Final Draft Summary for Policymakers IPCC WGIII AR5

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1 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 Title: Drafting Authors: Draft Contributing Authors SummaryforPolicymakers OttmarEdenhofer(Germany),RamónPichsMadruga (Cuba),YoubaSokona(Mali), ShardulAgrawala(France),IgorAlexeyevichBashmakov(Russia),GabrielBlanco (Argentina),JohnBroome(UK),ThomasBruckner(Germany),SteffenBrunner (Germany),MercedesBustamante(Brazil),LeonClarke(USA),FelixCreutzig (Germany),ShobhakarDhakal(Nepal/Thailand),NavrozK.Dubash(India),Patrick Eickemeier(Germany),EllieFarahani(Canada/Iran),ManfredFischedick(Germany), MarcFleurbaey(France),ReyerGerlagh(Netherlands),LuisGómezEcheverri (Colombia/Austria),ShreekantGupta(India),SujataGupta(India/Philippines),Jochen Harnisch(Germany),KejunJiang(China),SusanneKadner(Germany),SivanKartha (USA),StephanKlasen(Germany),CharlesKolstad(USA),VolkerKrey (Austria/Germany),HowardKunreuther(USA),OswaldoLucon(Brazil),OmarMasera (México),JanMinx(Germany),YacobMulugetta(UK/Ethiopia),AnthonyPatt(USA), NijavalliH.Ravindranath(India),KeywanRiahi(Austria),JoyashreeRoy(India), RobertoSchaeffer(Brazil),SteffenSchlömer(Germany),KarenSeto(USA),Kristin Seyboth(USA),RalphSims(NewZealand),JimSkea(UK),PeteSmith(UK),Eswaran Somanathan(India),RobertStavins(USA),ChristophvonStechow(Germany),Thomas Sterner(Sweden),TaishiSugiyama(Japan),SangwonSuh(RepublicofKorea/USA), KevinChikaUrama(Nigeria/UK),DianaÜrgeVorsatz(Hungary),DavidVictor(USA), DadiZhou(China),JiZou(China),TimmZwickel(Germany) GiovanniBaiocchi(UK/Italy),HelenaChum (USA/Brazil),JanFuglestvedt(Norway), HelmutHaberl(Austria),EdgarHertwich(Norway/Austria),ElmarKriegler(Germany), JoeriRogelj(Switzerland/Belgium),H.HolgerRogner(Austria/Germany),Michiel Schaeffer(Netherlands),SteveSmith(USA),DetlefvanVuuren(Netherlands),Ryan Wiser(USA) 1of33

2 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 SPM: SummaryforPolicymakers Contents SPM.1Introduction...3 SPM.2Approachestoclimatechangemitigation...3 SPM.3Trendsinstocksandflowsofgreenhousegasesandtheirdrivers...5 SPM.4Mitigationpathwaysandmeasuresinthecontextofsustainabledevelopment...10 SPM.4.1Longtermmitigationpathways...10 SPM.4.2Sectoralandcrosssectoralmitigationpathwaysandmeasures...20 SPM.4.2.1Crosssectoralmitigationpathwaysandmeasures...20 SPM.4.2.2Energysupply...23 SPM.4.2.3Energyendusesectors...24 SPM.4.2.4Agriculture,ForestryandOtherLandUse(AFOLU)...27 SPM.4.2.5HumanSettlements,InfrastructureandSpatialPlanning...28 SPM.5Mitigationpoliciesandinstitutions...29 SPM.5.1Sectoralandnationalpolicies...29 SPM.5.2Internationalcooperation of33

3 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 SPM.1 Introduction TheWorkingGroupIIIcontributiontotheIPCC sfifthassessmentreport(ar5)assessesliterature onthescientific,technological,environmental,economicandsocialaspectsofmitigationofclimate change.itbuildsupontheworkinggroupiiicontributiontotheipcc sfourthassessmentreport (AR4),theSpecialReportonRenewableEnergySourcesandClimateChangeMitigation(SRREN)and previousreportsandincorporatessubsequentnewfindingsandresearch.thereportalsoassesses mitigationoptionsatdifferentlevelsofgovernanceandindifferenteconomicsectors,andthe societalimplicationsofdifferentmitigationpolicies,butdoesnotrecommendanyparticularoption formitigation. ThisSummaryforPolicymakers(SPM)followsthestructureoftheWorkingGroupIIIreport.The narrativeissupportedbyaseriesofhighlightedconclusionswhich,takentogether,provideaconcise summary.thebasisforthespmcanbefoundinthechaptersectionsoftheunderlyingreportandin thetechnicalsummary(ts).referencestothesearegiveninsquaredbrackets. Thedegreeofcertaintyinfindingsinthisassessment,asinthereportsofallthreeWorkingGroups, isbasedontheauthorteams evaluationsofunderlyingscientificunderstandingandisexpressedas aqualitativelevelofconfidence(fromverylowtoveryhigh)and,whenpossible,probabilistically withaquantifiedlikelihood(fromexceptionallyunlikelytovirtuallycertain).confidenceinthe validityofafindingisbasedonthetype,amount,quality,andconsistencyofevidence(e.g.,data, mechanisticunderstanding,theory,models,expertjudgment)andthedegreeofagreement. 1 Probabilisticestimatesofquantifiedmeasuresofuncertaintyinafindingarebasedonstatistical analysisofobservationsormodelresults,orboth,andexpertjudgment. 2 Whereappropriate, findingsarealsoformulatedasstatementsoffactwithoutusinguncertaintyqualifiers.within paragraphsofthissummary,theconfidence,evidence,andagreementtermsgivenforabolded findingapplytosubsequentstatementsintheparagraph,unlessadditionaltermsareprovided. SPM.2 Approachestoclimatechangemitigation Mitigationisahumaninterventiontoreducethesourcesorenhancethesinksofgreenhouse gases.mitigation,togetherwithadaptationtoclimatechange,contributestotheobjective expressedinarticle2oftheunitednationsframeworkconventiononclimatechange(unfccc): TheultimateobjectiveofthisConventionandanyrelatedlegalinstrumentsthatthe ConferenceofthePartiesmayadoptistoachieve,inaccordancewiththerelevant provisionsoftheconvention,stabilizationofgreenhousegasconcentrationsinthe atmosphereatalevelthatwouldpreventdangerousanthropogenicinterferencewiththe climatesystem.suchalevelshouldbeachievedwithinatimeframesufficienttoallow 1 Thefollowingsummarytermsareusedtodescribetheavailableevidence:limited,medium,orrobust;and forthedegreeofagreement:low,medium,orhigh.alevelofconfidenceisexpressedusingfivequalifiers: verylow,low,medium,high,andveryhigh,andtypesetinitalics,e.g.,mediumconfidence.foragiven evidenceandagreementstatement,differentconfidencelevelscanbeassigned,butincreasinglevelsof evidenceanddegreesofagreementarecorrelatedwithincreasingconfidence.formoredetails,pleaserefer totheguidancenoteforleadauthorsoftheipccfifthassessmentreportonconsistenttreatmentof uncertainties. 2 Thefollowingtermshavebeenusedtoindicatetheassessedlikelihoodofanoutcomeoraresult:virtually certain99 100%probability,verylikely90 100%,likely66 100%,aboutaslikelyasnot33 66%,unlikely0 33%,veryunlikely0 10%,exceptionallyunlikely0 1%.Additionalterms(morelikelythannot>50 100%,and moreunlikelythanlikely0<50%)mayalsobeusedwhenappropriate.assessedlikelihoodistypesetinitalics, e.g.,verylikely. 3of33

4 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 ecosystemstoadaptnaturallytoclimatechange,toensurethatfoodproductionisnot threatenedandtoenableeconomicdevelopmenttoproceedinasustainablemanner. Climatepoliciescanbeinformedbythefindingsofscience,andsystematicmethodsfromother disciplines.[1.2,2.4,2.5,box3.1] Sustainabledevelopmentandequityprovideabasisforassessingclimatepoliciesandhighlight theneedforaddressingtherisksofclimatechange. 3 Limitingtheeffectsofclimatechangeis necessarytoachievesustainabledevelopmentandequity,includingpovertyeradication.atthe sametime,somemitigationeffortscouldundermineactionontherighttopromotesustainable development,andontheachievementofpovertyeradicationandequity.consequently,a comprehensiveassessmentofclimatepoliciesinvolvesgoingbeyondafocusonmitigationand adaptationpoliciesalonetoexaminedevelopmentpathwaysmorebroadly,alongwiththeir determinants.[4.2,4.3,4.4,4.5,4.6,4.8] Effectivemitigationwillnotbeachievedifindividualagentsadvancetheirowninterests independently.climatechangehasthecharacteristicsofacollectiveactionproblemattheglobal scale,becausemostgreenhousegases(ghgs)accumulateovertimeandmixglobally,andemissions byanyagent(e.g.,individual,community,company,country)affectotheragents. 4 International cooperationisthereforerequiredtoeffectivelymitigateghgemissionsandaddressotherclimate changeissues[1.2.4,2.6.4,3.1,4.2,13.2,13.3].furthermore,researchanddevelopmentinsupport ofmitigationcreatesknowledgespillovers.internationalcooperationcanplayaconstructiverolein thedevelopment,diffusionandtransferofknowledgeandenvironmentallysoundtechnologies [1.4.4,3.11.6,11.8,13.9,14.4.3]. Issuesofequity,justice,andfairnessarisewithrespecttomitigationandadaptation. 5 Countries pastandfuturecontributionstotheaccumulationofghgsintheatmospherearedifferent,and countriesalsofacevaryingchallengesandcircumstances,andhavedifferentcapacitiestoaddress mitigationandadaptation.theevidencesuggeststhatoutcomesseenasequitablecanleadtomore effectivecooperation.[3.10,4.2.2,4.6.2] Manyareasofclimatepolicymakinginvolvevaluejudgementsandethicalconsiderations.These areasrangefromthequestionofhowmuchmitigationisneededtopreventdangerousinterference withtheclimatesystemtochoicesamongspecificpoliciesformitigationoradaptation[3.1,3.2]. Social,economicandethicalanalysesmaybeusedtoinformvaluejudgementsandmaytakeinto accountvaluesofvarioussorts,includinghumanwellbeing,culturalvaluesandnonhumanvalues. [3.4,3.10] Amongothermethods,economicevaluationiscommonlyusedtoinformclimatepolicydesign. Practicaltoolsforeconomicassessmentincludecostbenefitanalysis,costeffectivenessanalysis, multicriteriaanalysisandexpectedutilitytheory[2.5].thelimitationsofthesetoolsarewell documented[3.5].ethicaltheoriesbasedonsocialwelfarefunctionsimplythatdistributional weights,whichtakeaccountofthedifferentvalueofmoneytodifferentpeople,shouldbeapplied tomonetarymeasuresofbenefitsandharms[3.6.1,boxts.2].whereasdistributionalweightinghas notfrequentlybeenappliedforcomparingtheeffectsofclimatepoliciesondifferentpeopleata singletime,itisstandardpractice,intheformofdiscounting,forcomparingtheeffectsatdifferent times[3.6.2]. 3 SeeWGIIAR5SPM. 4 Inthesocialsciencesthisisreferredtoasa globalcommonsproblem.asthisexpressionisusedinthesocial sciences,ithasnospecificimplicationsforlegalarrangementsorforparticularcriteriaregardingeffort sharing. 5 SeeFAQ3.2forclarificationoftheseconcepts.Thephilosophicalliteratureonjusticeandotherliteraturecan illuminatetheseissues[3.2,3.3,4.6.2]. 4of33

