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Working Group III Mitigation of Climate Change
Chapter 3
Social, Economic and EthicalConcepts and Methods
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Note:
ThisdocumentisthecopyeditedversionofthefinaldraftReport,dated17December2013,ofthe
Working
Group
III
contribution
to
the
IPCC
5th
Assessment
Report
"Climate
Change
2014:
Mitigation
of
Climate
Change"
that
was
accepted
but
not
approved
in
detail
by
the
12th
Session
of
Working
Group
III
and
the
39th
Session
of
the
IPCC
on
12
April
2014
in
Berlin,
Germany.Itconsists
ofthefullscientific,technicalandsocioeconomicassessmentundertakenbyWorkingGroupIII.
The Report should be read in conjunction with the document entitled Climate Change 2014:
MitigationofClimateChange.WorkingGroup IIIContributiontothe IPCC5thAssessmentReport
ChangestotheunderlyingScientific/TechnicalAssessmenttoensureconsistencywiththeapproved
Summary for Policymakers (WGIII: 12th/Doc. 2a, Rev.2) and presented to the Panel at its 39th
Session.Thisdocument lists thechangesnecessary toensureconsistencybetweenthe fullReport
and the Summary for Policymakers, which was approved linebyline by Working Group III and
acceptedbythePanelattheaforementionedSessions.
Beforepublication,theReport(includingtext,figuresandtables)willundergofinalqualitycheckas
wellasanyerrorcorrectionasnecessary,consistentwiththeIPCCProtocolforAddressingPossible
Errors.Publication
of
the
Report
is
foreseen
in
September/October
2014.
Disclaimer:
Thedesignationsemployedandthepresentationofmaterialonmapsdonotimplytheexpressionof
anyopinionwhatsoeveronthepartoftheIntergovernmentalPanelonClimateChangeconcerning
the legal status of any country, territory, city or area or of its authorities, or concerning the
delimitationofitsfrontiersorboundaries.
A
report
accepted
by
Working
Group
III
of
the
IPCC
but
not
approved
in
detail.
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Chapter: 3
Title: Social,Economic,andEthicalConceptsandMethods
Authors: CLAs: CharlesKolstad,KevinUrama
LAs: JohnBroome,AnnegreteBruvoll,MichelineCario Olvera,Don
Fullerton,ChristianGollier,WilliamMichaelHanemann,Rashid
Hassan,FrankJotzo,MizanR.Khan,LukasMeyer,LuisMundaca
CAs: PhilippeAghion,HuntAllcott,GregorBetz,SeverinBorenstein,
AndrewBrennan,SimonCaney,DanFarber,AdamJaffe,Gunnar
Luderer,AxelOckenfels,DavidPopp
REs: MarleneAttzs,DanielBouille,SnorreKverndokk
CSAs: SheenaKatai,KatyMaher,LindseySarquilla
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Chapter3: Social,Economic,andEthicalConceptsandMethods
Contents
ExecutiveSummary
............................................................................................................................
5
3.1Introduction.................................................................................................................................. 9
3.2Ethicalandsocioeconomicconceptsandprinciples................................................................. 10
3.3Justice,equityandresponsibility................................................................................................ 12
3.3.1Causalandmoralresponsibility.......................................................................................... 12
3.3.2Intergenerationaljusticeandrightsoffuturepeople......................................................... 12
3.3.3Intergenerationaljustice:distributivejustice..................................................................... 13
3.3.4Historicalresponsibilityanddistributivejustice................................................................. 14
3.3.5Intragenerationaljustice:compensatoryjusticeandhistoricalresponsibility..................15
3.3.6Legalconceptsofhistoricalresponsibility.......................................................................... 16
3.3.7Geoengineering,ethics,andjustice.................................................................................... 17
3.4Valuesandwellbeing.................................................................................................................. 18
3.4.1Nonhumanvalues.............................................................................................................. 19
3.4.2Culturalandsocialvalues.................................................................................................... 20
3.4.3Wellbeing............................................................................................................................ 20
3.4.4Aggregationofwellbeing.................................................................................................... 21
3.4.5Lifetimewellbeing............................................................................................................... 21
3.4.6Social
welfare
functions
......................................................................................................
21
3.4.7Valuingpopulation.............................................................................................................. 23
3.5Economics,rights,andduties..................................................................................................... 24
3.5.1Limitsofeconomicsinguidingdecisionmaking................................................................. 25
3.6Aggregationofcostsandbenefits.............................................................................................. 26
3.6.1Aggregatingindividualwellbeing........................................................................................ 26
3.6.1.1Monetaryvalues.......................................................................................................... 27
3.6.2Aggregatingcostsandbenefitsacrosstime........................................................................ 30
3.6.3Co
benefits
and
adverse
side
effects
..................................................................................
36
3.6.3.1Ageneralframeworkforevaluationofcobenefitsandadversesideeffects............36
3.6.3.2Thevaluationofcobenefitsandadversesideeffects................................................ 37
3.6.3.3Thedoubledividendhypothesis.................................................................................. 39
3.7Assessingmethodsofpolicychoice............................................................................................ 40
3.7.1Policyobjectivesandevaluationcriteria............................................................................. 40
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3.7.1.1Economicobjectives.................................................................................................... 41
3.7.1.2Distributionalobjectives.............................................................................................. 42
3.7.1.3Environmentalobjectives............................................................................................ 43
3.7.1.4Institutionalandpoliticalfeasibility............................................................................. 44
3.7.2Analyticalmethodsfordecisionsupport............................................................................ 44
3.7.2.1Quantitativeorientedapproaches.............................................................................. 44
3.7.2.2Qualitativeapproaches................................................................................................ 46
3.8Policyinstrumentsandregulations............................................................................................ 46
3.8.1Economicincentives............................................................................................................ 46
3.8.1.1Emissionstaxesandpermittrading............................................................................. 46
3.8.1.2Subsidies...................................................................................................................... 47
3.8.2Directregulatoryapproaches.............................................................................................. 48
3.8.3Informationprogrammes.................................................................................................... 48
3.8.4Governmentprovisionofpublicgoodsandservices,andprocurement............................48
3.8.5Voluntaryactions................................................................................................................ 48
3.8.6Policyinteractionsandcomplementarity........................................................................... 48
3.8.7Governmentfailureandpolicyfailure................................................................................ 49
3.8.7.1Rentseeking................................................................................................................ 49
3.8.7.2Policyuncertainty........................................................................................................ 49
3.9Metricsofcostsandbenefits..................................................................................................... 50
3.9.1Thedamagesfromclimatechange..................................................................................... 51
3.9.2Aggregateclimatedamages................................................................................................ 54
3.9.3Theaggregatecostsofmitigation....................................................................................... 57
3.9.4Socialcostofcarbon........................................................................................................... 60
3.9.5TheReboundeffect............................................................................................................. 60
3.9.6Greenhousegasemissionsmetrics..................................................................................... 61
3.10Behaviouraleconomicsandculture......................................................................................... 64
3.10.1Behaviouraleconomicsandthecostofemissionsreduction........................................... 65
3.10.1.1Consumerundervaluationofenergycosts................................................................ 65
3.10.1.2Firmbehaviour........................................................................................................... 66
3.10.1.3Nonpriceinterventionstoinducebehaviouralchange............................................ 66
3.10.1.4Altruisticreductionsofcarbonemissions.................................................................. 66
3.10.1.5Humanabilitytounderstandclimatechange............................................................ 67
3.10.2Socialandculturalissues................................................................................................... 68
3.10.2.1Customs..................................................................................................................... 68
3.10.2.2Indigenouspeoples.................................................................................................... 68
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3.10.2.3WomenandClimateChange..................................................................................... 69
3.10.2.4Socialinstitutionsforcollectiveaction...................................................................... 69
3.11Technologicalchange............................................................................................................... 70
3.11.1MarketprovisionofTC...................................................................................................... 70
3.11.2Inducedinnovation........................................................................................................... 70
3.11.3LearningbydoingandotherstructuralmodelsofTC...................................................... 71
3.11.4EndogenousandexogenousTCandgrowth..................................................................... 71
3.11.5PolicymeasuresforinducingR&D.................................................................................... 72
3.11.6Technologytransfer(TT)................................................................................................... 72
3.12Gapsinknowledgeanddata.................................................................................................... 73
3.13FrequentlyAskedQuestions..................................................................................................... 74
References........................................................................................................................................ 76
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ExecutiveSummary
Thisframingchapterdescribesthestrengthsandlimitationsofthemostwidelyusedconceptsand
methodsineconomics,ethics,andothersocialsciencesthatarerelevanttoclimatechange.Italso
providesareferenceresourcefortheotherchaptersintheFifthAssessmentReport(AR5),aswellasfordecisionmakers.
Thesignificanceofthesocialdimensionandtheroleofethicsandeconomicsisunderscoredby
Article2oftheUnitedNationsFrameworkConventiononClimateChange,whichindicatesthatan
ultimateobjectiveoftheConventionistoavoiddangerousanthropogenicinterferencewiththeclimatesystem.Twomainissuesconfrontingsociety(andtheIPCC)are:whatconstitutesdangerous
interferencewiththeclimatesystemandhowtodealwiththatinterference.Determiningwhatis
dangerousisnotamatterfornaturalsciencealone;italsoinvolvesvaluejudgements asubject
matterofthetheoryofvalue,whichistreatedinseveraldisciplines,includingethics,economics,and
othersocialsciences.
Ethicsinvolvesquestionsofjusticeandvalue.Justiceisconcernedwithequityandfairness,and,in
general,withtherightstowhichpeopleareentitled.Valueisamatterofworth,benefit,orgood.
Valuecansometimesbemeasuredquantitatively,forinstance,throughasocialwelfarefunctionor
anindexofhumandevelopment.Economictoolsandmethodscanbeusedinassessingthepositiveandnegativevaluesthatresult
fromparticulardecisions,policies,andmeasures.Theycanalsobeessentialindeterminingthe
mitigationandadaptationactionstobeundertakenaspublicpolicy,aswellastheconsequencesof
differentmitigationandadaptationstrategies.Economictoolsandmethodshavestrengthsand
limitations,bothofwhicharedetailedinthischapter.
Economictoolscanbeusefulindesigningclimatechangemitigationpolicies(veryhighconfidence).Whilethelimitationsofeconomicsandsocialwelfareanalysis,includingcostbenefitanalysis,are
widelydocumented,economicsneverthelessprovidesusefultoolsforassessingtheprosandconsof
taking,ornottaking,actiononclimatechangemitigation,aswellasofadaptationmeasures,inachievingcompetingsocietalgoals.Understandingtheseprosandconscanhelpinmakingpolicy
decisionsonclimatechangemitigationandcaninfluencetheactionstakenbycountries,institutionsandindividuals.[Section3.2]
Mitigationisapublicgood;climatechangeisacaseofthetragedyofthecommons(highconfidence).Effectiveclimatechangemitigationwillnotbeachievedifeachagent(individual,
institutionorcountry)actsindependentlyinitsownselfishinterest,suggestingtheneedforcollectiveaction.Someadaptationactions,ontheotherhand,havecharacteristicsofaprivategood
asbenefitsofactionsmayaccruemoredirectlytotheindividuals,regions,orcountriesthat
undertakethem,atleastintheshortterm.Nevertheless,financingsuchadaptiveactivitiesremains
anissue,particularlyforpoorindividualsandcountries.[3.1]
Analysiscontainedintheliteratureofmoralandpoliticalphilosophycancontributetoresolvingethicalquestionsthatareraisedbyclimatechange(mediumconfidence).Thesequestionsincludehowmuchoverallclimatemitigationisneededtoavoiddangerousinterference,howtheeffortor
costofmitigatingclimatechangeshouldbesharedamongcountriesandbetweenthepresentand
future,howtoaccountforsuchfactorsashistoricalresponsibilityforemissions,andhowtochoose
amongalternativepoliciesformitigationandadaptation.Ethicalissuesofwellbeing,justice,fairness,
andrightsareallinvolved.[3.2,3.3,3.4]
Dutiestopayforsomeclimatedamagescanbegroundedincompensatoryjusticeanddistributivejustice(mediumconfidence).Ifcompensatorydutiestopayforclimatedamagesandadaptationcostsarenotduefromagentswhohaveactedblamelessly,thenprinciplesofcompensatoryjustice
willapplytoonlysomeoftheharmfulemissions[3.3.5].Thisfindingisalsoreflectedinthe
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predominantgloballegalpracticeofattributingliabilityforharmfulemissions[3.3.6].Dutiestopay
forclimatedamagescan,however,alsobegroundedindistributivejustice[3.3.4,3.3.5].
