Report

March 24, 2017

The Conference Center at the

Carnegie Endowment for International Peace

1779 Massachusetts Ave NW, Washington, DC 20036

Forum on U.S. Solar Geoengineering Research

This document was originally prepared as

background for participants at the Forum

on U.S. Solar Geoengineering Research.

It now also includes reflections written after the Forum. Moving forward, we

hope it proves useful for anyone seeking

to gain background information on solar

geoengineering.

For a full video of the event, see:

geoengineering.environment.harvard.edu

Table of Contents

Forum Agenda ............................................................ 1 Background Paper ...................................................... 3 Scott Barrett ............................................................... 15 Holly Jean Buck ......................................................... 18 Rose Cairns ................................................................ 21 Kerry Emanuel ........................................................... 24 Peter Fiekowsky ......................................................... 26 Peter C. Frumhoff and Jennie C. Stephens ........... 28 Anna-Maria Hubert ................................................... 32 Jane C. S. Long .......................................................... 35 Douglas G. MacMartin .............................................. 39 Joseph Majkut ........................................................... 41 Oliver Morton ............................................................ 44 Janos Pasztor ............................................................. 47 Joyce E. Penner ......................................................... 50 Jesse Reynolds .......................................................... 54 Kate Ricke ................................................................... 56 Alan Robock ............................................................... 60 Daniel P. Schrag ........................................................ 65 Kelly Wanser .............................................................. 68 Janie Wise Thompson .............................................. 72

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Forum Agenda March24,2017

8:45–9:00a.m.

Setting the Stage

• LizzieBurns—Fellow,HarvardJohnA.PaulsonSchoolofEngineeringandAppliedSciences• EdwardA.(Ted)Parson—DanandRaeEmmettProfessorofEnvironmentalLaw;Faculty

Co-Director,EmmettCenteronClimateChangeandtheEnvironment,UCLASchoolofLaw• GernotWagner—ResearchAssociate,HarvardJohnA.PaulsonSchoolofEngineeringand

AppliedSciences;Lecturer,EnvironmentalScienceandPublicPolicy;Associate,HarvardUniversityCenterfortheEnvironment

Part I: The Science 9:00–10:15a.mSocial Science: What we know, and what we ought to know

• EdwardA.(Ted)Parson[Moderator]—DanandRaeEmmettProfessorofEnvironmentalLaw;FacultyCo-Director,EmmettCenteronClimateChangeandtheEnvironment,UCLASchoolofLaw

• ScottBarrett—Lenfest-EarthInstituteProfessorofNaturalResourceEconomics,ColumbiaUniversity

• Holly Buck — Doctoral Candidate, Development Sociology, Cornell University; FacultyFellow,ForumforClimateEngineeringAssessment,AmericanUniversity

• RoseCairns—ResearchFellow,SPRU–SciencePolicyResearchUnit,UniversityofSussex• KateRicke—AssistantProfessor,ScrippsInstitutionofOceanographyandtheSchoolof

GlobalPolicyandStrategyatUniversityofCaliforniaSanDiego10:30a.m.–11:45a.m. Natural Science: What we know, and what we ought to know

• DougMacMartin[Moderator]—SeniorResearchAssociate,CornellUniversity• ThomasAckerman—ProfessorofAtmosphericSciencesandDirectoroftheJointInstitute

fortheStudyoftheAtmosphereandOcean(JISAO),UniversityofWashington• DavidKeith—GordonMcKayProfessorofAppliedPhysics,HarvardJohnA.PaulsonSchool

ofEngineeringandAppliedSciences;ProfessorofPublicPolicy,HarvardKennedySchool• Joyce Penner — Ralph J. Cicerone Distinguished University Professor of Atmospheric

Science,UniversityofMichigan• AlanRobock—DistinguishedProfessor,DepartmentofEnvironmentalSciences,Rutgers

University

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• DanielSchrag—SturgisHooperProfessorofGeology,ProfessorofEnvironmentalScienceand Engineering, Harvard University; Director, Harvard University Center for theEnvironment; Director, Harvard Kennedy School Program on Science, Technology, andPublicPolicy

11:45a.m.–12:45p.m Lunch Part II: Policy and Politics 12:45–2:00p.m. State of Play

• JesseReynolds [Moderator]—PostdoctoralResearcher,FacultyofLaw,EconomicsandGovernance,UtrechtUniversity,TheNetherlands

• PeterC.Frumhoff—DirectorofScienceandPolicy,UnionofConcernedScientists• StevenP.Hamburg—ChiefScientist,EnvironmentalDefenseFund• JosephMajkut—DirectorofClimateScience,NiskanenCenter• Janos Pasztor — Senior Fellow, Carnegie Council for Ethics in International Affairs;

ExecutiveDirector,CarnegieClimateGeoengineeringGovernanceInitiative(C2G2)• JanieWiseThompson—VicePresident,Cassidy&Associates

2:15–3:30p.m. The Path Forward

• OliverMorton[Moderator]—SeniorEditor,EssaysandBriefings,TheEconomist• Anna-MariaHubert—AssistantProfessor,FacultyofLaw,UniversityofCalgary;Associate

Fellow,InstituteforScience,InnovationandSociety(InSIS),UniversityofOxford• PeterKareiva—Director,InstituteoftheEnvironmentandSustainability,UCLA;Former

ChiefScientistandVicePresident,TheNatureConservancy• Andrew Light—Distinguished Senior Fellow in the Climate Program,World Resources

Institute;UniversityProfessor,GeorgeMasonUniversity• JaneC.S.Long—LawrenceLivermoreNationalLab(ret)• KellyWanser—PrincipalDirector,MarineCloudBrighteningProject

3:30–3:45p.m. Conclusion & Next Steps

• GernotWagner—ResearchAssociate,HarvardJohnA.PaulsonSchoolofEngineeringandAppliedSciences;Lecturer,EnvironmentalScienceandPublicPolicy;Associate,HarvardUniversityCenterfortheEnvironment

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Background Paper Forum on U.S. Solar Geoengineering Research

EdwardA.Parsoni,LizzieBurnsii,JohnDykemaii,PeterIrvineii,DavidKeithii,andGernotWagnerii

ThispaperwaspreparedasbackgroundfortheForumonU.S.SolarGeoengineeringResearch,whichwasheldattheConferenceCenteroftheCarnegieEndowmentforInternationalPeaceinWashington, DC onMarch 24, 2017. The Forum was co-hosted by the Solar GeoengineeringResearch Program at Harvard University and the Emmett Center on Climate Change and theEnvironment at the University of California, Los Angeles, and funded through the generoussupport of the Alfred P. Sloan Foundation. The paper provided background information ongeoengineeringandassociateddebatesforForumparticipantsunfamiliarwiththeseissues,andframedseveral keyquestions tobeaddressedat theForum. Inaddition, since thecontext fordiscussing solar geoengineering research changed substantially in the year betweenwhen theForumwasplannedandwhenittookplace,thepaperbrieflydiscussedthecurrentcontextanditsimplications.Importantly,whilethisbackgroundpaperwasinitiallyintendedforForumparticipants,wehopeitprovesusefulforthosewhoareseekingtogainbackgroundinformationonsolargeoengineeringmorebroadly.Background: Geoengineering Methods, Effects, and ConcernsGeoengineering–alsocalledclimateengineering,climateintervention,orclimateremediation–isathirdclassofpotentialresponsestoglobalclimatechange,additionaltomitigation(cuttinggreenhouse-gas emissions) and adaptation (reducing vulnerability to climate change). Whilegeoengineering responses have been recognized for decades and periodically discussed inscientificassessments–goingasfarbackasthefirstofficialreporttoaU.S.Presidentonglobalwarming,PresidentJohnsonin1965–theyreceivedlittleattentionuntilthepasttenyears.Geoengineeringisdefinedbyintentionalityandscale:intentionalinterventiontoaltertheclimateatglobalscale.Ofthetwobroadtypesofgeoengineering–modificationsoftheglobalcarboncycle,orofEarth’sradiativebalance–theForummainlyaddressedthelatter,whichwecallsolargeoengineering. Solargeoengineeringalters theenergybalanceof theEarth,eitherby slightlyincreasingthefractionofincomingsunlightthatisreflectedfromtheEarthratherthanabsorbed;orbyincreasingtheEarth’sabilitytocoolbyemittingthermal(infrared)radiation.

iUCLASchoolofLaw;parson@law.ucla.edu.iiHarvardJohnA.PaulsonSchoolofEngineeringandAppliedSciences.

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Three proposed methods of solar geoengineering are most prominent in current debate.Stratosphericaerosolinjectionwouldinvolvethedistributionofreflectiveaerosolsintheupperatmosphere.Marine cloud brighteningwould involvemodifying the properties of low-altitudemarine clouds tomake themmore reflective. Cirrus thinningwould reduce the density of iceparticlesinhigh-altitudecirrusclouds,whichwouldincreasetheemissionofthermalradiationtospace.Severalotherapproacheshavebeenproposedbuthavefallenoutofseriousconsiderationduetoearly indicationsof limitedeffectiveness,highcost,orrisk. It is likelythatnewformsofintervention,orimprovementstoexistingforms,willbeidentified.Themostpromisingofthesemethodsoffertheprospectofmodifyingglobal-scalecharacteristicswithextremelyhighleverage.Severaloftheirprominentcharacteristicsarerelatedtothishighleverage.First,solargeoengineeringcouldactfast.Likelargevolcaniceruptions,somemethodscould,ifdeployedatlargeenoughscale,significantlycoolglobaltemperatureswithinmonths.Theaerosol particles that figure in thesemethods have lifetimes of only a few days in the loweratmosphereandafewyearsintheupperatmosphere,thestratosphere.Thebenefitoftheseshortlifetimesisthataggregatecoolingcanbestarted,modified,or–ifsomeunfavorableconsequenceisdiscovered–stopped,quickly.Acorrespondingriskarisingfromtheseshortlifetimesisthat,ifalargeprogramofsolargeoengineeringweresuddenlyterminated,theheatingbeingoffsetbytheprogramwouldoccurrapidly,whichwouldbringevenmoresevererisksthanifgeoengineeringhadnotbeendoneandthesameheatinghadoccurredmoreslowly.Thisisbecausemanyoftherisksofclimatechangearisefromtherateofchange,notsimplythechangeitself.Additionally,mostsolargeoengineeringtechniqueswouldhaveaglobal,notlocal, impact.Onecountry,forexample,couldnotdeploysolargeoengineeringtoslowglobalwarmingoveritsownborderswithoutaffectingothernationsandecosystemsaroundtheglobe.Thisfactposesmanygovernancechallenges,particularlywhencombinedwithasecondfact:thatsolargeoengineeringisinexpensive,atleastbycomparisonofthedirectcostofmakingtheinterventionstothecostofachievingthesametotalcoolingbycarbonremovalormitigation.1Indeed,thedirectcostsofsolargeoengineeringarelikelytobetrivialrelativetootherrisksandbenefits.Asaresult,thecapabilityto deploy solar geoengineering and change the global climate may be within reach of manynations. This makes the problem of governing geoengineering the inverse of that posed bymitigation–astrategicstructurethathasbeencalleda“free-driver”problem,incontrasttothe“free-rider”problemofmitigation.Allsolargeoengineeringmethods,however,offeronlyimperfectcorrectionsfortheharmscausedbyelevatedgreenhousegases.TheytargetonlycertainclimateeffectsofelevatedCO2,not itseffectsonthechemistryoftheoceansthatmakesthemmoreacidic,itsalterationofcompetitiverelationshipsamongplants,whichdependsonhowtheyuseCO2inphotosynthesis,orotherkeyfactors.2Allidentifiedmethodsalsohaveenvironmentalsideeffectsinadditiontotheirtargetedclimateeffects.Fordifferentmethods,theseside-effectsmayincludealterationsofstratospheric

1Mitigationcanonlyreducefutureheating,notcooltheclimaterelativetoheatingalreadyrealizedorcommitted.2 Solar geoengineering will affect the carbon cycle indirectly via temperature-carbon feedbacks, for example byreducingthethawingofpermafrostandassociatedemissionsofmethaneandCO2

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chemistry,inparticularstratosphericozone(notingthatozonedecreasesforsomemethods,butincreasesforotherrecentlyproposedmethods);changesintheappearanceofthesky;andtheeffectsofanymaterialinjectedintotheatmospherewhenitisdepositedonthegroundsurface.Moreover,nosolargeoengineeringmethodcouldperfectlyoffsettheclimateeffectsofelevatedgreenhousegases.ThisismainlybecausetheeffectsofreducingabsorptionoflightattheEarth’ssurfacearequitedifferentfromthegreenhouseeffect,whichoccursaloft.Asaresult,comparedtogreenhouseheating,solargeoengineeringreducesprecipitationandevaporationmorestronglythantemperature.Inaddition,somemethods–marinecloudbrighteningandcirrusthinning–operate bymodifying naturally occurring phenomena (in this case, clouds), so their potentialimpactislimitedbythespatialdistributionofthosephenomena.Thesemethodsmaythushavepatchyeffects,orquantitativelimitstotheirglobaleffect.Still,modelstudiesshowmismatchesofeffectthataresmallerthanwasinitiallyexpected.Comparedtoclimateconditionswithprojectedincreasesingreenhousegases,modelstudiessuggestthatsolargeoengineeringinterventionsmaybeabletomovebothtemperatureandprecipitationclosertopre-industrialvaluesoveralargefractionofworldlandsurface.AstheIntergovernmentalPanelonClimateChange(IPCC)stated,“Models consistently suggest that [solar geoengineering] would generally reduce climatedifferencescomparedtoaworldwithelevatedGHGconcentrationsandno[solargeoengineering];however, there would also be residual regional differences in climate (e.g., temperature andrainfall)whencomparedtoaclimatewithoutelevatedGHGs.”3Thesebasicpropertiesofsolargeoengineeringinterventions–fasteffectandcontrollability,cross-borderimpacts,lowcost,andimperfectcorrectionfortheeffectsofelevatedgreenhousegases–definethelarge-scalenatureofthegovernanceproblemtheypose.Theyalsoexplainwhywearediscussingtheseinterventions,andwhynow.Debateonsolargeoengineeringbecameprominenttenyearsago.Thetriggerforthedebatewasa widely-noted essay by eminent atmospheric scientist Paul Crutzen, who argued theseinterventions merited investigation because their risks might be less severe than those ofcontinuing climate change. But beyond the specific triggering event of Crutzen’s essay, thebroader cause of renewed attention to solar geoengineering lay in the underlying realities hedescribed:increasinglysevererisksfromprojectedclimatechange,continueduncertaintyaboutthecharacterandtimingoftheserisks,andincreasedrecognitionthatmitigationandadaptationmaybeinadequatetomanagetherisks.Adaptationmayfallshortduetolimitedknowledgeorexperienceofhowtodoit,resourceconstraints,politicalconflict,orinstitutionalfailure–aswellasthepossibilitythatclimatechangesmayoverwhelmadaptationcapability.Mitigationmayfallshortbecauseitcannotreverserealizedorcommittedclimatechange,dueinparttothehugeamount of installed plant and equipment that must be changed – and the high costs oftransitioningthisinfrastructure–andduetotheslowresponseoftheclimatesystemtochangesin forcing. With the exception of measures that target short-lived gases, even intense andsuccessful mitigation efforts will only significantly deflect climate risks after a few decades.

3 IPCCAssessmentReport5,WorkingGroup1,Chapter7. (Differentterminology:“solargeoengineering”replaces“SolarRadiationManagement(SRM)”intheoriginal.)

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Moreover,even ifemissionsarereducedrapidlytozero,therearestill risksofglobalwarmingbecauseofcarbon’slongatmosphericlifetimeandthepresenceofcarbon-climatefeedbacks,suchasthereleaseofcarbondioxideandmethanefrommeltingpermafrost,whichcouldacceleratewarming. As a practical matter, mitigation may also fall short because, despite nearly threedecadesofattempts,nations’mitigationeffortshavenotbeenintense–oreven,inmanycases,serious.The Prospect of Future Operational Use: Benefits, Risks, ConditionsInthiscontext,solargeoengineeringoffersahigh-stakes,two-sidedprospect.Ontheonehand,itmay,undersomeconditions,beabletosubstantiallyreduceclimate-changerisksandharmsinways thatmitigation and adaptation alone cannot.On the other hand, it could be ignorantly,incompetently,dangerously,andillegitimatelyusedinwaysthatcausesevereharmstohumansintheenvironment–greaterthanthoseposedbyclimatechange.Theconditionsforthepotentialbenefits todominate,broadly,arethat interventionsare identifiedthatworkwellwith limitedharmful side-effects, and that they are developed and used competently, prudently, andlegitimately.Assuming these conditions, three broad ways have been proposed that solar geoengineeringmight be beneficially used – each of them subject to various scientific and socio-politicallimitationsandconcerns.First, it might be used in response to some future severe climate-change impacts beingexperienced or imminently anticipated. Thismode of use has been described as “emergencyresponse,”or“PlanB.”Usedthisway,solargeoengineeringdeploymentwouldbedelayed,rapidandstrong–notdeployedatallinthenearterm,butthendeployedquicklyandintenselyatsomefuturetime.Second, it might be used in conjunction with aggressive mitigation, adaptation, and carbonremoval,aspartofastrategic,integrated,multi-decadeclimateresponse.Thismodeofusehasbeendescribedas“buyingtime,”or“shavingthepeak”(reducingthe50to100yearperiodofheatingthatevenextrememitigationandcarbonremovalaretooslowtoavoid).Usedthisway,deploymentwouldbeimmediate,incremental,andtemporary–rampingup,thendown,astheotherresponsesgrowtofullscale.Evenifcarboncapturewerenotincludedinsuchanintegratedresponse–whichwouldimplythatclimatechangecouldonlybestopped,notreversed–suchatemporaryprogramofsolargeoengineeringcouldstillreducerisksbyslowingtherateofheatingtowardwhateverhotterclimatethegivenlevelofmitigationeffortismovingtheworldtoward.Third,deploymentsat lessthanglobalscalehavebeenproposed,totarget large-scaleregionalprocessesofglobalconcern,suchassummerlossofArcticseaiceortropicalcycloneformation.Earlyresearchsuggeststhatsuchproposalscouldhavethepotentialtobringcertainbenefits,suchasreducedsealevelrise,buttherearealsomanyuncertaintiesaswellasseveralpotentialrisks,includingchangestoregionalhydrology.Likeallmethods,moreresearchwouldneedtobedonetoincreaseourunderstandingofthepotentialbenefitsandrisks.