5 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 Climatepolicyintersectswithothersocietalgoalscreatingthepossibilityofcobenefitsoradverse sideeffects.theseintersections,ifwellmanaged,canstrengthenthebasisforundertaking climateaction.mitigationandadaptationcanpositivelyornegativelyinfluencetheachievementof othersocietalgoals,suchasthoserelatedtohumanhealth,foodsecurity,biodiversity,local environmentalquality,energyaccess,livelihoods,andequitablesustainabledevelopment;andvice versa,policiestowardothersocietalgoalscaninfluencetheachievementofmitigationand adaptationobjectives[4.2,4.3,4.4,4.5,4.6,4.8].theseinfluencescanbesubstantial,although sometimesdifficulttoquantify,especiallyinwelfareterms[3.6.3].thismultiobjectiveperspectiveis importantinpartbecauseithelpstoidentifyareaswheresupportforpoliciesthatadvancemultiple goalswillberobust[1.2.1,4.2,4.8,6.6.1]. Climatepolicymaybeinformedbyaconsiderationofadiversearrayofrisksanduncertainties, someofwhicharedifficulttomeasure,notablyeventsthatareoflowprobabilitybutwhichwould haveasignificantimpactiftheyoccur.sincear4,thescientificliteraturehasexaminedrisksrelated toclimatechange,adaptation,andmitigationstrategies.accuratelyestimatingthebenefitsof mitigationtakesintoaccountthefullrangeofpossibleimpactsofclimatechange,includingthose withhighconsequencesbutalowprobabilityofoccurrence.thebenefitsofmitigationmay otherwisebeunderestimated(highconfidence)[2.5,2.6,box3.9].thechoiceofmitigationactionsis alsoinfluencedbyuncertaintiesinmanysocioeconomicvariables,includingtherateofeconomic growthandtheevolutionoftechnology(highconfidence)[2.6,6.3]. Thedesignofclimatepolicyisinfluencedbyhowindividualsandorganizationsperceiverisksand uncertaintiesandtakethemintoaccount.peopleoftenutilizesimplifieddecisionrulessuchasa preferenceforthestatusquo.individualsandorganizationsdifferintheirdegreeofriskaversionand therelativeimportanceplacedonneartermversuslongtermramificationsofspecificactions[2.4]. Withthehelpofformalmethods,policydesigncanbeimprovedbytakingintoaccountrisksand uncertaintiesinnatural,socioeconomic,andtechnologicalsystemsaswellasdecisionprocesses, perceptions,valuesandwealth[2.5]. SPM.3 Trendsinstocksandflowsofgreenhousegasesandtheirdrivers TotalanthropogenicGHGemissionshavecontinuedtoincreaseover1970to2010withlarger absolutedecadalincreasestowardtheendofthisperiod(highconfidence).despiteagrowing numberofclimatechangemitigationpolicies,annualghgemissionsgrewonaverageby1.0giga tonnecarbondioxideequivalent(gtco 2 eq)(2.2%)peryearfrom2000to2010comparedto0.4 GtCO 2 eq(1.3%)peryearfrom1970to2000(figurespm.1). 6,7 TotalanthropogenicGHGemissions werethehighestinhumanhistoryfrom2000to2010andreached49(±4.5)gtco 2 eq/yrin2010.the globaleconomiccrisis2007/2008onlytemporarilyreducedemissions.[1.3,5.2,13.3,15.2.2,box TS.5,Figure15.1] CO 2 emissionsfromfossilfuelcombustionandindustrialprocessescontributedabout78%ofthe totalghgemissionincreasefrom1970to2010,withasimilarpercentagecontributionforthe period (highconfidence).FossilfuelrelatedCO 2 emissionsreached32(±2.7)gtco 2 /yr,in 2010,andgrewfurtherbyabout3%between2010and2011andbyabout12%between2011and 2012.Ofthe49(±4.5)GtCO 2 eq/yrintotalanthropogenicghgemissionsin2010,co 2 remainsthe majoranthropogenicghgaccountingfor76%(38±3.8gtco 2 eq/yr)oftotalanthropogenicghg emissionsin %(7.8±1.6gtco 2 eq/yr)comefrommethane(ch 4 ),6.2%(3.1±1.9GtCO 2 eq/yr) 6 ThroughouttheSPM,emissionsofGHGsareweightedbyGlobalWarmingPotentialswitha100yeartime horizon(gwp 100 )fromtheipccsecondassessmentreport.allmetricshavelimitationsanduncertaintiesin assessingconsequencesofdifferentemissions.[3.9.6,boxts.5,annexii.2.9,wgiar5spm] 7 InthisSPM,uncertaintyinhistoricGHGemissiondataisreportedusing90%uncertaintyintervalsunless otherwisestated.ghgemissionlevelsareroundedtotwosignificantdigitsthroughoutthisdocument. 5of33

6 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 fromnitrousoxide(n 2 O),and2.0%(1.0±0.2GtCO 2 eq/yr)fromfluorinatedgases(figurespm.1). Annually,since1970,about25%ofanthropogenicGHGemissionshavebeenintheformofnonCO 2 gases. 8 [1.2,5.2] Figure SPM.1. Total annual anthropogenic GHG emissions (GtCO 2 eq/yr) by groups of gases : CO 2 from fossil fuel combustion and industrial processes; CO 2 from Forestry and Other Land Use (FOLU); methane (CH 4 ); nitrous oxide (N 2 O); fluorinated gases 8 covered under the Kyoto Protocol (F-gases). At the right side of the figure GHG emissions in 2010 are shown again broken down into these components with the associated uncertainties (90% confidence interval) indicated by the error bars. Total anthropogenic GHG emissions uncertainties are derived from the individual gas estimates as described in Chapter 5 [ ]. Global CO 2 emissions from fossil fuel combustion are known within 8% uncertainty (90% confidence interval). CO 2 emissions from FOLU have very large uncertainties attached in the order of ±50%. Uncertainty for global emissions of CH 4, N 2 O and the F- gases has been estimated as 20%, 60% and 20%, respectively was the most recent year for which emission statistics on all gases as well as assessment of uncertainties were essentially complete at the time of data cut off for this report. Emissions are converted into CO 2 -equivalents based on GWP from the IPCC Second Assessment Report. The emission data from FOLU represents land-based CO 2 emissions from forest fires, peat fires and peat decay that approximate to net CO 2 flux from the FOLU as described in chapter 11 of this report. Average annual growth rate over different periods is highlighted with the brackets. [Figure 1.3, Figure TS.1] [Subject to final quality check and copy edit.] AbouthalfofcumulativeanthropogenicCO 2 emissionsbetween1750and2010haveoccurredin thelast40years(highconfidence).in1970,cumulativeco 2 emissionsfromfossilfuelcombustion, cementproductionandflaringsince1750were420±35gtco 2 ;in2010,thatcumulativetotalhad tripledto1300±110gtco 2 (FigureSPM.2).CumulativeCO 2 emissionsfromforestryandotherland Use(FOLU) 9 since1750increasedfrom490±180gtco 2 in1970to680±300gtco 2 in2010.[5.2] 8 Inthisreport,dataonnonCO 2 GHGs,includingfluorinatedgases,istakenfromtheEDGARdatabase(Annex II.9),whichcoverssubstancesincludedintheKyotoProtocolinitsfirstcommitmentperiod. 9 ForestryandOtherLandUse(FOLU) alsoreferredtoaslulucf(landuse,landusechange,and Forestry) isthesubsetofagriculture,forestryandotherlanduse(afolu)emissionsandremovalsofghgs relatedtodirecthumaninducedlanduse,landusechangeandforestryactivitiesexcludingagricultural emissionsandremovals(seewgiiiar5glossary). 6of33

7 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 AnnualanthropogenicGHGemissionshaveincreasedby10GtCO 2 eqbetween2000and2010,with thisincreasedirectlycomingfromenergysupply(47%),industry(30%),transport(11%)and buildings(3%)sectors(mediumconfidence).accountingforindirectemissionsraisesthe contributionsofthebuildingsandindustrysectors(highconfidence).since2000,ghgemissions havebeengrowinginallsectors,exceptafolu.ofthe49(±4.5)gtco 2 eqemissionsin2010,35%(17 GtCO 2 eq)ofghgemissionswerereleasedintheenergysupplysector,24%(12gtco 2 eq,net emissions)inafolu,21%(10gtco 2 eq)inindustry,14%(7.0gtco 2 eq)intransportand6.4%(3.2 GtCO 2 eq)inbuildings.whenemissionsfromelectricityandheatproductionareattributedtothe sectorsthatusethefinalenergy(i.e.indirectemissions),thesharesoftheindustryandbuildings sectorsinglobalghgemissionsareincreasedto31%and19%,respectively(figurespm.2).[7.3,8.2, 9.2,10.3,11.2] Figure SPM.2. Total anthropogenic GHG emissions (GtCO 2 eq/yr) by economic sectors. Inner circle shows direct GHG emission shares (in % of total anthropogenic GHG emissions) of five economic sectors in Pull-out shows how indirect CO 2 emission shares (in % of total anthropogenic GHG emissions) from electricity and heat production are attributed to sectors of final energy use. Other Energy refers to all GHG emission sources in the energy sector as defined in Annex II other than electricity and heat production [A.II.9.1]. The emissions data from Agriculture, Forestry and Other Land Use (AFOLU) includes land-based CO 2 emissions from forest fires, peat fires and peat decay that approximate to net CO 2 flux from the Forestry and Other Land Use (FOLU) sub-sector as described in Chapter 11 of this report. Emissions are converted into CO 2 -equivalents based on GWP from the IPCC Second Assessment Report. Sector definitions are provided in Annex II.9. [Figure 1.3a, Figure TS.3 a/b] [Subject to final quality check and copy edit.] Globally,economicandpopulationgrowthcontinuetobethemostimportantdriversofincreases inco 2 emissionsfromfossilfuelcombustion.thecontributionofpopulationgrowthbetween 2000and2010remainedroughlyidenticaltothepreviousthreedecades,whilethecontributionof economicgrowthhasrisensharply(highconfidence).between2000and2010,bothdrivers outpacedemissionreductionsfromimprovementsinenergyintensity(figurespm.3).increaseduse ofcoalrelativetootherenergysourceshasreversedthelongstandingtrendofgradual decarbonizationoftheworld senergysupply.[1.3,5.3,7.2,14.3,ts.2.2] 7of33

8 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 Figure SPM.3. Decomposition of the decadal change in total global CO 2 emissions from fossil fuel combustion by four driving factors; population, income (GDP) per capita, energy intensity of GDP and carbon intensity of energy. The bar segments show the changes associated with each factor alone, holding the respective other factors constant. Total decadal changes are indicated by a triangle. Changes are measured in giga tonnes (Gt) of CO 2 emissions per decade; income is converted into common units using purchasing power parities. [Figure 1.7] [Subject to final quality check and copy edit.] WithoutadditionaleffortstoreduceGHGemissionsbeyondthoseinplacetoday,emissions growthisexpectedtopersistdrivenbygrowthinglobalpopulationandeconomicactivities. Baselinescenarios,thosewithoutadditionalmitigation,resultinglobalmeansurfacetemperature increasesin2100from3.7to4.8 Ccomparedtopreindustriallevels 10 (medianvalues;therangeis 2.5 Cto7.8 Cwhenincludingclimateuncertainty,seeTableSPM.1) 11 (highconfidence).the emissionscenarioscollectedforthisassessmentrepresentfullradiativeforcingincludingghgs, troposphericozone,aerosolsandalbedochange.baselinescenarios(scenarioswithoutexplicit additionaleffortstoconstrainemissions)exceed450partspermillion(ppm)co 2 eqby2030and reachco 2 eqconcentrationlevelsbetween750andmorethan1300ppmco 2 eqby2100.thisis similartotherangeinatmosphericconcentrationlevelsbetweenthercp6.0andrcp8.5pathways 10 Basedonthelongestglobalsurfacetemperaturedatasetavailable,theobservedchangebetweenthe averageoftheperiod andofthear5referenceperiod( )is0.61 C(5 95%confidence interval:0.55to0.67 C)[WGIAR5SPM.E],whichisusedhereasanapproximationofthechangeinglobal meansurfacetemperaturesincepreindustrialtimes,referredtoastheperiodbefore Theclimateuncertaintyreflectsthe5thto95thpercentileofclimatemodelcalculationsdescribedinTable SPM.1. 8of33