Distributionalweightsmaybeadvisableincostbenefitanalysis(mediumconfidence).Ethicaltheoriesofvaluecommonlyimplythatdistributionalweightsshouldbeappliedtomonetary
measuresofbenefitsandharmswhentheyareaggregatedtoderiveethicalconclusions[3.6.1].Such
weightingcontrastswithmuchofthepracticeofcostbenefitanalysis.
Theuseofatemporaldiscountratehasacrucialimpactontheevaluationofmitigationpoliciesandmeasures.Thesocialdiscountrateistheminimumrateofexpectedsocialreturnthatcompensatesfortheincreasedintergenerationalinequalitiesandthepotentialincreasedcollective
riskthatanactiongenerates.Evenwithdisagreementonthelevelofthediscountrate,aconsensus
favoursusingdecliningriskfreediscountratesoverlongertimehorizons(highconfidence).[3.6.2]
Anappropriatesocialriskfreediscountrateforconsumptionisbetweenoneandthreetimestheanticipatedgrowthrateinrealpercapitaconsumption(mediumconfidence).ThisjudgementisbasedonanapplicationoftheRamseyruleusingtypicalvaluesintheliteratureofnormative
parametersintherule.Ultimately,however,thesearenormativechoices.[3.6.2]
Cobenefitsmaycomplementthedirectbenefitsofmitigation(mediumconfidence).Whilesomedirectbenefitsofmitigationarereductionsinadverseclimatechangeimpacts,cobenefitscan
includeabroadrangeofenvironmental,economic,andsocialeffects,suchasreductionsinlocalair
pollution,lessacidrain,andincreasedenergysecurity.However,whethercobenefitsarenet
positiveornegativeintermsofwellbeing(welfare)canbedifficulttodeterminebecauseof
interactionbetweenclimatepoliciesandpreexistingnonclimatepolicies.Thesameresultsapplyto
adversesideeffects.[3.6.3]
Taxdistortionschangethecostofallabatementpolicies(highconfidence).Acarbontaxoratradableemissionspermitsystemcanexacerbatetaxdistortions,or,insomecases,alleviatethem;
carbontaxorpermitrevenuecanbeusedtomoderateadverseeffectsbycuttingothertaxes.
However,regulationsthatforgorevenue(e.g.,bygivingpermitsaway)implicitlyhavehighersocial
costsbecauseofthetaxinteractioneffect.[3.6.3]
Manydifferentanalyticmethodsareavailableforevaluatingpolicies.Methodsmaybe
quantitative(forexample,costbenefitanalysis,integratedassessmentmodelling,andmulticriteriaanalysis)orqualitative(forexample,sociologicalandparticipatoryapproaches).However,nosingle
bestmethodcanprovideacomprehensiveanalysisofpolicies.Amixofmethodsisoftenneededto
understandthebroadeffects,attributes,tradeoffs,andcomplexitiesofpolicychoices;moreover,policiesoftenaddressmultipleobjectives.[3.7]
Fourmaincriteriaarefrequentlyusedinevaluatingandchoosingamitigationpolicy(mediumconfidence).Theyare:costeffectivenessandeconomicefficiency(excludingenvironmentalbenefits,
butincludingtransactioncosts);environmentaleffectiveness(theextenttowhichtheenvironmental
targetsareachieved);distributionaleffects(impactondifferentsubgroupswithinsociety);andinstitutionalfeasibility,includingpoliticalfeasibility.[3.7.1]
Abroadrangeofpolicyinstrumentsforclimatechangemitigationisavailabletopolicymakers.
Theseinclude:economicincentives,directregulatoryapproaches,informationprogrammes,governmentprovision,andvoluntaryactions.Interactionsbetweenpolicyinstrumentscanenhanceorreducetheeffectivenessandcostofmitigationaction.Economicincentiveswillgenerallybemorecosteffectivethandirectregulatoryinterventions.However,theperformanceandsuitabilityof
policiesdependsonnumerousconditions,includinginstitutionalcapacity,theinfluenceofrent
seeking,andpredictabilityoruncertaintyaboutfuturepolicysettings.Theenablingenvironment
maydifferbetweencountries,includingbetweenlowincomeandhighincomecountries.These
differencescanhaveimplicationsforthesuitabilityandperformanceofpolicyinstruments.[3.8]
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Impactsofextremeeventsmaybemoreimportanteconomicallythanimpactsofaverageclimatechange(highconfidence).Risksassociatedwiththeentireprobabilitydistributionofoutcomesintermsofclimateresponse[WGI]andclimateimpacts[WGII]arerelevanttotheassessmentof
mitigation.Impactsfrommoreextremeclimatechangemaybemoreimportanteconomically(in
termsoftheexpectedvalueofimpacts)thanimpactsofaverageclimatechange,particularlyifthe
damagefromextremeclimatechangeincreasesmorerapidlythantheprobabilityofsuchchange
declines.Thisisimportantineconomicanalysis,wheretheexpectedbenefitofmitigationmaybetradedoffagainstmitigationcosts.[3.9.2]
Impactsfromclimatechangearebothmarketandnonmarket.Marketeffects(wheremarketpricesandquantitiesareobserved)includeimpactsofstormdamageoninfrastructure,tourism,andincreasedenergydemand.Nonmarketeffectsincludemanyecologicalimpacts,aswellaschanged
culturalvalues,noneofwhicharegenerallycapturedthroughmarketprices.Theeconomicmeasure
ofthevalueofeitherkindofimpactiswillingnesstopaytoavoiddamage,whichcanbeestimated
usingmethodsofrevealedpreferenceandstatedpreference.[3.9]
Substitutabilityreducesthesizeofdamagesfromclimatechange(highconfidence).Themonetarydamagefromachangeintheclimatewillbelowerifindividualscaneasilysubstituteforwhatis
damaged,comparedtocaseswheresuchsubstitutionismoredifficult.[3.9]
DamagefunctionsinexistingIntegratedAssessmentModels(IAMs)areoflowreliability(highconfidence).TheeconomicassessmentsofdamagesfromclimatechangeasembodiedinthedamagefunctionsusedbysomeexistingIAMs(thoughnotintheanalysisembodiedinWGIII)are
highlystylizedwithaweakempiricalfoundation.Theempiricalliteratureonmonetizedimpactsis
growingbutremainslimitedandoftengeographicallynarrow.Thissuggeststhatsuchdamage
functionsshouldbeusedwithcautionandthattheremaybesignificantvalueinundertakingresearchtoimprovetheprecisionofdamageestimates.[3.9,3.12]
Negativeprivatecostsofmitigationariseinsomecases,althoughtheyaresometimesoverstatedintheliterature(mediumconfidence).Sometimesmitigationcanlowertheprivatecostsofproductionandthusraiseprofits;forindividuals,mitigationcanraisewellbeing.Expostevidence
suggeststhatsuchnegativecostopportunitiesdoindeedexistbutaresometimesoverstatedin
engineeringanalyses.[3.9]
ExchangeratesbetweenGHGswithdifferentatmosphericlifetimesareverysensitivetothechoiceofemissionmetric.Thechoiceofanemissionmetricdependsonthepotentialapplicationandinvolvesexplicitorimplicitvaluejudgements;noconsensussurroundsthequestionofwhichmetricisbothconceptuallybestandpracticaltoimplement(highconfidence).Intermsofaggregate
mitigationcostsalone,theGlobalWarmingPotential(GWP),witha100yeartimehorizon,may
performsimilarlytoselectedothermetrics(suchasthetimedependentGlobalTemperatureChange
PotentialortheGlobalCostPotential)ofreachingaprescribedclimatetarget;however,variousmetricsmaydiffersignificantlyintermsoftheimplieddistributionofcostsacrosssectors,regions,
andovertime(limitedevidence,mediumagreement).[3.9]
Thebehaviourofenergyusersandproducersexhibitsavarietyofanomalies(highconfidence).Understandingclimatechangeasaphysicalphenomenonwithlinkstosocietalcausesandimpactsis
averycomplexprocess.Tobefullyeffective,theconceptualframeworksandmethodologicaltoolsusedinmitigationassessmentsneedtotakeintoaccountcognitivelimitationsandotherregardingpreferencesthatframetheprocessesofeconomicdecisionmakingbypeopleandfirms.[3.10]
Perceivedfairnesscanfacilitatecooperationamongindividuals(highconfidence).Experimentalevidencesuggeststhatreciprocalbehaviourandperceptionsoffairoutcomesandproceduresfacilitatevoluntarycooperationamongindividualpeopleinprovidingpublicgoods;thisfindingmay
haveimplicationsforthedesignofinternationalagreementstocoordinateclimatechangemitigation.[3.10]
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Socialinstitutionsandculturecanfacilitatemitigationandadaptation(mediumconfidence).Socialinstitutionsandculturecanshapeindividualactionsonmitigationandadaptationandbe
complementarytomoreconventionalmethodsforinducingmitigationandadaptation.Theycan
promotetrustandreciprocityandcontributetotheevolutionofcommonrules.Theyalsoprovide
structuresforactingcollectivelytodealwithcommonchallenges.[3.10]
Technologicalchangethatreducesmitigationcostscanbeencouragedbyinstitutionsand
economicincentives(highconfidence).Aspollutionisnotfullypricedbythemarket,privateindividualsandfirmslackincentivestoinvestsufficientlyinthedevelopmentanduseofemissions
reducingtechnologiesintheabsenceofappropriatepolicyinterventions.Moreover,imperfect
appropriabilityofthebenefitsofinnovationfurtherreducesincentivestodevelopnewtechnologies.[3.11]
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3.1 Introduction
Thisframingchapterhastwoprimarypurposes:toprovideaframeworkforviewingand
understandingthehuman(social)perspectiveonclimatechange,focusingonethicsandeconomics;
andtodefineanddiscusskeyconceptsusedinotherchapters.Itcomplementsthetwootherframingchapters:Chapter2onriskanduncertaintyandChapter4onsustainability.Theaudience
forthischapter(indeedforthisentirevolume)isdecisionmakersatmanydifferentlevels.
Thesignificanceofthesocialdimensionandtheroleofethicsandeconomicsisunderscoredby
Article2oftheUnitedNationsFrameworkConventiononClimateChange(UNFCCC),whichindicatesthattheultimateobjectiveoftheConventionistoavoiddangerousanthropogenicinterferencewith
theclimatesystem.Twomainissuesconfrontingsocietyare:whatconstitutesdangerous
interferencewiththeclimatesystemandhowtodealwiththatinterference.Providinginformation
toanswertheseinterrelatedquestionsisaprimarypurposeoftheIPCC.Althoughnaturalscience
helpsusunderstandhowemissionscanchangetheclimate,and,inturn,generatephysicalimpacts
onecosystems,people,andthephysicalenvironment,determiningwhatisdangerousinvolves
judgingthelevelofadverseconsequences,thestepsnecessarytomitigatetheseconsequences,and
theriskthathumanityiswillingtotolerate.Thesearequestionsrequiringvaluejudgement.
