THEINTERNATIONALCOUNCILNCTHEINTERNATIONALCOUNCILNCEANTRANPRTATIONSEPTEMBER2025AviationVision2050Thepotentialforclimate-neutralgrowthXINYISOLAZHENG,JAYANTMUKHOPADHAYAPH.D.,JONATHANBENOIT,SUPRAJAN.KUMAR,DANRUTHERFORDPH.D.,DENIZRHODE,DANIELSITOMPULEXECUTIVESUMMARYAviationisagrowingcontributortoclimatechange,witheffectsextendingbeyondcarbondioxide(CO2)emissionstoincludeshort-livedclimatepollutants(SLCPs)suchasnitrogenoxides,blackcarbon,andcontrailcirrus.In2022,theInternationalCivilAviationOrganizationagreedtoachievenet-zeroCO2emissionsby2050,buttheindustryisnotontracktodeliverthescaleoffuelefficiencyimprovements,sustainableaviationfuel(SAF)uptake,andzero-emissionaircraftdevelopmentrequiredtomeetthatgoal.RecentadvancesinthescientificunderstandingofSLCPshaveattractedattentiontothepotentialrapidreductionsinaviation-attributablewarmingthroughcontrailmitigation.ButnodeepdecarbonizationroadmapsforaviationhavebeenupdatedtoreflectSLCPcontrols.ThisreportupdatestheICCT’sVision2050decarbonizationroadmapfortheaviationsectorbyquantifyinghowSLCPmitigationcancomplementgreenhousegas(GHG)strategiestoalignaviationwiththeParisAgreement.Usingahigh-fidelity2023flightemissioninventory(JETSTREAM),anemissionprojectionmodel(PACE2.0),andasimplifiedclimatemodel(FaIR),thereportestimatesaviation’swarmingpotentialthrough2050acrossfivescenariosthatspanthefullrangeofGHGandSLCPcontrol:HistoricalTrends,CurrentCommitments,GHGForward,SLCPForward,andFullBreakthrough.TheParisAgreement,adoptedin2015,commitscountriestolimitglobalwarmingtowellbelow2°Candtopursueeffortstolimitthetemperatureincreaseto1.5°Cabovepre-industriallevels.Thisreportcomparesaviation’swarmingcontributionstotheremaining1.7°Cwarmingbudget,reflectingrecentfindingsthatglobalwarmingislikelytosurpassthe1.5°Cthresholdbefore2030.AsshowninFigureES1,undertheHistoricalTrendsscenario,weprojectanadditional60millidegreesCelsius(mC),or0.06°C,ofwarmingfromaviationactivitybetween2025and2050,whichisdoubleitscontributiontotemperaturechangeoveritsentirehistoryfrom1940to2024.TheCurrentCommitmentsscenario,whichaccountsforpoliciestocurbaviationGHGemissionsannouncedtodate,projectsan11mC(19%)reductioninwarmingbymid-century.TheGHGForwardcase,whichmodelsmaximumlevelsofGHGmitigationthroughSAFuptake,zero-emissionplanes(ZEPs),andimprovedfuelefficiency,isprojectedtocutfuturewarmingby29mC,or48%belowtheHistoricalTrendscase.However,aviationwoulddoubleitshistorical4%shareofglobalwarming,to9%oftheremaining1.7°Cbudget,underthisscenario.iICCTREPORT|AVIATIONVISION2050:THEPOTENTIALFORCLIMATE-NEUTRALGROWTHiiICCTREPORT|AVIATIONVISION2050:THEPOTENTIALFORCLIMATE-NEUTRALGROWTHFigureES1Aviation’sprojectedcontributiontoglobalwarmingbyscenario,1940to2050Aviation’sshareofremaining1.7°Cbudgetconsumedby2050Attributablewarming(?C)0.120.110.100.090.080.070.060.050.040.03Attributablewarming(?C)0.000.1180.1070.0890.072(Historicalwarmingupto2025)0.0630.058(Historicalwarmingupto2025)195019701990201020302050ScenarioHistoricalTrendsCurrentCommitmentsGHGForwardSLCPForwardFullBreakthroughTHEINTERNATIONALCOUNCILONCLEANTRANSPORTATIONTHEICCT.ORGLargerreductionsaremodeledviatheSLCPForwardscenario,whichaddscontrailavoidance,fuelqualityimprovements,andadvancedenginestotheCurrentCommitmentsscenario;inthisscenario,additionalwarmingisreducedby