9 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 in Forcomparison,theCO 2 eqconcentrationin2011isestimatedtobe430ppm(uncertainty range ppm) 13.[6.3,BoxTS.6;WGIAR5FigureSPM.5,WGI8.5,WGI12.3] 12 Forthepurposeofthisassessment,roughly300baselinescenariosand900mitigationscenarioswere collectedthroughanopencallfromintegratedmodellingteamsaroundtheworld.thesescenariosare complementarytotherepresentativeconcentrationpathways(rcps,seewgiiiar5glossary).thercpsare identifiedbytheirapproximatetotalradiativeforcinginyear2100relativeto1750:2.6wattspersquare meter(wm 2 )forrcp2.6,4.5wm 2 forrcp4.5,6.0wm 2 forrcp6.0,and8.5wm 2 forrcp8.5.thescenarios collectedforthisassessmentspanaslightlybroaderrangeofconcentrationsintheyear2100thanthefour RCPs. 13 Thisisbasedontheassessmentoftotalanthropogenicradiativeforcingfor2011relativeto1750inWGI,i.e. 2.3Wm 2,uncertaintyrange1.1to3.3Wm 2.[WGIAR5FigureSPM.5,WGI8.5,WGI12.3] 9of33

10 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 SPM.4 Mitigationpathwaysandmeasuresinthecontextofsustainable development SPM.4.1 Longtermmitigationpathways Therearemultiplescenarioswitharangeoftechnologicalandbehavioraloptions,withdifferent characteristicsandimplicationsforsustainabledevelopment,thatareconsistentwithdifferent levelsofmitigation.forthisassessment,about900mitigationscenarioshavebeencollectedina databasebasedonpublishedintegratedmodels. 14 Thisrangespansatmosphericconcentration levelsin2100from430ppmco 2 eqtoabove720ppmco 2 eq,whichiscomparabletothe2100 forcinglevelsbetweenrcp2.6andrcp6.0.scenariosoutsidethisrangewerealsoassessed includingsomescenarioswithconcentrationsin2100below430ppmco 2 eq(foradiscussionof thesescenariosseebelow).themitigationscenariosinvolveawiderangeoftechnological, socioeconomic,andinstitutionaltrajectories,butuncertaintiesandmodellimitationsexistand developmentsoutsidethisrangearepossible(figurespm.4,toppanel).[6.1,6.2,6.3,ts.3.1,box TS.6] 14 ThelongtermscenariosassessedinWGIIIweregeneratedprimarilybylargescale,integratedmodelsthat projectmanykeycharacteristicsofmitigationpathwaystomidcenturyandbeyond.thesemodelslinkmany importanthumansystems(e.g.,energy,agricultureandlanduse,economy)withphysicalprocessesassociated withclimatechange(e.g.,thecarboncycle).themodelsapproximatecosteffectivesolutionsthatminimize theaggregateeconomiccostsofachievingmitigationoutcomes,unlesstheyarespecificallyconstrainedto behaveotherwise.theyaresimplified,stylizedrepresentationsofhighlycomplex,realworldprocesses,and thescenariostheyproducearebasedonuncertainprojectionsaboutkeyeventsanddriversoveroften centurylongtimescales.simplificationsanddifferencesinassumptionsarethereasonwhyoutputgenerated fromdifferentmodels,orversionsofthesamemodel,candiffer,andprojectionsfromallmodelscandiffer considerablyfromtherealitythatunfolds.[boxts.7,6.2] 10of33

11 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 Figure SPM.4. Pathways of global GHG emissions (GtCO 2 eq/yr) in baseline and mitigation scenarios for different long-term concentration levels (upper panel) and associated upscaling requirements of low-carbon energy (% of primary energy) for 2030, 2050 and 2100 compared to 2010 levels in mitigation scenarios (lower panel). The upper and lower panels exclude scenarios with limited technology availability and the lower panel in addition excludes scenarios that assume exogenous carbon price trajectories. [Figure 6.7, Figure 7.16] [Subject to final quality check and copy edit.] Mitigationscenariosinwhichitislikelythatthetemperaturechangecausedbyanthropogenic GHGemissionscanbekepttolessthan2 Crelativetopreindustriallevelsarecharacterizedby atmosphericconcentrationsin2100ofabout450ppmco 2 eq(highconfidence).mitigation scenariosreachingconcentrationlevelsofabout500ppmco 2 eqby2100aremorelikelythannotto limittemperaturechangetolessthan2 Crelativetopreindustriallevels,unlesstheytemporarily overshoot concentrationlevelsofroughly530ppmco 2 eqbefore2100,inwhichcasetheyare aboutaslikelyasnottoachievethatgoal. 15 Scenariosthatreach530to650ppmCO 2 eq concentrationsby2100aremoreunlikelythanlikelytokeeptemperaturechangebelow2 Crelative topreindustriallevels.scenariosthatreachabout650ppmco 2 eqby2100areunlikelytolimit temperaturechangetobelow2 Crelativetopreindustriallevels.Mitigationscenariosinwhich 15 Mitigationscenarios,includingthosereaching2100concentrationsashighasorhigherthan550ppmCO 2 eq, cantemporarily overshoot atmosphericco 2 eqconcentrationlevelsbeforedescendingtolowerlevelslater. Suchconcentrationovershootinvolveslessmitigationintheneartermwithmorerapidanddeeperemissions reductionsinthelongrun.overshootincreasestheprobabilityofexceedinganygiventemperaturegoal.[6.3, TableSPM.1] 11of33

12 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 temperatureincreaseismorelikelythannottobelessthan1.5 Crelativetopreindustriallevelsby 2100arecharacterizedbyconcentrationsin2100ofbelow430ppmCO 2 eq.temperaturepeaks duringthecenturyandthendeclinesinthesescenarios.probabilitystatementsregardingother levelsoftemperaturechangecanbemadewithreferencetotablespm.1.[6.3,boxts.6] 12of33

13 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 Table SPM.1: Key characteristics of the scenarios collected and assessed for WGIII AR5. For all parameters, the 10th to 90th percentile of the scenarios is shown 1,2. [Table 6.3] CO2eq Concentrationsin 2100(CO2eq) Categorylabel (concentration range) 9 Subcategories Relative positionof thercps 5 CumulativeCO2emission 3 (GtCO2) ChangeinCO2eq emissionscomparedto 2010in(%) Temperature change( C) 7 Temperaturechange(relativeto ) 5,6 Likelihoodofstayingbelowtemperatureleveloverthe21 st century C 2.0 C 3.0 C 4.0 C Onlyalimitednumberofindividualmodelstudieshaveexploredlevelsbelow430ppmCO2eq 1,10 RCP2.6 72to Moreunlikely thanlikely Likely Morelikelythan not Aboutaslikely asnot Unlikely Moreunlikely thanlikely to50 RCP4.5 Morelikelythan 11to Unlikely not Moreunlikely RCP thanlikely Unlikely 11 RCP Unlikely 11 Unlikely Likely Likely Moreunlikely thanlikely 1 The'totalrange'forthe ppmCO 2 eqscenarioscorrespondstotherangeofthe10 90thpercentileofthesubcategoryofthesescenariosshownin table Baselinescenarios(seeSPM.3)arecategorizedinthe>1000and ppmCO 2 eqcategories.thelattercategoryincludesalsomitigation scenarios.thebaselinescenariosinthelattercategoryreachatemperaturechangeof Cabovepreindustrialin2100.Togetherwiththebaseline scenariosinthe>1000ppmco 2 eqcategory,thisleadstoanoverall2100temperaturerangeof C(median: C)forbaselinescenariosacross bothconcentrationcategories. 3 ForcomparisonofthecumulativeCO 2 emissionsestimatesassessedherewiththosepresentedinwgi,anamountof515 [445to585]GtC(1890[1630to2150]GtCO 2 ),wasalreadyemittedby2011since1870[sectionwgi12.5].notethatcumulativeemissionsarepresented herefordifferentperiodsoftime( and )whilecumulativeemissionsinWGIarepresentedastotalcompatibleemissionsfortheRCPs ( )orfortotalcompatibleemissionsforremainingbelowagiventemperaturetargetwithagivenlikelihood.[WGITableSPM.3,WGISPM.E.8] 4 Theglobal2010emissionsare31%abovethe1990emissions(consistentwiththehistoricGHGemissionestimatespresentedinthisreport).CO 2 eq emissionsincludethebasketofkyotogases(co 2,CH 4,N 2 OaswellasFgases). 5 TheassessmentinWGIIIinvolvesalargenumberofscenariospublishedin thescientificliteratureandisthusnotlimitedtothercps.toevaluatethegreenhousegasconcentrationandclimateimplicationsofthesescenarios,the MAGICCmodelwasusedinaprobabilisticmode(seeAnnexII).ForacomparisonbetweenMAGICCmodelresultsandtheoutcomesofthemodelsusedin WGI,seeSectionWGI andWGI12.4.8and ReasonsfordifferenceswithWGISPMTable.2includethedifferenceinreferenceyear( of33

14 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 2005vs here),differenceinreportingyear( vs2100here),setupofsimulation(CMIP5concentrationdrivenversusMAGICC emissiondrivenhere),andthewidersetofscenarios(rcpsversusthefullsetofscenariosinthewgiiiar5scenariodatabasehere). 6 Temperaturechange isreportedfortheyear2100,whichisnotdirectlycomparabletotheequilibriumwarmingreportedinar4(table3.5,chapter3wgiii).forthe2100 temperatureestimates,thetransientclimateresponse(tcr)isthemostrelevantsystemproperty.theassumed90thpercentileuncertaintyrangeofthe TCRforMAGICCis C(median1.8 C).Thiscomparestothe90thpercentilerangeofTCRbetween CforCMIP5(WGI9.7)andanassessed likelyrangeof1 2.5 CfrommultiplelinesofevidencereportedintheIPCCAR5WGIreport(Box12.2inchapter12.5). 7 Temperaturechangein2100is providedforamedianestimateofthemagicccalculations,whichillustratesdifferencesbetweentheemissionspathwaysofthescenariosineach category.therangeoftemperaturechangeintheparenthesesincludesinadditionalsothecarboncycleandclimatesystemuncertaintiesasrepresented bythemagiccmodel(see forfurtherdetails).thetemperaturedatacomparedtothe referenceyearwascalculatedbytakingall projectedwarmingrelativeto ,andadding0.61 Cfor comparedto ,basedonHadCRUT4(seeWGITableSPM.2). 8 The assessmentinthistableisbasedontheprobabilitiescalculatedforthefullensembleofscenariosinwgiiiusingmagiccandtheassessmentinwgiofthe uncertaintyofthetemperatureprojectionsnotcoveredbyclimatemodels.thestatementsarethereforeconsistentwiththestatementsinwgi,whichare basedonthecmip5runsofthercpsandtheassesseduncertainties.hence,thelikelihoodstatementsreflectdifferentlinesofevidencefrombothwgs. ThisWGImethodwasalsoappliedforscenarioswithintermediateconcentrationlevelswherenoCMIP5runsareavailable.Thelikelihoodstatementsare indicativeonly(6.3),andfollowbroadlythetermsusedbythewgispmfortemperatureprojections:likely66 100%,morelikelythannot>50 100%,about aslikelyasnot33 66%,andunlikely0 33%.Inadditionthetermmoreunlikelythanlikely0<50%isused. 9 TheCO 2 equivalentconcentrationincludesthe forcingofallghgsincludinghalogenatedgasesandtroposphericozone,aerosolsandalbedochange(calculatedonthebasisofthetotalforcingfroma simplecarboncycle/climatemodelmagicc). 10 Thevastmajorityofscenariosinthiscategoryovershootthecategoryboundaryof480ppmCO 2 eq concentrations. 11 ForscenariosinthiscategorynoCMIP5run(WGIAR5:Chapter12,Table12.3)aswellasnoMAGICCrealization(6.3)staysbelowthe respectivetemperaturelevel.still,an unlikely assignmentisgiventoreflectuncertaintiesthatmightnotbereflectedbythecurrentclimatemodels. 12 Scenariosinthe ppmCO 2 eqcategoryincludebothovershootscenariosandscenariosthatdonotexceedtheconcentrationlevelatthehighend ofthecategory(likercp4.5).thelattertypeofscenarios,ingeneral,haveanassessedprobabilityofmoreunlikelythanlikelytoexceedthe2 C temperaturelevel,whiletheformeraremostlyassessedtohaveanunlikelyprobabilityofexceedingthislevel.[subjecttofinalqualitycheckandcopyedit.] 14of33