Althougheconomicsisessentialtoevaluatingtheconsequencesandtradeoffsassociatingwith
climatechange,howsocietyinterpretsandvaluesthemisanethicalquestion.
Box 3.1Dangerous interference with the climate system
Article2oftheUnitedNationsFrameworkConventiononClimateChangestatesthattheultimate
objectiveoftheConvention...istoachieve...stabilizationofgreenhousegasconcentrationsintheatmosphereatalevelthatwouldpreventdangerousanthropogenicinterferencewiththe
climatesystem.Judgingwhetherourinterferenceintheclimatesystemisdangerous,i.e.,risks
causingaverybadoutcome,involvestwotasks:estimatingthephysicalconsequencesofour
interferenceandtheirlikelihood;andassessingtheirsignificanceforpeople.Thefirstfallstoscience,
but,astheSynthesisReportoftheIPCCFourthAssessmentReport(AR4)states,Determiningwhat
constitutesdangerousanthropogenicinterferencewiththeclimatesysteminrelationtoArticle2oftheUNFCCCinvolvesvaluejudgements(IPCC,2007,p.42).Valuejudgementsaregovernedbythe
theoryofvalue.Inparticular,valuingriskiscoveredbydecisiontheoryandisdealtwithinChapter2.
Centralquestionsofvaluethatcomewithinthescopeofethics,aswellaseconomicmethodsfor
measuringcertainvaluesareexaminedinthischapter.
Ourdiscussionofethicscentresontwomainconsiderations:justiceandvalue.Justicerequiresthat
peopleandnationsshouldreceivewhattheyaredue,orhavearightto.Forsome,anoutcomeis
justiftheprocessthatgenerateditisjust.Othersviewjusticeintermsoftheactualoutcomes
enjoyedbydifferentpeopleandgroupsandthevaluestheyplaceonthoseoutcomes.Outcome
basedjusticecanrangefrommaximizingeconomicmeasuresofaggregatewelfaretorightsbased
viewsofjustice,forexample,believingthatallcountrieshavearighttocleanair.Differentviews
havebeenexpressedaboutwhatisvaluable.Allvaluesmaybeanthropocentricortheremaybe
nonhumanvalues.Economicanalysiscanhelptoguidepolicyaction,providedthatappropriate,
adequate,andtransparentethicalassumptionsarebuiltintotheeconomicmethods.
Thesignificanceofeconomicsintacklingclimatechangeiswidelyrecognized.Forinstance,central
tothepoliticsoftakingactiononclimatechangearedisagreementsoverhowmuchmitigationthe
worldshouldundertake,andtheeconomiccostsofaction(thecostsofmitigation)andinaction(the
costsofadaptationandresidualdamagefromachangedclimate).Uncertaintyremainsabout(1)the
costsofreducingemissionsofgreenhousegases(GHGs),(2)thedamagecausedbyachangeintheclimate,and(3)thecost,practicality,andeffectivenessofadaptationmeasures(and,potentially,
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geoengineering).Prioritizingactiononclimatechangeoverothersignificantsocialgoalswithmore
neartermpayoffsisparticularlydifficultindevelopingcountries.Becausesocialconcernsand
objectives,suchasthepreservationoftraditionalvalues,cannotalwaysbeeasilyquantifiedor
monetized,economiccostsandbenefitsarenottheonlyinputintodecisionmakingaboutclimate
change.Butevenwherecostsandbenefitscanbequantifiedandmonetized,usingmethodsof
economicanalysistosteersocialactionimplicitlyinvolvessignificantethicalassumptions.This
chapterexplainstheethicalassumptionsthatmustbemadeforeconomicmethods,includingcostbenefitanalysis(CBA),tobevalid,aswellastheethicalassumptionsthatareimplicitlybeingmadewhereeconomicanalysisisusedtoinformapolicychoice.
Theperspectiveofeconomicscanimproveourunderstandingofthechallengesofactingonmitigation.Foranindividualorfirm,mitigationinvolvesrealcosts,whilethebenefitstothemselves
oftheirownmitigationeffortsaresmallandintangible.Thisreducestheincentivesforindividualsor
countriestounilaterallyreduceemissions;freeridingontheactionsofothersisadominant
strategy.Mitigatinggreenhousegas(GHG)emissionsisapublicgood,whichinhibitsmitigation.Thisalsopartlyexplainsthefailureofnationstoagreeonhowtosolvetheproblem.
Incontrast,adaptationtendsnottosufferfromfreeriding.Gainstoclimatechangefrom
adaptation,suchasplantingmoreheattolerantcrops,aremainlyrealizedbythepartieswhoincur
thecosts.AssociatedexternalitiestendtobemorelocalizedandcontemporaneousthanforGHG
mitigation.Fromapublicgoodsperspective,globalcoordinationmaybelessimportantformany
formsofadaptationthanformitigation.Forautonomousadaptationinparticular,thegainsfrom
adaptationaccruetothepartyincurringthecost.However,publicadaptationrequireslocalor
regionalcoordination.Financialandotherconstraintsmayrestrictthepursuitofattractive
adaptationopportunities,particularlyindevelopingcountriesandforpoorerindividuals.
Thischapteraddressestwoquestions:whatshouldbedoneaboutactiontomitigateclimatechange
(anormativeissue)andhowtheworldworksinthemultifacetedcontextofclimatechange(a
descriptiveorpositiveissue).Typically,ethicsdealswithnormativequestionsandeconomicswith
descriptiveornormativequestions.Descriptivequestionsareprimarilyvalueneutral,forexample,howfirmshavereactedtocapandtradeprogrammestolimitemissions,orhowsocietieshavedealt
withresponsibilityforactionsthatwerenotknowntobeharmfulwhentheyweretaken.Normative
questionsuseeconomicsandethicstodecidewhatshouldbedone,forexample,determiningtheappropriatelevelofburdensharingamongcountriesforcurrentandfuturemitigation.Inmakingdecisionsaboutissueswithnormativedimensions,itisimportanttounderstandtheimplicitassumptionsinvolved.Mostnormativeanalysesofsolutionstotheclimateproblemimplicitly
involvecontestableethicalassumptions.
Thischapterdoesnotattempttoanswerethicalquestions,butratherprovidespolicymakerswith
thetools(concepts,principles,arguments,andmethods)tomakedecisions.Summarizingtheroleof
economicsandethicsinclimatechangeinasinglechapternecessitatesseveralcaveats.Whilerecognizingtheimportanceofcertainnoneconomicsocialdimensionsoftheclimatechange
problemandsolutionstoit,spacelimitationsandourmandatenecessitatedfocusingprimarilyon
ethicsandeconomics.Furthermore,manyoftheissuesraisedhavealreadybeenaddressedin
previousIPCCassessments,particularlyAR2(publishedin1995).Inthepast,ethicshasreceivedless
attentionthaneconomics,althoughaspectsofbothsubjectsarecoveredinAR2.TheliteraturereviewedhereincludespreAR4literatureinordertoprovideamorecomprehensiveunderstanding
oftheconceptsandmethods.WehighlightnewdevelopmentsinthefieldsincethelastIPCCassessmentin2007.
3.2 Ethicalandsocioeconomicconceptsandprinciples
WhenacountryemitsGHGs,itsemissionscauseharmaroundtheglobe.Thecountryitselfsuffersonlyapartoftheharmitcauses.Itisthereforerarelyintheinterestsofasinglecountrytoreduce
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itsownemissions,eventhoughareductioninglobalemissionscouldbenefiteverycountry.Thatis
tosay,theproblemofclimatechangeisatragedyofthecommons(Hardin,1968).Effective
mitigationofclimatechangewillnotbeachievedifeachpersonorcountryactsindependentlyinits
owninterest.
Consequently,effortsarecontinuingtoreacheffectiveinternationalagreementonmitigation.They
raiseanethicalquestionthatiswidelyrecognizedandmuchdebated,namely,burdensharingor
effortsharing.Howshouldtheburdenofmitigatingclimatechangebedividedamongcountries?Itraisesdifficultissuesofjustice,fairness,andrights,allofwhichliewithinthesphereofethics.
Burdensharingisonlyoneoftheethicalquestionsthatclimatechangeraises.1Anotheristhe
questionofhowmuchoverallmitigationshouldtakeplace.UNFCCCsetstheaimofavoiding
dangerousanthropogenicinterferencewiththeclimatesystem,andjudgingwhatisdangerousis
partlyataskforethics(seeBox3.1).Besidesjustice,fairness,andrights,acentralconcernofethics
isvalue.Judgementsofvalueunderliethequestionofwhatinterferencewiththeclimatesystemwouldbedangerous.
Indeed,ethicaljudgementsofvalueunderliealmosteverydecisionthatisconnectedwithclimate
change,includingdecisionsmadebyindividuals,publicandprivateorganizations,governments,and
groupingsofgovernments.Someofthesedecisionsaredeliberatelyaimedatmitigatingclimate
changeoradaptingtoit.Manyothersinfluencetheprogressofclimatechangeoritsimpacts,sotheyneedtotakeclimatechangeintoaccount.
Ethicsmaybebroadlydividedintotwobranches:justiceandvalue.Justiceisconcernedwith
ensuringthatpeoplegetwhatisduetothem.Ifjusticerequiresthatapersonshouldnotbetreated
inaparticularwayuprootedfromherhomebyclimatechange,forexamplethenthepersonhas
arightnottobetreatedthatway.Justiceandrightsarecorrelativeconcepts.Ontheotherhand,criteriaofvalueareconcernedwithimprovingtheworld:makingitabetterplace.Synonymsforvalueinthiscontextaregood,goodnessandbenefit.Antonymsarebad,harmandcost.
Toseethedifferencebetweenjusticeandvalue,thinkofatransferofwealthmadebyarichcountry
toapoorone.Thismaybeanactofrestitution.Forexample,itmaybeintendedtocompensatethepoorcountryforharmthathasbeendonetoitbytherichcountrysemissionsofGHG.Inthiscase,
thetransferismadeongroundsofjustice.Thepaymentistakentobeduetothepoorcountry,andtosatisfyarightthatthepoorcountryhastocompensation.Alternatively,therichcountrymay
makethetransfertosupportthepoorcountrysmitigationeffort,becausethisisbeneficialto
peopleinthepoorcountry,therichcountry,andelsewhere.Therichcountrymaynotbelievethepoorcountryhasarighttothesupport,butmakesthepaymentsimplybecauseitdoesgood.This
transferismadeongroundsofvalue.Whatwouldbegoodtodoisnotnecessarilyrequiredasa
matterofjustice.Justiceisconcernedwithwhatpeopleareentitledtoasamatteroftheirrights.