46mC,or76%belowHistoricalTrends.TheSLCPForwardscenariokeepsaviationtoa4%shareoftheremaining1.7°Cclimatebudgetuntil2050,butthesharewilllikelyincreasebeyond2050asunmitigatedGHGemissionscontinuetodrivewarming.IntheFullBreakthroughscenario,whichblendsmaximumGHGandSLCPmitigation,aviation’scontributiontoglobalwarmingiscutby91%belowtheHistoricalTrendsscenarioandlimitsaviation’sshareofadditionalcontributiontotheremaining1.7°Cbudgetto2%.BycomparingtheHistoricalTrendsandFullBreakthroughscenarios,wecancharacterizetherelativecontributionthatdifferentmitigationleversmayplayincurbingaviation’sclimateimpact.TableES1summarizestherelativecontributionofeachmitigationlevertoavoidablewarmingin2050.Theshareoftotalwarmingbymitigationleverisshownatthefarright;thebreakdownofGHGversusSLCPcontrolisshownatthebottomofthetable.iiiICCTREPORT|AVIATIONVISION2050:THEPOTENTIALFORCLIMATE-NEUTRALGROWTHTableES1Shareofavoidablewarmingbymitigationleverin2050undertheFullBreakthroughscenarioMitigationleverAvoidedwarming(mC)%oftotalRankGHGsSLCPsTotal1Contrailavoidance0.07-23.4-23.342.5%2Sustainableaviationfuel-5.90-5.68-11.621.1%3Hydrotreating0.05-6.35-6.3011.5%4Operationalefficiency-1.37-4.58-5.9510.8%5LowNOX/nvPMengines0.00-4.39-4.398.0%6Technicalefficiency-0.84-1.80-2.644.8%7Demandresponse-0.12-0.30-0.420.8%8Modalshift-0.07-0.17-0.250.5%9Zero-emissionplanes-0.02-0.02-0.050.1%Total-8.20-46.6-54.9100%%oftotal100%Asshowninthetable,contrailavoidancecontributesthelargestshare(23mC,ormorethan40%)ofallpotentialavoidablewarming.Thatincludesasmall(0.07mC)temperatureincreaseduetothefuelburnpenaltyofrerouting.TheuseofSAFcontributes21%ofavoidedtemperatureincrease,thesecondlargestamount.Hydrotreatingandoperationalefficiencyarethethirdandfourthmostimportantlevers,bothcontributingabout11%ofthetotalavoidablewarming;three-quartersoftheoperationalefficiency-enabledmitigationcomesfromSLCPsdueinparttoareductioninkilometersflown.Otherlevers,includinglowNOXandlownon-volatileparticulatematter(nvPM)engines,hydrotreating,technicalefficiency,ZEPs,demandresponse,andmodalshiftcontributeonlymodestlytoavoidablewarming.Overall,85%oftheavoidedtemperatureincreaseislinkedtoSLCPs.BecausecontrailabatementtechnologieswouldtakelesstimetodevelopandscalecomparedtoSAF,andatlowercost($5–$20pertonneCO2e,versusmorethan$300pertonneCO2e),SLCPreductionemergesasamorefeasibleoptionwithlargepotentialinmitigatingaviation’sclimateimpact.Keyconclusionsofthisworkinclude:?A2050net-zeroCO2targetisanecessarybutnotsufficientconditiontoalignaviationwiththeParisAgreement.WhileamaximumlevelofGHGmitigationthroughaircraftandfuelsisestimatedtocutadditionalaviationwarmingby48%belowtheHistoricalTrendsscenario,westillprojecta31mCtemperatureriseduetoaviationin2050,withcontinuingwarmingafterwards.Givenaremainingclimatebudgetof340mCtoachieve1.7°C(Forsteretal.,2024),aviationwouldconsume9%oftheremaining1.7°CclimatebudgetunderamaximumGHGreductionscenario,morethandoubleitshistoricalshareof4%.?SLCPcontrols,notablycontrailavoidance,cancomplementGHGmitigationbydeliveringsubstantialnear-termreductionsviaeasier-to-implementtechnologysolutions.Contrailavoidanceinparticularismodeledtobethemostimpactfulandcost-effectivelever,accountingfor40%oftotalavoidablewarmingby2050ivICCTREPORT|AVIATIONVISION2050:THEPOTENTIALFORCLIMATE-NEUTRALGROWTHintheFullBreakthroughscenario,withmitigationcostsordersofmagnitudelowerthanforSAFs.Still,withoutadditionalactiononlowercarbonplanesandfuels,theshort-termcoolingduetoSLCPcutsisprojectedtobeoverwhelmedby2045duetoaccumulatingGHGsintheatmosphere,drivingmorewarming.?AggressiveGHGandSLCPcontrolswillbeneededtocontainaviation’scontributiontoglobalwarmingandachieveclimate-neutralgrowth.CombiningaggressiveGHGandSLCPcontrolsundertheFullBreakthroughscenarioisprojectedtocutmorethan90%ofadditionalaviation-attributablewarmingby2050comparedwiththeHistoricalTrendsscenario,limitingaviation’sshareoftheremaining1.5°Cclimatebudgetconsumedby2050to4%anditsshareoftheremaining1.7°Cbudgetconsumedto2%.Thisreductioncanbeachieveddespitea150%increaseintrafficcomparedwith2023,resultinginclimate-neutralgrowthbetween2035and2050—andpotentiallybeyondwithfurtherGHGcontrols.?Fourmitigationlevers—contrailavoidance,SAFs,hydrotreating,andoperationalefficiency—accountfornearly90%ofavoidablewarmingin2050.Policymakerscouldprioritizemeasurestomaturethesekeytechnologies,suchaswidescaleavoidancetrialscoordinatedbyairnavigationserviceproviders,mandatesandincentivesforSAFandhydrotreatingfossiljetfuel,andcarbonpricingpoliciestopromotemorefuel-efficientoperations.DeploymentofSAFinparticularwoulddeliverbothGHGandSLCPmitigationbenefits.?ControlofSLCPisestimatedtoresultinaclimatebenefitdespitetheexpectedincreaseinGHGemissionsfromtheirimplementation.ThebenefitofreducingSLCPsisprojectedtooutweightheincreasedfuelconsumptionfromapplyingSLCPcontrolmeasures.ThisisstilltruewhenassumingtheclimateimpactofSLCPsisatthelowerendofthe95%confidenceintervalfromouruncertaintyanalysis.ThereportconcludesthatcurrentactionsfocusedonGHGemissionsareinsufficienttoalignaviationwiththeParisAgreement.Toachievemid-termclimatestabilization,policymakerscanincentivizeSLCPcontrols—especiallycontrailmitigation—whilecontinuingtodevelopGHG-reductiontechnologiesforreducinglong-termclimateimpact.vICCTREPORT|AVIATIONVISION2050:THEPOTENTIALFORCLIMATE-NEUTRALGROWTHTABLEOFCONTENTSExecutivesummary iIntroduction 1Background 2Methodology 4Scenariosmodeled 4Climateimpactinventory 6ProjectionofAviationClimateEffectsmodel Temperatureresponse 25Results 27Pollutantemissions 27Temperatureresponse 33Conclusions 42Policyimplications 43Futurework 44References 46AppendixA:Trafficsensitivityanalysis 52AppendixB:ContrailabatementpropertiesofSAFsandhydrotreatedfossiljetfuel 53AppendixC:Contrailuncertaintyanalysis 56AppendixD:UncertaintyanalysisofallSLCPs 62viICCTREPORT|AVIATIONVISION2050:THEPOTENTIALFORCLIMATE-NEUTRALGROWTHLISTOFTABLESTableES1.Shareofavoidablewarmingbymitigationleverin2050undertheFullBreakthroughscenario iiiTable1.Scenariosinvestigated 5Table2.Modelingassumptionsbyscenario 5Table3.Enginemappingappliedforengineemissionestimates 8Table4.Fuelburnandpollutantemissionsbydepartureregion 8Table5.Shareofrevenuetonne-kilometersandcontraileffectiveradiativeforcingbyICAOdepartureregion,2023 Table6.ERFvaluesandtheirrangesfornon-contrailSLCPs Table7.Passengerandfreighttrafficassumptionsforallscenarios,2025to2050 Table8.Technicalefficiencyassumptionsbyaircraftclass Table9.Cruise-phaseNOXemissionindicesbyaircraftclassandscenariofornewdeliveries(gNOX/kgfuel) 