP2-NPiTIAM-ECN1.1EN_NPi2100_COVEN_INDCi2100_COVEN_INDCi2030_1400EN_INDCi2030_1200EN_NPi2020_1200EN_NPi2020_1400EN_INDCi2100_NDCpWITCH5.0EN_NPi2100CO_CurPolEN_INDCi2100_NDCpEN_INDCi2030_1200_NDCpEN_NPi2020_1200CO_NDCplusAIM/CGE=Asia-PacificIntegratedModeling/ComputableGeneralEquilibrium;CEMICS=ContextualizingClimateEngineeringandMitigation:Illusion,ComplementorSubstitute;CO=COMMITorClimatepOlicyassessmentandMitigationModelingtoIntegratenationalandglobalTransitionpathways;COFFEE=ComputableIntegratedFrameworkforEnergyandtheEnvironment;COV=COVID-19;COVID-19=coronavirusdisease;CurPol=currentpolicies;EN=ExploringNationalandGlobalActionstoreduceGreenhousegasEmissions(ENGAGE);GEME-3=GeneralEquilibriumModelforEconomy-Energy-Environment;IMAGE=IntegratedModeltoAssesstheGlobalEnvironment;INDC=CurrentIntendedNationallyDeterminedContributions;MESSAGEix-GLOBIOM=ModelforEnergySupplyStrategyAlternativesandtheirGeneralEnvironmentalImpact-GLobalBIOsphereManagement;NGFS=NetworkforGreeningtheFinancialSystem;Npi=implementednationalpolicies;POLES=ProspectiveOutlookonLong-termEnergySystems;REMIND-MAgPIE=REgionalModelofINvestmentandDevelopment-ModelofAgriculturalProductionanditsImpactontheEnvironment;SSP=sharedsocioeconomicpathways;SusDev=sustainabledevelopment;TIAM-ECN=TIMESIntegratedAssessmentModel-EnergyResearchCentreoftheNetherlands;WITCH=WorldInducedTechnicalChangeHybrid.Source:AuthorsbasedontheAR6scenarioexplorer.InternationalInstituteforAppliedSystemsAnalysis(IIASA).AR6ScenarioExplorer.https://data.ece.iiasa.ac.at/ar6/

(accessed13April2023).AmajorityofscenariorunssubmittedtotheAR6databaseisbymodelinter-comparisonprojects.Modelinter-comparisonprojectshavebeenimportantforthedevelopmentofIAMssincetheearly1990s.IAMsencompassaheterogenousgroupsofmodellingframeworksthatborrowfromvariousintellectualtraditionsincludingenergysystemsmodellingandmacroeconomic16forecasting.ThismeansthatIAMshavedifferentsetsofstrengthsandlimitations.ModelintercomparisonprojectsallowamoreconsistentandsystematicassessmentacrosstheIAMsandorganizeresearchtowardprovidingpolicy-relevantinsights(Beeketal.2020,Cointeetal.2019).Table3providesabriefoverviewofthemajorintercomparisonprojectsthatsubmittedscenariorunstotheAR6database.Thescenariorunsselectedforthisp