Thedivisionbetweenjusticeandvalueiscontestedwithinmoralphilosophy,andsoisthenatureof
theinteractionbetweenthetwo.Someauthorstreatjusticeasinviolable(Nozick,1974):justicesets
limitsonwhatwemaydoandwemaypromotevalueonlywithinthoselimits.Anoppositeview
calledteleologicalbyRawls(1971)isthattherightdecisiontomakeisalwaysdeterminedbythe
valueofthealternatives,sojusticehasnorole.Butdespitethecomplexityoftheirrelationshipand
thecontroversiesitraises,thedivisionbetweenjusticeandvalueprovidesausefulbasisfororganizingthediscussionofethicalconceptsandprinciples.Wehaveadopteditinthischapter:sections3.3 and3.4 coverjusticeandvalue,respectively.Onetopicappearsinbothsections
becauseitbridgesthedivide:thistopicisdistributivejusticeviewedonewayandthevalueof
equalityviewedtheother.Section3.3.7 ongeoengineeringisalsoinanintermediateposition
1AsurveyoftheethicsofclimatechangeisGardiner(2004),pp.555600.
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becauseitraisesethicalissuesofbothsorts.Section3.6 explainshowsomeethicalvaluescanbe
measuredbyeconomicmethodsofvaluation.Section3.5 describesthescopeandlimitationsof
thesemethods.Latersectionsdeveloptheconceptsandmethodsofeconomicsinmoredetail.
PracticalwaystotakeaccountofdifferentvaluesinpolicymakingarediscussedinSection3.7.1 .
3.3 Justice,equityandresponsibility
Justice,fairness,equity,andresponsibilityareimportantininternationalclimatenegotiations,as
wellasinclimaterelatedpoliticaldecisionmakingwithincountriesandforindividuals.
Inthissectionweexaminedistributivejustice,which,forthepurposeofthisreview,isabout
outcomes,andproceduraljusticeorthewayinwhichoutcomesarebroughtabout.Wealsodiscuss
compensationfordamageandhistoricresponsibilityforharm.Inthecontextofclimatechange,
considerationsofjustice,equity,andresponsibilityconcerntherelationsbetweenindividuals,as
wellasgroupsofindividuals(e.g.,countries),bothatasinglepointintimeandacrosstime.
Accordingly,wedistinguishintragenerationalfromintergenerationaljustice.Theliteraturehasnoagreementonacorrectanswertothequestion,whatisjust?Weindicatewhereopinionsdiffer.
3.3.1 Causalandmoralresponsibility
Fromtheperspectiveofcountriesratherthanindividualsorgroupsofindividuals,historicemissionscanhelpdeterminecausalresponsibilityforclimatechange(denElzenetal.,2005;Lamarqueetal.,
2010;Hhneetal.,2011).Manydevelopedcountriesareexpectedtosufferrelativelymodestphysicaldamageandsomeareevenexpectedtorealizebenefitsfromfutureclimatechange(see
Tol,2002a;b).Ontheotherhand,somedevelopingcountriesbearlesscausalresponsibility,but
couldsuffersignificantphysicaldamagefromclimatechange(IPCC,2007WGIIAR4SPM).This
asymmetrygivesrisetothefollowingquestionsofjusticeandmoralresponsibility:doconsiderations
ofjusticeprovideguidanceindeterminingtheappropriatelevelofpresentandfutureglobal
emissions;thedistributionofemissionsamongthosepresentlyliving;andtheroleofhistorical
emissionsindistributingglobalobligations?Thequestionalsoarisesofwhomightbeconsideredmorallyresponsibleforachievingjustice,and,thus,abearerofdutiestowardsothers.Thequestion
ofmoralresponsibilityisalsokeytodeterminingwhetheranyoneowescompensationforthe
damagecausedbyemissions.
3.3.2 IntergenerationaljusticeandrightsoffuturepeopleIntergenerationaljusticeencompassessomeofthemoraldutiesowedbypresenttofuturepeople
andtherightsthatfuturepeopleholdagainstpresentpeople.2Alegitimateacknowledgmentthat
futureorpastgenerationshaverightsrelativetopresentgenerationsisindicativeofabroad
understandingofjustice.3Whilejusticeconsiderationssounderstoodarerelevant,theycannot
coverallourconcernsregardingfutureandpastpeople,includingthecontinuedexistenceof
humankindandwithahighlevelofwellbeing.4
Whatdutiesdopresentgenerationsowefuturegenerationsgiventhatcurrentemissionswillaffect
theirqualityoflife?Somejusticetheoristshaveofferedthefollowingargumenttojustifyacapon
2Inthephilosophical literature,justicebetweengenerationstypicallyreferstotherelationsbetweenpeople
whoselifetimesdonotoverlap(Barry,1977).Incontrast,justicebetweenagegroupsreferstotherelations
ofpeoplewhoselifetimesdooverlap(LaslettandFishkin,1992).SeealsoGardiner(2011),pp.14548.
3SeeRawls(1971,1999),Barry(1977),SikoraandBarry(1978),Partridge(1981),Parfit(1986),Birnbacher
(1988),andHeyd(1992).
4SeeBaier(1981),DeShalit(1995),Meyer(2005),andforAfricanphilosophicalperspectivessee,Behrens
(2012).SeeSection3.4 onthewellbeingoffuturepeople.
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emissions(Shue,1993,1999;Caney,2006a;MeyerandRoser,2009;Wolf,2009).Iffuturepeoples
basicrightsincludetherighttosurvival,health,andsubsistence,thesebasicrightsarelikelytobe
violatedwhentemperaturesriseaboveacertainlevel.However,currentlylivingpeoplecanslowthe
riseintemperaturebylimitingtheiremissionsatareasonablecosttothemselves.Therefore,living
peopleshouldreducetheiremissionsinordertofulfiltheirminimaldutiesofjusticetofuture
generations.Normativetheoristsdisputethestandardoflivingthatcorrespondstopeoplesbasic
rights(Page,2007;Huseby,2010).Alsoindisputeiswhatlevelofharmimposedonfuturepeopleismorallyobjectionable.Somearguethatcurrentlylivingpeoplewrongfullyharmfuturepeopleiftheycausethemtohavealowerlevelofwellbeingthantheirown(e.g.,Barry,1999);othersthat
currentlylivingpeopleowefuturepeopleadecentlevelofwellbeing,whichmightbelowerthan
theirown(Wolf,2009).Thisargumentraisesobjectionsongroundsofjusticesinceitpresupposes
thatpresentpeoplecanviolatetherightsoffuturepeople,andthattheprotectionoffuture
peoplesrightsispracticallyrelevantforhowpresentpeopleoughttoact.
Sometheoristsclaimthatfuturepeoplecannotholdrightsagainstpresentpeople,owingtospecialfeaturesofintergenerationalrelations:someclaimthatfuturepeoplecannothaverightsbecause
theycannotexercisethemtoday(Steiner,1983;Wellman,1995,ch.4).Otherspointoutthat
interactionbetweennoncontemporariesisimpossible(Barry,1977,pp.243244,1989,p.189).
However,somejusticetheoristsarguethatneithertheabilityto,northepossibilityof,mutual
interactionarenecessaryinattributingrightstopeople(Barry,1989;Buchanan,2004).Theyholdthatrightsareattributedtobeingswhoseinterestsareimportantenoughtojustifyimposingduties
onothers.
Themainsourceofscepticismabouttherightsoffuturepeopleandthedutiesweowethemisthe
socallednonidentityproblem.Actionswetaketoreduceouremissionswillchangepeopleswayoflifeandsoaffectnewpeopleborn.Theyaltertheidentitiesoffuturepeople.Consequently,our
emissionsdonotmakefuturepeopleworseoffthantheywouldotherwisehavebeen,sincethose
futurepeoplewouldnotexistifwetookactiontopreventouremissions.Thismakesithardtoclaim
thatouremissionsharmfuturepeople,orthatweoweittothemasamatteroftheirrightstoreduceouremissions.5
Itisoftenarguedthatthenonidentityproblemcanbeovercome(McMahan,1998;Shiffrin,1999;
Kumar,2003;Meyer,2003;Harman,2004;Reiman,2007;Shue,2010).Inanycase,dutiesofjusticedonotincludeallthemoralconcernsweshouldhaveforfuturepeople.Otherconcernsaremattersofvalueratherthanjustice,andtheytoocanbeunderstoodinsuchawaythattheyarenotaffectedbythenonidentityproblem.TheyareconsideredinSection3.4 .
Ifpresentpeoplehaveadutytoprotectfuturepeoplesbasicrights,thisdutyiscomplicatedby
uncertainty.Presentpeoplesactionsoromissionsdonotnecessarilyviolatefuturepeoplesrights;
theycreateariskoftheirrightsbeingviolated(Bell,2011).Todeterminewhatcurrentlyliving
peopleowefuturepeople,onehastoweighsuchuncertainconsequencesagainstotherconsequencesoftheiractions,includingthecertainorlikelyviolationoftherightsofcurrentlyliving
people(Oberdiek,2012;Temkin,2012).Thisisimportantinassessingmanylongtermpolicies,
includingongeoengineering(seeSection3.3.7 ),thatriskviolatingtherightsofmanygenerations
ofpeople(Crutzen,2006;Schneider,2008;Victoretal.,2009;Baer,2010;Ott,2012).
3.3.3 Intergenerationaljustice:distributivejusticeSupposethataglobalemissionsceilingthatisintergenerationallyjusthasbeendetermined
(recognizingthataceilingisnottheonlywaytodealwithclimatechange),thequestionthenarises
ofhowtheceilingoughttobedividedamongstates(and,ultimately,theirindividualmembers)
5ForanoverviewoftheissueseeMeyer(2010).SeealsoSchwartz(1978),Parfit(1986),andHeyd(1992).Fora
differentperspectiveseePerrett(2003).
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(Jamieson,2001;Singer,2002;MeyerandRoser,2006;Caney,2006a).Distributingemissionpermits
isawayofarrivingatagloballyjustdivision.Amongthewidelydiscussedviewsondistributive
justicearestrictegalitarianism(Temkin,1993),indirectegalitarianviewsincludingprioritarianism
(Parfit,1997),andsufficientarianism(Frankfurt,1999).Strictegalitarianismholdsthatequalityhas
valueinitself.Prioritarianismgivesgreaterweighttoapersonswellbeingthelesswelloffsheis,as
describedinSection3.4 .Sufficientarianismrecommendsthateveryoneshouldbeabletoenjoya
particularlevelofwellbeing.Forexample,twooptionscanhelpapplyprioritarianismtothedistributionoffreelyallocatedand
globallytradeableemissionpermits.Thefirstistoignorethedistributionofothergoods.Thenstrict
egalitarianismorprioritarianismwillrequireemissionpermitstobedistributedequally,sincetheywillhaveonepriceandarethusequivalenttoincome.Thesecondistotakeintoaccountthe
unequaldistributionofotherassets.Sincepeopleinthedevelopingworldarelesswelloffthanin
thedevelopedworld,strictegalitarianismorprioritarianismwouldrequiremostorallpermitstogo
tothedevelopingworld.However,itisquestionablewhetheritisappropriatetobringtheoveralldistributionofgoodsclosertotheprioritarianidealthroughthedistributionofjustonegood(Wolff
anddeShalit,2007;Caney,2009,2012).
3.3.4 Historicalresponsibilityanddistributivejustice
HistoricalresponsibilityforclimatechangedependsoncountriescontributionstothestockofGHGs.TheUNFCCCreferstocommonbutdifferentiatedresponsibilitiesamongcountriesofthe
world.6Thisissometimestakentoimplythatcurrentandhistoricalcausalresponsibilityforclimate
changeshouldplayaroleindeterminingtheobligationsofdifferentcountriesinreducingemissions
andpayingforadaptationmeasuresglobally(Rajamani,2000;Riveetal.,2006;Friman,2007).