20Table10.nvPMnumberemissionindicesbyaircraftclassandscenariofornewdeliveries(#ofparticles/kgfuel) Table11.nvPMmassemissionindicesbyaircraftclassandscenariofornewdeliveries(mgnvPM/kgfuel) Table12.Aviation-attributablewarmingandshareofremainingclimatebudgetundereachscenario 34Table13.Shareoftotalaviationwarmingin2050bypollutantandscenario 38Table14.Shareofavoidablewarmingbymitigationleverin2050undertheFullBreakthroughscenario 40TableC1.ModelingdetailsandestimatedglobalcontrailcirrusRFofallthestudiesusedinthisstudy 57TableC2.ScalingdetailsforeachstudywiththeprocessedRFperkmvaluesandassociateduncertaintybands 58TableC3.Studiesthatquantifyefficacywithprovided95%confidenceintervalsinparenthesis 59TableD1.Valuesusedinuncertaintyanalysisofclimateimpactofcontrails 62TableD2.Temperatureresponsein2050withboundsthataccountfortheuncertaintyintheclimateimpactofSLCPs 62viiICCTREPORT|AVIATIONVISION2050:THEPOTENTIALFORCLIMATE-NEUTRALGROWTHLISTOFFIGURESFigureES1.Aviation’sprojectedcontributiontoglobalwarmingbyscenario,1940to2050 iiFigure1.Contrailcirrusannualmeannetradiativeforcing,2023 9Figure2.PACE2.0modelflow Figure3.Technicalefficiencyassumptionsbyscenarioforregional,narrowbody,widebody,andfreighteraircraft Figure4.SAFblendpercentageversuspercentchangeinannualnetmeanradiativeforcing 22Figure5.Scale-upofcontrailavoidancebyhigh-incomeandupper-middle-incomecountries 24Figure6.Fleetwidefuelburnpenaltybasedondesiredavoidanceeffectiveness 25Figure7.Aviationfuelefficiencybyscenario,2023–2050 27Figure8.JetAshareofglobalaviationkeroseneconsumptionbyscenario,2023–2050 28Figure9.ShareofkerosenefeedstockinSLCPForward(left)andFullBreakthrough(right)scenarios 29Figure10.Annual(left)andcumulative(right)GHGemissionsbyscenario,2023–2050 30Figure11.NOXandnvPMemissionsbyscenario,2023–2050 Figure12.Annualcontraileffectiveradiativeforcingbyscenario,2023–2050 32Figure14.Aviation’shistoricalandcontributiontoglobalwarmingbyscenario,1940–2050 33Figure15.Aviation’shistoricalandprojectedcontributiontoglobalwarmingbypollutantandscenario,1940–2050 35Figure16.Aviation’shistoricalandprojectedcontributiontoglobalwarmingbyGHGandSLCPundertheSLCPForwardscenario,1940–2050 36Figure17.Totalwarmingbypollutantfrom1940to2050(left)andGHGversusSLCPwarmingin2050(right) 37Figure18.Avoidable2050globalwarmingbypollutantandscenarioandaggregatedbyGHGsversusSLCPsgroups 39FigureA1.Trafficsensitivityofaviation’swarmingcontribution,1940–2050 52FigureB1.CorrelationbetweenSAFblendingrateandnvPMemissionindex 53FigureB2.CorrelationbetweenchangeinnvPMemissionindexandchangeiniceparticlenumber 54FigureB3.Correlationbetweenchangeiniceparticlenumberandchangeinannualmeancontrailradiativeforcing 55FigureC1.DistributionoftheERFperkmusedinthisstudy 60FigureC2.Centralestimateanduncertaintyintervalsusedforthismeta-analysis FigureD1.TemperatureresponsefortheHistoricalTrendsandtheFullBreakthroughscenarios 