15 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 Scenariosreachingatmosphericconcentrationlevelsofabout450ppmCO 2 eqby2100(consistent withalikelychancetokeeptemperaturechangebelow2 Crelativetopreindustriallevels) includesubstantialcutsinanthropogenicghgemissionsbymidcenturythroughlargescale changesinenergysystemsandpotentiallylanduse(highconfidence).scenariosreachingthese concentrationsby2100arecharacterizedbylowerglobalghgemissionsin2050thanin2010,40% to70%lowerglobally 16,andemissionslevelsnearzeroGtCO 2 eqorbelowin2100.inscenarios reaching500ppmco 2 eqby2100,2050emissionslevelsare25%to55%lowerthanin2010globally. Inscenariosreaching550ppmCO 2 eq,emissionsin2050arefrom5%above2010levelsto45% below2010levelsglobally(tablespm.1).atthegloballevel,scenariosreaching450ppmco 2 eqare alsocharacterizedbymorerapidimprovementsofenergyefficiency,atriplingtonearlya quadruplingoftheshareofzeroandlowcarbonenergysupplyfromrenewables,nuclearenergy andfossilenergywithcarbondioxidecaptureandstorage(ccs),orbioenergywithccs(beccs)by theyear2050(figurespm.4,lowerpanel).thesescenariosdescribeawiderangeofchangesinland use,reflectingdifferentassumptionsaboutthescaleofbioenergyproduction,afforestation,and reduceddeforestation.alloftheseemissions,energy,andlandusechangesvaryacrossregions. 17 Scenariosreachinghigherconcentrationsincludesimilarchanges,butonaslowertimescale.Onthe otherhand,scenariosreachinglowerconcentrationsrequirethesechangesonafastertimescale. [6.3,7.11] Mitigationscenariosreachingabout450ppmCO 2 eqin2100typicallyinvolvetemporaryovershoot ofatmosphericconcentrations,asdomanyscenariosreachingabout500ppmto550ppmco 2 eq in2100.dependingontheleveloftheovershoot,overshootscenariostypicallyrelyonthe availabilityandwidespreaddeploymentofbeccsandafforestationinthesecondhalfofthe century.theavailabilityandscaleoftheseandothercarbondioxideremoval(cdr)technologies andmethodsareuncertainandcdrtechnologiesandmethodsare,tovaryingdegrees,associated withchallengesandrisks(seesectionspm4.2)(highconfidence). 18 CDRisalsoprevalentinmany scenarioswithoutovershoottocompensateforresidualemissionsfromsectorswheremitigationis moreexpensive.thereisonlylimitedevidenceonthepotentialforlargescaledeploymentofbeccs, largescaleafforestation,andothercdrtechnologiesandmethods.[2.6,6.3,6.9.1,figure6.7,7.11, 11.13] EstimatedglobalGHGemissionslevelsin2020basedontheCancúnPledgesarenotconsistent withcosteffectivelongtermmitigationtrajectoriesthatareatleastaslikelyasnottolimit temperaturechangeto2 Crelativetopreindustriallevels(2100concentrationsofabout450and about500ppmco 2 eq),buttheydonotprecludetheoptiontomeetthatgoal(highconfidence). Meetingthisgoalwouldrequirefurthersubstantialreductionsbeyond2020.TheCancúnPledgesare broadlyconsistentwithcosteffectivescenariosthatarelikelytokeeptemperaturechangebelow 3 Crelativetopreindustriallevels.[6.4,13.13,FiguresTS.11,TS.13] 16 ThisrangediffersfromtherangeprovidedforasimilarconcentrationcategoryinAR4(50%to85%lower than2000forco 2 only).reasonsforthisdifferenceincludethatthisreporthasassessedasubstantiallylarger numberofscenariosthaninar4andlooksatallghgs.inaddition,alargeproportionofthenewscenarios includenetnegativeemissionstechnologies(seebelow).otherfactorsincludetheuseof2100concentration levelsinsteadofstabilizationlevelsandtheshiftinreferenceyearfrom2000to2010.scenarioswithhigher emissionsin2050arecharacterizedbyagreaterrelianceoncarbondioxideremoval(cdr)technologies beyondmidcentury. 17 Atthenationallevel,changeisconsideredmosteffectivewhenitreflectscountryandlocalvisionsand approachestoachievingsustainabledevelopmentaccordingtonationalcircumstancesandpriorities[6.4, ,WGIIAR5SPM]. 18 AccordingtoWGI,CDRmethodshavebiogeochemicalandtechnologicallimitationstotheirpotentialonthe globalscale.thereisinsufficientknowledgetoquantifyhowmuchco 2 emissionscouldbepartiallyoffsetby CDRonacenturytimescale.CDRmethodscarrysideeffectsandlongtermconsequencesonaglobalscale. [WGIAR5SPM.E.8] 15of33

16 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 Delayingmitigationeffortsbeyondthoseinplacetodaythrough2030isestimatedtosubstantially increasethedifficultyofthetransitiontolowlongertermemissionslevelsandnarrowtherange ofoptionsconsistentwithmaintainingtemperaturechangebelow2 Crelativetopreindustrial levels(highconfidence).costeffectivemitigationscenariosthatmakeitatleastaslikelyasnotthat temperaturechangewillremainbelow2 Crelativetopreindustriallevels(2100concentrations betweenabout450and500ppmco 2 eq)aretypicallycharacterizedbyannualghgemissionsin 2030ofroughlybetween30GtCO 2 eqand50gtco 2 eq(figurespm.5,leftpanel).scenarioswith annualghgemissionsabove55gtco 2 eqin2030arecharacterizedbysubstantiallyhigherratesof emissionsreductionsfrom2030to2050(figurespm.5,middlepanel);muchmorerapidscaleupof lowcarbonenergyoverthisperiod(figurespm.5,rightpanel);alargerrelianceoncdrtechnologies inthelongterm(figurespm.4,toppanel);andhighertransitionalandlongtermeconomicimpacts (TableSPM.2).Duetotheseincreasedmitigationchallenges,manymodelswithannual2030GHG emissionshigherthan55gtco 2 eqcouldnotproducescenariosreachingatmosphericconcentration levelsthatmakeitaslikelyasnotthattemperaturechangewillremainbelow2 Crelativetopre industriallevels.[6.4,7.11,figurests.11,ts.13] Figure SPM.5. The implications of different 2030 GHG emissions levels for the rate of CO 2 emissions reductions and low-carbon energy upscaling from 2030 to 2050 in mitigation scenarios reaching about 450 to 500 ( ) ppm CO 2 eq concentrations by The scenarios are grouped according to different emissions levels by 2030 (coloured in different shades of green). The left panel shows the pathways of GHG emissions (GtCO 2 eq/yr) leading to these 2030 levels. The black bar shows the estimated uncertainty range of GHG emissions implied by the Cancún Pledges. The middle panel denotes the average annual CO 2 emissions reduction rates for the period It compares the median and interquartile range across scenarios from recent intermodel comparisons with explicit 2030 interim goals to the range of scenarios in the Scenario Database for WGIII AR5. Annual rates of historical emissions change (sustained over a period of 20 years) are shown in grey. The arrows in the right panel show the magnitude of zero and low-carbon energy supply up-scaling from 2030 to 2050 subject to different 2030 GHG emissions levels. Zero- and low-carbon energy supply includes renewables, nuclear energy, and fossil energy with carbon dioxide capture and storage (CCS), or 16of33

17 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 bioenergy with CCS (BECCS). Note: Only scenarios that apply the full, unconstrained mitigation technology portfolio of the underlying models (default technology assumption) are shown. Scenarios with large net negative global emissions (>20 GtCO 2 eq/yr), scenarios with exogenous carbon price assumptions, and scenarios with 2010 emissions significantly outside the historical range are excluded. [Figure 6.32, 7.16] [Subject to final quality check and copy edit.] Estimatesoftheaggregateeconomiccostsofmitigationvarywidelyandarehighlysensitiveto modeldesignandassumptionsaswellasthespecificationofscenarios,includingthe characterizationoftechnologiesandthetimingofmitigation(highconfidence).scenariosinwhich allcountriesoftheworldbeginmitigationimmediately,thereisasingleglobalcarbonprice,andall keytechnologiesareavailable,havebeenusedasacosteffectivebenchmarkforestimating macroeconomicmitigationcosts(tablespm.2,greensegments).undertheseassumptions, mitigationscenariosthatreachatmosphericconcentrationsofabout450ppmco 2 eqby2100entail lossesinglobalconsumption notincludingbenefitsofreducedclimatechangeaswellasco benefitsandadversesideeffectsofmitigation 19 of1%to4%(median:1.7%)in2030,2%to6% (median:3.4%)in2050,and3%to11%(median:4.8%)in2100relativetoconsumptioninbaseline scenariosthatgrowsanywherefrom300%tomorethan900%overthecentury.thesenumbers correspondtoanannualizedreductionofconsumptiongrowthby0.04to0.14(median:0.06) percentagepointsoverthecenturyrelativetoannualizedconsumptiongrowthinthebaselinethatis between1.6%and3%peryear.estimatesatthehighendofthesecostrangesarefrommodelsthat arerelativelyinflexibletoachievethedeepemissionsreductionsrequiredinthelongruntomeet thesegoalsand/orincludeassumptionsaboutmarketimperfectionsthatwouldraisecosts.under theabsenceorlimitedavailabilityoftechnologies,mitigationcostscanincreasesubstantially dependingonthetechnologyconsidered(tablespm.2,orangesegment).delayingadditional mitigationfurtherincreasesmitigationcostsinthemediumtolongterm(tablespm.2,blue segment).manymodelscouldnotachieveatmosphericconcentrationlevelsofabout450ppm CO 2 eqby2100ifadditionalmitigationisconsiderablydelayedorunderlimitedavailabilityofkey technologies,suchasbioenergy,ccs,andtheircombination(beccs).[6.3] 19 Thetotaleconomiceffectsatdifferenttemperaturelevelswouldincludemitigationcosts,cobenefitsof mitigation,adversesideeffectsofmitigation,adaptationcostsandclimatedamages.mitigationcostand climatedamageestimatesatanygiventemperaturelevelcannotbecomparedtoevaluatethecostsand benefitsofmitigation.rather,theconsiderationofeconomiccostsandbenefitsofmitigationshouldinclude thereductionofclimatedamagesrelativetothecaseofunabatedclimatechange. 17of33