Anumberofobjectionshavebeenraisedagainsttheviewthathistoricalemissionsshouldplayarole(see,e.g.,Gosseries,2004;Caney,2005;MeyerandRoser,2006;PosnerandWeisbach,2010).First,
ascurrentlylivingpeoplehadnoinfluenceovertheactionsoftheirancestors,theycannotbeheld
responsibleforthem.Second,previouslylivingpeoplemaybeexcusedfromresponsibilityonthe
groundsthattheycouldnotbeexpectedtoknowthattheiremissionswouldhaveharmfulconsequences.Thirdly,presentindividualswiththeirparticularidentitiesarenotworseorbetteroff
asaresultoftheemissiongeneratingactivitiesofearliergenerationsbecause,owingtothenon
identityproblem,theywouldnotexistastheindividualstheyarehadearliergenerationsnotacted
astheydid.
Fromtheperspectiveofdistributivejustice,however,theseobjectionsneednotpreventpastemissionsandtheirconsequencesbeingtakenintoaccount(MeyerandRoser,2010;Meyer,2013).
Ifweareonlyconcernedwiththedistributionofbenefitsfromemissiongeneratingactivitiesduring
anindividualslifespan,weshouldincludethebenefitspresentpeoplehavereceivedfromtheirown
emissiongeneratingactivities.Furthermore,presentpeoplehavebenefitedsincebirthor
conceptionfrompastpeoplesemissionproducingactions.Theyarethereforebetteroffasaresult
ofpastemissions,andanyprincipleofdistributivejusticeshouldtakethatintoaccount.Some
suggestthattakingaccountoftheconsequencesofsomepastemissionsinthiswayshouldnotbe
subjecttotheobjectionsmentionedinthepreviousparagraph(seeShue,2010).Otherconcepts
associatedwithhistoricalresponsibilityarediscussedinChapter4.
6Specifically,Article3oftheUNFCCCincludesthesentence:ThePartiesshouldprotecttheclimatesystemfor
thebenefitofpresentandfuturegenerationsofhumankind,onthebasisofequityandinaccordancewith
theircommonbutdifferentiatedresponsibilitiesandrespectivecapabilities.
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3.3.5 Intragenerationaljustice:compensatoryjusticeandhistoricalresponsibilityDothosewhosufferdisproportionatelyfromtheconsequencesofclimatechangehavejustclaimsto
compensationagainstthemainperpetratorsorbeneficiariesofclimatechange(see,e.g.,Neumayer,
2000;Gosseries,2004;Caney,2006b)?
Onewayofdistinguishingcompensatoryfromdistributiveclaimsistorelyontheideaofajustbaselinedistributionthatisdeterminedbyacriterionofdistributivejustice.Underthisapproach,
compensationforclimatedamageandadaptationcostsisowedonlybypeoplewhohaveacted
wrongfullyaccordingtonormativetheory(Feinberg,1984;Coleman,1992;McKinnon,2011).Other
deviationsfromthebaselinemaywarrantredistributivemeasurestoredressundeservedbenefitsor
harms,butnotascompensation.Somedeviations,suchasthosethatresultfromfreechoice,may
notcallforanyredistributionatall.
Thedutytomakecompensatorypayments(Gosseries,2004;Caney,2006b)mayfallonthosewho
emitorbenefitfromwrongfulemissionsorwhobelongtoacommunitythatproducedsuch
emissions.Accordingly,threeprinciplesofcompensatoryjusticehavebeensuggested:thepolluterpaysprinciple(PPP),thebeneficiarypaysprinciple(BPP),andthecommunitypaysprinciple(CPP)
(MeyerandRoser,2010;Meyer,2013).Noneofthethreemeasuresisgenerallyaccepted,though
thePPPismorewidelyacceptedthantheothers.ThePPPrequirestheemittertopaycompensation
iftheagentemittedmorethanitsfairshare(determinedasoutlinedinSection3.3.2 )anditeitherknew,orcouldreasonablybeexpectedtoknow,thatitsemissionswereharmful.Thevictimshould
beabletoshowthattheemissionseithermadethevictimworseoffthanbeforeorpushed belowa
specifiedthresholdofharm,orboth.
TherighttocompensatorypaymentsforwrongfulemissionsunderPPPhasatleastthreebasic
limitations.TwohavealreadybeenmentionedinSection3.3.4 .Emissionsthattookplacewhileit
waspermissibletobeignorantofclimatechange(whenpeopleneitherdidknownorcouldbereasonablybeexpectedtoknowabouttheharmfulconsequencesofemissions)maybeexcused
(Gosseries,2004,pp.3941).SeealsoSection3.3.6 .Thenonidentityproblem(seeSection3.3.2 )
impliesthatearlieremissionsdonotharmmanyofthepeoplewhocomeintoexistencelater.
Potentialdutybearersmaybedeadandcannotthereforehaveadutytosupplycompensatory
measures.ItmaythereforebedifficulttousePPPinascribingcompensatorydutiesandidentifying
wrongedpersons.Thefirstandthirdlimitationsrestricttheassignmentofdutiesofcompensationtocurrentlylivingpeoplefortheirmostrecentemissions,eventhoughmanymorepeoplearecausally
responsiblefortheharmfuleffectsofclimatechange.Forfutureemissions,thethirdlimitationcould
beovercomethroughaclimatechangecompensationfundintowhichagentspayleviesforimposing
theriskofharmonfuturepeople(McKinnon,2011).
AccordingtoBPP,apersonwhoiswrongfullybetteroffrelativetoajustbaselineisrequiredto
compensatethosewhoareworseoff.Pastemissionsbenefitsomeandimposecostsonothers.If
currentlylivingpeopleacceptthebenefitsofwrongfulpastemissions,ithasbeenarguedthatthey
takeonsomeofthepastwrongdoersdutyofcompensation(Gosseries,2004).Also,wehaveaduty
tocondemninjustice,whichmayentailadutynottobenefitfromaninjusticethatcausesharmtoothers(Butt,2007).However,BPPisopentoatleasttwoobjections.First,dutiesofcompensation
ariseonlyfrompastemissionsthathavebenefitedpresentpeople;nocompensationisowedfor
otherpastemissions.Second,ifvoluntaryacceptanceofbenefitsisaconditionoftheirgivingriseto
compensatoryduties,thebearersofthedutiesmustbeabletoforgothebenefitsinquestionata
reasonablecost.
UnderCPP,moraldutiescanbeattributedtopeopleasmembersofgroupswhoseidentitypersists
overgenerations(DeShalit,1995;Thompson,2009).Theprincipleclaimsthatmembersofa
community,includingacountry,canhavecollectiveresponsibilityforthewrongfulactionsofother
pastandpresentmembersofthecommunity,eventhoughtheyarenotmorallyorcausally
responsibleforthoseactions(Thompson,2001;Miller,2004;Meyer,2005).Itisamatterofdebate
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underwhatconditionspresentpeoplecanbesaidtohaveinheritedcompensatoryduties.Although
CPPpurportstoovercometheproblemthatapollutermightbedead,itcanjustifycompensatory
measuresonlyforemissionsthataremadewrongfully.Itdoesnotcoveremissionscausedbyagents
whowerepermissiblyignorantoftheirharmfulness.(Theagentinthiscasemaybethecommunity
orstate).
Thepracticalrelevanceofprinciplesofcompensatoryjusticeislimited.Insofarastheharmsand
benefitsofclimatechangeareundeserved,distributivejusticewillrequirethemtobeevenedout,independentlyofcompensatoryjustice.Dutiesofdistributivejusticedonotpresupposeany
wrongdoing(seeSection3.3.4 ).Forexample,ithasbeensuggestedongroundsofdistributive
justicethatthedutytopayforadaptationshouldbeallocatedonthebasisofpeoplesabilitytopay,whichpartlyreflectsthebenefittheyhavereceivedfrompastemissions(Jamieson,1997;Shue,
1999;Caney,2010;Gardiner,2011).However,presentpeopleandgovernmentscanbesaidtoknow
aboutboththeseriouslyharmfulconsequencesoftheiremissiongeneratingactivitiesforfuture
peopleandeffectivemeasurestopreventthoseconsequences.Ifsoandiftheycanimplementthesemeasuresatareasonablecosttothemselvestoprotectfuturepeoplesbasicrights(see,e.g.,
Birnbacher,2009;Gardiner,2011),theymightbeviewedasowingintergenerationaldutiesofjustice
tofuturepeople(seeSection3.3.2 ).
3.3.6 LegalconceptsofhistoricalresponsibilityLegalsystemshavestruggledtodefinetheboundariesofresponsibilityforharmfulactionsandare
onlynowbeginningtodosoforclimatechange.Itremainsunclearwhethernationalcourtswill
acceptlawsuitsagainstGHGemitters,andlegalscholarsvigorouslydebatewhetherliabilityexists
undercurrentlaw(Mank,2007;BurnsandOsofsky,2009;FaureandPeeters,2011;Haritz,2011;Kosolapova,2011;Kysar,2011;GerrardandWannier,2012).Thissectionisconcernedwithmoralresponsibility,whichisnotthesameaslegalresponsibility.Butmoralthinkingcandrawuseful
lessonsfromlegalideas.
Harmfulconductisgenerallyabasisforliabilityonlyifitbreachessomelegalnorm(Tunc,1983),
suchasnegligence,orifitinterferesunreasonablywiththerightsofeitherthepublicorpropertyowners(Mank,2007;Grossman,2009;Kysar,2011;Bruneetal.,2012;GoldbergandLord,2012;
Kochetal.,2012).Liabilityfornuisancedoesnotexistiftheagentdidnotknow,orhavereasonto
know,theeffectsofitsconduct(AntoliniandRechtschaffen,2008).Thelawinconnectionwith
liabilityforenvironmentaldamagestillhastobesettled.TheEuropeanUnion,butnottheUnited
States,recognizesexemptionfromliabilityforlackofscientificknowledge(UnitedStatesCongress,
1980;EuropeanUnion,2004).UnderEuropeanlaw,andinsomeUSstates,defendantsarenot
responsibleifaproductdefecthadnotyetbeendiscovered(EuropeanCommission,1985;Dana,
2009).SomelegalscholarssuggestthatassigningblameforGHGemissionsdatesbackto1990when
theharmfulnessofsuchemissionswasestablishedinternationally,butothersargueinfavourofan
earlierdate(FaureandNollkaemper,2007;HunterandSalzman,2007;Haritz,2011).Legalsystemsalsorequireacausallinkbetweenadefendantsconductandsomeidentifiedharmtotheplaintiff,
inthiscasefromclimatechange(Tunc,1983;FaureandNollkaemper,2007;Kosolapova,2011;Kysar,2011;Bruneetal.,2012;EwingandKysar,2012;GoldbergandLord,2012).Acausallink
mightbeeasiertoestablishbetweenemissionsandadaptationcosts(Farber,2007).Legalsystems
generallyalsorequirecausalforeseeabilityordirectness(Mank,2007;Kosolapova,2011;vanDijk,2011;EwingandKysar,2012),althoughsomestatutesrelaxthisrequirementinspecificcases(such
astheUSComprehensiveEnvironmentalResponse,Compensation,andLiabilityAct(CERCLA),
commonlyknownasSuperfund.EmittersmightarguethattheircontributiontoGHGlevelswastoo
smallandtheharmfuleffectstooindirectanddiffusetosatisfythelegalrequirements(Sinnot
Armstrong,2010;FaureandPeeters,2011;Hiller,2011;Kysar,2011;vanDijk,2011;GerrardandWannier,2012).