631ICCTREPORT|AVIATIONVISION2050:THEPOTENTIALFORCLIMATE-NEUTRALGROWTHINTRODUCTIONAircraftarealargeandgrowingsourceofgreenhousegas(GHG)emissions,accountingfor2.4%ofannualanthropogenicCO2emissionsin2018(Leeetal.,2021)and4%ofanthropogenicglobalwarmingtodate(Kloweretal.,2021).1Whileindustryandgovernmentshavebeenfocusingonreachingnet-zerocarbondioxide(CO?)emissionsby2050,lessattentionhasbeenpaidtotheroleofshort-livedclimatepollutant(SLCP)mitigationinaligningaviationwiththeParisAgreement.ThisisinpartduetothescientificuncertaintyaroundthewarmingimpactsofaviationSLCPs,butevenatthelowerendofestimatedeffects,mitigationwoulddeliversubstantialnear-termclimatebenefits.Contrailactivityishighlyconcentratedovercertainregionsandflightcorridors,makingtargetedmitigationbothfeasibleandcost-effectivewithtechnologiesthatcanbeimplementedrelativelyquickly.Tocapturethefullsuiteofclimatemitigationleversavailabletotheaviationsector,thisreportupdatestheICCT’sVision2050decarbonizationroadmapfortheaviationsectorbyquantifyinghowSLCPmitigationcancomplementGHGreductionstrategiestoalignaviationwiththeParisagreement.Thisstudyisorganizedasfollows.Wefirstprovidebackgroundonaviation’sclimateimpactsandthecurrentstateoftechnologyandpolicyroadmaps.Thenextsectiondescribesthemethodology,includingemissionsinventorydevelopment,climatemodeling,andscenariodesign.Next,wepresentaviation’sprojectedemissionsthrough2050anditsprojectedcontributiontoglobalwarmingacrossfivescenarios.Weclosewithdiscussionontheimplicationsofthesefindingsforclimatepolicydesignandfutureresearch.1InthecontextofKyotoProtocolgreenhousegases,aviation’sGHGemissionsarecomposedalmostentirelyofcarbondioxide(CO?),withsmallamountsofnitrousoxide(NO)andmethane(CH).BesidesGHGs,aviation’scontributiontoclimatechangealsoinvolveshort-livedclimatepollutants(withatmosphericlifetimesoflessthan20years)suchascontrails,NO,nvPM,watervapor,andsulfuroxides.2ICCTREPORT|AVIATIONVISION2050:THEPOTENTIALFORCLIMATE-NEUTRALGROWTHBACKGROUNDIn2021,theaviationindustryestablishedagoaltoachievenet-zeroCO2emissionsfromoperationsby2050.ThisvoluntarycommitmentwassubsequentlycodifiedforinternationalaviationbytheUN’sInternationalCivilAviationOrganization(ICAO)in2022(ICAO,2022b).UnderlyingICAO’sagreementaretechnologyroadmapsfordeepdecarbonization.AccordingtotheInternationalAirTransportAssociation(IATA)’ssynthesisofallmajor2050net-zeroCO2roadmaps,includingtheICCT’sVision2050(Graveretal.,2022),morethanhalfofcumulativeCO2reductionsthrough2050wouldneedtocomefromsustainableaviationfuels(SAFs);about30%fromfuelefficiency;andthebalancefromacombinationofeconomicmeasures,CO2removal,anddemandreduction(IATA,2024a).Sometechnologyroadmapsincludehydrogen-poweredaircraft,whichemitnoCO2duringoperationandverylittleCO2onalife-cyclebasiswhenthefuelisproducedfromrenewablepower.TheICCT’spreviousVision2050reportincludedfourpotentialscenariosforhowaviation’sCO2emissionsmayevolvethrough2050(Graveretal.,2022).Underthereport’sBreakthroughscenario,early,aggressive,andsustainedgovernmentinterventionwasassumedtotriggerwidespreadinvestmentsinzero-carbonaircraftandfuels,whichwouldpeakfossilfuelusein2025andenditsuseby2050.Asaresult,cumulativeaviationCO2woulddeclinebyabout55%through2050,andmorethan90%comparedwiththereport’sHistoricalTrendsscenariothatyear.Theresultingemissiontrajectoryisconsistentwitha1.75°Cwarminggoal,subjecttotheconstraintthataviationdoesnotincreaseitsshareofemissionsovertime.Inaggregate,thevariousnet-zeroroadmapsforaviationimplythataircraftCO2emissionswillneedtopeakthisdecadetoachievenet-zeroemissionsin2050(Mithal&Rutherford,2023).Unfortunately,evidenceisbuildingthataviationisunlikelytofollowtheambitioustechnologyuptakeneededtoachievethisgoal(Rutherford,2024).MarketdatasuggestthatSAFsaccountedforonly0.3%ofglobaljetfuelusein2024(IATA,2024b),oraboutone-fiftiethofwhatwillberequiredin2030underanet-zeropathway.LegallybindingSAFrequirementsinBrazil,Europe,Japan,andtheUnitedKingdomareconsistentwith2%globalSAFuptakeby2030.Similardelayshavebeenseenforzero-emissionplanes(ZEPs)poweredbyelectricityandhydrogen.Electricaircraft,whichcouldcoverasmall(upto0.2%)shareofaviationrevenuepassengerkilometers(RPKs)by2050,havehitturbulence(Mukhopadhaya&Graver,2022),withmanystartupspivotingtohybriddesigns.Airbushasrolledbackplanstodevelopanarrowbodyhydrogenaircraftandisnowfocusingonputtingasmallerregionalaircraftintoservice(Kaminski-Morrow,2024).Mostrecently,Airbusannouncedthatitsplantodevelophydrogenaircraftby2035wouldbedelayed(Hepher,2025).Intheabsenceoflow-emissionaircraftandfueldeploymentatlargescale,theprimaryopportunityforreducingGHGemissionsliesinfuelefficiency,mostlythroughtheintroductionofnewaircraft.AirbusandBoeingareworkingtodevelopnext-generationnarrowbodyplanesthatreducefuelburnby20%–25%relativetocurrentaircrafttypes(Airbus,2025).ThatiswellshortofthefuelburnreductionsenvisionedundertheVision2050Breakthroughscenario.Hameed&Rutherford(2025)foundthatthemajorcommercialairframersarecertifyingfewerofthenewaircrafttypesthatdrivefuelefficiencyimprovements.Countingvariantswithinafamily,newtypeintroductionsfellfromapeakof6peryearinthelate1990stoonly1peryearafter2020.3ICCTREPORT|AVIATIONVISION2050:THEPOTENTIALFORCLIMATE-NEUTRALGROWTHGiventhatin-sectorCO2abatementaloneisunlikelytomeetthenet-zerogoal,muchlessalignaviationwitha1.5°Cpathway,interestinclimatemitigationthroughreductionsinSLCPsisgrowing.SLCPscausetransientwarmingthatdissipatesquicklyonceemissionscease(Smithetal.,2018;Berntsen&Fuglestvedt,2008).ThisisincontrasttoCO?,whoselongatmosphericlifetimecommitstheplanettopersistentwarming.Becauseoftheirshortatmosphericlifetime,SLCPreductionscanproduceafasterclimatebenefit—helpingtoslownear-termwarmingandbuytimeforlonger-termCO?strategiestotakeeffect.ThemajorsourceofSLCPsfromaviationiscondensationtrails(contrails)generatedbyaircraftoperatingincold,humidareasofthetroposphere,whichmaydriveatleastasmuchglobalwarmingasCO2alone(Burkhardt&K?rcher,2011;Leeetal.,2021;Teohetal.,2024).Anestimated2%–5%offlightscrossingicesuper-saturatedregions—atmosphericzoneswithrelativehumiditygreaterthan100%overice—cause80%ofshort-livedcontrail-cirruswarming.Estimatesforthemarginalcostofcontrailabatementrangefromlessthan$5/tonneofcarbondioxideequivalent(CO2e)to$25/tonneofCO2e,comparedwithmorethan$300/tonneforSAFs(GoogleResearch,2023;Andrewsetal.,2024;Transport&Environment,2024).2Followingcontrails,NOXistheSLCPwiththesecond-largestclimateimpactintheaviationsector.Cruise-phaseNOXemissionsleadtotheformationoftroposphericozoneandthereductionofmethanelevelsintheatmosphere.Atpresent,thenetimpactoftheseemissionsisexpectedtobewarming,butfuturetemperatureresponsewilldependonbackgroundconcentrationsofthesegases(Terrenoireetal.,2022).3Non-volatileparticulatematter(nvPM),orblackcarbon,isalsoexpectedtohaveanetwarmingimpactandplayakeyroleincontrailformation.Thus,aircraftenginestandardstoreducecruise-phaseNOXemissionsandfuelswithhigherhydrogencontenttoreduceblackcarbonemissionsmayhelpmitigateaviation’sclimateimpact.Kl?weretal.