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Moreover,foranyofthesemodesofusetobebeneficial,certainconditionsmusthold.Someofthese conditions are matters of knowledge and technical capability: are feasible methodsidentifiedthatwouldconfidentlyhavetheintendedeffectandnotcarryseveresideeffects?Otherconditions arematters of the social, ethical, institutional, legal, and political setting in whichinterventionswouldbeconsidered,decidedupon,and(ifadopted)implementedandmanaged:isthere basis for confidence that these decisions would in fact be competent, prudent, andlegitimate? Of these two groups of conditions, the first are fundamentally about research –research intoproposedmethods,andthenaturalsystemswithwhichtheywould interact.Thesecond are fundamentally about governance,mainly at the international level because of theinternationalscopeandimpactsoftheseinterventions.Thegovernancerequirementsposedbypotential futureproposals foroperationaluseof solargeoengineeringarenovelandsevere.Manyseriousgovernance-relatedriskshavebeenidentifiedrelatedtogeoengineeringbeingusedincompetently,recklessly,rivalrously,orreliedontoomuch.Examplesofsuchdangerousconditionsofgeoengineeringuseareeasytoimagine:forexample,use in a crisis with inadequate risk assessment; uncoordinated or opposing interventions bymultiplestatesorotheractors;relyingonthese imperfect interventionstoomuch,makingtheneglect of essential mitigation and adaptationmeasures evenmore severe; use in ways thatundermineordestabilizeinstitutionsforinternationalcooperation,onclimateorrelatedissues;oruseinwaysthatgenerateinternationaldestabilizationandconflict,particularlyintheeventofwide differences in severity of climate impacts, or interventions that suggest the prospect ofregionalclimatecontrol.Whilewe recognize thenovelty andhigh stakesof thesegovernance challenges raisedby theprospectoffutureoperationalinterventions,thesewerenotthefocusoftheForum.Rather,theForumfocusedonthefirstclassofconditionsidentifiedabove:theneedforsolargeoengineering-relatedresearch, therisksandchallengesassociatedwithresearch,andthegovernanceneedsposedbyresearch.Incontrasttothelargerbutmoredistantgovernancechallengesraisedbytheprospectoffutureoperationaldeployment,theseresearchissuesareimmediateandconcrete.Longer-termquestionsrelatedtooperationalgovernancewereonthetableat theForum,butonlyinsofarastheywereimplicatedby,orlikelytobeinfluencedby,near-termdecisionsrelatedtoresearch.Solar Geoengineering Research: Arguments in Favor, Experience, ProposalsThebasicargumentforexpandedresearchisstraightforward.Ifitislikelythatfuturedecisionswillhave tobemade regardingproposals, demands,or chargesaboutoperational geoengineeringdeployment–whatevertheoutcomeofsuchdecisions,whethertoauthorize,prohibit,orregulateandcontrolproposedinterventions–thenprovidinganybasistoinformthosedecisionsrequiresresearch. Research is needed to identify and characterizemethods and capabilities, to designpossibleimplementationscenarios,toidentifyandcharacterizeefficacyandassociatedrisks,andtounderstandthesocial,ethical,institutional,legal,andpoliticalsettingwithinwhichtheymightbeused.

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Beyond informing such futuredecisions, there are also additional reasons research is needed,includingdeveloping theability todetect, identify, andmonitor interventions (for example, toprotect against clandestine interventions, or to improve our understanding of legitimateinterventionsbyobservingtheirrisksandefficacyinthenaturalenvironment);andinformingtheparticularsoffuturegovernanceneeds,sincethesewillbestronglyinfluencedbyspecifictechnicalcapabilitiesandanticipatedrisks.Certainresearchintosolargeoengineeringhasalreadybeenconducted.Therehavebeenmanycomputer-modeling studies, including comprehensive inter-comparisons of climate-modelprojections driven by standardized scenarios of future greenhouse-gas emissions and solargeoengineering interventions conducted under the Geoengineering Model IntercomparisonProject(GeoMIP).Therehavealsobeenmanyobservationalstudiesofnaturaloralreadyexistinganthropogenic (human-influenced) processes relevant to likely effects of solar geoengineeringmethods, e.g., atmospheric aerosols, volcanic plumes, and tracks left by ships and aircraft.Moreover, there have been lab-bench studies of related processes and a few preliminaryengineering studies of potential methods to estimate performance, effectiveness, technicalrequirements,andcost.Oneofthekeysitesofcontroversyoversolargeoengineeringresearch–andthekeymarginofnear-term decision that made the Forum timely – concerns active outdoor perturbationexperiments.Thesewouldinvolveintentionalintroductionofmaterialsintotheopenenvironmentor some other active manipulation of environmental conditions in ways that aim to informunderstandingoftheefficacyandrisksofpotentialfutureinterventions.Thecasefordoingsuchstudiesthataresmall inscaleappearsstrong.Allsuchstudiesthusfarproposed (and the few thathavebeenattemptedordone)areof tiny scale,posingnegligibleenvironmentalrisk,yetoffertosubstantiallyadvanceknowledgeonatmosphericprocessescrucialtounderstandingwhatpotentialfutureinterventionsmightdo.Theproposedstudieswouldaddknowledgetothatgainedbylaboratoryorcomputer-modelstudies,whichcannotfullyreplicateconditionsintheopenenvironmentofpotentialrelevancetotheeffectsofinterventions.Theyare thus likely to inform understanding of whether and how potential geoengineeringinterventionscanbedone,whattheireffectsarelikelytobe(bothintendedandunintended),howinterventionscanbedetected,whatriskstheymaycarry,andhowtheseriskscanbemanaged.Butfewtonosuchactiveperturbationstudieshavebeendone.Twosmall-scaleinterventionsthatareknowntohavebeendone,bothusingexistingfundingonrelatedtopics,includeoneintheUnitedStates(the2011E-PEACEexperimentsprayedsmokeandsaltparticlesfromabargeofftheCaliforniacoasttostudyeffectsoncloudformation),andoneinRussia(a2009experimentsprayedsmokefromahelicopterandatruckandobservedresultantradiativeeffects).Inaddition,one study, a proof-of-concept experiment to spraywater from a tethered balloon (the SPICEexperiment),wasproposed,funded,andpartlyimplementedintheUnitedKingdom,thendelayedduetoobjectionsthattheassociatedpublicconsultationprocesswasinadequate,andcancelled

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afterthe(unrelated)discoveryofpreviouslyundisclosedfinancialconflict-of-interestofoneoftheresearchers.Severaladditionalsolargeoengineeringexperimentshavebeenproposedinscientific literatureandsomehavetakenvariousdegreestowardtechnologydevelopmentandimplementation.Noneofthesehasyetbeenimplementedorfullyfunded,however,andallhaveraisedcontroversyandopposition.Leadingexamplesoftheseinclude:

1. Astratosphericcontrolledperturbationexperiment(SCoPEx),whichwoulduseaballoontorelease100gto1kgofaerosolmaterialinthestratosphere,tostudyresultantaerosolsizedistribution,radiativeforcing,andchemicaleffects;

2. Anexperimentinmarinecloudbrightening,whichwouldloftseasaltsprayintothemarineboundarylayertostudyresultanteffectsoncloudformationandproperties;

3. Astudy,describedinthescientificliterature,whichwouldseedhigh-latitudecirruscloudswithaerosolstoreducetheiropticalthicknessandsoincreaseinfraredradiationfromthetopoftheatmosphere.

Solar Geoengineering Research: Concerns and Arguments Against The slow pace of developing, funding, and implementing solar geoengineering field researchreflectsnotjustconstrainedresourcesandbureaucraticinertia,butalsowidespreadnervousnessabouttheendeavor,basedonexistenceofsignificantconcernsandsomepoliticalopposition.Webrieflyoutlinetheseconcernsandobjections,groupedinfivecategories: First, someobjections toexpanded researchoriginate in concerns thatpertain, reasonably, topotentialfuturedeployment–e.g.,difficultiesofcontrol,disruptiontotheclimate-policyagenda,risk of excessive reliance (potentially leading to future termination-shock scenarios), orinternationalconflict–butextendtheseconcernstoassertthattheyalsosupportoppositiontoresearch. But opposing future deployment does not necessarily imply opposing research,particularly since research can inform and benefit any future decisions about deployment,includingthedecisiontorejectit.Onewaytomakethisinferencefromopposingdeploymenttoopposing research valid would be by making an extreme prior assumption: that operationaldeployment is certain never to be warranted, at any time or under any circumstances. Suchcategoricaloppositiontodeploymentmightbebasedonpriorcertaintythattheconsequencesoffuturedeploymentcanonlybeworsethantheconsequencesoftheclimatechangethatitmightreduceordelay.Butsuchoppositionismoretypicallybasedonsomenon-consequentialmoralstance:geoengineeringdeploymentwouldbeintrinsicallywrong–e.g.,becauseitismessingwithnature,ishubris,orisanimpermissiblesteptotheAnthropocene–andcannotberedeemedbyanyevidencethatitmightbringbenefitsrelativetotheavailablealternative.Wefindthisextremepremiseimplausible,butifyouacceptit,theargumentforresearchtoinformfuturedecisionsisgreatlyweakened–althoughnotcompletely:evenunderthisassumption,researchcouldstillbewarrantedtobuildcapacitytomonitoranddetectunauthorizedorclandestineuse.

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Second,somerelatedobjectionsstatethatthereisnowaytodistinguishbetweensmall-scalefieldresearchandglobal-scaleoperationaldeployment.Inparttheseobjectionsrelyonthecontinuityof intervention scale, from tiny to global. They thus reduce to a “where-to-draw-the-line”argument,andarevulnerabletothenormalrejoindertoargumentsofthistype:wemightnotknowpreciselywheretodrawtheline,yetstillbeconfidentthatthesethingslieononeside,thosethings on the other. A subtler formof this argument relies on the complexity of atmosphericprocesses,whichmakestheeffectsofanyinterventionalwaysuncertainuntilitisactuallydone.Tiny-scaleexperimentsgiveinformationaboutatmosphericprocessesthatcanhelpunderstandlikely responses to larger interventions. But some uncertainties about large interventions –includingtheoverallquantitativeresponseoftheclimatesystem–canonlybepartiallyinformedorconstrainedbyanysmallerintervention.Thereisthusanimportantsenseinwhichanyfutureoperationalinterventionwillalsobeanexperiment–uncertainofoutcome,andsoneedingactivemonitoringandreal-timeadaptationandcontrol.Butthisinferenceonlygoesoneway.Itdoesnotfollowthattinyexperimentsarealsooperational interventions:theyarenot.Thelinebetweenexperimentsandoperationaldeploymentbecomesmuddier ifandwhenexperimentsat largerscalesthanpresentlyproposedarebeingconsidered,perhapsusingnewinterventionmethods.Suchlargerexperimentswouldstillberesearch,evenastheygrowinsizeandsocometoraisethesameconcernsandgovernancechallengesasglobaloperationalinterventions.Butthisdoesnotmeanthatallresearchinterventions,eventhesmallest,raisetheseconcernsandgovernancechallenges. Athirdtypeofobjectionisbasedontheexpectationofsubstantialdirectrisk–environmental,health,orsafety–fromanyactive-perturbationresearch,eventhesmallestexperiments.Liketheprior objection, this one is also a line-drawing question. The direct environmental risks fromcurrentlyproposedexperimentsdoconfidentlyappeartobenegligible.Butiffieldexperimentsweretoexpandinscaleorintensity,atsomepointtheirdirectriskswouldceasetobenegligible.Sinceitisunclearinadvancewherethisfuzzyboundarywillbecrossed,itisnecessarytoconductseriousassessmentofpotentialrisksandrisk-limitationmeasuresforeventhesmallestproposedexperiments.Butwhetherrisksarenon-negligible is–at leasttoa largedegree–anempiricalquestion,toberesolvedbyexaminingspecificexperiments.Theprospectofnon-negligiblerisksemergingfromfutureresearchdoesnotsupportwholesaleoppositiontoallactive-perturbationresearch. Fourth, oneobjectionhasbeen raised thatpotentially applies toboth futuredeployment andresearch.Itistheprospectthatsolargeoengineering–doingit,consideringit,orevenknowingaboutit–mightweakenordistractfrommitigation.Thisisaplausibleconcern,andisoftenthefirstconcernthatcomestomindoninitiallyhearingaboutgeoengineering.Butsimilarlyplausibleaccounts can be constructed that support the opposite effect: that the mere prospect ofgeoengineeringseemssoextremeorunnatural,ormakestheseverityofclimate-changeriskssosalient,thatpeoplearemore,notless,seriousaboutcuttingemissions.Whichdirectionthiseffectgoesisanempiricalquestion,whichhasbeeninvestigatedbyafewstudiesusingsurveys,focusgroups, and social experiments. Results have beenmixed, with different studies finding bothdirectionsofeffect.Moreover,studiesofindividualattitudesareatbestimperfectproxiesforthecrucial questions: how geoengineering effects mitigation commitment in political systems –

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nationalandinternational–andwhetherstrategiescanbeimplementedtomakegeoengineeringandmitigationmutuallyreinforcing,e.g.,howcanincreasedeffortsaroundgeoengineeringoccuralongsideincreasedeffortsaroundmitigation.Thesequestionshavebeenclearlyframed,butnotyetinvestigatedbyanyempiricalstudy.Theriskofdisplacingmitigationthusremainsanidentifiedpossibility,uncertainastotheseverityoftheeffectandwhetherandhowitcanbecontrolledorreversed.Inviewoftheevidentchallengesofanyresearchpersuasivelyresolvingthesequestions,itmightbemost fruitful toregardtheseconcernsaschallengestogovernance–challengestoidentifyconditionsofresearchprogramdesignandgovernance,orconditionstoshapedecisionagendasongeoengineeringandclimatechangemorebroadly,thatwouldpersuasivelylimittheprospectsforgeoengineeringunderminingmitigation,oreventurnittosupportingmitigation. Fifth,someobjectionstosolargeoengineeringresearcharebasedon“lock-in”or“slipperyslope”mechanisms. These posit political, bureaucratic, or other social processes by which small,seeminglyinnocuousearlyactions(e.g.,research)createforcesthatfavorsubsequentexpansion,or otherwise impair ability to exercise meaningful societal control. In the extreme, suchmechanismswouldmeanthatstartingevensmallfieldstudieswouldimpairfutureabilitytostoporcontrolfull-scaledeployment,evenifwhatwaslearnedintheinterimconfidentlydemonstratedthatsuchdeploymentwouldbeharmful.Theseobjectionsusuallyrelyonmetaphorsoranalogiesto other social processes that have demonstrated lock-in, such as technology adoption withpositivereturnstoscale(VHSversusBetamax),orescalationdynamicssuchasarmsraces.Inourview, there are good reasons for skepticism about the presence and strength of proposedmechanisms for geoengineering – no explicit causal mechanism driving lock-in from solargeoengineeringresearchhasbeenproposed,andtheoft-citedanalogiesfromotherissuesdonotfit this issuewell –but thesedonot fully rebut the concerns.Research tobetter characterizepotentiallock-inmechanisms,theirrelevanceandseverityforsolargeoengineeringresearch,andhowtheymightbeavoidedor limited, is lackingandneeded.Still, it ishard toseehowtodoresearchonsuchaspeculativeandnovelissuethatwouldpersuasivelyresolvetheconcernsonewayortheother.Perhaps,likethepreviousconcern,thisoneisbestaddressedbyre-framingitasapracticalproblemofgovernanceandresearchprogramdesign:howcanresearchprogramsbedesigned, funded, and managed to ensure maintenance of legitimate societal control overcontinuanceorexpansionoftheprogram,andthatnewinformationonalternativeapproaches,effectiveness,societalcosts,andrisksisadequatelytakenintoaccount? Afinalsetofobjectionstosolargeoengineeringresearcharebasedonclaimsofpublicopinionanddemocraticlegitimacy:peopledonotwantit.Thisisalsoanempiricalquestion,whichislikelytodependstronglyonsocialconditionsandonhowpeople’sviewsareelicited.Butincontrasttothe previous two concerns, this one readily lends itself to practical research strategies toinvestigate whether people support or oppose solar geoengineering research; which people,underwhatconditions,andwhy;howtheirsupportoroppositioninteractswiththeirviewsonclimatechangeandclimatepolicy;andwhat,ifany,decisionsonthemanagementordesignofexperimentsorresearchprogramsarelikelytobeassociatedwithgreateroppositionorgreatersupport?