18 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 Table SPM.2: Global mitigation costs in cost-effective scenarios and estimated cost increases due to assumed limited availability of specific technologies and delayed additional mitigation. Cost estimates shown in this table do not consider the benefits of reduced climate change as well as co-benefits and adverse side-effects of mitigation. The green columns show consumption losses in the years 2030, 2050, and 2100 (green) and annualized consumption growth reductions (bright green) over the century in cost-effective scenarios relative to a baseline development without climate policy. 1 The orange columns show the percentage increase in discounted costs 2 over the century, relative to cost-effective scenarios, in scenarios in which technology is constrained relative to default technology assumptions. 3 The blue columns show the increase in mitigation costs over the periods and , relative to scenarios with immediate mitigation, due to delayed additional mitigation through 2020 or These scenarios with delayed additional mitigation are grouped by emission levels of less or more than 55 GtCO 2 eq in 2030, and two concentration ranges in 2100 ( ppm CO 2 eq and CO 2 eq). In all figures, the median of the scenario set is shown without parentheses, the range between the 16th and 84th percentile of the scenario set is shown in the parentheses, and the number of scenarios in the set is shown in square brackets. 5 [Figures TS.12, TS.13, 6.21, 6.24, 6.25, Annex II.10] 2100 Concentration (ppmco 2 eq) 450( ) 500( ) 550( ) Consumptionlossesincosteffectiveimplementation scenarios [%reductioninconsumption relativetobaseline] [percentage pointreduction inannualized consumption growthrate] NoCCS Nuclear phase out 1.7( ) [N:14] 1.7( ) [N:32] 3.4( ) 4.8( ) 0.06( ) Increaseintotaldiscountedmitigationcostsin scenarioswithlimitedavailabilityof technologies [%increaseintotaldiscountedmitigationcosts ( )relativetodefaulttechnology assumptions] 138(29 297) [N:4] 2.7( ) 4.7( ) 0.06( ) 0.6( ) [N:46] 1.7( ) 3.8( ) 0.04( ) 0.3(0 0.9) [N:16] 1.3( ) 2.3( ) 0.03( ) 39(18 78) [N:11] 7(4 18) [N:8] 13(2 23) [N:10] Limited Solar/ Wind 6(2 29) [N:8] 8(5 15) [N:10] Limited Bio energy 64(44 78) [N:8] 18(4 66) [N:12] Increaseinmid andlongterm mitigationcostsduedelayed additionalmitigationupto2030 [%increaseinmitigationcostsrelative toimmediatemitigation] 55GtCO 2 eq (14 50) [N:34] 3(5 16) [N:14] (5 59) 4(4 11) >55GtCO 2 eq Notes: 1 Cost-effective scenarios assume immediate mitigation in all countries and a single global carbon price, and impose no additional limitations on technology relative to the models default technology assumptions. 2 Percentage increase of net present value of consumption losses in percent of baseline consumption (for scenarios from general equilibrium models) and abatement costs in percent of baseline GDP (for scenarios from partial equilibrium models) for the period , discounted at 5% per year. 3 No CCS: CCS is not included in these scenarios. Nuclear phase out: No addition of nuclear power plants beyond those under construction, and operation of existing plants until the end of their lifetime. Limited Solar/Wind: a maximum of 20% global electricity generation from solar and wind power in any year of these scenarios. Limited Bioenergy: a maximum of 100 EJ/yr modern bioenergy supply globally (modern bioenergy used for heat, power, combinations, and industry was around 18 EJ/yr in 2008 [ ]). 4 Percentage increase of total undiscounted mitigation costs for the periods and The range is determined by the central scenarios encompassing the 16th and 84th percentile of the scenario set. Only scenarios with a time horizon until 2100 are included. Some models that are included in the cost ranges for concentration levels above 530 ppm CO 2eq in 2100 could not produce associated scenarios for concentration levels below 530 ppm CO 2eq in 2100 with assumptions about limited availability of technologies or delayed additional mitigation. [Subject to final quality check and copy edit] (2 78) [N:29] 15(3 32) [N:10] (16 82) 16(5 24) 18of33

19 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 Onlyalimitednumberofstudieshaveexploredscenariosthataremorelikelythannottobring temperaturechangebacktobelow1.5 Cby2100relativetopreindustriallevels;thesescenarios bringatmosphericconcentrationstobelow430ppmco 2 eqby2100(highconfidence).assessing thisgoaliscurrentlydifficultbecausenomultimodelstudieshaveexploredthesescenarios.the limitednumberofpublishedstudiesconsistentwiththisgoalproducesscenariosthatare characterizedby(1)immediatemitigationaction;(2)therapidupscalingofthefullportfolioof mitigationtechnologies;and(3)developmentalongalowenergydemandtrajectory. 20 [6.3,7.11] Mitigationscenariosreachingabout450or500ppmCO 2 eqby2100showreducedcostsfor achievingairqualityandenergysecurityobjectives,withsignificantcobenefitsforhumanhealth, ecosystemimpacts,andsufficiencyofresourcesandresilienceoftheenergysystem;these scenariosdidnotquantifyothercobenefitsoradversesideeffects(mediumconfidence).these mitigationscenariosshowimprovementsintermsofthesufficiencyofresourcestomeetnational energydemandaswellastheresilienceofenergysupply,resultinginenergysystemsthatareless vulnerabletopricevolatilityandsupplydisruptions.thebenefitsfromreducedimpactstohealth andecosystemsassociatedwithmajorcutsinairpollutantemissions(figurespm.6)areparticularly highwherecurrentlylegislatedandplannedairpollutioncontrolsareweak.thereisawiderangeof cobenefitsandadversesideeffectsforadditionalobjectivesotherthanairqualityandenergy security.overall,thepotentialforcobenefitsforenergyendusemeasuresoutweighthepotential foradversesideeffects,whereastheevidencesuggeststhismaynotbethecaseforallenergy supplyandafolumeasures.[wgiii4.8,5.7,6.3.6,6.6,7.9,8.7,9.7,10.8,11.7, ,12.8,figure TS.14,Table6.7,TablesTS.3 TS.7;WGII11.9] Figure SPM.6. Air pollutant emission levels for black carbon (BC) and sulfur dioxide (SO 2 ) in 2050 relative to 2005 (0=2005 levels). Baseline scenarios without additional efforts to reduce GHG emissions beyond those in place today are compared to scenarios with stringent mitigation policies, which are consistent with reaching atmospheric CO 2 eq concentration levels between 430 and 530 ppm CO 2 eq by [Figure 6.33] [Subject to final quality check and copy edit.] 20 Inthesescenarios,thecumulativeCO 2 emissionsrangebetween GtCO 2 fortheperiod andbetween90 350GtCO 2 fortheperiod GlobalCO 2 eqemissionsin2050arebetween70 95% below2010emissions,andtheyarebetween %below2010emissionsin of33

20 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 Thereisawiderangeofpossibleadversesideeffectsaswellascobenefitsandspilloversfrom climatepolicythathavenotbeenwellquantified(highconfidence).whetherornotsideeffects materialize,andtowhatextentsideeffectsmaterialize,willbecaseandsitespecific,astheywill dependonlocalcircumstancesandthescale,scope,andpaceofimplementation.important examplesincludebiodiversityconservation,wateravailability,foodsecurity,incomedistribution, efficiencyofthetaxationsystem,laboursupplyandemployment,urbansprawl,andthe sustainabilityofthegrowthofdevelopingcountries.[boxts.11] Mitigationeffortsandassociatedcostsvarybetweencountriesinmitigationscenarios.The distributionofcostsacrosscountriescandifferfromthedistributionoftheactionsthemselves (highconfidence).ingloballycosteffectivescenarios,themajorityofmitigationeffortstakesplacein countrieswiththehighestfutureemissionsinbaselinescenarios.somestudiesexploringparticular effortsharingframeworks,undertheassumptionofaglobalcarbonmarket,haveestimated substantialglobalfinancialflowsassociatedwithmitigationforscenariosleadingto2100 atmosphericconcentrationsofabout450to550ppmco 2 eq.[box3.5,4.6,6.3.6,table6.4,figure 6.9,Figure6.27,Figure6.28,Figure6.29, ] Mitigationpolicycoulddevaluefossilfuelassetsandreducerevenuesforfossilfuelexporters,but differencesbetweenregionsandfuelsexist(highconfidence).mostmitigationscenariosare associatedwithreducedrevenuesfromcoalandoiltradeformajorexporters(highconfidence).the effectofmitigationonnaturalgasexportrevenuesismoreuncertain,withsomestudiesshowing possiblebenefitsforexportrevenuesinthemediumtermuntilabout2050(mediumconfidence). TheavailabilityofCCSwouldreducetheadverseeffectofmitigationonthevalueoffossilfuelassets (mediumconfidence).[6.3.6,6.6,14.4.2] SPM.4.2 Sectoralandcrosssectoralmitigationpathwaysandmeasures SPM Crosssectoralmitigationpathwaysandmeasures Inbaselinescenarios,GHGemissionsareprojectedtogrowinallsectors,exceptfornetCO 2 emissionsintheafolusector 21 (robustevidence,mediumagreement).energysupplysector emissionsareexpectedtocontinuetobethemajorsourceofghgemissions,ultimatelyaccounting forthesignificantincreasesinindirectemissionsfromelectricityuseinthebuildingsandindustry sectors.inbaselinescenarios,whilenonco 2 GHGagriculturalemissionsareprojectedtoincrease, netco 2 emissionsfromtheafolusectordeclineovertime,withsomemodelsprojectinganetsink towardstheendofthecentury(figurespm.7). 22 [ ,6.8,FigureTS.15] InfrastructuredevelopmentsandlonglivedproductsthatlocksocietiesintoGHGintensive emissionspathwaysmaybedifficultorverycostlytochange,reinforcingtheimportanceofearly actionforambitiousmitigation(robustevidence,highagreement).thislockinriskiscompounded bythelifetimeoftheinfrastructure,bythedifferenceinemissionsassociatedwithalternatives,and themagnitudeoftheinvestmentcost.asaresult,lockinrelatedtoinfrastructureandspatial planningisthemostdifficulttoreduce.however,materials,productsandinfrastructurewithlong lifetimesandlowlifecycleemissionscanfacilitateatransitiontolowemissionpathwayswhilealso reducingemissionsthroughlowerlevelsofmaterialuse.[5.6.3, ,9.4,10.4,12.3,12.4] Therearestronginterdependenciesinmitigationscenariosbetweenthepaceofintroducing mitigationmeasuresinenergysupplyandenergyenduseanddevelopmentsintheafolusector 21 NetAFOLUCO 2 emissionsincludeemissionsandremovalsofco 2 fromtheafolusector,includingland underforestryand,insomeassessments,co 2 sinksinagriculturalsoils. 22 AmajorityoftheEarthSystemModelsassessedinWGIAR5projectacontinuedlandcarbonuptakeunder allrcpsthroughto2100,butsomemodelssimulatealandcarbonlossduetothecombinedeffectofclimate changeandlandusechange.[wgiar5spm.e.7,wgi6.4] 20of33