(2021)investigatedthepotentialforSLCPcutstomakesubstantialshort-termreductionsinclimatechange.Usingasimplifiedclimatemodel,theauthorsinvestigatedtwoscenarios:1)long-termcutsintrafficof2.5%perannum,and2)theadoptionofSAFswithlowlife-cyclecarbonandhighhydrogencontentuptoa90%blend.Underbothscenarios,aviation’scontributiontoglobalwarmingwashaltedthisdecadeatabout0.04°C,comparedwithincreasesofabout0.09°Cin2050underacaseof3%trafficgrowth.Integraltothesefindingsisthatquickshort-termcutsinradiativeforcing(RF)—thatis,thenetchangeinEarth’senergybalanceduetoclimateforcers,includingatmosphericadjustments—fromSLCPscanoffsetlonger-termRFimpactsfromaccumulatingCO2emissions.4Kl?wer’swork,whilenotable,didnotfullyexploreallmitigationlevers(e.g.,fuelefficiencyimprovementandcontrailavoidance)andusedsimplifiedrepresentationsofaircrafttechnologyandoperations.Moreover,itgeneratedonlyglobalaverageresultsandcannotbelinkedtoconcretepoliciestosupporttheadoptionoflowGHGandSLCPtechnologiesandpractices.2AllmonetaryvaluesinthisreportareinU.S.dollars.3Theclimateimpactofaviationcruise-phaseNOisdependentonthenetforcingresultingfromincreasesinozoneanddecreasesinmethane,whichiscurrentlywarming.However,thiscouldbecomenegativeinthefutureduetochangingemissionsfromothersectorsaffectingbackgroundmethaneconcentrations.4Theterm“radiativeforcing”hasbeenusedinInternationalPanelonClimateChangeassessmentstodenoteanexternallyimposedperturbationintheradiativeenergybudgetoftheEarth’sclimatesystem.Suchaperturbationcanbecausedbychangesintheconcentrationsofradiativelyactivespecies,thesolarirradianceincident,orsurfacereflectionproperties.Thisimbalanceintheradiationbudgetcanleadtochangesinclimateparametersandresultinanewequilibriumstateoftheclimatesystem(Albrittonetal.,2001).4ICCTREPORT|AVIATIONVISION2050:THEPOTENTIALFORCLIMATE-NEUTRALGROWTHMETHODOLOGYSCENARIOSMODELEDThisreportconsidersfivescenarios—aHistoricalTrendsscenarioplusfouractionscenarios—tomodelhowaviationemissionsmightevolveoverthenext25years.ThesescenariosaredescribedbelowandsummarizedinTable1.?HistoricalTrends:Thisisacounterfactualscenarioinwhichgovernmentstakenoadditionalactiontoaddressaviation’sclimateimpact.Onlynominalmarket-drivenimprovementsinfuelefficiencyandexistingaircraftandenginestandardsaremodeled.TheexistingICAOCommitteeonAviationEnvironmentalProtection(CAEP)standardsincludetheCAEP/10CO2standard,CAEP/8NOXstandard,andCAEP/11nvPMstandard(ICAO,2023d;ICAO,2017).?CurrentCommitments:Thisscenarioprojectsemissionsgivenexistinggovernmentandindustrygoals,measures,andcommitments.Theseincludedeclaredmanufacturerplanstodevelopnewaircrafttypesthrough2035(includingaregionalhydrogenfuel-cellaircraft)andannouncedSAFmandatesinBrazil,theEuropeanUnion,Japan,andtheUnitedKingdom.Thisscenarioisusedtomeasureprogresstodate.?GHGForward:Thisscenarioestimatestheimpactsofdedicatedeffortsbygovernmentsandindustrytoshiftfromfossilfuelusetolow-carbonaircraftandfuels,peakingGHGemissionsin2030andnearlyhalving2050aviationCO2comparedwith2023levels.Becauseprogresstowardsnet-zerohasnotbeenalignedwiththe2025peakofaviationemissionsmodeledintheICCT’spreviousVision2050report,theTransformationscenariowasselectedtopresentthemaximumpotentialforGHGreductionsfromaircraftandfuelsinthisstudy(Rutherford,