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The Forum: Solar Geoengineering Research and its Governance Intheirstrongestform,someoftheprecedingobjectionswouldimplycategoricalrejectionofallsolar geoengineering research – possibly includingnot just field experiments, but also passiveobservational research and indoor (climate-model and lab-bench) studies. In our judgment,however,thoseobjectionsthatwouldcategoricallyrejectanyresearcharetheleastpersuasive.Rather,wefindthebest-foundedobjectionstosolargeoengineeringresearchtobethosebasedon:1)theriskofdisplacingothernecessaryelementsofclimate-changeresponse;2)lock-inorslippery-slopearguments;and3)publicacceptanceand/oropposition. Theseobjectionsshare twonotableattributes.Theyallpertain toempiricalquestions thatarethemselves subject to research, at least in principle. And they all hold the prospect of beingmitigatedbyappropriatedecisionsonresearchgovernanceandprogrammanagement.TheythusleaddirectlytothefocusoftheForum:solargeoengineeringresearchanditsgovernance.Whilethisbackgroundpaperaddressedsomeoftheobjectionsataconceptualortheoreticallevel,theForumalsoaddressedconcreteandpracticalmatters:specifictypesofresearchthathavebeenormightsoonbeproposed; riskspotentiallyassociatedwith these,orwith researchprogramstosupport them; governance challenges or needs these may pose; and concrete actions anddecisionsthatmightmitigatetheserisksormeetthesegovernanceneeds.WeconsideredthesequestionsmainlyintheU.S.context,whilealsoaimingtobeattentivebothtoinsightsfromotherjurisdictionsandtoimplicationsforotherjurisdictions. Examplesofspecificquestionsthatwereandstillneedtobeconsideredincludethefollowing:

• What types of solar geoengineering research proposals are likely, including both fieldexperimentsandotherpotentialnewproposals?

• Dothegovernanceneedsforsolargeoengineeringresearchdifferfromnormalgovernancepracticesinotherresearchfields?Ifso,howandwhydotheydiffer,andhowshouldthemeaning and boundaries of “geoengineering research” be defined that trigger thesedifferentgovernancerequirements?

• How(ifatall)aretheimplicationsoftheaboveobjections,orspecificgovernanceneeds,likely to vary among research projects? How are they likely to vary with othercharacteristics of proposed research, e.g., the identity and affiliation of projectparticipants;fundingsources;orothercharacteristics?

• How do these concerns or governance needs vary with larger-scale aspects of theorganizationandmanagementofresearch,e.g.,onwhetherresearchisconductedunderaseparatefederalprogram,orunderseveralfederalprogramsinrelatedareas,orwithmultipleanddiversesponsoringorganizationsandfundingsources?

• Howshouldexpandedresearchanddevelopmentofgovernancebesequenced?Giventhewidelynotedchicken-and-eggdilemma–researchisneededtoinformgovernanceneeds,butgovernanceisneededtomanagerisksofresearch–manyobservershavecalledforthe twoactivities toco-evolveadaptively.While this soundsgood inprinciple, it leavespractical first steps unspecified. Can the two activities start simultaneously, and what

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wouldthatmeanconcretely?Ifnot,whichshouldmoveforwardfirst?Moreover,inviewofthepolarizationofviewsonexpandedresearch,includingsomecategoricalopposition,howcanprudentearlygovernancestepsbedistinguishedfromprovisionsthataimtobesoburdensomeastoblockallresearch?

• Whatspecificgovernancerequirementswouldbeimpliedbyconcernsaboutunderminingmitigation,lock-in,andpublicopposition?Dogovernancerequirementsvary,dependingonwhichoftheseconcernstheyaimtoaddress?

• Severalspecificgovernancefunctionshavebeenproposedasneededforgeoengineeringresearch: research program design and management; external advice and oversight;proposal evaluation and approval; risk assessment; transparency; public consultation;treatmentofprivateIP;andprogramevaluationandadaptation.Foreachofthese,whatarethemainoptionsandthefactorsfavoringeach?

• How do risks and concerns differ between government-funded and privately fundedresearch (foundation,philanthropic,andcommercial)? Is it reasonable toassume,as inother areas of controversial research, that privately funded projects will follow thepractices of public funding agencies?What additional institutional structuresmight bedesirabletodeployconsistentgovernanceforallsolargeoengineeringresearch?

• IfresearchgovernanceisdevelopedatthenationallevelintheUnitedStates–whetherjustforfederalprogramsorcomprehensivelyinsomenewinstitutionalstructure–whatistheroleforinformalorformalinternationalco-operation,andhowshoulditbepursued?

• Isnationalgovernanceofsolargeoengineeringresearchsufficient?Ifso,forhowlongorunderwhatconditionswillthisremainthecase?Whatscaleorotherattributesofresearchprojectsarelikelytomakethemobjectsofinternationalconcern?Whatformandsiteofgovernancewouldbeappropriateresponsetothoseconcerns?

• What implicationsdo theprospectof futuregeoengineeringdeploymentand concernsaboutitsgovernanceneedshavefornear-termgovernanceofresearch?

Closing Thoughts: Context for the Forum, Recent Changes, and their Implications TheproposalfortheForumwasdevelopedinsummer2016,nearlyayearbeforeitwasheldinApril2017.Atthattime,itseemedtimelytodiscusssolargeoengineeringresearchgovernancebecause it appeared that researchprogrammanagers, in theU.S.governmentandelsewhere,weregrowingmoreinterestedinsupportingsuchresearch.Sincethen,thepoliticaleventsofthepastyearhavechangedthecontextforthesediscussions,havingimplicationsthatarenotentirelycleartous,butwhichwejudgeitusefultolayoutexplicitly. First,whilethefutureofawell-conceivedfederalU.S.researchprogramisuncertain,tosaytheleast,therehasbeenasignificantincreaseinresourcescomingintothefieldfromothersources,includingbothnationalresearchprogramsoutsidetheUnitedStates,andfoundationsandotherprivatephilanthropies.Followingfromthesenewresources,severalnewresearchprogramsandprojectsarebeingestablished–includingatUCLAandHarvard,thetwoconveninginstitutionsfortheForum,and theCarnegieClimateGeoengineeringGovernance Initiative.Muchof thisnew

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activityissupportingactivitiesalreadyunderway,suchascomputermodeling,socialscience,andgovernance studies.But the increase in resourcesalso represents an increased likelihood thatfundingwillbeavailable,perhapssoon,foroutdoorfieldexperiments. Second,atleastoneoftheproposedfieldexperimentsistakingstepstowardimplementation.TheHarvard team developing the SCoPEx experiment is investigating hardware options andgovernancestructurestoassessviabilityofatestflightinthesecondhalfof2018orlater.WhiletheForumdidnotaimtofocusonanyparticularexampleofthesefundingsources,projects,orproposedexperiments,theyallprovidedconcreteillustrationsofthegovernanceissuesthattheForumsoughttoaddress.Thisconfluenceoftrends–increasedresources,includingsubstantialincreasesfromprivatefoundationsandphilanthropies,andthedevelopmentofconcreteresearchproposals–alsohastheeffectofraisingthesaliencyandimmediacyoftheresearchgovernancequestionstheForumconsidered. Finally,whileitwasalsonottheaimoftheForumtospeculateontheimplicationsofthechangeofU.S.administrationforsolargeoengineeringresearch,itisnotpossible,orhelpful,tofullyavoidtheimplicationsofthiselephantintheroom.Whileconcretestepsbythenewadministrationonclimate change and scientific research are still emerging – and possibly contested inside theadministration–itstrikesusasreasonabletoguessthatU.S.commitmentstocutsingreenhouse-gasemissions,tointernationalconsultationandcollaborationonglobalproblems,andtosupportforandauthorityvestedinscientificresearch,arealllikelytobesubstantiallyweakened.Ifthesetrendsarerealizedandsustained,severalspeculative–andworrisome– implications forsolargeoengineering research and governance may follow. We sketch a few of these speculativepossibilities:

• TotheextentcurrentU.S.trendscontributetoawidespreadandsustainedweakeningofexpectedgreenhouse-gasmitigation,thelikelihoodthatsomemajorworldstateorstatesseriouslyproposessolargeoengineeringinterventionsoverthenextfewdecades,astheirexperiencedclimate-changeimpactsgrowmoresevere,isincreased.

• IftheUnitedStatespullsbackfromconstructiveinternationalengagementinasignificantand sustained way, the prospects for effective governance grow weaker, particularlybefore some crisis or challenge demands an international response, grow moreproblematic.

• Theriskthatsolargeoengineeringisperceivedorcharacterizednotasanadditionaloptionto strengthen climate risk management beyond the capabilities of mitigation andadaptation,butasanalternativetothem,maygrowmoreserious.

Theimplicationsoftheseandother,relatedspeculativetrendsforresponsiblenear-termdecisionsabout geoengineering research and its governance are obviously unclear in details, but theassociatedstakesmaybehigh.

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Some Thoughts on Solar Geoengineering Research

ScottBarrettLenfest-EarthInstituteProfessorofNaturalResourceEconomics,ColumbiaUniversity

Theinvitationtowriteanoteonthistopicasksforeachauthor’sperspectiveonUnitedStates’solargeoengineeringresearch,implyingthatUSpolicyonthismattercanbeviewedinisolationofwhatothercountriesdoorcanbeexpectedtodo.Itseemstome,however,thatgeoengineeringresearchmustbelookedatinastrategiccontext.Geoengineeringdeploymentismoreobviouslystrategic in nature, but research and deployment are intimately connected activities. Becausedeploymentisstrategic,aprogramforgeoengineeringresearchmustalsobestrategic.IftheUShadafreehandtodecideaboutdeployment,itwouldstillwantevidencethattheuseofgeoengineering would address the problem it was meant to address, and that, from a USperspective,therisksofusingitwerelessthantherisksofnotusingit.Atamostbasiclevel,thesetwoissuesshouldbethehighestprioritiesforUSgeoengineeringresearch.ButtheUSwillnothaveatrulyfreehandtodeploygeoengineering.Itwouldneedtojustifyitsplanstootherstates.Ataminimum,theUSwouldneedtoconvinceotherpowerfulstatesthatthe risk-risk tradeoffs were not unfavorable to them. Relatedly, if the US believes that othercountriesmight somedaydeploygeoengineering, then theUSwillwant todo researchon theeffectssuchdeploymentwouldhaveontheUS,andonthethingstheUScoulddotodeterorprevent these states from geoengineering or to reduce the negative impacts of thegeoengineering that the US could not deter or prevent, to include possible “counter-geoengineering.”Whatmightsolargeoengineeringentail?Will itbeglobalinnature,aimedatinfluencingglobalmeantemperature,orwillitbemoretargeted,aimedatinfluencingtheregionalclimate(Quaasetal.2016)oraparticulargeophysicalsystem(suchasArcticsummericeortheGreenlandIceSheet;seeMacCracken2016)?Themainadvantageofamoretargetedapproachisthatitcanlimitcollateral harm—and, hence, limit the risk of a response by other countries to aUS-led solargeoengineeringeffort.(Ofcourse,thislimitismerelyamatterofdegree,fortherewillinevitablybe“spillover”effectstoregionalgeoengineering.)Anotherimplicationoftargetedgeoengineeringis that a multiple of regional efforts might be attempted, perhaps by different countries orcoalitions.Researchintothiscoordinationproblemisalsoneeded.All of the world’s countries have agreed that concentrations of greenhouse gases in theatmospheremustbelimitedsoastopreventglobalmeantemperaturechangefromexceeding2°C,butdespitethenewParisAgreement,“[t]heworldisstillmovingalongatrajectorythatcanleadto3-5°Cofwarmingby2100,andprobablymoreafterthat”Knuttietal(2017:17).EvenifcountriesfulfillthepledgestheymadeinParis,the2°Cgoalisvirtuallycertaintobemissed;andthere is reason tobelieve thatcountrieswillnot fulfill thesepledges (BarrettandDannenberg2016). Concern is often voiced that knowledge of the effectiveness of geoengineering will

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discourageeffortstolimitemissions(theincorrectlylabeledphenomenonof“moralhazard”),butit’sreallythefailuretolimitemissionsthatismakingitnecessaryfortheworldtoconsiderdoingsolar geoengineering. Getting the world to reduce emissions is a colossal collective actionproblem. Solar geoengineering, by contrast, can be done unilaterally and at relatively littlefinancialcost(Barrett2008).Iflimitingtemperaturechangeto2°Cwereatrueimperative,researchonsolargeoengineeringwouldbeaglobalpriority;andyet it isn’t.Why?Onereasonmightbethatthegoalof limitingtemperaturechangeto2°Cwasameretacticaldevicemeanttospuraction.Asthereareveryrealthreatstoclimatechangeexceedingthistarget,however,Idon’tfindthisexplanationsatisfactory.Anotherreasonmightbethattherisksofdeployinggeoengineeringaretoogreat.Ialsodon’tfindthisexplanationsatisfactory,becausewedon’tknowthatthisistrue.Thisiswhymoreresearchisneeded on the full consequences of geoengineering, the good and the bad. A third reasongeoengineeringhasnotbecomeapriority for research is thatpeople feeluneasyaboutdoinggeoengineering,eveniftheycouldbeconvincedthattherisksfromdoingitweresmall.A best guess is that about half of the “global warming” due to the increase in atmosphericconcentrations has been masked by the effect of aerosols (Ramanathan and Feng 2009),principallysulfuremissionsfromburningcoal.Thishasasimilareffectasgeoengineering,onlytheintervention isn’t deliberate. One of the things that I think really bothers people is thatgeoengineeringentailsalteringtheclimatedeliberately.The distinction between deliberate and inadvertent interventions (known as the doctrine ofdouble effect) has been studied extensively in moral philosophy (Thomson 1985) anddemonstratedempiricallyinmoralpsychologyresearch(Greeneetal.2001).Peoplerespondverydifferentlytoactionsthatleadtopreciselythesameconsequencesdependingonwhetherthoseactions are perceived to be deliberate or a side effect. The idea is neatly demonstrated bycontrasting twowell-studieddilemmas. In the first,a runawaytrolley issure tokill fivepeopleunlessyoupullaswitchthatwilldivertthetrolleyontoanothertrackwhereitwillkilloneperson.Willyoupulltheswitch?Mostpeoplesayyes.Intheseconddilemma,arunawaytrolleyissuretokillfivepeopleunlesssomethingisdonetostopit,butthistimeyouarestandingonafootbridgenexttoalargestranger,andtheonlywayyoucanstopthetrolleyisbypushingthestrangerontothetracksbelow.Wouldyoupushthestranger?Mostpeoplesayno.Inthefirstinstance,peoplethinklikeconsequentialists,reasoningthatitisbetterforonepersontodiethanfive.Inthesecondsituation,peoplethinkmorelikedeontologists,believingthatitiswrongtokilloneperson,evenifdoingsowouldsavefiveothers(again,seeGreeneetal.2001).Geoengineeringismorelikethesecondsituation,andIthinktherepulsionpeoplefeelaboutthisinterventionmaycauseustomakeabaddecision:adecisionnottousegeoengineeringwhentheevidencesuggeststhatweshoulduseit.Researchintohowtoaddressthisrepulsionshouldbeanotherpriority.Finally,wemustalsobegin thinkingabout the consequencesofpossiblyusinggeoengineeringsomeday—the consequences not only for the climate and the environment but for the

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relationshiphumanshavewiththeenvironment.Thebiggestchallengeposedbygeoengineeringisunlikelytobetechnical,butratherinvolvethewaywegoverntheuseofthisunprecedentedtechnology(Barrett2014).References Barrett,Scott(2008),“TheIncredibleEconomicsofGeoengineering,”EnvironmentalandResource

Economics39:45-54.Barrett,Scott(2014),“SolarGeoengineering’sBraveNewWorld:ThoughtsontheGovernanceofAnUnprecedentedTechnology,”ReviewofEnvironmentalEconomicsandPolicy8(2):249-269.Barrett, Scott and Astrid Dannenberg (2016), “An Experimental Investigation into ‘Pledge andReview’inClimateNegotiations,”ClimaticChange138(1):339-351.Greene,JoshuaD.,R.BrianSommerville,LeighE.Nystrom,JohnM.DarleyandJonathanD.Cohen(2001),“AnfMRIInvestigationofEmotionalEngagementinMoralJudgment,”Science293(5537):2105-2108.Knutti,Reto,JoeriRogelj,JanSedlacek,andErichM.Fischer(2016),“AScientificCritiqueoftheTwo-DegreeClimateChangeTarget,”NatureGeoscience9:13-19.MacCracken, Michael C. (2016), “The Rationale for Accelerating Regionally Focused ClimateInterventionResearch,”Earth’sFuture4:649-657.Quaas,Johannes,MartinF.Quaas,OlivierBoucher,andWilfriedRickels(2016),“RegionalClimateEngineeringbyRadiationManagement:PrerequisitesandProspects,”Earth’sFuture4:618-625.Ramanathan,V.andY.Feng(2009),“AirPollution,GreenhouseGasesandClimateChange:GlobalandRegionalPerspectives,”AtmosphericEnvironment43:37-50.Thomson,JudithJarvis(1985).“TheTrolleyProblem,”TheYaleLawJournal94(6):1395-1415.