21 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 (highconfidence).thedistributionofthemitigationeffortacrosssectorsisstronglyinfluencedby theavailabilityandperformanceofbeccsandlargescaleafforestation(figurespm.7).thisis particularlythecaseinscenariosreachingco 2 eqconcentrationsofabout450ppmby2100.well designedsystemicandcrosssectoralmitigationstrategiesaremorecosteffectiveincutting emissionsthanafocusonindividualtechnologiesandsectors.attheenergysystemlevelthese includereductionsintheghgemissionintensityoftheenergysupplysector,aswitchtolowcarbon energycarriers(includinglowcarbonelectricity)andreductionsinenergydemandintheenduse sectorswithoutcompromisingdevelopment(figurespm.8).[6.3.5,6.4,6.8,7.11,tablets.2] Mitigationscenariosreachingaround450ppmCO 2 eqconcentrationsby2100showlargescale globalchangesintheenergysupplysector(robustevidence,highagreement).intheseselected scenarios,globalco 2 emissionsfromtheenergysupplysectorareprojectedtodeclineoverthenext decadesandarecharacterizedbyreductionsof90%ormorebelow2010levelsbetween2040and 2070.Emissionsinmanyofthesescenariosareprojectedtodeclinetobelowzerothereafter.[6.3.4, 6.8,7.1,7.11] Figure SPM.7. Direct emissions of CO 2 by sector and total non-co 2 GHGs (Kyoto gases) across sectors in baseline (left panel) and mitigation scenarios that reach around 450 ( ) ppm CO 2 eq with CCS (middle panel) and without CCS (right panel). The numbers at the bottom of the graphs refer to the number of scenarios included in the range which differs across sectors and time due to different sectoral resolution and time horizon of models. Note that many models cannot reach 450 ppm CO 2 eq concentration by 2100 in the absence of CCS, resulting in a low number of scenarios for the right panel [Figures 6.34 and 6.35]. [Subject to final quality check and copy edit.] Efficiencyenhancementsandbehaviouralchanges,inordertoreduceenergydemandcompared tobaselinescenarioswithoutcompromisingdevelopment,areakeymitigationstrategyin scenariosreachingatmosphericco 2 eqconcentrationsofabout450or500ppmby2100(robust evidence,highagreement).neartermreductionsinenergydemandareanimportantelementof costeffectivemitigationstrategies,providemoreflexibilityforreducingcarbonintensityinthe energysupplysector,hedgeagainstrelatedsupplysiderisks,avoidlockintocarbonintensive infrastructures,andareassociatedwithimportantcobenefits.bothintegratedandsectoralstudies providesimilarestimatesforenergydemandreductionsinthetransport,buildingsandindustry sectorsfor2030and2050(figurespm.8).[6.3.4,6.6,6.8,7.11,8.9,9.8,10.10] 21of33

22 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 Figure SPM.8. Final energy demand reduction relative to baseline (upper row) and low-carbon energy carrier shares in final energy (lower row) in the transport, buildings, and industry sectors by 2030 and 2050 in scenarios from two different CO 2 eq concentration categories compared to sectoral studies assessed in Chapters The demand reductions shown by these scenarios do not compromise development. Low-carbon energy carriers include electricity, hydrogen and liquid biofuels in transport, electricity in buildings and electricity, heat, hydrogen and bioenergy in industry. The numbers at the bottom of the graphs refer to the number of scenarios included in the ranges which differ across sectors and time due to different sectoral resolution and time horizon of models. [Figures 6.37 and 6.38] [Subject to final quality check and copy edit.] Behaviour,lifestyleandculturehaveaconsiderableinfluenceonenergyuseandassociated emissions,withhighmitigationpotentialinsomesectors,inparticularwhencomplementing 22of33

23 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 technologicalandstructuralchange 23 (mediumevidence,mediumagreement).emissionscanbe substantiallyloweredthroughchangesinconsumptionpatterns(e.g.,mobilitydemandandmode, energyuseinhouseholds,choiceoflongerlastingproducts)anddietarychangeandreductionin foodwastes.anumberofoptionsincludingmonetaryandnonmonetaryincentivesaswellas informationmeasuresmayfacilitatebehaviouralchanges.[6.8,7.9,8.3.5,8.9,9.2,9.3,9.10,box 10.2,10.4,11.4,12.4,12.6,12.7,15.3,15.5,TableTS.2] SPM Energysupply InthebaselinescenariosassessedinAR5,directCO 2 emissionsfromtheenergysupplysectorare projectedtoalmostdoubleoreventripleby2050comparedtothelevelof14.4gtco 2 /yearin 2010,unlessenergyintensityimprovementscanbesignificantlyacceleratedbeyondthehistorical development(mediumevidence,mediumagreement).inthelastdecade,themaincontributorsto emissiongrowthwereagrowingenergydemandandanincreaseoftheshareofcoalintheglobal fuelmix.theavailabilityoffossilfuelsalonewillnotbesufficienttolimitco 2 eqconcentrationto levelssuchas450ppm,550ppm,or650ppm.[6.3.4,7.2,7.3,figures6.15,spm.2,spm.7] Decarbonizing(i.e.reducingthecarbonintensityof)electricitygenerationisakeycomponentof costeffectivemitigationstrategiesinachievinglowstabilizationlevels( ppmCO 2 eq);in mostintegratedmodellingscenarios,decarbonizationhappensmorerapidlyinelectricity generationthanintheindustry,buildings,andtransportsectors(mediumevidence,high agreement)(figurespm.7).inthemajorityoflowstabilizationscenarios,theshareoflowcarbon electricitysupply(comprisingrenewableenergy(re),nuclearandccs)increasesfromthecurrent shareofapproximately30%tomorethan80%by2050,andfossilfuelpowergenerationwithout CCSisphasedoutalmostentirelyby2100.[6.8,7.11,Figures7.14,TS.18,SPM.7] SinceAR4,manyREtechnologieshavedemonstratedsubstantialperformanceimprovementsand costreductions,andagrowingnumberofretechnologieshaveachievedalevelofmaturityto enabledeploymentatsignificantscale(robustevidence,highagreement).regardingelectricity generationalone,reaccountedforjustoverhalfofthenewelectricitygeneratingcapacityadded globallyin2012,ledbygrowthinwind,hydroandsolarpower.however,manyretechnologiesstill needdirectand/orindirectsupport,iftheirmarketsharesaretobesignificantlyincreased;re technologypolicieshavebeensuccessfulindrivingrecentgrowthofre.challengesforintegrating REintoenergysystemsandtheassociatedcostsvarybyREtechnology,regionalcircumstances,and thecharacteristicsoftheexistingbackgroundenergysystem(mediumevidence,medium agreement).[7.5.3,7.6.1,7.8.2,7.12,table7.1] NuclearenergyisamaturelowGHGemissionsourceofbaseloadpower,butitsshareofglobal electricitygenerationhasbeendeclining(since1993).nuclearenergycouldmakeanincreasing contributiontolowcarbonenergysupply,butavarietyofbarriersandrisksexist(robustevidence, highagreement).thoseinclude:operationalrisks,andtheassociatedconcerns,uraniummining risks,financialandregulatoryrisks,unresolvedwastemanagementissues,nuclearweapon proliferationconcerns,andadversepublicopinion(robustevidence,highagreement).newfuel cyclesandreactortechnologiesaddressingsomeoftheseissuesarebeinginvestigatedandprogress inresearchanddevelopmenthasbeenmadeconcerningsafetyandwastedisposal.[7.5.4,7.8,7.9, 7.12,FigureTS.19] GHGemissionsfromenergysupplycanbereducedsignificantlybyreplacingcurrentworldaverage coalfiredpowerplantswithmodern,highlyefficientnaturalgascombinedcyclepowerplantsor combinedheatandpowerplants,providedthatnaturalgasisavailableandthefugitiveemissions associatedwithextractionandsupplyarelowormitigated(robustevidence,highagreement).in 23 Structuralchangesrefertosystemstransformationswherebysomecomponentsareeitherreplacedor potentiallysubstitutedbyothercomponents(seewgiiiar5glossary). 23of33

24 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 mitigationscenariosreachingabout450ppmco 2 eqconcentrationsby2100,naturalgaspower generationwithoutccsactsasabridgetechnology,withdeploymentincreasingbeforepeakingand fallingtobelowcurrentlevelsby2050anddecliningfurtherinthesecondhalfofthecentury(robust evidence,highagreement).[7.5.1,7.8,7.9,7.11,7.12] Carbondioxidecaptureandstorage(CCS)technologiescouldreducethelifecycleGHGemissionsof fossilfuelpowerplants(mediumevidence,mediumagreement).whileallcomponentsofintegrated CCSsystemsexistandareinusetodaybythefossilfuelextractionandrefiningindustry,CCShasnot yetbeenappliedatscaletoalarge,operationalcommercialfossilfuelpowerplant.ccspower plantscouldbeseeninthemarketifthisisincentivizedbyregulationand/oriftheybecome competitivewiththeirunabatedcounterparts,iftheadditionalinvestmentandoperationalcosts, causedinpartbyefficiencyreductions,arecompensatedbysufficientlyhighcarbonprices(ordirect financialsupport).forthelargescalefuturedeploymentofccs,welldefinedregulationsconcerning shortandlongtermresponsibilitiesforstorageareneededaswellaseconomicincentives.barriers tolargescaledeploymentofccstechnologiesincludeconcernsabouttheoperationalsafetyand longtermintegrityofco 2 storageaswellastransportrisks.thereis,however,agrowingbodyof literatureonhowtoensuretheintegrityofco 2 wells,onthepotentialconsequencesofapressure buildupwithinageologicformationcausedbyco 2 storage(suchasinducedseismicity),andonthe potentialhumanhealthandenvironmentalimpactsfromco 2 thatmigratesoutoftheprimary injectionzone(limitedevidence,mediumagreement).[7.5.5.,7.8,7.9,7.11,7.12,11.13] CombiningbioenergywithCCS(BECCS)offerstheprospectofenergysupplywithlargescalenet negativeemissionswhichplaysanimportantroleinmanylowstabilizationscenarios,whileit entailschallengesandrisks(limitedevidence,mediumagreement).thesechallengesandrisks includethoseassociatedwiththeupstreamlargescaleprovisionofthebiomassthatisusedinthe CCSfacilityaswellasthoseassociatedwiththeCCStechnologyitself.[7.5.5,7.9,11.13] SPM Energyendusesectors Transport Thetransportsectoraccountedfor27%offinalenergyuseand6.7GtCO 2 directemissionsin2010, withbaselineco 2 emissionsprojectedtoapproximatelydoubleby2050(mediumevidence, mediumagreement).thisgrowthinco 2 emissionsfromincreasingglobalpassengerandfreight activitycouldpartlyoffsetfuturemitigationmeasuresthatincludefuelcarbonandenergyintensity improvements,infrastructuredevelopment,behaviouralchangeandcomprehensivepolicy implementation(highconfidence).overall,reductionsintotaltransportco 2 emissionsof15 40% comparedtobaselinegrowthcouldbeachievedin2050(mediumevidence,mediumagreement). [FigureTS.15,6.8,8.1,8.2,8.9,8.10] Technicalandbehaviouralmitigationmeasuresforalltransportmodes,plusnewinfrastructure andurbanredevelopmentinvestments,couldreducefinalenergydemandin2050byaround40% belowthebaseline,withthemitigationpotentialassessedtobehigherthanreportedinthear4 (robustevidence,mediumagreement).projectedenergyefficiencyandvehicleperformance improvementsrangefrom30 50%in2030relativeto2010dependingontransportmodeand vehicletype(mediumevidence,mediumagreement).integratedurbanplanning,transitoriented development,morecompacturbanformthatsupportscyclingandwalking,canallleadtomodal shiftsascan,inthelongerterm,urbanredevelopmentandinvestmentsinnewinfrastructuresuch ashighspeedrailsystemsthatreduceshorthaulairtraveldemand(mediumevidence,medium agreement).suchmitigationmeasuresarechallenging,haveuncertainoutcomes,andcouldreduce transportghgemissionsby20 50%in2050comparedtobaseline(limitedevidence,low agreement).[8.2,8.3,8.4,8.5,8.6,8.7,8.8,8.9,12.4,12.5,figurespm.8toppanel] Strategiestoreducethecarbonintensitiesoffuelandtherateofreducingcarbonintensityare constrainedbychallengesassociatedwithenergystorageandtherelativelylowenergydensityof 24of33