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Climatechangeclaimscouldalsobeclassifiedasunjustenrichment(Kull,1995;Birks,2005),but
legalsystemsdonotremedyallformsofenrichmentthatmightberegardedasethicallyunjust
(Zimmermann,1995;AmericanLawInstitute,2011;Laycock,2012).Undersomelegalsystems,
liabilitydependsonwhetherbenefitswereconferredwithoutlegalobligationorthrougha
transactionwithnoclearchangeofownership(Zimmermann,1995;AmericanLawInstitute,2011;
Laycock,2012).Itisnotclearthattheseprinciplesapplytoclimatechange.
Asindicated,legalsystemsdonotrecognizeliabilityjustbecauseapositiveornegativeexternalityexists.Theirresponsedependsonthebehaviourthatcausedtheexternalityandthenatureofthe
causallinkbetweentheagentsbehaviourandtheresultinggainorlosstoanother.
3.3.7 Geoengineering,ethics,andjusticeGeoengineering(alsoknownasclimateengineering[CE]),islargescaletechnicalinterventioninthe
climatesystemthataimstocancelsomeoftheeffectsofGHGemissions(formoredetailsseeWGI
6.5andWGIII6.9).Geoengineeringrepresentsathirdkindofresponsetoclimatechange,besidesmitigationandadaptation.Variousoptionsforgeoengineeringhavebeenproposed,includingdifferenttypesofsolarradiationmanagement(SRM)andcarbondioxideremoval(CDR).Thissection
reviewsthemajormoralargumentsforandagainstgeoengineeringtechnologies(forsurveyssee
Robock,2008;CornerandPidgeon,2010;Gardiner,2010;Ott,2010;BetzandCacean,2012;
Preston,2013).Thesemoralargumentsdonotapplyequallytoallproposedgeoengineeringmethodsandhavetobeassessedonacasespecificbasis.7
Threelinesofargumentsupporttheviewthatgeoengineeringtechnologiesmightbedesirableto
deployatsomepointinthefuture.First,thathumanitycouldendupinasituationwheredeploying
geoengineering,particularlySRM,appearsasalesserevilthanunmitigatedclimatechange(Crutzen,
2006;Gardiner,2010;Keithetal.,2010;Svoboda,2012a;Betz,2012).Second,thatgeoengineeringcouldbeamorecosteffectiveresponsetoclimatechangethanmitigationoradaptation(Barrett,
2008).Suchefficiencyargumentshavebeencriticizedintheethicalliteratureforneglectingissues
suchassideeffects,uncertainties,orfairness(Gardiner,2010,2011;Buck,2012).Third,thatsome
aggressiveclimatestabilizationtargetscannotbeachievedthroughmitigationmeasuresaloneandthusmustbecomplementedbyeitherCDRorSRM(Greeneetal.,2010;Sandler,2012).
Geoengineeringtechnologiesfaceseveraldistinctsetsofobjections.Someauthorshavestressedthesubstantialuncertaintiesoflargescaledeployment(foroverviewsofgeoengineeringrisksseealso
Schneider(2008)andSardemannandGrunwald(2010)),whileothershavearguedthatsomeintendedandunintendedeffectsofbothCDRandSRMcouldbeirreversible(Jamieson,1996)andthatsomecurrentuncertaintiesareunresolvable(Bunzl,2009).Furthermore,ithasbeenpointed
outthatgeoengineeringcouldmakethesituationworseratherthanbetter(HegerlandSolomon,
2009;Fleming,2010;Hamilton,2013)andthatseveraltechnologieslackaviableexitoption:SRMin
particularwouldhavetobemaintainedaslongasGHGconcentrationsremainelevated(TheRoyal
Society,2009).
Argumentsagainstgeoengineeringonthebasisoffairnessandjusticedealwiththeintra
generationalandintergenerationaldistributionaleffects.SRMschemescouldaggravatesome
inequalitiesif,asexpected,theymodifyregionalprecipitationandtemperaturepatternswith
unequalsocialimpacts(Bunzl,2008;TheRoyalSociety,2009;Svobodaetal.,2011;Preston,2012).Furthermore,someCDRmethodswouldrequirelargescalelandtransformations,potentially
7Whiletheliteraturetypicallyassociatessomeargumentswithparticulartypesofmethods(e.g.,the
terminationproblemwithSRM),itisnotclearthattherearetwogroupsofmoralarguments:thoseapplicable
toallSRMmethodsontheonesideandthoseapplicabletoallCDRmethodsontheotherside.Inotherwords,
themoralassessmenthingesonaspectsofgeoengineeringthatarenotconnectedtothedistinctionbetween
SRMandCDR.
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competingwithagriculturallanduse,withuncertaindistributiveconsequences.Otherarguments
againstgeoengineeringdealwithissuesincludingthegeopoliticsofSRM,suchasinternational
conflictsthatmayarisefromtheabilitytocontroltheglobalthermostat(e.g.,Schelling,1996;
Hulme,2009),ethics(HaleandGrundy,2009;Preston,2011;HaleandDilling,2011;Svoboda,2012b;
Hale,2012b),andacriticalassessmentoftechnologyandmoderncivilizationingeneral(Fleming,
2010;Scott,2012).
Oneofthemostprominentargumentsagainstgeoengineeringsuggeststhatgeoengineeringresearchactivitiesmighthampermitigationefforts(e.g.,Jamieson,1996;Keith,2000;Gardiner,
2010),whichpresumesthatgeoengineeringshouldnotbeconsideredanacceptablesubstitutefor
mitigation.Thecentralideaisthatresearchincreasestheprospectofgeoengineeringbeingregardedasaseriousalternativetoemissionreduction(foradiscussionofdifferentversionsofthis
argumentseeHale,2012a;Hourdequin,2012).Otherauthorshaveargued,basedonhistorical
evidenceandanalogiestoothertechnologies,thatgeoengineeringresearchmightmakedeployment
inevitable(Jamieson,1996;Bunzl,2009),orthatlargescalefieldtestscouldamounttofullfledgeddeployment(Robocketal.,2010).Ithasalsobeenarguedthatgeoengineeringwouldconstitutean
unjustimpositionofrisksonfuturegenerations,becausetheunderlyingproblemwouldnotbe
solvedbutonlycounteractedwithriskytechnologies(Gardiner,2010;Ott,2012;Smith,2012).The
latterargumentisparticularlyrelevanttoSRMtechnologiesthatwouldnotaffectgreenhousegas
concentrations,butitwouldalsoapplytosomeCDRmethods,astheremaybeissuesoflongtermsafetyandcapacityofstorage.
Argumentsinfavourofresearchongeoengineeringpointoutthatresearchdoesnotnecessarily
prepareforfuturedeployment,butcan,onthecontrary,uncovermajorflawsinproposedschemes,
avoidprematureCEdeployment,andeventuallyfostermitigationefforts(e.g.,Keithetal.,2010).AnotherjustificationforResearchandDevelopment(R&D)isthatitisrequiredtohelpdecision
makerstakeinformeddecisions(LeisnerandMllerKlieser,2010).
3.4 Valuesandwellbeing
Onebranchofethicsisthetheoryofvalue.Manydifferentsortsofvaluecanarise,andclimate
changeimpingesonmanyofthem.Valueaffectsnatureandmanyaspectsofhumanlife.Thissectionsurveyssomeofthevaluesatstakeinclimatechange,andexamineshowfarthesevalues
canbemeasured,combined,orweighedagainsteachother.Eachvalueissubjecttodebateand
disagreement.Forexample,itisdebatablewhethernaturehasvalueinitsownright,apartfromthe
benefititbringstohumanbeings.Decisionmakingaboutclimatechangeisthereforelikelytobe
contentious.
Sincevaluesconstituteonlyonepartofethics,ifanactionwillincreasevalueoverallitbynomeans
followsthatitshouldbedone.Manyactionsbenefitsomepeopleatthecostofharmingothers.This
raisesaquestionofjusticeevenifthebenefitsintotalexceedthecosts.Whereasacosttoaperson
canbecompensatedforbyabenefittothatsameperson,acosttoapersoncannotbe
compensatedforbyabenefittosomeoneelse.Tosupposeitcanisnottotakeseriouslythe
distinctionbetweenpersons,asJohnRawlsputsit(1971,p.27).Harmingapersonmayinfringe
theirrights,oritmaybeunfairtothem.Forexample,whenanationseconomicactivitiesemitGHG,theymaybenefitthenationitself,butmayharmpeopleinothernations.Evenifthebenefitsare
greaterinvaluethantheharms,theseactivitiesmayinfringeothernationsrights.Othernationsmaythereforebeentitledtoobjecttothemongroundsofjustice.
Anydecisionaboutclimatechangeislikelytopromotesomevaluesanddamageothers.Thesemay
bevaluesofverydifferentsorts.Indecisionmaking,differentvaluesmustthereforebeputtogether
orbalancedagainsteachother.Somepairsofvaluesdiffersoradicallyfromeachotherthatthey
cannotbedeterminatelyweighedtogether.Forexample,itmaybeimpossibletoweighthevalueofpreservingatraditionalcultureagainstthematerialincomeofthepeoplewhosecultureitis,orto
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weighthevalueofbiodiversityagainsthumanwellbeing.Someeconomistsclaimthatonepersons
wellbeingcannotbeweighedagainstanothers(Robbins,1937;Arrow,1963).Whenvaluescannot
bedeterminatelyweighed,theyaresaidtobeincommensurableorincomparable(Chang,1997).
MultiCriteriaAnalysis(MCA)(discussedinSection3.7.2.1 )isatechniquethatisdesignedtotake
accountofseveralincommensurablevalues(DeMontisetal.,2005;ZelenyandCochrane,1982).
3.4.1 NonhumanvaluesNatureprovidesgreatbenefitstohumanbeingsinwaysthatrangefromabsorbingourwaste,tobeautifyingtheworldweinhabit.Anincreasingnumberofphilosophershavearguedinrecentyearsthatnaturealsohasvalueinitsownright,independentlyofitsbenefitstohumanbeings(Leopold,
1949;Palmer,2011).Theyhavearguedthatweshouldrecognizeanimalvalues,thevalueoflifeitself,andeventhevalueofnaturalsystemsandnatureitself.
Inmoraltheory,rationaladulthumans,whoareselfconscioussubjectsofalife,areoftentaken
(followingKant,1956)tohaveakindofunconditionalmoralworthsometimescalleddignitythatisnotfoundelsewhereonearth.Othersbelievethatmoralworthcanbefoundelsewhere(Dryzek,1997).Manyhumanbeingsthemselveslackrationalityorsubjectivity,yetstillhavemoral
worththeveryyoung,theveryoldandpeoplewithvariouskindsofimpairmentamongthem.
Giventhat,whydenymoralworthtothoseanimalsthataretosomeextentsubjectsofalife,who
showemotionalsophistication(Regan,2004),andwhoexperiencepleasure,pain,suffering,andjoy(Singer,1993)?
AnargumentforrecognizingvalueinplantsaswellasanimalswasproposedbyRichardRoutley
(1973).Routleygivesthenamehumanchauvinismtotheviewthathumansarethesolepossessors
ofintrinsicvalue.Heasksustoimaginethatthelastmanonearthsetsouttodestroyeveryliving
thing,animalorplant.Mostpeoplebelievethiswouldbewrong,buthumanchauvinistsareunabletoexplainwhy.Humanchauvinismappearstobesimplyaprejudiceinfavourofthehumanspecies
(RoutleyandRoutley,1980).Incontrast,somephilosophersarguethatvalueexistsinthelivesofall
organisms,totheextentthattheyhavethecapacitytoflourish(Taylor,1986;Agar,2001).