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The Past, Present, and Future of Social Science on Solar Geoengineering

HollyJeanBuck

DoctoralCandidate,DevelopmentSociology,CornellUniversity;

FacultyFellow,ForumforClimateEngineeringAssessment,AmericanUniversity

The past: After ten years of social science research, we have some experience discussing solar geoengineering with publics — but very little of this may apply to a US context Around30empiricalsocialsciencestudieshavebeendoneonsolargeoengineeringworldwide.Abouthalfwerelarge-nsurveys,andhalfweredeliberativeworkshopsorfocusgroups.4Findingsincluded: (1) framings around “naturalness” or “climate emergencies”matter; (2) publics areconcernedwith unexpected side effects aswell as governance challenges; (3) discussing solargeoengineeringmayimprovethewilltomitigate,aswellasdecreaseit,indifferingcontexts;and(4)thereisconditionalorambivalentsupportforresearch.5Little isknownaboutUSperspectivesonsolargeoengineering,andtherehasbeenvirtuallynoengagement with US publics. The United Kingdom, Sweden, and Japan have had deliberativepublic engagements on geoengineering.6 In the US, empirical research has been limited, andalmost entirely in the formof surveys.My initial qualitative fieldwork on perceptions of solargeoengineering in the US has suggested significant differences between the US and otherdevelopedcountries,duetoclimateskepticism,politicalpolarization,lossoftrustininstitutions,andthepoliticizationofclimatescience.The present: Policymakers should consider a “CDR first” agenda Givenanextremelypolarizedelectorate,therisksofpressingforafederalresearchprogrammayoutweigh the benefits. Eagerness on a federal level could torpedo the social acceptability of

4Foranoverview,seeE.Burnsetal,“Whatdopeoplethinkwhentheythinkaboutsolargeoengineering?Areviewofempiricalsocialscienceliterature,andprospectsforfutureresearch,”Earth’sFuture,doi:10.1002/2016EF000461,2016.5Cautionshouldbeused in interpretingthefindingsofresearchsupport,asthephrasingofthequestionmattersimmensely.Respondentsmaysupportresearchinthesensethattheybelieveinscientificfreedom,andwouldn’twanttorestrictsomeone’srighttodoresearch—butthistypeof“support”wouldplaydifferentlythanthesupportofsomeonewhobelievesresearchonthisinparticularshouldtakeplace.6SeeS.Asayamaetal,“Ambivalentclimateofopinions:Tensionsanddilemmas inunderstandinggeoengineeringexperimentation,”Geoforum,http://dx.doi.org/10.1016/j.geoforum.2017.01.012,2017;V.Wibecketal,“Questioningthetechnologicalfixtoclimatechange–Laysense-makingofgeoengineeringinSweden,”EnergyResearch&SocialScience, http://dx.doi.org/10.1016/j.erss.2015.03.001, 2015; also R. Bellamy and J. Lezaun, “Crafting a public forgeoengineering,”PublicUnderstandingofScience,doi:10.1177/0963662515600965,2015.

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research on solar geoengineering.More social science research could indicatewhether this isactually thecase. If it isseenthattheTrumpadministrationorRepublicanCongress is fundingresearch into geoengineering, the field of researchwould be tarnished by association; expectoutcryfromtheleftworldwide.Conversely,ifitisseenthatliberalscientistsandNGOsarepushingforresearch, itwillbederidedbythoseontherightascrazy/stupid.Thelattersituationwouldlikelybeashort-lived,inconvenientmediaflare-upratherthananongoingissue.Buttheformerscenariowoulddelegitimizesolarengineeringresearchandcoulddelayitbyadecadeormore—potentiallymaking the technologiesunavailable ina futurewhere theymightbeuseful. Socialscientistshavepointedoutthatastratosphericaerosolfieldtrial,forexample,shouldbeseenasa “social experiment” with unknown and uncontrollable social and political consequences.7Researchersandpolicymakersmustappreciate that the context for this social experimenthasshifteddramatically.Othercountriesandinstitutionsmusttaketheleadonsolargeoengineeringresearch,becausetheUSG isnotcurrently inapositionto lead. Ideally,private fundersandregionalor internationalbodiescancarryonlaboratory-scaleresearchwiththesamestandardsoftransparencyandaccessthatalarge-scalepublicprogrammightuse.Importantaspectsinclude:(1)reviewofproposalsusing establishedpublic-interest criteria,with the process open for brightminds from variousbackgrounds to apply, (2) integration of social science, (3) balancing perspectives tomitigategroupthink,(4)transparencyanddata-sharing.CertainresearchactivitiesshouldstillbepromotedrightnowbyUSfederalagencies,asunlikelyasthismaybe.Theseinclude:

1. R&Dforcarbonremovalpractices/technologies.ThisiswhatIcalla“CDRfirst”strategy.RespondentsinmyresearchpreferredtheideaofSRMbeingatemporarymeasureratherthananendgame.Ifthat’sgoingtobeaplausiblescenario,CDRneedstobemuchfartheralong,technicallyandsocially.Theinfluentialtaxonomyofthe2009reportbytheUKRoyalSocietywasmisleadinginthatitdepicteddiscretegeoengineering“choices”.Fromasolargeoengineeringpolicystandpoint,SRM&CDRneedtobelookedatasapackagedeal.CDRisunlikelytoadvancewithoutstrongpolicyincentives.

2. International consortium-based or co-financed projects on solar geoengineering thatcontinuetobuildaninterdisciplinaryresearchnetwork.

3. Educationalopportunities forbuilding climate science capacity indeveloping countries,perhapswithinamitigation-adaptation-geoengineeringframework.

The future: Multi-stakeholder engagement should bring solar geoengineering under a sustainable development frame The next four years should be used to build solid partnerships between climate engineeringresearchers and organizations working in sustainable development, in order to ground

7 Asayama et al, 2017, also see Stilgoe, J, “Geoengineering as collective experimentation”, Sci. Eng. Ethics,http://dx.doi.org/10.1007/s11948-015-9646-0.,2016.

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geoengineeringwithin this framebeforepursuing a large-scale federal researcheffort. If SRMemerges from a development-oriented frame, then the research goals draw upon a broaderconversation.Thiscouldinformthedesignofbothsolargeoengineeringstrategiesandresearchquestions, influencingaspectsofsolargeoengineeringsuchastiming,deploymentlocations,oramountsdeployed.There are three basic reasons to ground geoengineering in sustainable development. First,developmentpractitionersareusedtothinkingaboutthefuturewewant,notjustthefuturewewanttoavoid.Theycanapplyvaluableexperiencefrombothsuccessfulandfailedenvironmentalmanagementprojectsandsocialinterventions.Second,acknowledgingclimatechangeisatrootadevelopmentproblem,andnotjustan“environmental”ora“science”problem,bringsustoamore honest discussion that can recognize inequality and incorporate it into the problemdefinition.8Third,researchindicatesthatpublicswanttodiscussgeoengineeringnotasayes/noverdictonaparticulartechnology,butinthecontextofabroadarrayofclimatefutures.NGOsandcommunityorganizationsalreadyholdthesetypesofconversationsaroundmitigationandadaptation pathways and “deep decarbonization”. If science can address whether solargeoengineering can ameliorate harms to species and vulnerable peoples, civil societyorganizationsmaybemoreopentofacilitatingconversations.

Inthefuture,fourkeyinterdisciplinarylinesofresearchinclude:

1. Worldwideunderstandings about climateengineering, inorder to incorporatepeople’svisions,preferences,concerns,orgoalsintotheresearchprocess—particularlybeyondtheglobalnorth,withsocialscientistsintheglobalsouthdesigningtheresearch.

2. Ecosystem interactions of solar geoengineering: impacts on biodiversity and species’adaptation,andwhatthismeansforcommunitiesthatusebiologicalresources.

3. Howcitizensseek,find,andinterpretinformationaboutclimateengineering.4. PublicunderstandingsofclimateengineeringintheUS.

8Seethediscussionof“moralresponsibility”inD.E.Winickoffetal,“EngagingtheGlobalSouthonclimateengineeringresearch”,NatureClimateChange,doi:10.1038/NCLIMATE2632,2015.

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Solar Geoengineering Research and the Social Sciences

RoseCairnsResearchFellow,SPRU–SciencePolicyResearchUnit,UniversityofSussex

There is a rich body literature examining the potential social and political implications of animagined future solargeoengineeringprogram.From this corpusofworkanumberof seriousissueshavebeenhighlighted,including:convincingargumentsthatsolargeoengineeringwouldbeungovernable(inanydesirablesense)[1];thatitwouldbeunabletosolvetheproblemsassociatedwithclimatechangeatthelocalandregionalscalesthatmatter[2];thatitwouldinevitablyhaveunexpected, and endlessly contested, negative consequences due to its fundamentallyexperimental nature [3] [4]; that it would necessitate a hugely costly, militarized securityinfrastructure,withpotentiallydestabilizingconsequencesforglobalsecurity[5];andwouldbesusceptibleto‘lock-in’,beingdifficultorimpossibletochangeevenunderconditionsofcrisis[6].Although inevitably speculative to a degree (given that solar geoengineering remains a socio-technicalimaginary),theseverityandmagnitudeoftheseissuessuggestthatsolargeoengineeringwouldbenon-viableasapolicyoptionfordealingwithclimatechange,andcallsintoquestionthewisdomofcontinuingtocarryoutresearchinthisdomain.Butthen…isitperhapsthecasethatwejustneedtodomoreresearchtobesureonewayortheother?Proponentsmight justify suchaneed in termsofa ‘gap’ inknowledge thatneeds filling,orofuncertaintiesthatneedreducing.However,withregardtocontentioussocio-technicalimaginarieslikesolargeoengineeringthenotionofa‘gap’inknowledgeisasomewhatdangerousfictionbuiltondubiousassumptions.Framingknowledgeproductioninthiswayimpliesthat(with‘theright’kindofresearch)suchagapcouldbefilled:uncertaintyreducedtothepointofclarityaboutthebestwayforward,providingclosureorjustificationforaparticularcourseofaction.Inturnthisimpliesthatthekindsofuncertaintiesassociatedwiththesocialandpolitical(andindeedphysical)dimensionsofsolargeoengineeringareindeedreducible.AsDanSarewitzremarks:‘bypresentinguncertaintyasavaguebutputativelycoherentconceptthatis“reduced”throughmoreresearch,

the scientific community assures that the phenomenon of uncertainty remains located in our

imperfect(butalways-improving)understandingofnature,andisnotanattributeofnatureitself,

ofthestructureofdisciplinaryscience,orofthesocialandpoliticalcontextwithinwhichresearch

is conducted.’ [7] On the contrary, with regard to both the social and physical aspects ofgeoengineering,it isnotsimplythatthereexistsuncertainty,butthereismuchthatisradicallyunknowable. Furthermore, what we do already know is that there are multiple, competing

meanings [8] associatedwith geoengineering and that notions such as feasibility, desirability,purpose, relevant knowledge and so on, are all fundamentally contested. Despite powerfulpolitical pressure for research to provide artificial closure, further study will not reduce thediversity (or incommensurability)of theseperspectives: it is awidely recognizedbutoft-mademistaketobelievethat‘moresciencewillreducepoliticalorvaluedisputes’[9]wheninrealitytheopposite isoftenthecase.Withregardtosolargeoengineering,uncertainties,ambiguitiesandcontestationwillonly increaseasmoreactors (e.g. in theglobalsouth)arebrought intotheseconversations.

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Secondly,suchcallsformoreresearch,implythatknowledgeproductionisaneutralactivity,thatknowledge and action are separate, and that the process of investigating, instigatingconversations,canvassingopinionandsoon,doesnotitselfchangethematerialsocialcontext.Itisentirelyplausiblethatthereverseistrue,andthattheflowofresearchfunds,andthesustainedattentionfromresearchersandothers,has importantmaterialconsequences(this isrelatedtotheso-called‘slipperyslope’argument[10],[11]).Thusevenwhatisintendedtobea‘balanced’discussion might inadvertently lend discursive policy momentum towards geoengineering,throughforexample:establishingthecredibilityofthediscussionorlendingtacitlegitimacytotheidea itself through association with particular institutions; drawing policy attention (withconsequentopportunitycostsforotherapproaches);orprovidingadiscursiveresourceforactivestrategicmanipulationbyprotagonists.Similarly,apparently ‘neutral’activitiessuchascalls for‘governancebeforedeployment’or‘craftingagovernanceframework’,mayalsohaveimportantfacilitatoryeffects,andriskrepeatinginthesocialdomainthefallaciesofcontrolwhichnotionsofgeoengineeringembodywithregardtothenatural/physicalenvironment.Despitetheseconcerns,giventhesheerscaleandambitionofscientificresearchintothephysicalfeasibilityofclimategeoengineering,barringamoratorium(whichseemsunlikelyevenif,perhaps,desirable?)itisinevitablethatsocialscientistswillbedrawntothetopictobetterunderstandandcontributetothesediscussions.Whatrolethen,shouldtheyplay?Therewillbepressurefromsomequartersforsocialscientiststogather‘socialintelligence’(inthemilitary/surveillancesenseof intelligence provision), to provide a body of information and knowledge about society to‘decisionmakers’framedassomehowoutsideorabovethosebeingstudiedinordertopre-emptorovercomedissent(theymightasksuchquestionsas:‘whatframingsofsolargeoengineering

resonatewith‘thepublic’?Whatproportionofpeoplearealreadyopentotheidea?Howcanone

craftagovernanceframeworkthatwillbeseenas‘fair’,orensurethelegalityofresearch?)Ontheother hand, one might understand the notion of providing social intelligence differently: asintelligence of the collective, aimed at alerting those who would embark on research in thisdomaintofundamental‘questionsemergingfromhumanimaginationandpublicconcern’[10].Inthisguise,socialscientists,alongwithothersocialactorssuchasNGOs,mightplayacriticalrolefacilitating spaces (both physical and conceptual) for collective societal reflection, to examinewhetherthisdirectionforresearch,andtheassociatedimplicationsforlifeonearth,isethically,sociallyandpoliticallyacceptableordesirable.Butinordertoavoidtokenism,orbecomesimplya‘tickbox’publicengagementexercise,therehastobeasensethatdissentwillbetakenseriously.Which raises a key question that remains unansweredby thosewhowish to pursue scientificresearchinthisarea:‘whatwouldconstituteasufficientlygravecritiquetowarrantabandoningthislineofinquiry?’Iftheanswertoallcritiqueanddissentissimplytodismisstheseasminorityor‘specialinterestgroup’concerns,ortoframethemas‘areasrequiringmoreresearch’,thenthenotionofaslipperyslopemaybeaptindeed,andthedangerofco-optionofsocialsciencesintheserviceoffacilitatingthisendeavour,seemshighlylikely.

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References

[1] B.Szerszynski,M.Kearnes,P.Macnaghten,R.Owen,andJ.Stilgoe,“Whysolarradiationmanagementgeoengineeringanddemocracywon’tmix,”Environ.Plan.A,vol.45,no.12,pp.2809–2816,2013.

[2] M.Hulme,CanScienceFixClimateChange?:ACaseAgainstClimateEngineering.Oxford,UK:PolityPress,2014.

[3] A.Robock,M.Bunzl,B.Kravitz,andG.L.Stenchikov,“ATestforGeoengineering?,”Science(80-.).,vol.327,pp.530–531,2010.

[4] H.D.MatthewsandS.E.Turner,“Ofmongoosesandmitigation:ecologicalanaloguestogeoengineering,”Environ.Res.Lett.,vol.4,no.4,p.045105,Oct.2009.

[5] P.NightingaleandR.Cairns,“TheSecurityImplicationsofGeoengineering:Blame,ImposedAgreementandtheSecurityofCriticalInfrastructure,”CGGWork.Pap.,2014.

[6] R.Cairns,“Climategeoengineering:issuesofpath-dependenceandsocio-technicallock-in,”WileyInterdiscip.Rev.Clim.Chang.,vol.5,no.5,pp.649–661,Jun.2014.

[7] D.Sarewitz,“Howsciencemakesenvironmentalcontroversiesworse,”Environ.Sci.Policy,vol.7,no.5,pp.385–403,2004.

[8] R.CairnsandA.Stirling,“‘Maintainingplanetarysystems’or‘concentratingglobalpower?’Highstakesincontendingframingsofclimategeoengineering,”Glob.Environ.Chang.,vol.28,pp.25–38,Sep.2014.

[9] R.A.Pielke,Thehonestbroker:makingsenseofscienceinpolicyandpolitics.Cambridge:CambridgeUnivPress,2007.

[10] M.Hulme,“Climatechange:Climateengineeringthroughstratosphericaerosolinjection,”Prog.Phys.Geogr.,vol.36,no.5,pp.694–705,Aug.2012.