25 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 lowcarbontransportfuels(mediumconfidence).integratedandsectoralstudiesbroadlyagreethat opportunitiesforswitchingtolowcarbonfuelsexistintheneartermandwillgrowovertime. Methanebasedfuelsarealreadyincreasingtheirshareforroadvehiclesandwaterbornecraft. Electricityproducedfromlowcarbonsourceshasneartermpotentialforelectricrailandshortto mediumtermpotentialaselectricbuses,lightdutyand2wheelroadvehiclesaredeployed. Hydrogenfuelsfromlowcarbonsourcesconstitutelongertermoptions.Commerciallyavailable liquidandgaseousbiofuelsalreadyprovidecobenefitstogetherwithmitigationoptionsthatcanbe increasedbytechnologyadvances.reducingtransportemissionsofparticulatematter(including blackcarbon),troposphericozoneandaerosolprecursors(includingno x )canhavehumanhealth andmitigationcobenefitsintheshortterm(mediumevidence,mediumagreement).[8.2,8.3,11.13, FigureTS.20,rightpanel] Thecosteffectivenessofdifferentcarbonreductionmeasuresinthetransportsectorvaries significantlywithvehicletypeandtransportmode(highconfidence).thelevelizedcostsof conservedcarboncanbeverylowornegativeformanyshorttermbehaviouralmeasuresand efficiencyimprovementsforlightandheavydutyroadvehiclesandwaterbornecraft.in2030,for someelectricvehicles,aircraftandpossiblyhighspeedrail,levelizedcostscouldbemorethan USD100/tCO 2 avoided(limitedevidence,mediumagreement).[8.6,8.8,8.9,figurests.21,ts.22] Regionaldifferencesinfluencethechoiceoftransportmitigationoptions(highconfidence). Institutional,legal,financialandculturalbarriersconstrainlowcarbontechnologyuptakeand behaviouralchange.establishedinfrastructuremaylimittheoptionsformodalshiftandleadtoa greaterrelianceonadvancedvehicletechnologies;aslowingofgrowthinlightdutyvehicledemand isalreadyevidentinsomeoecdcountries.foralleconomies,especiallythosewithhighratesof urbangrowth,investmentinpublictransportsystemsandlowcarboninfrastructurecanavoidlock intocarbonintensivemodes.prioritizinginfrastructureforpedestriansandintegratingnon motorizedandtransitservicescancreateeconomicandsocialcobenefitsinallregions(medium evidence,mediumagreement).[8.4,8.8,8.9,14.3,table8.3] Mitigationstrategies,whenassociatedwithnonclimatepoliciesatallgovernmentlevels,canhelp decoupletransportghgemissionsfromeconomicgrowthinallregions(mediumconfidence). Thesestrategiescanhelpreducetraveldemand,incentivisefreightbusinessestoreducethecarbon intensityoftheirlogisticalsystemsandinducemodalshifts,aswellasprovidecobenefitsincluding improvedaccessandmobility,betterhealthandsafety,greaterenergysecurity,andcostandtime savings(mediumevidence,highagreement).[8.7,8.10] Buildings In2010,thebuildingsector 24 accountedforaround32%finalenergyuseand8.8gtco 2 emissions, includingdirectandindirectemissions,withenergydemandprojectedtoapproximatelydouble andco 2 emissionstoincreaseby50 150%bymidcenturyinbaselinescenarios(mediumevidence, mediumagreement).thisenergydemandgrowthresultsfromimprovementsinwealth,lifestyle change,accesstomodernenergyservicesandadequatehousing,andurbanisation.thereare significantlockinrisksassociatedwiththelonglifespansofbuildingsandrelatedinfrastructure,and theseareespeciallyimportantinregionswithhighconstructionrates(robustevidence,high agreement).[9.4,figurets.15] Recentadvancesintechnologies,knowhowandpoliciesprovideopportunitiestostabilizeor reduceglobalbuildingssectorenergyusebymidcentury(robustevidence,highagreement).for newbuildings,theadoptionofverylowenergybuildingcodesisimportantandhasprogressed substantiallysincear4.retrofitsformakeypartofthemitigationstrategyincountrieswith 24 Thebuildingsectorcoverstheresidential,commercial,publicandservicessectors;emissionsfrom constructionareaccountedforintheindustrysector. 25of33

26 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 26of33 establishedbuildingstocks,andreductionsofheating/coolingenergyuseby50 90%inindividual buildingshavebeenachieved.recentlargeimprovementsinperformanceandcostsmakeverylow energyconstructionandretrofitseconomicallyattractive,sometimesevenatnetnegativecosts. [9.3] Lifestyle,cultureandbehavioursignificantlyinfluenceenergyconsumptioninbuildings(limited evidence,highagreement).athreetofivefolddifferenceinenergyusehasbeenshownfor provisionofsimilarbuildingrelatedenergyservicelevelsinbuildings.fordevelopedcountries, scenariosindicatethatlifestyleandbehaviouralchangescouldreduceenergydemandbyupto20% intheshorttermandbyupto50%ofpresentlevelsbymidcentury.indevelopingcountries, integratingelementsoftraditionallifestylesintobuildingpracticesandarchitecturecouldfacilitate theprovisionofhighlevelsofenergyserviceswithmuchlowerenergyinputsthanbaseline.[9.3] Mostmitigationoptionsforbuildingshaveconsiderableanddiversecobenefitsinadditionto energycostsavings(robustevidence,highagreement).theseincludeimprovementsinenergy security,health(suchasfromcleanerwoodburningcookstoves),environmentaloutcomes, workplaceproductivity,fuelpovertyreductionsandnetemploymentgains.studieswhichhave monetizedcobenefitsoftenfindthattheseexceedenergycostsavingsandpossiblyclimatebenefits (mediumevidence,mediumagreement).[9.6,9.7,3.6.3] Strongbarriers,suchassplitincentives(e.g.,tenantsandbuilders),fragmentedmarketsand inadequateaccesstoinformationandfinancing,hinderthemarketbaseduptakeofcosteffective opportunities.barrierscanbeovercomebypolicyinterventionsaddressingallstagesofthebuilding andappliancelifecycles(robustevidence,highagreement).[9.8,9.10,16,box3.10] Thedevelopmentofportfoliosofenergyefficiencypoliciesandtheirimplementationhas advancedconsiderablysincear4.buildingcodesandappliancestandards,ifwelldesignedand implemented,havebeenamongthemostenvironmentallyandcosteffectiveinstrumentsfor emissionreductions(robustevidence,highagreement).insomedevelopedcountriestheyhave contributedtoastabilizationof,orreductionin,totalenergydemandforbuildings.substantially strengtheningthesecodes,adoptingtheminfurtherjurisdictions,andextendingthemtomore buildingandappliancetypes,willbeakeyfactorinreachingambitiousclimategoals.[9.10, ] Industry In2010,theindustrysectoraccountedforaround28%offinalenergyuse,and13GtCO 2 emissions, includingdirectandindirectemissionsaswellasprocessemissions,withemissionsprojectedto increaseby50 150%by2050inthebaselinescenariosassessedinAR5,unlessenergyefficiency improvementsareacceleratedsignificantly(mediumevidence,mediumagreement).emissionsfrom industryaccountedforjustover30%ofglobalghgemissionsin2010andarecurrentlygreaterthan emissionsfromeitherthebuildingsortransportendusesectors.[spm.3,figurespm.7,10.3] Theenergyintensityoftheindustrysectorcouldbedirectlyreducedbyabout25%comparedto thecurrentlevelthroughthewidescaleupgrading,replacementanddeploymentofbestavailable technologies,particularlyincountrieswherethesearenotinuseandinnonenergyintensive industries(highagreement,robustevidence).additionalenergyintensityreductionsofabout20% maypotentiallyberealizedthroughinnovation(limitedevidence,mediumagreement).barriersto implementingenergyefficiencyrelatelargelytoinitialinvestmentcostsandlackofinformation. Informationprogrammesareaprevalentapproachforpromotingenergyefficiency,followedby economicinstruments,regulatoryapproachesandvoluntaryactions.[10.7,10.9,10.11] ImprovementsinGHGemissionefficiencyandintheefficiencyofmaterialuse,recyclingandre useofmaterialsandproducts,andoverallreductionsinproductdemand(e.g.,throughamore intensiveuseofproducts)andservicedemandcould,inadditiontoenergyefficiency,helpreduce GHGemissionsbelowthebaselinelevelintheindustrysector(mediumevidence,highagreement). Manyemissionreducingoptionsarecosteffective,profitableandassociatedwithmultipleco

27 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 benefits(betterenvironmentalcompliance,healthbenefitsetc.).inthelongterm,ashifttolow carbonelectricity,newindustrialprocesses,radicalproductinnovations(e.g.,alternativesto cement),orccs(e.g.,tomitigateprocessemissions)couldcontributetosignificantghgemission reductions.lackofpolicyandexperiencesinmaterialandproductserviceefficiencyarethemajor barriers.[10.4,10.7,10.8,10.11] CO 2 emissionsdominateghgemissionsfromindustry,buttherearealsosubstantialmitigation opportunitiesfornonco 2 gases(robustevidence,highagreement).ch 4,N 2 Oandfluorinatedgases fromindustryaccountedforemissionsof0.9gtco 2 eqin2010.keymitigationopportunitiesinclude, e.g.,thereductionofhydrofluorocarbonemissionsbyprocessoptimizationandrefrigerantrecovery, recyclingandsubstitution,althoughtherearebarriers.[tables10.2,10.7] Systemicapproachesandcollaborativeactivitiesacrosscompaniesandsectorscanreduceenergy andmaterialconsumptionandthusghgemissions(robustevidence,highagreement).the applicationofcrosscuttingtechnologies(e.g.,efficientmotors)andmeasures(e.g.,reducingairor steamleaks)inbothlargeenergyintensiveindustriesandsmallandmediumenterprisescan improveprocessperformanceandplantefficiencycosteffectively.cooperationacrosscompanies (e.g.,inindustrialparks)andsectorscouldincludethesharingofinfrastructure,information,and wasteheatutilization.[10.4,10.5] Importantoptionsformitigationinwastemanagementarewastereduction,followedbyreuse, recyclingandenergyrecovery(robustevidence,highagreement).wasteandwastewateraccounted for1.5gtco 2 eqin2010.astheshareofrecycledorreusedmaterialisstilllow(e.g.,globally,around 20%ofmunicipalsolidwasteisrecycled),wastetreatmenttechnologiesandrecoveringenergyto reducedemandforfossilfuelscanresultinsignificantdirectemissionreductionsfromwaste disposal.[10.4,10.14] SPM Agriculture,ForestryandOtherLandUse(AFOLU) TheAFOLUsectoraccountsforaboutaquarter(~10 12GtCO 2 eq/yr)ofnetanthropogenicghg emissionsmainlyfromdeforestation,agriculturalemissionsfromsoilandnutrientmanagement andlivestock(mediumevidence,highagreement).mostrecentestimatesindicateadeclinein AFOLUCO 2 fluxes,largelyduetodecreasingdeforestationratesandincreasedafforestation. However,theuncertaintyinhistoricalnetAFOLUemissionsislargerthanforothersectors,and additionaluncertaintiesinprojectedbaselinenetafoluemissionsexist.nonetheless,inthefuture, netannualbaselineco 2 emissionsfromafoluareprojectedtodecline,withnetemissions potentiallylessthanhalfthe2010levelby2050andthepossibilityoftheafolusectorsbecominga netco 2 sinkbeforetheendofcentury(mediumevidence,highagreement).[ ,11.2,figures 6.5,SPM.7] AFOLUplaysacentralroleforfoodsecurityandsustainabledevelopment.Themostcosteffective mitigationoptionsinforestryareafforestation,sustainableforestmanagementandreducing deforestation,withlargedifferencesintheirrelativeimportanceacrossregions.inagriculture,the mostcosteffectivemitigationoptionsarecroplandmanagement,grazinglandmanagement,and restorationoforganicsoils(mediumevidence,highagreement).theeconomicmitigationpotential ofsupplysidemeasuresisestimatedtobe7.2to11gtco 2 eq/year 25 in2030formitigationefforts consistentwithcarbonprices 26 upto100usd/tco 2 eq,aboutathirdofwhichcanbeachievedata <20USD/tCO 2 eq(mediumevidence,mediumagreement).therearepotentialbarriersto implementationofavailablemitigationoptions[11.7,11.8].demandsidemeasures,suchaschanges indietandreductionsoflossesinthefoodsupplychain,haveasignificant,butuncertain,potential 25 Fullrangeofallstudies: GtCO 2 eq/year 26 Inmanymodelsthatareusedtoassesstheeconomiccostsofmitigation,carbonpriceisoftenusedasa proxytorepresentthelevelofeffortinmitigationpolicies(seewgiiiar5glossary). 27of33