Goingfurther,otherphilosophershavearguedthatbiologicalcommunitiesandholisticecological
entitiesalsohavevalueintheirownright.Somehavearguedthataspecieshasmorevaluethanall
ofitsindividualshavetogether,andthatanecosystemhasstillmorevalue(Rolston,1988,1999;comparediscussioninBrennanandLo,2010).Ithasfurtherbeenproposedthat,justasdomination
ofonehumangroupbyanotherisamoralevil,showingdisrespectforthevalueofothers,thensoisthedominationofnaturebyhumansingeneral.Ifnatureanditssystemshavemoralworth,thenthedominationofnatureisalsoakindofdisrespect(Jamieson,2010).
Ifanimals,plants,species,andecosystemsdohavevalueintheirownright,thenthemoralimpactof
climatechangecannotbegaugedbyitseffectsonhumanbeingsalone.Ifclimatechangeleadsto
thelossofenvironmentaldiversity,theextinctionofplantandanimalspecies,andthesufferingofanimalpopulations,thenitwillcausegreatharmsbeyondthoseitdoestohumanbeings.Itseffectsonspeciesnumbers,biodiversity,andecosystemsmaypersistforaverylongtime,perhapseven
longerthanthelifetimeofthehumanspecies(Nolt,2011).
Itisverydifficulttomeasurenonhumanvaluesinawaythatmakesthemcommensuratewithhumanvalues.Economistsaddressthisissuebydividingvalueintousevalue(associatedwithactual
useofnatureinstrumentalvalue)andnonuseorexistencevalue(intrinsicvalueofnature).Asanexample,biodiversitymighthavevaluebecauseofthemedicaldrugsthatmightbediscovered
amongthediversebiota(usevalue).Orbiodiversitymightbevaluedbyindividualssimplybecause
theybelievethatbiologicdiversityisimportant,overandaboveanyusetopeoplethatmightoccur.
Thetotalamountpeoplearewillingtopayhassometimesbeenusedasaneconomicmeasureofthe
totalvalue(instrumentalandintrinsic)ofthesefeatures(Aldred,1994).Asthediscussionofthepast
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fewparagraphshassuggested,naturemayhaveadditionalvalue,overandabovethevaluesplaced
byindividualhumans(Broome,2009;Spashetal.,2009).
3.4.2 CulturalandsocialvaluesThevalueofhumanwellbeingisconsideredinSection3.4.3 ,butthehumanworldmayalso
possessothervaluesthatdonotformpartofthewellbeingofindividualhumans.Livingina
flourishingcultureandsocietycontributestoapersonswellbeing(Kymlicka,1995;Appiah,2010),butsomeauthorsclaimthatculturesandsocietiesalsopossessvaluesintheirownright,overand
abovethecontributiontheymaketowellbeing(Taylor,1995).Climatechangethreatensdamagetoculturalartefactsandtoculturesthemselves(Adgeretal.,2012).Evidencesuggeststhatitmay
alreadybedamagingthecultureofArcticindigenouspeoples(Fordetal.,2006,2008;Crate,2008;Hassol,2004;seealsoWGIIChapter12).Culturalvaluesandindigenouspeoplesarediscussedin
Section3.10.2 .
Thedegreeofequalityinasocietymayalsobetreatedasavaluethatbelongstoasocietyasawhole,ratherthantoanyoftheindividualswhomakeupthesociety.Variousmeasuresofthisvalueareavailable,includingtheGinicoefficientandtheAtkinsonmeasure(Gini,1912;Atkinson,1970);
foranassessmentsee(Sen,1973).Section3.5 explainsthatthevalueofequalitycanalternatively
betreatedasafeatureoftheaggregationofindividualpeopleswellbeings,ratherthanassocial
valueseparatefromwellbeing.
3.4.3 WellbeingMostpolicyconcernedwithclimatechangeaimsultimatelyatmakingtheworldbetterforpeopleto
livein.Thatistosay,itaimstopromotepeopleswellbeing.Apersonswellbeing,asthetermis
usedhere,includeseverythingthatisgoodorbadforthepersoneverythingthatcontributestomakingtheirlifegowellorbadly.Whatthingsarethosewhatconstitutesapersonswellbeing?
Thisquestionhasbeenthesubjectofanextensiveliteraturesinceancienttimes.8Oneviewisthata
personswellbeingisthesatisfactionoftheirpreferences.Anotheristhatitconsistsingoodfeelings
suchaspleasure.Athirdisthatwellbeingconsistsinpossessingtheordinarygoodthingsoflife,suchashealth,wealth,alonglife,andparticipatingwellinagoodcommunity.Thecapabilitiesapproach
ineconomics(Sen,1999)embodiesthislastview.Ittreatsthegoodthingsoflifeasfunctionings
andcapabilitiesthingsthatapersondoesandthingsthattheyhavearealopportunityofdoing,suchaslivingtooldage,havingagoodjob,andhavingfreedomofchoice.
Apersonswellbeingwillbeaffectedbymanyoftheothervaluesthatarementionedabove,andby
manyoftheconsiderationsofjusticementionedinSection3.3 .Itisbadforapersontohavetheirrightsinfringedortobetreatedunfairly,anditisgoodforapersontolivewithinahealthyculture
andsociety,surroundedbyflourishingnature.
Variousconcretemeasuresofwellbeingareinuse(Fleurbaey,2009;Stiglitzetal.,2009).Eachreflectsaparticularviewaboutwhatwellbeingconsistsin.Forexample,manymeasuresof
subjectivewellbeing(OswaldandWu,2010;KahnemanandDeaton,2010)assumethatwellbeing
consistsingoodfeelings.Monetarymeasuresofwellbeing,whichareconsideredinSection3.6 ,
assumethatwellbeingconsistsinthesatisfactionofpreferences.Othermeasuresassumewellbeing
consistsinpossessinganumberofspecificgoodthings.TheHumanDevelopmentIndex(HDI)is
intendedtobeanapproximatemeasureofwellbeingunderstoodascapabilitiesandfunctionings
(UNDP,2010).Itisbasedonthreecomponents:lifeexpectancy,education,andincome.Thecapabilitiesapproachhasinspiredothermeasuresofwellbeingtoo(DervisandKlugman,2011).In
thecontextofclimatechange,manydifferentmetricsofvalueareintendedtomeasureparticular
8Forexample:Aristotle,NicomacheanEthics.Recentworkincludes:Griffin(1986);Sumner(1999);Kraut
(2007).
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componentsofwellbeing:amongthemarethenumbersofpeopleatriskfromhunger,infectious
diseases,coastalflooding,orwaterscarcity.Thesemetricsmaybecombinedtocreateamore
generalmeasure.Schneideretal.(2000)advocatestheuseofasuiteoffivemetrics:(1)monetary
loss,(2)lossoflife,(3)qualityoflife(takingaccountofforcedmigration,conflictoverresources,
culturaldiversity,andlossofculturalheritagesites),(4)speciesorbiodiversityloss,and(5)
distributionandequity.
3.4.4 AggregationofwellbeingWhateverwellbeingconsistsof,policymakingmusttakeintoaccountthewellbeingofeveryoneinthesociety.Sothewellbeingsofdifferentpeoplehavesomehowtobeaggregatedtogether.Howdo
theycombinetomakeupanaggregatevalueofwellbeingforasocietyasawhole?Socialchoicetheorytakesupthisproblem(Arrow,1963;Sen,1970).Section3.6 willexplainthattheaimof
economicvaluationistomeasureaggregatewellbeing.
Assumethateachpersonhasalevelofwellbeingateachtimetheyarealive,andcallthistheirtemporalwellbeingatthattime.Inasociety,temporalwellbeingisdistributedacrosstimesandacrossthepeople.Whenachoiceistobemade,eachoftheoptionsleadstoaparticulardistribution
ofwellbeing.Ouraimistoassessthevalueofsuchdistributions.Doingsoinvolvesaggregating
wellbeingsacrosstimesandacrosspeople,toarriveatanoverall,socialvalueforthedistribution.
3.4.5 LifetimewellbeingNextletusassumethateachpersonstemporalwellbeingscanbeaggregatedtodeterminea
lifetimewellbeingfortheperson,andthatthesocialvalueofthedistributionofwellbeingdepends
onlyontheselifetimewellbeings.Thisistheassumptionthateachpersonswellbeingisseparable,
touseatechnicalterm.Itallowsustosplitaggregationintotwosteps.First,weaggregateeachpersonstemporalwellbeingsacrossthetimesintheirlifeinordertodeterminetheirlifetime
wellbeing.Thesecondstepinthenextsectionistoaggregateacrossindividualsusingasocial
welfarefunction.
Ononeaccount,apersonslifetimewellbeingissimplythetotaloftheirtemporalwellbeingsateach
timetheyarealive.Ifapersonswellbeingdependedonlyonthestateoftheirhealth,thisformula
wouldbeequivalenttoqalysordalys(qualityadjustedlifeyearsordisabilityadjustedlifeyears),
whicharecommonlyusedintheanalysisofpublichealth(Murray,1994;Sassi,2006).Thesemeasurestakeapersonslifetimewellbeingtobethetotalnumberofyearstheylive,adjustedfor
theirhealthineachyear.Sincewellbeingactuallydependsonotherthingsaswellashealth,qalysor
dalysprovideatbestanapproximatemeasureoflifetimewellbeing.Iftheyareaggregatedacrosspeoplebysimpleaddition,itassumesimplicitlythatayearofhealthylifeisequallyasvaluableto
onepersonasitistoanother.Thatmaybeanacceptableapproximationforthebroadevaluationof
climatechangeimpactsandpolicies,especiallyforevaluatingtheireffectsonhealth(Nordetal.,
1999;Mathersetal.,2009;butalsoseeCurrieetal.,2008).
Otheraccountsgiveeitherincreasing,(Velleman,1991)oralternativelydecreasing,(Kaplowetal.,
2010)weighttowellbeingthatcomesinlateryearsoflife,indeterminingapersonslifetime
wellbeing.
3.4.6 SocialwelfarefunctionsOncewehavealifetimewellbeingforeachperson,thenextstepistoaggregatetheselifetime
wellbeingsacrosspeople,todetermineanoverallvalueforsociety.Thisinvolvescomparingone
personswellbeingwithanothers.Manyeconomistshaveclaimedthatinterpersonalcomparisonsof
wellbeingareimpossible.9Iftheyareright,thewellbeingsofdifferentpeopleareincommensurable
9Examplesare:Robbins(1937),Archibald(1959),Arrow(1963).Asurveyanddiscussionofthisscepticalview
appearsinHammond(1993).
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andcannotbeaggregated.Inthissectionwesetthisviewaside,andassumethattemporal
wellbeingsaremeasuredinawaythatiscomparableacrosspeople.10Thisallowsustoaggregate
differentpeopleslifetimewellbeingsthroughasocialwelfarefunction(SWF)toarriveatanoverall
valueorsocialwelfare.11
WeshallfirstconsiderSWFsunderthesimplifyingbutunrealisticassumptionthatthedecisionsthat
aretobemadedonotaffecthowmanypeopleexistorwhichpeopleexist:alltheoptionscontain
thesamepeople.AtheoremofHarsanyis(1955)givessomegroundsforthinkingthat,giventhisassumption,theSWFisadditivelyseparablebetweenpeople.Thismeansithastheform:
Equation3.4.1. V=v1(w1)+v2(w2)++vJ(wJ).
Herewiispersonislifetimewellbeing.Thisformulasaysthateachpersonswellbeingcanbe
assignedavaluevi(wi),andallthesevaluesoneforeachpersonareaddeduptodeterminethesocialvalueofthedistribution.