[11] M.Bunzl,“Researchinggeoengineering:shouldnotorcouldnot?,”Environ.Res.Lett.,vol.4,p.045104,2009.

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A Perspective on Solar Geoengineering

KerryEmanuelProfessorofAtmosphericScience,MassachusettsInstituteofTechnology

MyperspectiveonsolargeoengineeringarisesfrommanyconversationsIhavebeenfortunatetohaveoverthelastdecadewithcolleagueswhohavedoneseriousworkinthisfield,onmyreadingofsomeoftheseminalpapersonthetopic,andalsoonwhatIhavelearnedfrommyeffortstoinform thosewhoare inclinedagainstanykindof climateactionaboutboth the risksand theopportunitiesposedbyanthropogenicclimatechange.Thepolitical,ethical,economic,legal,scientific,andtechnicalaspectsofsolargeoengineeringaresotightlyinterwovenastorenderproblematicadiscussionofanyoftheseaspectsinisolation.Evenpureresearchontheissueconstitutesapoliticalactasitsendsamessagethatwemightbeabletoengineerourwayaroundtheconsequencesofgreenhousegasemissions.Perhapsforthisreasonitseemsprudenttobeginwithadiscussionofethicsasitaffectsthequestionofwhetherweshouldevenbeundertakinggeoengineeringresearch.Heremyownviewevolved somewhat in response toa conversationmyMIT colleaguePennyChisholmhadwiththeDaliLamaafewyearsago.SheandIandseveralothershadbeeninvitedtohaveapublicconversationwiththeDaliLamaaboutclimatechange,andIhadjustbriefedhimonthecurrentstateofthescience.Pennywaschargedwithexplaininggeoengineering,whichshedidwithgreatproficiency.Helistenedintently,andwhenshewasdonehestated,tooursurprise,thatinhisviewweshouldbegintodosolargeoengineeringimmediately.WethoughthemighthavemissedPenny’sdescriptionoftherisks,whichsherepeatedforhim.Butheheldfastandexpressedthattodootherwisewouldbeunethical.Needlesstosay,hehadabsolutelynoqualmsaboutresearchingthetopic.Itoccurredtome laterthatperhapsoursurprisewasgrounded ina fundamentalriftbetweenEasternandWesternethics.We in theWestattachgreat importancetoagency in judgingthemorality of any action. Actively and knowingly doing harm is considered worse than doingsomethingharmfulasanunintendedside-effectofsomeactivity,andthisisreflectedinwesternlaw.Notsavingsomeonewhenwehavethepowertodoso,whileheinous,isputinadifferentcategoryfrompre-mediatedmurder.ApparentlytheimportanceofintentionrelativetooutcomeisnotasimportantinTibetanphilosophy.ThusperhapstheDaliLamafeltthatnottogeo-engineerourwayoutoftheadverseeffectsofclimatechangewasasseriousanethicalfailureascausingtheprobleminthefirstplace,inspiteoftherisksofgeoengineering.It seems tome thatwehaveamoralobligation toexploreallplausible responses to the risksassociatedwithglobalwarming,fromcarbon-freeenergy,tocarboncapture,togeoengineering,andtoadaptation.Onlybyfullyunderstandingtherisklandscapeandourvariousoptionswillwebeabletomakeintelligentandcompassionatedecisions.Idonotbuytheideathatweshouldnotresearch any form of geoengineering on the grounds that it will discourage investment in

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alternative energy sources. On the contrary, by quantifying the downsides and risks ofgeoengineering, we will be able to argue, if necessary, against deploying such technology.Especiallysincesolarradiationmanagementissocheap,wewouldneedstrongargumentstostoprenegadegovernmentsorindividualsfrompursuingthisapproach,ifitindeedisshowntohaveunacceptablerisks.Muchhasbeenwrittenaboutharmfulside-effectsofsolarradiationmanagement.Buttheremayalsobebeneficialside-effectsbeyondtheintendedbenefitsoflowertemperatureandmitigationofsealevelrise.Someofmyownworkisontheresponseoftropicalcyclonestoclimatechange,andwehavebeenabletoshowthatvariationsofsolarradiationareroughlytwiceaseffectiveaschanges in longwave radiation, per unit sea surface temperature change, in changing tropicalcyclonepotentialintensity.Thismeansthatifseasurfacetemperatureisfirstraisedbyincreasinglongwaveemittersandthenbroughtbacktobaselinebydecreasingsolarradiation,therewillbeanetdeclineinthethermodynamicpotentialfortropicalcyclones.Thisisgenerallygoodnews,astropicalcyclonescausefarmoredamagethanbenefits,globally.This finding shouldnotbe interpretedas advocacy for solar radiationmanagement,but as anillustration of the importance of a full accounting of the potential risks and benefits of anygeoengineeringstrategy.Butweshouldnotbetemptedtothinkthatevenacomprehensiverisk-benefitanalysiswill leadtostraightforwarddecisions.Reasonablepeoplewilldifferinweighingtheunanticipatedharmfulconsequencesofanintendedaction(solargeoengineering)againsttheunintendedbutknownharmfulsideeffectsofanongoingactivity(greenhousegasemissions).Itmaytakeagreatdealofthelatterbeforetheformerbecomesthepreferredoption.

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Reflection on the Forum on

U.S. Solar Geoengineering Research

PeterFiekowsky9100-yearplanleader,CitizensClimateLobby

Where are we going (climate-wise)? The Forum on Solar Geoengineering (also called solar radiation management or SRM) was avaluablegatheringreflectingsignificanttechnicalprogressandpoliticalchange inthe lastyear.WiththenewUSadministration,thingscouldmovequickly,forwardand/orbackwards.It’suptoustomakesurethatthingsmovetowardssuccess.Tosucceed,wemustdefinesuccessclearlyandassomethingwewant.What would successful SRM achieve? OneofthepanelistsattheforumsaidthatSRMsuccessisstayingbelowtwodegreeswarming.Thatgoalisarguablytoovaguetoelicitspecificandeffectiveaction.IthinkexpertswillagreethatSRMactionsasawholehavebeenindecisiveandhesitant;actionsconsistentwithavagueandunappealinggoal.Asaparent, I’mclear that success is restoringahealthyclimate forourchildren,anddoing itbeforewelosemuchmoreofthebeautyandgloryofourplanet.AlthoughtheIPCCmaydisagreewiththatgoal,thatisIwant,andwhatalmosteveryoneIspeakwithwants,andwhattheclergyIspeakwithnowdemands.Wehaveamoralobligationtogiveourchildrenandgrandchildrenaclimateclosetothatwhichweweregiven.Ifwedon’tyetknowhowtoachieveitthenweareobligatedtoinventthemethodsrequired.Notknowinghowtodoitdoesnotabsolveusfromthatobligationtoourchildrenandgrandchildren.AsanSRMoutsiderwithchildrenhere’swhatIwantfromSRM:Be prepared to cool the planet with SRM during the time during which carbon dioxide removal is operating. Assumethatwewillimplementcarbondioxideremoval(CDR)andreduceatmosphericCO2backtolevelsthathavesupportedhumansinthepast,i.e.below300ppm.Weshouldtargetachievingthisby2050,althoughitcouldtakeuntil2100.RecentworkconfirmswhatDr.JimHansensaidin2008,thatCDR investmentofabout1%ofglobalGDPcouldremovethetrilliontonsofexcessatmospheric CO2 in 20-50 years. This requires removing 50 GT / year, which scale could beachieved by any one of at least seven techniques, using direct air capture (DAC), or oceanprocesses.

9Oneparticipant,PeterFiekowsky,respondedtoourrequesttoallForumparticipants,offeringthesereflections.

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Be ready to start SRM within 2-3 years—by 2020. Waitinglongeristoolate,arguablycriminal,givenrapidlyworseningclimatetrendsfromthearctictotheequator.WeneedtheinsurancepolicyofSRM.Ifwedon’tprovidethat,ourchildrenshouldsueusforderelictionofduty—perhapsaspartof“OurChildren’sTrust”lawsuit.InsofaraswearetheleadershipforSRM,wearemorally,ifnotlegallyliable.Thisisaharshassertion,butarguablytrue.This isn’t saying that we must implement SRM—implementation is a moral decision. Thiscommunitymustprepareto implementSRM.Astechnologists,ourobligation is toprovidethetools.SocietycouldintheendinsistthatSRMnotbeimplemented,althoughthatcouldwellbethepathwayintothesixthextinction.Withgooddataavailable,IconsidersuchanSRMvetotobeunlikely.Withoutthisdata,we’veseenthatfewpeoplearewillingtoseriouslyconsiderSRM.InadditiontotheextensiveliteratureonSRMrisks,wemustprovidecriticaldataaboutbenefitsofSRM:

1. Whatarethebestoptionsforstoppingsea-levelrise,andforhaltingicesheetcollapseinAntarcticaandGreenland?

2. WhatarethebestoptionsforweakeningthecyclonesdecimatingthePhilippinesandotherareas?

3. Whatarethebestoptionsforstoppingpermafrostmeltanda“methaneburp”?4. WhatarethebestoptionsforrestoringtheGulfStreamandotheroceancurrents?5. Whatarethebenefitstosocietyandnatureof implementingSRM?Wehavedozensof

articlesabouttherisks,butpreciouslittleaboutthebenefits.Giventhepublicdata,it’snosurprisethatthereislowpublicsupportforSRM.

6. IfSRMisrequired,whataretherealoptionsforimplementingSRMquickly?Whatarethetechnical,financial,andlogisticaloptions?Thereisgreatfictionaboutthat,butlittlepolicywork.

Iamproposing thata“ClimateRestoration”centerbeestablished in2017tohost research toanswerthesecriticalquestionswhichwillallowprogresstowardsrestoringtheclimate.

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The Siren Call of US Funding for Solar Geoengineering Research

PeterC.Frumhoff

DirectorofScienceandPolicy,UnionofConcernedScientists

JennieC.StephensDean'sProfessorofSustainabilityScienceandPolicy,AssociateDirector,GlobalResilienceInstitute,

NortheasternUniversity

Mounting evidence now indicates that even very aggressive reductions in greenhouse gasemissionsmay not be sufficient tomeet the Paris Agreement’s long-term goal of limiting theincreaseinglobalaveragetemperaturestowellbelow2degreesCabovepre-industriallevels.Asaconsequence,vexingquestionsaroundwhether,whenandunderwhatconditionssocietymightneedtoconsiderdeployingotherlarge-scale“climateinterventions”areincreasinglycomingtothefore.Thestateofknowledgeofsuchinterventionswasprominentlysummarizedintwo2015NationalResearch Council (NRC) reports, written by a committee chaired by Marcia McNutt. TheCommitteeseparatelyconsideredtechnologiestoremovecarbondioxidefromtheatmosphereatscale, and “albedomodification” or solar geoengineering technologies to reflect sunlight andlowertemperatures.Intheirsolargeoengineeringreport,theNRCCommitteefirmlyopposeddeployment,notingbothsignificant risks that include secondary impacts on “the ozone layer, precipitation patterns,terrestrial and marine ecosystems, and human health, with unknown social, political, andeconomicoutcomes,”andimportantlimitationsinourcurrentearthsystemmonitoringcapacitytounderstandtheseimpacts.TheCommitteedid,however,cautiouslyendorsefieldexperiments,callingforrelatively“small-scalefieldexperimentswithcontrolledemissions”thatcouldadvancebothbasicunderstandingoftheclimatesystemandquantifysomeimpacts,bothintendedandunintended.Recognizingthatfield experiments themselves have important and uncertain ethical, social and politicalramifications, the NRC Committee also called for an open and deliberative research planningprocess,informedbytheactiveparticipationofcivilsociety,toweighoptionsfortheirgovernance.TheCommittee’srecommendationsserveasavaluablestartingpointforthenarrowerquestiononthetableforthisForum:thatis,whetherandunderwhatconditionstheUSgovernmentshouldfundsolargeoengineeringresearch.Forresearcherswhohavelongsoughttomoveforwardwithfieldexperiments,theallureofsuchfundingissurelystrong.Buttherisksarealsostrongthatsuchfunding,ifill-timedorill-designed,would,likethecalloftheSirens,drawusontodangerousand

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rockyshoresandunderminethegoalofensuringthatbothcivilsocietystakeholdersandothergovernmentsseeUS-fundedsolargeoengineeringfieldresearchasalegitimateendeavor.TobuildandsustainaresearchprogramwithlegitimacyintheeyesofkeystakeholderswithintheUSandaroundtheworld,wearguethatthefollowingfourconditionsshouldbemetbeforetheUSgovernmentfundssolargeoengineeringfieldresearch:

1. The US is aggressively supporting climate mitigation and adaptation and substantiallyinvestingincleanenergyresearchanddevelopment;

2. Anearthsystemmonitoringcapacityis inplacethatissufficienttodetectandattributeenvironmentalimpacts,bothintendedandunintended,fromfieldresearch;

3. TheUS is part of an international coalition of nations supporting solar geoengineeringresearch–acoalitionthatincludesnationsparticularlyvulnerabletoclimatechangeandhighcarbon-emittingnationsfullycommittedtoemissionsreductions;and

4. A research governance system is in place that is sufficient to address concerns overtransparency, liability and equity and is open to civil society input into its design andreview.

Weare,unfortunately,farfrommeetingtheseconditionstoday.Withregardtoconditions1and2(UScommitmentstomitigationandadaptationandaviableearth system monitoring system), it is almost surreal to be discussing US funding for solargeoengineeringresearchintheearlymonthsofanewAdministrationandCongressthatarebentonbackingawayfromournation’semissionsreductionscommitmentsundertheParisAgreementand slashing climate science and clean energy research and development budgets across thefederal government. TheTrumpAdministrationhasalsoproposeddeep cuts in satellite-basedearthsystemmonitoringsystemsthataresoessentialforthisresearch.FundingundertheseconditionswouldviolateacorepremiseoftheForum(ascharacterizedinthe invitation to participate in it) that “[d]ecisions about solar geoengineering research, andpossibly deployment, must be established with the understanding that it could only be asupplement–notasubstitute–foremissionsreductions”…andthat“[t]heworldmustcontinuetofullyimplementandgobeyond,thecommitmentsintheParisagreement.”Inthispoliticalclimate,astrongpushforUSfundingforsolargeoengineeringfieldexperimentswould almost certainly bemetwith very strong opposition from awide swath of civil societyorganizations–oppositionthatwouldjeopardizethesocietalacceptancethatsuchresearchwouldneedtobesustainedandpolicy-relevant.With regard to condition 3 (an international coalition of nations), the history of anothercontentiousclimatedebateisinstructive.WhentheKyotoProtocolwasestablished,aquestionhotlydebatedwaswhethermeasurestoslowtropicaldeforestationshouldbeincludedforcarboncredits in the Protocol’s Clean Development Mechanism. The scientific justification for theirinclusionwasstrong:tropicaldeforestationaccountedforroughly20%ofthesourceofannual

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anthropogeniccarbonemissionsatthetime.ASpecialReportoftheIntergovernmentalPanelonClimateChangeonthisissueprovidedfirmscientificsupportandseveralmajorUS-basedNGOs,including the Union of Concerned Scientists and the Environmental Defense Fund, advocatedforcefullythatclimatepoliciestoreduceemissionsfromtropicaldeforestationwouldcomplementenergysectorreductionsinemissionsfromtheUSandothermajorindustrializedcountries.ButdespitegoodscienceandthesupportofprominentNGOsandmajorUSfoundations,effortstobuildsupportforslowingdeforestationasaclimatemitigationmeasurewereangrilydenouncedbyinternationalNGOsanddevelopingcountriesthatweresurethiswasatricktoallowtheUSandothermajoremittersoffthehook.Advocatesforitwerenotseenaslegitimatemessengersandoureffortsfailed.Itwasonlyseveralyearslater,whenasmallgroupofrainforestnations,ledbyPapuaNewGuineawithNorwayasamajorfunder,steppedforwardtoembraceandleadsupportforthisthatanideatowhichmanyweredeeplyhostilebecamewidelyembraced.Today, support formeasures toreduceemissionsbyprotectingandrestoringtropicalforestsarelargelyuncontroversialandfirmlyestablishedwithintheParisAgreement.Thetropicaldeforestationcaseremindsusthatlegitimacydependsontheparticipationoftrustedactors.EstablishinglegitimacyofsolargeoengineeringresearchwilllikelyonlybeachievedoncethereisaninternationalcoalitionofcollaboratorsthatincludesnationsthatbringalegitimacythattheUSactingalonecannot,i.e.,vulnerabledevelopingnationsandothermajoremittingnationsunequivocallycommittedtodomesticemissionsreductions.Finally,with regard to condition4ondevelopingan inclusiveprocessof researchgovernance,thereareclearlymanyunansweredquestionsonwhatthiswouldlooklikeandmuchworkstillneedstobedoneinthisdomain.WelookforwardtotheoutcomesofthegovernanceinitiativeledbyJanosPasztorthroughtheCarnegieCouncil. It isessentialthatmeaningful“civilsociety”participationnotbelimitedtolargeUS-basedNGOs,butthattheprocessbringsintothedialogueparticipationfromorganizationsrepresentingdiverseconstituenciesandcommunitiesaroundtheworld.Thiswilltakeagooddealofwork,butitwillbecriticaltobuildandsustainlegitimacy.Today,averysmallnumberofexpertsandthought-leadersarewrestlingwithquestionsofsolargeoengineering. The potential value to society of understanding more about the risks andpossibilitiesofsolargeoengineeringtechnologiesisnotcurrentlyontheradarscreenofthevastmajority of colleagues working within the climate science advocacy and policy communities.Nevertheless,thesalienceofunderstandingthesetechnologieswillonlyincreaseasthesocietalrisks of temperatures rising well above the Paris targets become more widely apparent andacknowledged.Theopportunityandresponsibilityinfrontofusistoensurethatresearchisdesigned–andfunded–withgreatcareandinclusiontoensureitscredibility,salienceandlegitimacy.