28 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 toreduceghgemissionsfromfoodproduction(mediumevidence,mediumagreement).estimates varyfromroughly GtCO 2 eq/yrby2050(limitedevidence,mediumagreement).[11.4,11.6, Figure11.14] Policiesgoverningagriculturalpracticesandforestconservationandmanagementaremore effectivewheninvolvingbothmitigationandadaptation.somemitigationoptionsintheafolu sector(suchassoilandforestcarbonstocks)maybevulnerabletoclimatechange(medium evidence,highagreement).whenimplementedsustainably,activitiestoreduceemissionsfrom deforestationandforestdegradation(redd+ 27 isanexampledesignedtobesustainable)arecost effectivepolicyoptionsformitigatingclimatechange,withpotentialeconomic,socialandother environmentalandadaptationcobenefits(e.g.,conservationofbiodiversityandwaterresources, andreducingsoilerosion)(limitedevidence,mediumagreement).[11.3.2,11.10] Bioenergycanplayacriticalroleformitigation,butthereareissuestoconsider,suchasthe sustainabilityofpracticesandtheefficiencyofbioenergysystems(robustevidence,medium agreement)[11.4.4,box11.5, , ].barrierstolargescaledeploymentofbioenergy includeconcernsaboutghgemissionsfromland,foodsecurity,waterresources,biodiversity conservationandlivelihoods.thescientificdebateabouttheoverallclimateimpactrelatedtoland usecompetitioneffectsofspecificbioenergypathwaysremainsunresolved(robustevidence,high agreement).[11.4.4,11.13]bioenergytechnologiesarediverseandspanawiderangeofoptionsand technologypathways.evidencesuggeststhatoptionswithlowlifecycleemissions(e.g.,sugarcane, Miscanthus,fastgrowingtreespecies,andsustainableuseofbiomassresidues),somealready available,canreduceghgemissions;outcomesaresitespecificandrelyonefficientintegrated biomasstobioenergysystems,andsustainablelandusemanagementandgovernance.insome regions,specificbioenergyoptions,suchasimprovedcookstoves,andsmallscalebiogasand biopowerproduction,couldreduceghgemissionsandimprovelivelihoodsandhealthinthe contextofsustainabledevelopment(mediumevidence,mediumagreement).[11.13] SPM HumanSettlements,InfrastructureandSpatialPlanning Urbanizationisaglobaltrendandisassociatedwithincreasesinincome,andhigherurban incomesarecorrelatedwithhigherconsumptionofenergyandghgemissions(mediumevidence, highagreement).asof2011,morethan52%oftheglobalpopulationlivesinurbanareas.in2006, urbanareasaccountedfor67 76%ofenergyuseand71 76%ofenergyrelatedCO 2 emissions.by 2050,theurbanpopulationisexpectedtoincreaseto billion,or64 69%ofworld population.citiesinnonannexicountriesgenerallyhavehigherlevelsofenergyusecomparedto thenationalaverage,whereascitiesinannexicountriesgenerallyhavelowerenergyusepercapita thannationalaverages(mediumevidence,mediumagreement).[12.2,12.3] Thenexttwodecadespresentawindowofopportunityformitigationinurbanareas,asalarge portionoftheworld surbanareaswillbedevelopedduringthisperiod(limitedevidence,high agreement).accountingfortrendsindecliningpopulationdensities,andcontinuedeconomicand populationgrowth,urbanlandcoverisprojectedtoexpandby56 310%between2000and2030. [12.2,12.3,12.4,12.8] Mitigationoptionsinurbanareasvarybyurbanizationtrajectoriesandareexpectedtobemost effectivewhenpolicyinstrumentsarebundled(robustevidence,highagreement).infrastructure andurbanformarestronglyinterlinked,andlockinpatternsoflanduse,transportchoice,housing, andbehaviour.effectivemitigationstrategiesinvolvepackagesofmutuallyreinforcingpolicies, includingcolocatinghighresidentialwithhighemploymentdensities,achievinghighdiversityand integrationoflanduses,increasingaccessibilityandinvestinginpublictransportandotherdemand managementmeasures.[8.4,12.3,12.4,12.5,12.6] 27 SeeWGIIIAR5Glossary. 28of33

29 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 Thelargestmitigationopportunitieswithrespecttohumansettlementsareinrapidlyurbanizing areaswhereurbanformandinfrastructurearenotlockedin,butwherethereareoftenlimited governance,technical,financial,andinstitutionalcapacities(robustevidence,highagreement).the bulkofurbangrowthisexpectedinsmalltomediumsizecitiesindevelopingcountries.the feasibilityofspatialplanninginstrumentsforclimatechangemitigationishighlydependentona city sfinancialandgovernancecapability.[12.6,12.7] Thousandsofcitiesareundertakingclimateactionplans,buttheiraggregateimpactonurban emissionsisuncertain(robustevidence,highagreement).therehasbeenlittlesystematic assessmentontheirimplementation,theextenttowhichemissionreductiontargetsarebeing achieved,oremissionsreduced.currentclimateactionplansfocuslargelyonenergyefficiency. Fewerclimateactionplansconsiderlanduseplanningstrategiesandcrosssectoralmeasuresto reducesprawlandpromotetransitorienteddevelopment 28.[12.6,12.7,12.9] Successfulimplementationofurbanscaleclimatechangemitigationstrategiescanprovideco benefits(robustevidence,highagreement).urbanareasthroughouttheworldcontinuetostruggle withchallenges,includingensuringaccesstoenergy,limitingairandwaterpollution,and maintainingemploymentopportunitiesandcompetitiveness.actiononurbanscalemitigationoften dependsontheabilitytorelateclimatechangemitigationeffortstolocalcobenefits(robust evidence,highagreement).[12.5,12.6,12.7,12.8] SPM.5 Mitigationpoliciesandinstitutions SPM.5.1 Sectoralandnationalpolicies Substantialreductionsinemissionswouldrequirelargechangesininvestmentpatterns.Mitigation scenariosinwhichpoliciesstabilizeatmosphericconcentrations(withoutovershoot)intherange from430to530ppmco 2 eqby2100leadtosubstantialshiftsinannualinvestmentflowsduringthe period comparedtobaselinescenarios(FigureSPM.9).Overthenexttwodecades(2010 to2029),annualinvestmentinconventionalfossilfueltechnologiesassociatedwiththeelectricity supplysectorisprojectedtodeclinebyaboutusd30(2 166)billion(median:20%comparedto 2010)whileannualinvestmentinlowcarbonelectricitysupply(i.e.,renewables,nuclearand electricitygenerationwithccs)isprojectedtorisebyaboutusd147(31 360)billion(median: +100%comparedto2010)(limitedevidence,mediumagreement).Forcomparison,globaltotal annualinvestmentintheenergysystemispresentlyaboutusd1200billion.inaddition,annual incrementalenergyefficiencyinvestmentsintransport,buildingsandindustryisprojectedto increasebyaboutusd336(1 641)billion(limitedevidence,mediumagreement),frequently involvingmodernizationofexistingequipment.[13.11,16.2.2] Thereisnowidelyagreeddefinitionofwhatconstitutesclimatefinance,butestimatesofthe financialflowsassociatedwithclimatechangemitigationandadaptationareavailable.published assessmentsofallcurrentannualfinancialflowswhoseexpectedeffectistoreducenetghg emissionsand/ortoenhanceresiliencetoclimatechangeandclimatevariabilityshowusd343to 385billionperyearglobally(mediumconfidence)[BoxTS.14].Mostofthisgoestomitigation.Outof this,totalpublicclimatefinancethatflowedtodevelopingcountriesisestimatedtobebetweenusd 35to49billion/yrin2011and2012(mediumconfidence).Estimatesofinternationalprivateclimate financeflowingtodevelopingcountriesrangefromusd10to72billion/yrincludingforeigndirect investmentasequityandloansintherangeofusd10to37billion/yrovertheperiodof (mediumconfidence).[16.2.2] 28 SeeWGIIIAR5Glossary. 29of33

30 FinalDraft SummaryforPolicymakers IPCCWGIIIAR5 Figure SPM.9. Change in annual investment flows from the average baseline level over the next two decades (2010 to 2029) for mitigation scenarios that stabilize concentrations within the range of approximately ppm CO 2 eq by Investment changes are based on a limited number of model studies and model comparisons. Total electricity generation (leftmost column) is the sum of renewables, nuclear, power plants with CCS and fossil power plants without CCS. The vertical bars indicate the range between minimum and maximum estimate; the horizontal bar indicates the median. Proximity to this median value does not imply higher likelihood because of the different degree of aggregation of model results, the low number of studies available and different assumptions in the different studies considered. The numbers in the bottom row show the total number of studies in the literature used for the assessment. This underscores that investment needs are still an evolving area of research that relatively few studies have examined. [Figure 16.3] [Subject to final quality check and copy edit] Therehasbeenaconsiderableincreaseinnationalandsubnationalmitigationplansand strategiessincear4.in2012,67%ofglobalghgemissionsweresubjecttonationallegislationor strategiesversus45%in2007.however,therehasnotyetbeenasubstantialdeviationinglobal emissionsfromthepasttrend[figure1.3c].theseplansandstrategiesareintheirearlystagesof developmentandimplementationinmanycountries,makingitdifficulttoassesstheiraggregate impactonfutureglobalemissions(mediumevidence,highagreement).[14.3.4,14.3.5,15.1,15.2] SinceAR4,therehasbeenanincreasedfocusonpoliciesdesignedtointegratemultipleobjectives, increasecobenefitsandreduceadversesideeffects(highconfidence).governmentsoften explicitlyreferencecobenefitsinclimateandsectoralplansandstrategies.thescientificliterature hassoughttoassessthesizeofcobenefits(seesectionspm.4.1)andthegreaterpoliticalfeasibility anddurabilityofpoliciesthathavelargecobenefitsandsmalladversesideeffects.[4.8,5.7,6.6, 13.2,15.2]DespitethegrowingattentioninpolicymakingandthescientificliteraturesinceAR4,the analyticalandempiricalunderpinningsforunderstandingmanyoftheinteractiveeffectsareunder developed[1.2,3.6.3,4.2,4.8,5.7,6.6]. 30of33