TheproofofHarsanyisTheoremdependsonassumptionsthatcanbechallenged(Diamond,1967;
Broome,2004;Fleurbaey,2010).So,althoughtheadditivelyseparableformshowninEquation3.4.1
iscommonlyassumedineconomicvaluations,itisnotentirelysecure.Inparticular,thisformmakes
itimpossibletogiveanyvaluetoequalityexceptindirectlythroughprioritarianism,whichwas
introducedinSection3.3.2 andisdefinedbelow.ThevalueofinequalitycannotbemeasuredbytheGinicoefficient,forexample,sincethismeasureisnotadditivelyseparable(Sen,1973).
Itisoftenassumedthatthefunctionsvi()allhavethesameform,whichmeansthateachpersons
wellbeingisvaluedinthesameway:
Equation3.4.2. V=v(w1)+v(w2)++v(wJ)
Alternatively,thewellbeingofpeoplewholivelaterissometimesdiscountedrelativetothe
wellbeingofpeoplewholiveearlier;thisimpliesthatthefunctionalformofvi()variesaccordingtothedatewhenpeoplelive.Discountingoflaterwellbeingisoftencalledpurediscounting.Itis
discussedinSection3.6.2 .
EvenifweacceptEquation3.4.2,differentethicaltheoriesimplydifferentSWFs.Utilitarianism
valuesonlythetotalofpeopleswellbeing.TheSWFmaybewritten:
Equation3.4.3. V=w1+w2++wJ
Utilitarianismgivesnovaluetoequalityinthedistributionofwellbeing:agiventotalofwellbeing
hasthesamevaluehoweverunequallyitisdistributedamongpeople.
ButtheideaofdistributivejusticementionedinSection3.3.3 suggeststhatequalityofwellbeing
doeshavevalue.Equation3.4.2willgivevaluetoequalityifthefunctionv()isstrictlyconcave.Thismeansthegraphofv()curvesdownwards,asFigure3.1illustrates.(Section3.6.1.1 explainsthata
personswellbeingwiiscommonlyassumedtobeastrictlyconcavefunctionofherconsumption,
butthisisadifferentpoint.)Theresultingethicaltheoryiscalledprioritarianism.AsFigure3.1
shows,accordingtoprioritarianism,improvingapersonswellbeingcontributesmoretosocial
welfareifthepersonisbadlyoffthaniftheyarewelloff.Theprioritariansloganisprioritytothe
worseoff.Prioritarianismindirectlygivesvaluetoequality:itimpliesthatagiventotalofwellbeing
ismorevaluablethemoreequallyitisdistributed(Sen,1973;Weirich,1983;Parfit,1997).In
10Potentialbasesofinterpersonalcomparisonsareexaminedin:FleurbaeyandHammond(2004);Sen(1982);
ElsterandRoemer(1993);Mirrlees(1982);Broome,(2004);Arrow(1977);Harsanyi(1977);Adler(2011).
11ArecentmajorstudyisAdler(2011).
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judgementsaboutclimatechange,aprioritarianfunctionwillgiverelativelymoreimportancetothe
interestsofpoorerpeopleandpoorercountries.
Figure 3.1.The prioritarian view of social welfare. The figure compares the social values of increasesin wellbeing for a better-off and a worse-off person.
3.4.7 ValuingpopulationThenextprobleminaggregatingwellbeingistotakeaccountofchangesinpopulation.Climate
changecanbeexpectedtoaffecttheworldshumanpopulation.Severeclimatechangemightevenleadtoacatastrophiccollapseofthepopulation(Weitzman,2009),andeventotheextinctionof
humanbeings.Anyvaluationoftheimpactofclimatechangeandofpoliciestomitigateclimate
changeshouldthereforetakechangesinpopulationintoaccount.
TheutilitarianandprioritarianSWFsforafixedpopulationmaybeextendedinavarietyofwaystoavariablepopulation.Forexample,theutilitarianfunctionmaybeextendedtoaverageutilitarianism(Hurka,1982),whoseSWFistheaverageofpeopleswellbeing.Averageutilitarianismgivesnovalue
toincreasingnumbersofpeople.Theimplicitorexplicitgoalofagreatdealofpolicymakingisto
promotepercapitawellbeing(Hardin,1968).Thisistoadoptaverageutilitarianism.Thisgoaltends
tofavourantinatalistpolicies,aimedatlimitingpopulation.Itwouldstronglyfavourpopulation
controlasameansofmitigatingclimatechange,anditwouldnottakeacollapseofpopulationto
be,initself,abadthing.
Theutilitarianfunctionmayalternativelybeextendedtocriticallevelutilitarianism,whoseSWFis
thetotaloftheamountbywhicheachpersonswellbeingexceedssomefixedcriticallevel.Itis
Equation3.4.4. V=(w1c)+(w2c)++(wJc)
wherecisthecriticallevel(Broome,2004;Blackorbyetal.,2005).Otherthingsbeingequal,criticallevelutilitarianismfavoursaddingpeopletothepopulationiftheirwellbeingisabovethecritical
level.
Totalutilitarianism(Sidgwick,1907)iscriticallevelutilitarianismwiththecriticallevelsettozero.ItsSWFisthetotalofpeopleswellbeing.TotalutilitarianismisimplicitinmanyIntegrated
AssessmentModels(IAMs)ofclimatechange(e.g.,Nordhaus,2008).Itsmeaningisindeterminate
untilitissettledwhichleveloflifetimewellbeingtocountaszero.Manytotalutilitarianssetthe
zeroatthelevelofalifethathasnogoodorbadexperiencesthatislivedinacomathroughout,
forinstance(Arrhenius,forthcoming).Sincepeopleonaverageleadbetterlivesthanthis,total
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utilitarianismwiththiszerotendstobelessantinatalistthanaverageutilitarianism.However,it
doesnotnecessarilyfavourincreasingpopulation.Eachnewpersondamagesthewellbeingof
existingpeople,throughtheiremissionsofGHG,theirotherdemandsonEarthslimitedresources,
andtheemissionsoftheirprogeny.Ifthedamageanaveragepersondoestoothersintotalexceeds
theirownwellbeing,totalutilitarianism,likeaverageutilitarianism,favourspopulationcontrolasa
meansofmitigatingclimatechange.12
Eachoftheexistingethicaltheoriesaboutthevalueofpopulationhasintuitivelyunattractiveimplications(Parfit,1986).Averageutilitarianismissubjecttoparticularlysevereobjections.
Arrhenius(forthcoming)crystallizestheproblemsofpopulationethicsintheformofimpossibility
theorems.Sofar,noconsensushasemergedaboutthevalueofpopulation.Yetclimatechangepoliciesareexpectedtoaffectthesizeoftheworldspopulation,anddifferenttheoriesofvalue
implyverydifferentconclusionsaboutthevalueofthesepolicies.Thisisaseriousdifficultyfor
evaluatingpoliciesaimedatmitigatingclimatechange,whichhaslargelybeenignoredinthe
literature(Broome,2012).
3.5 Economics,rights,andduties
Sections3.2 ,3.3 and3.4 haveoutlinedsomeoftheethicalprinciplesthatcanguidedecision
makingforclimatechange.Theremainderofthischapterislargelyconcernedwiththeconceptsandmethodsofeconomics.Theycanbeusedtoaggregatevaluesatdifferenttimesandplaces,and
weighaggregatevaluefordifferentpolicyactions.Theycanalsobeusedtodrawinformationabout
valuefromthedataprovidedbypricesandmarkets.Economicscanmeasurediversebenefitsand
harms,takingaccountofuncertainty,toarriveatoveralljudgementsofvalue.Italsohasmuchto
contributetothechoiceanddesignofpolicymechanisms,asSection3.8 andlaterchaptersshow.
Valuationsprovidedbyeconomicscanbeusedonalargescale:IAMscanbeusedtosimulatethe
evolutionoftheworld'seconomyunderdifferentclimateregimesanddetermineaneconomically
efficientreductioninGHGemissions.Onasmallerscale,economicmethodsofCBAcanbeusedin
choosingbetweenparticularpoliciesandtechnologiesformitigation.
Economicsismuchmorethanamethodofvaluation.Forexample,itshowshowdecisionmaking
canbedecentralizedthroughmarketmechanisms.Thishasimportantapplicationsinpolicyinstrumentsformitigationwithpotentialforcosteffectivenessandefficiency(Chapters6and15).
Economicanalysiscanalsogiveguidanceonhowpolicymechanismsforinternationalcooperation
onmitigationcanbedesignedtoovercomefreeriderproblems(Chapters13and14).However,the
methodsofeconomicsarelimitedinwhattheycando.Theycanbebasedonethicalprinciples,asSection3.6 explains.Buttheycannottakeaccountofeveryethicalprinciple.Theyaresuitedto
measuringandaggregatingthewellbeingofhumans,butnottotakingaccountofjusticeandrights
(withtheexceptionofdistributivejustice seebelow),orothervaluesapartfromhumanwellbeing.
Moreover,eveninmeasuringandaggregatingwellbeing,theydependoncertainspecificethical
assumptions.Thissectiondescribesthelimitsofeconomicmethods.
Becauseoftheirlimitations,economicvaluationsareoftennotontheirownagoodbasisfor
decisionmaking.Theyfrequentlyneedtobesupplementedbyotherethicalconsiderations.Itmay
thenbeappropriatetoapplytechniquesofmulticriteriaanalysis(MCA),discussedinSection3.7.2.1
(ZelenyandCochrane,1982;KeeneyandRaiffa,1993;DeMontisetal.,2005).
12Harford(1998)showsthatanadditionalpersoncausesdamagefromherownemissionsandtheemissions
ofherchildren(andoftheirchildren,etc.).KellyandKolstad(2001)examinethisissueinthespecificcontext
ofclimatechange.
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3.5.1 LimitsofeconomicsinguidingdecisionmakingEconomicscanmeasureandaggregatehumanwellbeing,butSections3.2 ,3.3 and3.4 explainthat
wellbeingmaybeonlyoneofseveralcriteriaforchoosingamongalternativemitigationpolicies.
Otherethicalconsiderationsarenotreflectedineconomicvaluations,andthoseconsiderationsmay
beextremelyimportantforparticulardecisionsthathavetobemade.Forexample,somehavecontendedthatcountriesthathaveemittedagreatdealofGHGinthepastowerestitutionto
countriesthathavebeenharmedbytheiremissions.Ifso,thisisanimportantconsiderationindetermininghowmuchfinancerichcountriesshouldprovidetopoorercountriestohelpwiththeir
mitigationefforts.Itsuggeststhateconomicsalonecannotbeusedtodeterminewhoshouldbeartheburdenofmitigation.
Whatethicalconsiderationscaneconomicscoversatisfactorily?Sincethemethodsofeconomicsare
concernedwithvalue,theydonottakeaccountofjusticeandrightsingeneral.However,
distributivejusticecanbeaccommodatedwithineconomics,becauseitcanbeunderstoodasa
value:specificallythevalueofequality.Thetheoryoffairnesswithineconomics(Fleurbaey,2008)is
anaccountofdistributivejustice.Itassumesthatthelevelofdistributivejusticewithinasocietyisa
functionofthewellbeingsofindividuals,whichmeansitcanbereflectedintheaggregationof
wellbeing.Inparticular,itmaybemeasuredbythedegreeofinequalityinwellbeing,usingoneof
thestandardmeasuresofinequalitysuchastheGinicoefficient(Gini,1912),asdiscussedinthe
previoussection.TheAtkinsonmeasureofinequality(Atkinson,1970)isbasedonanadditivelyseparableSWF,andisthereforeparticularlyappropriateforrepresentingth
top related