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References Cash,D.W.,W.C.Clark,F.Alcock,N.M.Dickson,N.Eckley,D.H.Guston,J.JagerandR.B.Mitchell2003.Knowledgesystemsforsustainabledevelopment.ProceedingsoftheNationalAcademyofSciencesoftheUnitedStatesofAmerica.100:8086-8091.doi:10.1073/pnas.1231332100Gullison,R.E.,P.C.Frumhoff,J.G.Canadell,C.B.Field,D.C.Nepstad,K.Hayhoe,R.Avissar,L.M.Curran,P.Friedlingstein,C.D.Jones,C.Nobre.2007.Tropicalforestsandclimatepolicy.Science316:985-986.doi:10.1126/science.1136163.National Research Council.2015. Climate Intervention: Reflecting Sunlight to Cool Earth.Washington,DC:TheNationalAcademiesPress.doi:10.17226/18988.

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Letter to the Editors of the U.S. Solar Geoengineering Symposium

Anna-MariaHubert

AssistantProfessor,FacultyofLaw,UniversityofCalgary;

AssociateFellow,InstituteforScience,InnovationandSociety(InSIS),UniversityofOxford

ThankyouforyourkindinvitationtoparticipateinthissymposiumonU.S.solargeoengineering.Myreflectionsonthisemergingareaofclimatelawandpolicyaimtosituateourdiscussionsatthismeetingwithinawiderglobalframe.It isfromtheparticularvantagepointasascholarofinternational law that I share my perspective on U.S. solar geoengineering research and itsgovernanceimplicationsinternationally.Solargeoengineeringmethods,inparticular,stratosphericaerosolinjection(SAI),standapartasthemore“radical”approachesforaddressinghuman-causedclimatechange.10EstimatessuggestthatSAIhasthepotentialtooffsetsomeoftherisksofrisingglobaltemperaturesinarelativelycheapandquickway.Atmosphericmodellingexperimentspredictthat,dependingonhowit isdeployed,suchmethodshavethepotentialtoreducesomeoftherisksofclimatechange.Ontheother hand, SAI also poses new risks and uncertainties, including possible distributionalconsequences.SAInecessarilyactsglobally.Castingoureyestothe long-termhorizon,afull-scaleuseofsuchmethods raises the prospect of environmental management at an earth systems level. Adeployment of this nature clearly engages obligations of international law, andwould requiresignificant, perhaps unprecedented levels of international cooperation and coordination to becarriedouteffectively.At themoment, however, solar geoengineering proposals currently only exist in atmosphericmodelsorinthelaboratory.Somescientistsandpolicy-makersarguethatitistimethatresearchmoves outdoors so that we can learn more about the potential efficacy and risks of solargeoengineering. Furthermore, environmental perturbation experiments may provide a morefundamentalunderstandingabouttheatmosphereandchangingclimate.Arecent legallynon-bindingdecisiontakenbycountriespartytotheConventiononBiologicalDiversity(CBD)reflectsan evolving global institutional understanding of the need for research into geoengineeringmethods, noting that “more transdisciplinary research and sharing of knowledge amongappropriate institutions isneededinordertobetterunderstandtheimpactsofclimate-relatedgeoengineeringonbiodiversityandecosystemfunctionsandservices, socio-economic, cultural

10InternationalBarAssociation(IBA),ClimateChangeJusticeandHumanRightsTaskForceReport,AchievingJustice

andHumanRightsinanEraofClimateDisruption(July2014)<http://www.ibanet.org/PresidentialTaskForceClimateChangeJustice2014Report.aspx>accessed9February2015,176–77.

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andethicalissuesandregulatoryoptions.”11Thenextstepinsolargeoengineeringresearchislikelytoinvolveverysmall-scaleoutdoorfieldresearchalongthelinesofwhatProfessorKeithandothershaveproposedintheir2014articleina special issue of Philosophical Transactions of the Royal Society A.12 The SCoPEx experimententailsseedingasmallvolumeofsulphateparticlesand/orwatervaportotestthereactionsthatlimitozonelossinthestratosphere.Presumably,SCoPExwouldconductedonU.S.territoryandpose“verysmall”directenvironmentalrisksfrominjectingamere1kgofsulphuricacidinthestratosphere,“anamountthat is less thantheamountofsulphurreleasedbyonecommercialpassengerjetin1minuteofflighttime.”13YetifwedocrosstheRubiconbyconductingfieldtestsinvolvingsolargeoengineering,whatotherconsiderationsshouldbetaken intoaccount?Socialscientistspoint tothesocial,political,andethicalrisksofsolargeoengineering,whichincludesocio-technicallock-inandcreationofvestedinterests.Theimportanceofexperimentstothedevelopmentofatechnologytodeliberatelyalterthe global climate system highlights the geographically unbounded risk profile of solargeoengineering–evenfromtheoutset.Whatistheinternationalinterestinexperimentsthatposeno risk of transboundary environmental harm?Howdo these interests shape the design of agovernancearchitectureforsolargeoengineeringresearchlookingahead?Itmaysoundabsurdtoasksuchquestionsatthisparticularmomentinwhichseriousreservationsarebeingraisedaboutthefateoftheinternationalsystemasawhole.RecentlyForeignAffairsmagazine featureda seriesofessayson theAmerican retreat from its roleasdefenderof theliberal international order towardsmore isolationist politics. But thismarked shift in the U.S.administration’sforeignpolicy–particularlyontheissueofclimate–doesnotchangethefactthatwe live inan increasingly interconnectedworld.RichardHaaspointsout inhispiece that“[c]limatechangeisinmanywaysthequintessentialmanifestationofglobalization.Itreflectsthesumtotalofwhat isgoingon;countriesareexposedtoandaffectedunevenlybytheproblemregardlessoftheircontributiontoit.Borderscountfornaught.Thereisbroad,ifnotuniversal,agreementthatclimatechangeisreal,causedinlargepartbyhumanactivity,andconstitutesamajorthreattothefutureoftheplanetanditsinhabitants.”14Theseideasareeloquentlysummedup incountries’declaration in theUNFCCCthat“change in theEarth'sclimateand itsadverseeffectsareacommonconcernofhumankind.”15Asanemergingissueofclimatelawandpolicy,solargeoengineeringtouchesuponmanyglobalcommoninterests,includingtheprotectionoftheenvironmentandsustainabledevelopment,peaceandsecurity,humanrights,andequity.This

11ConventiononBiologicalDiversity(CBD)“Climate-relatedgeoengineering”(8December2016)UNDocUNEP/CBD/COP/13/L.4.12JohnADykema,DavidWKeith,JamesGAndersonandDebraWeisenstein,“Stratosphericcontrolledperturbationexperiment:asmall-scaleexperimenttoimproveunderstandingoftherisksofsolargeoengineering”(2014)372PhilTransA<http://rsta.royalsocietypublishing.org/content/372/2031/20140059>13Ibid.14RichardHaass,“WorldOrder2.0:TheCaseforSovereignObligation”(2017)96ForeignAffairs2,5.15UnitedNationsFrameworkConventiononClimateChange(adopted9May1992,enteredintoforce21March1994)(1992)31ILM851(UNFCCC),Preamble.

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global public goods character of solar geoengineering argues in favor of a degree of earlyinternationalcooperationandcoordinationofresearch,andthatitshouldbecarriedoutinawaythat is respectful of core principles and values, particularly those expressed in the 2015 ParisAgreement.Jurists distinguish between lex lata and lex ferenda – concepts that demarcate the differencebetween“lawasitis”and“lawasitshouldbe”.Thisspreadissignificantwhenoneconsidersthecurrent legal landscape of national and international law relevant to geoengineering research(which in my view remains underdeveloped and not fit for purpose) and more ‘optimal’governanceconditionsproposedintheacademicandpolicyliterature.Fromtheperspectiveofadvancingscientificunderstandingofsolargeoengineering,developmentofarobustgovernanceframework could actually facilitate research by providing legal certainty in the form of clearprocessesandgroundrulesgiventhatsolargeoengineeringissocontroversial.Theexamplesofnuclearenergyandgeneticallymodifiedcropsdemonstratethepossibilityofabacklashifwedonot handle solar geoengineering governance correctly. Bottom line, it is too important to getwrong.Researchandgovernancewillhavetoevolveinparallel,eachinformingtheother.Moreover,onecanenvisagethatgovernancewillbeamulti-stagedprocess,involvingdifferentlevelsandactors.Ausefulcontributionatthisstagewouldbeto initiateaprocesstodevelopanewgovernanceinstrument,suchasacodeofconduct,toprovideearly,flexibleguidancefordifferentresearchprojects,togetherwithgeneralprinciplesandprocedurestoguideresponsibleresearchandtoinformgovernanceprocessesforinnovationasitdevelops.16Coregovernanceprinciplesincludethe precautionary approach, risk assessment, public participation and transparency. Theinstrumentcouldprovideagap-fillingfunctionbypromotingearlycooperationandcoordinationof research consistent with the general principles, and notions of equity and sustainabledevelopmentadoptedinthe2015ParisAgreement.

16Anna-MariaHubertandDavidReichwein,“Anexplorationofacodeofconductforresponsiblescientificresearchinvolvinggeoengineering:introduction,draftarticlesandcommentaries”(2015)IASSWorkingPaper,InSISOccasionalPaperNo1.Potsdam&Oxford<http://www.insis.ox.ac.uk/occasional-papers/a-code-of-conduct-for-geoengineering-research/>.SeealsoGeoengineeringResearchGovernanceProjecthttp://www.ucalgary.ca/grgproject/;Anna-MariaHubert,TimKrugerandSteveRayner,“CodeofConductforGeoengineering”(2016)537Nature(Correspondence).

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Thoughts About Future Geoengineering Research

JaneC.S.LongLawrenceLivermoreNationalLab(ret)

Co-development of climate intervention technology and governance Callsforgeoengineeringresearchcontinuetogrow.Thetopicremainshighlycontroversial,inpartbecauseanypossiblechoiceaboutdeploymentofaglobalinterventionrequiresgovernancethatdoes not yet exist and perhaps never will. At least some governance capacity could grow bydevelopinggovernancesimultaneouslywithresearch.Researchshouldstartsmallwithoutdoorexperimentsthatposenegligibleriskbut illuminatephysical,chemicalandbiologicalprocessesthat underlie the behavior of intervention technologies. Such experiments provide an idealopportunitytodevelopsomeofthebasicelementsofgovernancebeforethereanyseriousrisksareinvolved.Imaginehowdifficultitwouldbetogovernexperimentsthatactuallyposedsomeriskifnoneofthebasicelementsofgovernancehadbeenassembledandexercised.Independent Advisory Body Proto-governancecanstartwiththeformationofanindependentadvisoryboardthatresearcherscanconsultforguidance.Anadvisoryboardcanprovideadviceonmanyoftheissuesdiscussedbelow, including the interface between science and society, methods to make transparencymeaningful, how to assess the value of research to society, and develop requirements andmethodologyforreviewandassessmentoftheresearch.Learningabouthowtocharterandstaffsuch a board should start early, perhaps informally, with the start of one-off early outdoorresearch.An advisory board can help with the interface between science and the public and policycommunities.Evenearlyresearchcanbenefitfromthecreationofapublicandpolicyinterface.Theinterfaceshouldbecomeanidentifiableeffortratherthantalkingacrossasharplinebetweenwhatisscienceandwhatissociety.Ittakesspecialskillstorepresentthescienceinawaythatismeaningful andenablesdiscussionof societal concernsandneeds. Even inearly research thisinterface effort can function to articulate key questions for research that both scientists andmembersofsocietycanrelateto.Forexample,scientistsmightbetryingtoanswerthequestion:Is technology X safe?More specifically:We know this potential harm that could accrue fromphenomenaY. This experimentwill help to answer thequestion:Will X affect Y?Membersofsocietymightagree(ornot)thattheywouldliketheanswerstothesequestions,buttheymightalso have their own questions, such as: Will X affect Z? The dialogue can help to focus andarticulate researchquestions.Thismaybeconceptuallyeasy,but inpractice it takes timeandattention.Evenifanengagedpublicagreeswiththeresearchquestions,theymayquestiontheneed for theproposedexperiment to answer them.Dialogueat this interface canhelp to geteveryoneinvolvedtounderstandthevalueofanswerstothequestionsbeingposedandwhetherthemethodsproposedaretrulyefficaciousandnecessary.

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Reliable Research Researchprogramsshouldbedesignedtoincreasetrustandconfidenceintheresults.Manyhaveidentified transparency as important for trust, but transparencywill have tomeanmore thanrevealingwhatresearchisbeingdoneorpostingtheexperimentaldata.Meaningfultransparencywill include exposing the intent of thework,why it is being done,whatwere the alternativemethodsof getting these results,what thequalityof theassociated information is,what isn’tknown,whataretheresearchers’hypothesesabouttheresult,andaftertheexperiment,howdotheresultscomportwiththathypothesis,whatwaslearnedandwhatshouldbedonenextandwhy.Wecanneverhopetohaveaprecisepredictionoftheresultsofaclimateintervention.Wecanhoperesearchincreasestheaccuracyofourunderstandingaboutthedirectionaninterventionwillgo. Ifovertimeresearchersbecomebetterandbetteratpredictingtheoutcomesof theirexperiments,thiswillincreaseconfidence.Ifpredictionsarenotmadeapriori,thisopportunityistruncated.Twenty-twentyhindsighthasmuch less impactonconfidencebuilding thanaprioripredictionandpostfactocomparisonofpredictionsandactualoutcomes.Reliability will also require more than the normal peer-review process to ensure that thegeoengineered system as a whole has been properly defined and appropriately investigated.Consequently,researchreviewandassessmentprocesswilllikelyneedtouseothermethodssuchasfundingteamsofresearcherstoidentifyweaknessesorerrorsmaybeonewaydealwiththisissue.Anadvisoryboardcanhelpguidesuchareviewprocess.Strategic Research Oneofthecommonethicalconcernsaboutgeoengineeringisthatitwilldistractpeoplefromthenecessity ofmitigation, known as the “slippery slope” problem. In truth, geoengineering-typetechnologiescouldnotkeepupwithanever-growingconcentrationofGHGsintheatmosphere.Theresearchcommunityknowsthatgeoengineeringascurrentlydefinedmakesnosensewithoutavigorousattempttomitigategreenhousegasesandthatadaptationwillbenecessary.However,the researchcommunityhas– likelyunwittingly --played into the“slippery slope”concernbydifferentiatingdifferent typesof geoengineering according towhat they think the governanceissuesare.Forexample,therecentNASreportongeoengineeringwasseparatedintoareportonSRMandoneonCDRbecausethesetechnologiesarecurrentlyseenasquitedistinct.Suchasplitserves the interests of scientists because it could minimize or tailor required governance ofresearchprojects.Butseparatingthegovernanceofthesetechnologiesforfeitstheopportunityandrequirementtodevelopaholisticclimatestrategy.Geoengineeringshouldonlybeused(ifatall)inconcertwitheveryothertoolwehavetocontrolclimatechange.Geoengineeringshouldneverbethoughtofasanindependenttechnology.But,unlikemitigationandadaptation,thecharacterofgeoengineeringinterventionisfundamentallystrategic. Because geoengineering cannot be used alone and the very idea of intervention isstrategic,theresearchenterpriseongeoengineeringcreatestheenvironmenttoatleastdiscussholisticclimatestrategies.Tocapturethisopportunity,geoengineeringbothcurrentcategoriesofgeoengineering should be brought under the same governance umbrella withmitigation and

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adaptationtheever-presentcontextforresearchandwhenever–ifever-possible,allstrategiesshouldbeencouragedintothesamegovernanceumbrella.Mission-Driven, Systematic Research Earlyexploratoryresearchtodatehaslargelybeeninvestigatordriven.Asresearchbecomesmoreserious and focused on specific technologies, the nature of research should become moreorganized. Geoengineering represents a large and complex systems problem involving manymoving parts. Investigator-driven research will not necessarily engage all the variousinterconnected aspects. For these reasons, at somepoint a geoengineering researchprogrammustbeasystems-investigation.Afterall,thefundamentalcharacteristicofgeoengineeringisthatitisengineering,i.e.asolutiondesignedtosolveaproblem.Anengineeringproject,particularlyoneofthismagnitudeandcomplexityrequiresathoroughinvestigationoftheentiresystem,oftencalleda“systemsapproach”.Mission-drivenresearchwascommoninthepast,buthasfallenoutoffavorforseveralreasons.Researchersoftenfindthattop-downmanagementofresearchleadstocorrupt,narrowcontrolorarecklessdisregardforcollateraldamage.Examplesincludethenuclearweaponsenterprisethatcreatedsignificantlong-lastingenvironmental insults,theChallengerdisasterthat lackedabottomupcommunicationmechanism,andevensomerecenttop-downbasicresearchprogramsthat led to management perceived as corrupt and self-serving. Never-the-less, defining thegeoengineeredsystemandinsuringathoroughinvestigationrequiressomeorganizedeffort.Careful thought about how to reinvent mission-driven research should attempt to ensuresystematicresearchinthepublicinterestwhileindividualcreativityandinitiativeremainstrong.This should startwith careful thought about defining themission itself. Certainly, themissionshouldnotbesimplytodevelopatechnologyforuse.Thedefinitionwillhavetobemuchmorenuanced and include articulation of a requirement to find out asmuch as possible about theeffectiveness,advisabilityandfeasibilityofgivenconcepts.Itshouldalsoincludearequirementtoreportfindingsthatindicateatechnologyisnotsuitablefordeployment.Thedefinitionofthemissionofresearchcouldbeanexcellenttopicforengagementwithpolicymakersandpublics,especiallyifthesegoalscanbearticulatedintermsofquestionspeoplehave.Forexample,nucleartestbantreatieswereenabledbyansweringthequestion:Cannucleartestsbe detected? Geophysicists demonstrated they could detect any weapons test conductedanytime,andthisinturnenabledratificationofthenucleartestbantreaty.(Likelydetectionandattributionwillalsobeamongthegoalsthatpolicymakerswouldlikeforgeoengineeringresearchaswell.)Institutionaldesignformission-drivenresearchwillrequirecare.Alloftheabovefunctionsneedtohaveahomeordefinedproceduresandprocessestoupdatethem.Beyondthat,bothindividualandinstitutionalmotivationandspecialinterestswillrequiremoderation.Researchersarelikelytopushforresearchonideastheythinkcouldbeimportantandtheywillnaturallyfeelidentifiedwiththeirsuccess.But,theresearchcharterneedstosomehowrewardbothresearchersandtheir

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institutionsforfindingthataproposedtechnologyisabadidea.Ourcurrentresearchenterpriserarelyrewardsnegativeresults.Summary Researchshouldstartsoonbecausetheremayonlybedecadesbeforeclimateconditionsbecomeextremelydifficultandtheknowledgebasewehaveaboutgeoengineeringremainsthin.Startingcarefullywithsmall,verylowriskexperimentsbutinawaythatdevelopsgovernancecapacityincaseitbecomesadvisabletodohigherriskexperimentsseemswise.

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Comments on Solar Geoengineering

DouglasG.MacMartinSeniorResearchAssociate,CornellUniversity

Toavoiddangerousanthropogenicclimatechange,theinternationalcommunityhasagreedonatargetofholdingthe increase intheglobalaveragetemperaturetowellbelow2°Cabovepre-industrial levels and to pursue efforts to limit the increase to 1.5°C. However, currentcommitmentstomitigationofCO2emissionsareexpectedtoresultinatemperatureriseoforder3°C.Achievinga2°Ctargetwithoutsolargeoengineeringremainstheoreticallypossible,butwouldrequireanimmediatetransformationofourenergysystemonamassiveandunprecedentedscale,along with rapid deployment of unproven “negative emissions” technologies; achieving 1.5°Cwouldberoughlytwiceashard.Furthermore,(i)thethresholdfor“dangerous”climatechangeisunclear, and 2°Cmay be insufficient, (ii) estimates of the climate sensitivity to increased CO2concentrationsremainuncertainandthereisa1/3chancethatthetemperaturerisefromcurrentmitigationcommitmentswouldexceed3°C,and(iii)this3°Cestimateassumesthatgovernmentsfollowthroughoncommitmentstoreduceemissions.Thesubstantialgapbetweenambitionsandlikely outcomes, combinedwith these additional risks,means that the potential role for solargeoengineeringtechnologiesneedstobeseriouslyconsidered.Solargeoengineering,suchasaddingaerosolstothestratospheretoreflectsomesunlight,cannotbeasubstituteforcuttingemissions,asthatwouldrequirelargeforcinglevelstobesustainedformillennia (Figure 1). However, climate modeling research to date suggests that solargeoengineeringusedinadditiontomitigationhasthepotentialtoreducemanyclimaterisks.The current state of knowledge is insufficient to assess whether the risks of deployinggeoengineeringoutweightherisksofnotdeployingit.Neitheroftheserisksarewellunderstood,andfuturedecisionscouldbedrivenasmuchbyanincreaseintheperceivedriskofnotdeployingastheyarebyimprovementsinourunderstandingofgeoengineering.Theworldcouldpass1.5°Cwithin the next few decades, and there is a risk of poorly-informed decisions being made ifresearch is not conductedwith some degree of urgency. Developing the required knowledgedemandsastrategic(mission-drivenorgoal-oriented)researchprogram.Informed decisions will require identifying different options for deployment (including nodeployment),projectionsoftheclimateresponseandhuman/ecosystemimpactsforeachoption,togetherwithanassessmentoftheconfidenceinthoseprojections,andstrategiesformanagingadeployment;decisionswillalsorequireincreasedconfidencerelativetotoday.Thisfocusontheend-goalofsupportinginformeddecisionsleadstobroaderresearchquestionsthatgobeyondtheexploratory researchconducted todate.Forexample,climate impactswilldepend on how geoengineering is deployed (e.g., the latitude(s) for injecting stratosphericaerosols). How well could we design a deployment to achieve specified objectives, whileminimizing risks, in the presence of uncertainty in the climate response? This problem is an

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engineeringdesignchallengerequiringasystems-levelapproach,andnotsimplyaclimatesciencequestion.Questionssuchas“whathappensifweinjectaerosolsattheequator”havearoleinunderstandingtheclimateresponseinmodels,butshouldnotbeinterpretedasanindicationofwhatgeoengineeringmightdo.Asasecondexample,simplystatingthatimpactsareuncertainisnot sufficient. Assessing the confidence in projected impacts requires an assessment ofuncertainties in climate models: how uncertain some process could be, how sensitive theconclusionsaretothatuncertainty,whatdataorexperimentsmightreducethatuncertainty,andwhether there are strategies that couldmanage the remaining uncertainty. Large engineeringprojectsmaintaina formal risk registry toprioritizeand track such issues; a strategic researchprogram might benefit from similar methodology. These examples are not exhaustive; forexample,researchwillalsoberequiredtomorethoroughlyexplorestrategiesforattribution,andinterdisciplinaryresearchbetweenthephysicalandsocialsciencesisalsoessential,associetyistheultimate“customer”ofthisresearch.However,theseexamplesaresufficienttoillustratetheneedforsystems-level,mission-drivenstrategicresearch,withthefirststepbeingtoclearlydefinewhatsuchaprogramwouldlooklike,takinginputfromtheclimate-policycommunityonwhattheyneedasoutputsfromresearch,anddefiningaplantogeneratethatknowledge.Mitigation alone is unlikely to avoid serious climate damages, and we need to exploregeoengineeringaspartofanintegratedportfolioofoptionsformanagingclimatechange.Therewillalwaysbebothknownandunknownimpactsfromeitherthechoicetodeploygeoengineeringorthechoicenotto.However, ignorance isnotanoption.Weurgentlyneedastrategic,goal-orientedresearchprogramwiththeaimofsupportinginformeddecisionsinnomorethan15to20 years. This program needs to determinewhat geoengineering can and can’t do,what theimpactswouldbe,andwhattheuncertaintiesandrisksare.

Figure 1. Reducinggreenhousegasemissions,combinedwithfuturelarge-scaleatmosphericCO2removal,mayleadtolong-termclimatestabilizationwithsomeovershootofdesiredtemperaturetargets.Thereisaplausiblerolefortemporaryandlimitedsolargeoengineeringaspartofanoverallstrategytoreduceclimaterisksduringtheovershootperiod.(Geoengineeringinsteadofmitigationwouldrequireextremelylargeforcingtobesustainedformillennia,andisthusnotrealistic.)Thisgraphrepresentsclimateimpactsconceptually,notquantitatively.

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Essay for the Forum on U.S. Solar Geoengineering Research

JosephMajkut

DirectorofClimateScience,NiskanenCenter

The recordhighglobal temperaturesof thepast fewyearshavepreviewedofaworld inchingclosertodangerouswarming.Encouragingly,thefallingcostsoflow-carbonenergyandpoliticalagreementachievedinParisalsosuggestaworldmovingtowarddecarbonization.However,itisincreasinglyclearthatavertingdangerousclimatechangethroughmitigationalonewillbeabigreach.Solargeoengineeringcouldcomplementmitigationand further reduceclimate risk;butlittle is known regarding how or when to use it.We should not leave future leaders in suchignorance.Research into solar geoengineering has always had a frustrating dual character. Scientistsinterested in the climate have routinely supported geoengineering research programs andsporadicallyofferspecificplans.YetadedicatedresearchprogramhasnotfoundpoliticalsupportintheUnitedStates.Conservativesmaintainthatclimaterisksarenotworthmuchconcern,andenvironmental groups are wary of implementing solar geoengineering, worrying that evenresearchingtheideawilldiminishsupportforreducingCO2emissions.Withoutpoliticalbacking,theidearemainsontheshelf.TheprospectsforsolargeoengineeringresearchdependonhowmuchpoliticalsupportcanbebuiltwithintheAdministrationandCongress.Supportwouldideallybedurableandwidespread,toprovidestablefundingandagovernanceprocessforanysolargeoengineeringexperiments,especially in situ. Examining the reasons why different constituencies would support solargeoengineeringmayrevealopportunitiesofthemoment.Republicans General ambivalence about climate risk amongst Republicans in Washington is increasinglyuntenable. Mounting political pressure and shifting public opinion are starting to crack thebedrock of climate skepticism on the political right, resulting in increasing interest in climatesolutions from congressional Republicans. This presents an opportunity to build support fromRepublicanmembersofCongressforsolargeoengineeringresearchprograms.SupportingsolargeoengineeringresearchcouldhelpRepublicansgainsomepolitical legitimacyon climate change. Unlike smaller forays into clean energy research and development, solargeoengineeringresearchisresponsivetotheactualscaleofclimaterisks,andcouldbeparticularlyattractive if the costs of adaptation ormitigation suddenly appear too high.Moreover, someconservativesmaybeswayedbythenationalsecurityargumentforbeefingupthecapabilityofthe United States to monitor whether other countries are testing or implementing solargeoengineeringthemselves.

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Furtherstudymayreveal that therisksofsolargeoengineeringareunacceptable,or thesamereluctance to accept central planning and internationalism hindering support for mitigationpoliciesmaykeepConservativesfromfullyembracingsolargeoengineering.Thepoliticalquestionsaboutwhosetsandpaysfortheglobalthermostatareimmenseandmightnothavepoliticallyacceptableanswersforconservatives.Yetwemayalsofindthatsupportforsolargeoengineeringcould help climate-interested Republicans move toward a strategy of managing climate risksthrough other policies. Doing so could inspire positive developments not just for climateengineeringresearchandgovernance,butmitigationandadaptationpolicyaswell.Environmental Groups Environmentalgroupsfearthatpolicymakerswillembracesolargeoengineeringasanexcusetoallow unmitigated greenhouse gas emissions. Indeed, this seems like the central reason whyenvironmentalgroupshavebeenreluctanttosupportresearchprograms.Thisisvalidconcern,butnotaguaranteedoutcomeofaresearchprogram.Basic cost-benefit analyses predict massive returns associated with solar geoengineering, farbeyond those of mitigation policies. The calculations can look almost comical, with solargeoengineering returning incredible reductions in climate damages and implying thatdevelopment of solar geoengineering capability should be a priority. Indeed, Bickel and Lanesupportedmassivefundingforsolargeoengineeringresearch17basedoncost-benefitcalculationsshowingthatitpaysbackatahugerate.Itisreasonabletothinkthatsolargeoengineering,onceproperlyvetted,couldbetoogoodforpolicymakerstoignore.Thepoliticalcostsofclimateactionandinternalizingthecostsofclimatechangetobusinessesandconsumersgloballyarelarge.Forthosewaryofthecostsofclimatechange,solargeoengineeringcouldlooklikeaneasyoutfromthehardworkofmitigation.Towhat extent should environmentalists fear the temptation to replacemitigationwith solargeoengineering?TheParisAgreementestablished internationalclimateactionas thenorm.Asfinancial investments shift to low-carbon energy infrastructure and cost curves plummet, thequestionsaboutdecarbonizationseemmoreabout“when”than“if”.Thesedevelopmentsdrainsomepowerfromtheargumentsthatsolargeoengineeringresearchwillcreateamoralhazardbydisincentivizingmitigationactivities.ThefearthatsolargeoengineeringwillgivefossilfuelsafreepasstoraiseatmosphericCO2andburdenfuturegenerationswiththeneedtoforevercounteranenormousgreenhousewarmingseemsoutofdate.There is a large range of possible climate outcomes between the worst-case and best-caseemissionsscenarios.AkeyinsightfromBickelandLaneisthatthebenefitsofsolargeoengineeringare largest when mitigation policies fall short in terms of ambition or participation. Astemperaturesclimbhigher,marginal reductions fromsomesolargeoengineeringhavea largerimpactforthesamecostofdeployment.Whilethisfindingresultsfromtherelativelyneatcost-benefit analysis of an integrated assessment model, it makes intuitive sense that solar

17http://www.copenhagenconsensus.com/sites/default/files/ap_climate_engineering_bickel_lane_v.5.0.pdf

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geoengineeringinterventionswillbemostneededifmitigationpoliciesfallshort.Despiterecentprogress in clean energy and climate politics, we may well find ourselves on too anemic amitigationpath,andenvironmentalgroupsshouldconsiderthispossibility.Trump Administration Ifaseriousefforttoresearchsolargeoengineeringistobeginsoon,theTrumpAdministrationisthe crux. The new Administration is uninterested in addressing climate risk and plans to cutfunding for climate science and monitoring efforts. Despite generally favoring technologicalprogressandincreaseduseofspace,theAdministrationisunlikelytopursueasoberandcarefulsolargeoengineeringresearchprogram.While funding support can come from Congress, a reasonable research program for solargeoengineering is impossible without administrative support. Making solar geoengineeringresearchacceptabletothepublic,membersofCongress,andothercountriesrequiresinteragencycoordinationandexecutivebranchoversight.U.S.governmentoversightwillbekeytoavoidtreatyconflictsor conflicts fromdomestic environmental regulationand lawsuits. Thepotential legalliabilities,politicalopposition,andinternationaldiscordthatcouldcomefromanythingbutthesmallestexperimentsaremassive.Lackofadministrationsupportmaybethebiggestchallengetogettingaresearchprogramoffthegroundinthenextfewyears.FindingawaytoconvincetheTrumpAdministrationtojudiciouslysupportsolargeoengineeringresearchwillprobablybeataskoftrialanderror.Givenitsfocusonnationalsecurityanddefense,aresearchprogramgearedtowardnationalsecurityandcompetitivenessisadecentfirstbet.WithgrowingresearchprogramsinChinaandEurope,theUnitedStatesisindangeroffallingbehindtheforefrontofresearchintosolargeoengineering.WhetheracompetitivedisadvantagewillspurtheAdministration’sinterestisupinair.Path Forward In anydedicated researchprogram, thegapbetween researchand implementation shouldbeclearly articulated. While geoengineering technologies might provide a viable and relativelyinexpensivewayofwardingofftheworstimpactsofwarming,thereareplentyofreasonstobewaryoftheirimplementation.Howtheclimatewillrespondandhowanyimplementationofsolargeoengineering would be monitored and governed must be thoroughly explored. Near termresearchintothesequestionswillhelpfuturegenerationsmakebetterdecisions.Butbeforewegettoneartermresearch,wewillneedtoperformapoliticalbalancingacttoworkagainstdeflatingresearchbudgets,ambivalenceaboutclimateriskintheAdministrationandsomepartsofCongress,andthereluctanceof theenvironmentalgroups.Thestrangebrewofsomeclimateaction,butnotenough,andthenewprominenceofclimate-interestedRepublicanscouldhelpusgetthere.

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Lessons for Geoengineering from Same-Sex Marriage

OliverMortonSeniorEditor,EssaysandBriefings,TheEconomist

Itiseasiertochangeyourmindthantochangethephysicalbasisofhowyoulive;butyoustillneed

areasontodoso

Some years ago, in a public debate about geoengineering, a liberal American brought up thesubjectofsame-sexmarriage.Itdemonstrated,heargued,howquicklyapolicyobjectivecouldgofrombeingmoreorlessunthinkabletobeingprettynearlyunstoppable.Ifthatcouldhappenforsamesex-marriage,heasked,whycoulditnothappenforswiftanddeepemissionreductions?And if it could, surely it would be better to concentrate onmaking that happen rather thandistractingourselveswithideasofgeoengineering?Isawthisasaflawed–indeed,rathersilly–analogy.Theshiftawayfromfossilfuelsraiseshugeissuesaboutinvestment,vestedinterestsandinfrastructure,aswellastechnologicalreadiness,inawaythatthefightforsame-sexmarriage–demandingthoughitwas–simplydidnot.Butlateritstruckmethat,whiletherapidandlinkedshiftsinpolicyandopiniononsame-sexmarriageheldfewlessonsforemissionsreduction,theymightbeilluminatingintermsofwhatcouldbepossiblein the field of geoengineering itself. After all, the objections to pursuing policy and researchagendasthatmightresult ingeoengineeringarenotthatitwouldbeverydifficulttotryitout.Theyarethatitwouldbeabadideatotryitout–justasmanypeoplethoughtthattryingoutsame-sexmarriagewasabadidea.Andastheexampleofsame-sexmarriageshows,argumentsaboutideasthatareunpopularbutnotparticularlyimpracticalcanbeturnedaroundfairlyquickly.Two aspects of the fight for same-sex marriage seemed particularly salient. One: it had toovercomeoppositionbasedonadistinctionbetweenthe“natural”andthe“unnatural”.Two:itencounteredsignificantoppositionfromestablishedadvocatesfortherightsofgaypeople–theveryrightsthatthemarriageactivistssoughttoextend.Manyopponentsofsame-sexmarriageconsideredhomosexualactsunnatural--thoughtheyare,as it happens, common throughout the animal kingdom--and/or held that the natural role ofmarriagewasprimarilyasasettingforprocreation.TheirsenseofthenaturalinthesematterswasoftenconflatedwithabeliefthatintheserespectsnaturereflectedthewillofGod.Counteringtheseargumentswasnotamatterofshowingthemtobewrong,butofprovidingotherplausibleand indeed attractive frames in which same-sex marriage looked much more natural. Thusproponentsstressedthenaturalurgeforhumanstoformlovingpair-bondsandaninterpretationofhumannatureassomethingwhichincludedthepossessionofcertainnaturalrights.Toweakenresistancetogeoengineering,then,thetaskwouldbetofindwaysinwhichitmightseemmorenatural.StressingthefactthatvolcaniceruptionsalreadycooltheEarthinsimilarwaysmighthelp,butprobablynotthatmuch:thekeytogeoengineeringistheintention,andvolcanoes

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havenoplanswhentheyblowtheirtops.Morepromising,perhaps,wouldbetostressargueanaturalurgetocarefortheenvironment–abiophiliathatcanbeitsownjustification.Naturalizethereasonsforgeoengineering,nottheprocess.Linked,butnotidentical,totheideaofthenatural isthatofthenormal.Marriagewas,andis,normal;successfulsame-sex-marriagerhetoricsoughttosimplyextendthisnormality(perhapsthemostinfluentialbookonthesubjectinthe1990swasAndrewSullivan’s“Virtuallynormal”)topeoplenotatthetimelicensedtoenjoyitscharms.Theanalogyisnottight,butsomethingsimilarmightbedoneforgeoengineeringifitwereregularlyportrayed,say,asanovelexpressionofanormal activity, suchas collectivemobilization in response to a threat, rather than somethingfundamentallyother.Thesecondpointofcomparisonisoppositionfromthosewhoostensiblysharethesamegoals.Initsearlyyearstheissueofgaymarriagewassidelinedbymainstreamgayactivismforanumberofreasons.Somesawitasafreedomthatwouldneverbegranted,orwouldbeofinteresttoveryfew,andthusthatputtingeffortintoitwouldnotbeworththeopportunitycost.Othersheldthatthe purpose of gay liberation was to establish freedoms of behavior that went beyond theinstitutions of heterosexual society, and that seeking to buy into an institutionalized norm ofmonogamyonthestraightworld’stermswasnotmerelyawasteoftimebutantitheticaltothatbroaderemancipatingideal.Boththeseargumentshaveanaloguesinthewaythatmanyintheenvironmentalmovementthinkaboutgeoengineering.Somethinkthatitwillsimplynothappen,perhapsbecausepeoplewouldnever want it to, and thus is not worth taking seriously. Others think that the purpose ofenvironmentalactivismistocreateanewrelationshipbetweenhumansaspoliticalandeconomicactorsandtheworldaroundthem.Thepromptdownfallofextractiveindustriesfitsthisagenda;themaintainingofthestatusquothattheyseeingeoengineeringseemstoruncountertoit.Here the response for people seeking to promote a climate of opinion more open togeoengineeringmight be to stress the reduction of harm, both to humans and to the widerenvironment,andacommitment toabroadchurch.Successful strategieswould includeneverportrayinggeoengineeringasanalternativetootherformsofenvironmentalaction,andinsteadalwaysportrayingitasacomplementtoallsortsofotherclimateactionthatisaimedspecificallyatreducingharm.Theshiftinclimatenegotiationstoagreaterfocusondamageandloss,aswellasagrowingapprehensionofneartermriskshouldbeusefuldevelopmentstothisend.Buttheyhaveyettoproveso.If this provides some hope for those who want to see a greater focus on proposals forgeoengineeringindiscussionsofclimateaction,though,otherlessonsfromthefightformarriageequalityarelesshelpful.Same-sex-marriagecampaignerswereabletofightpiecemeal,inmanydifferentjurisdictions,throughlegalaction;thosefightsbothhelpedtochangepublicopinionandcouldgoonwithoutitssupport.Theremaybesomeanalogieshereforgeoengineeringresearch(and if thereare, theymightcall intodoubt thewisdomofattempting to fixex-anteuniversal

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standardsforthegovernanceofsuchresearch).Butdiscussionsofdeploymentwould,andshould,beverydifferent.Anotherpointofdivergenceisthequestionofharm.Opponentsofsame-sexmarriageclaimedthatitwoulddoharmtomarriageasaninstitution.Neveraparticularlyplausibleargument,itwasfatallyweakenedasaresultoftheincreasedvisibilityofpeopleinlong-termgayrelationships–especiallythosewithchildren–andthroughvictoriesinthecourts.Theevidencethatgaymarriagehadnorealeffectofanysortonanyoneelse’smarriagebuiltupquitequicklywellbeforethefightwaswon—asdidtheevidencethatbeingabletoleadmarriedorclose-to-marriedlivesaddedtomanygaypeople’shappiness.Makingsomepeoplehappywhilenotreallyharminganyoneelsebecamearelativelyeasysell(thoughitshouldbenotedthatthereremainsasignificantresidueofopposition to same-secmarriage). Thisprovidesnomessageof cheer for geoengineering. Thepotentialfordamageandharmduetogeoengineering isfarmorepersuasivelydisturbingthanwasthecaseforsame-sexmarriage,anditwouldnotbeeasilyreducedthroughafewproofsofprinciple.Andthenthere isa third,andperhapsdefinitive,pointofdivergence.Therewerepeoplewhoreallywantedsame-sexmarriage,bothforthegoodofsocietyandasapersonalpossibility.Onlya few, tobeginwith–butenough tocometogether, to strategize, to influenceothersand tocampaign.And therewerealsopeoplewho thought itmadesensenot simply to ignore thesepeople,buttofightthem–thusraisingtheirvisibility.Thereisnoequivalentconstituencywhichbelievesingeoengineering.Therearesomewhothinkthatthepossibilityneedstobeexploredmuchmorethoroughlythaniscurrentlythecase,withaneye to developing safe, just and governable interventions for which it would be possible tocampaign.Butthatisafarmorenuancedpositionthan“MyrighttomarrythepersonI loveisbeingabridgedandIamsuffering”.Andeveninitsnuancedform,therearefewwhoadheretoit.Withoutanyonefightingforit,thereisnoneedforanyonetofightagainstit–andthusitispossibleformainstreamdiscoursetoignorethesubjectmoreorlesscompletely.Itmaybemucheasiertoshiftopinionongeoengineeringthanpeoplethink;itisquitelikelythatitwould be easier to shift opinion on geoengineering than itwould be to radically accelerateemissionsreduction.Butitwillneverhappenunlesstherearepeoplecampaigningforittohappen,andmakingafusswhenpeopledonotconsideritapossibility,orlaughaboutitasanaside.Intheabsenceofproponentsforchange,therewillonlyeverbethestatusquo.

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Toward Governance Frameworks for Solar Radiation Management

JanosPasztor

SeniorFellow,CarnegieCouncilforEthicsinInternationalAffairs;

ExecutiveDirector,CarnegieClimateGeoengineeringGovernanceInitiative(C2G2)

Climategeoengineering–large-scale,deliberateinterventionsintheEarthsystemtocounteractclimate change – has been a subject of growing interest and debate within the scientificcommunity,butisstillanewobjectofconsiderationwithinpolicycirclesandinthepublicsphere.The potential deployment of climate geoengineering interventions raises many questions,including uncertainty regarding their effectiveness and indirect effects, as well as questionsregardingtheethicsoftheiruseandtheirgovernance.Achieving the ambitious temperature goals of the Paris Agreement would require rates ofmitigationfarinexcessofwhathasbeenachievedtodate.Agrowingnumberofscientistsandpolicymakersbelievethatactionswellbeyondexistingmitigationplansmaybenecessarytokeeptemperaturesbetween1.5-2°Cabovepre-industriallevels.It is in thiscontext thatattention is turningtowardsawiderangeofproposedgeoengineeringtechniquestocooltheplanet.Suchtechniquesareusuallygroupedintotwocategories:carbondioxideremovaltechniques,whichaddresstheprimarysourceofclimatechange-excesscarbondioxideintheatmosphere,whilesolarradiationmanagementtechniquesaddressthesymptom–increasingtemperatures–byreflectingaproportionofthesun’sradiationbackintospace.Thelatter could provide a breathing space to undertake a radical decarbonization of the globaleconomy.Ultimately,inordertoachieveastableclimate,itwillbenecessarytoachievezeronetemissions– reducing emissions significantly and counteracting any remaining emissions through carbondioxideremoval.Untilwereachthispoint,policymakersmayconsideracombinationofbothsetsoftechniquesasameanstoavoidtheworsteffectsofclimatechange.However, governance issues arising out of the broad range of proposed geoengineeringtechniques, in particular solar radiation management, pose a range of challenges. There iscurrentlynosystematic,coherentsetofglobalgovernanceframeworksinplacetoguidefurtherresearch,facilitatedecisionmakingandguidepotentialdeployment.Governance,inthisinstance,goesbeyondcontrolanddecisionmaking,andincludestheeffectiveparticipationofthosewhowouldbeaffectedandimpacted,aswellastheiraccesstoprior,relevantinformation.A growing number of scientists believe that the aggregate risks of environmental and socio-economicimpactsfromsolarradiationmanagementwouldbesmallincomparisontothebenefitof reducing global temperatures. However, the distribution of benefits and harms would be

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unequallyspreadbothintermsofregionsoftheworldandintermsofbetweencurrentandfuturegenerations. Inaddition,currentscientificknowledge leavesasignificantmarginofuncertaintyregardingtheexacteffectsofinterventions,includingtheirnature,scaleandlocation.Deploymentthereforeraisesissuesregardingthecriteriaand,mostimportantly,themechanismsusedtomakedecisionsaboutwaysofbalancingpossiblepositiveglobalimpactsandnegativeregionalorlocalimpacts,includingtheneedforpotentialcompensationtoaffectedpopulations.Another set of issues relate to the dangers of unilateral interventions. In the absence ofmultilateralagreementsthereisapossibilitythatasmallgroupofcountries,asinglecountry,alarge company or indeed a wealthy individual might take unilateral action on climategeoengineering. This raises the possibility that thosewho do not like these actions and theirimpactscouldengageincounter-climate-geoengineering.Clearly,itwouldbebesttoavoidsuchachaoticanddangerousfuture.Climate geoengineeringwould require global governance frameworks, of which, at best, onlysome elements exist today. These frameworkswould have to be developed in parallel to thetechnologiesthemselves.Withinthecurrentglobalgovernancearchitecture,itwouldseemthat,givenitsglobalimpacts,onlytheUNGeneralAssemblycouldgive legitimacytoanygovernanceframeworkguidingthepotential deployment of climate geoengineering. Actualwork, however, could bemademoreefficient by other measures. One option could be to undertake it within a professionalinternationalauthoritywithamandate fromtheUNGeneralAssembly, similar to theway theinternationalcommunityaddressespeacekeepingornuclearproliferation.Thereisscopeforthedevelopmentofotherandpossiblybetterapproachesinvolvingallrelevantstakeholders.The following questions would need to be addressed in order to develop robust governanceframeworks. Who would control the “global thermostat”? How would decisions be made tobalancetheneedtoreducetheglobaltemperaturewithunequalregionalandlocalimpactsacrossthe globe? How would trans-border and transgenerational ethical issues be addressed? Howwould decisions bemade to balance the costs and benefits of traditionalmitigationmethodsversusclimategeoengineering?Whatwouldbetheimpactsintermsoflocalandglobaljustice,and in terms of human rights, and how could these be addressed? Howwould the requiredgovernanceframeworkswithstandpotentiallysubstantialgeopoliticalchangesoverthedecadesandpossiblycenturiesthattheyneedtobedeployed?Howmightsuchtechniquesbedeployedinamannerthatdoesnotunderminethewilltocutemissions?Howwoulddecisionsrelatingtotheprofile of deployment – the rate of starting, continuing and stopping such techniques – begoverned? This last issue is of particular concern with respect to proposed solar radiationmanagementtechniques,asasuddencessationofdeployment(the“terminationeffect”)wouldresultinarapidriseintemperatures.The research community has been addressing many of these issues, but the global policycommunityhasnot,anditistimetobegintodoso.

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Governance of research in this area also needs to be developed – ideally parallel to thedevelopment of further scientific and socio-economic understanding, so that as researchprogresses,governancemechanismsevolveandviceversa.Theresultsoffurtherresearchinthisarea could be much strengthened, and better accepted by different constituencies, ifaccompaniedby transparentprocedures for sharing researchplansandexpectedoutcomesofresearchexante;havingindependentbodiesreviewresearchplansandprovidefeedbackexante;andcommittingtomeaningfulpublicengagementintheprocessbothexanteandexpost.Governance in this spacehas two roles:on theonehand it couldact tocontrol, regulateandpotentiallyrestrictresearch,whileontheotherhanditcouldacttoenableresearch.Developingsuchgovernancerequiresactiveengagementwiththepublicandpolicymakersandwouldneedtobecongruentwiththeachievementofagreedobjectivesforsustainabledevelopment.TherecentlyinitiatedCarnegieClimateGeoengineeringGovernanceInitiative(C2G2)seekstohelpfillthegovernancegapinrelationtoresearchandpotentialdeploymentofclimategeoengineeringbyencouragingpolicydialogues;throughtransparentengagementofrelevantstakeholders;andbycatalyzingthedevelopmentofdifferentelementsofthegovernanceframeworksneeded.

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Geoengineering Using Aerosol Particles: Knowns and Unknowns

JoyceE.Penner

RalphJ.CiceroneDistinguishedUniversityProfessorofAtmosphericScience,UniversityofMichigan

Solargeoengineeringpromises tobeable todecreaseEarthsurface temperatures to staveoffdangerousincreasescausedbygreenhousegases.Yet,anysuchdecreaseisonlya“mask”fortheunderlyingcausesthatwouldalmostimmediatelyreturnifgeoengineeringstopped.Whilesomemay think that a temporarymasking, in combinationwithmitigation of CO2 emissions, couldpreventthehighesttemperaturescausedbyCO2increasestobeavoided,itisnotatallclearhowefficientlythismightbeaccomplished,nor is themaximumtemperaturechangethatmightbeavoided clear. A program of research that included a set of realistic field experiments wouldbenefitboththeuncertainknowledgeofhoweffectiveanygivengeoengineeringstrategymightbeandwouldalsobenefitimportantuncertainaspectsinEarthSystemScience.Solargeoengineeringworksbyreflectingincomingsolarradiation,therebydecreasingtheamountavailabletowarmtheEarth.Therearetwomainmechanismsthathavebeenstudied:1)injectingSO2intothelowerstratosphere,similartolarge-scalevolcaniceruptions;and2)injectingparticles(mainlyseasaltparticles)intotheboundarylayerneartheEarth’ssurfaceovertheoceans.WhilevolcanicaerosolshavebeenshowntodecreasetheEarth’stemperature,theimpactofthemost recent (and best studied) large-scale eruption, Pinatubo in 1991, on Earth’s surfacetemperature is debated (Canty et al., 2013), and so, even though we have estimated themagnitudeof the injectionofSulfur (approximately20TgSO2),wearenotentirely sureof itstemperatureimpact.In addition to being able to predict the temperature impact of any given strategy forgeoengineering,inordertoplananymitigationaugmentation,weneedtobeabletodeterminehowanygiven injectionstrategy impacts incomingsolar (andoutgoingterrestrial) radiation. Inordertoknowthis,weneedtoknowthesizeoftheparticlesthatwillform,therateatwhichtheparticles are removed from the stratosphere (and then their rate of removal from thetroposphere),andfinallywhethertheseparticlesmightformcirruscloudswithinthetroposphere,andiftheydo,whetherthesecirrusfurthercoolorwarmtheclimate.HowtheinjectionchangestheEarth’sradiativebalanceistermedits“radiativeforcing”andalltheabovequestionsareaimedatgettingabetterhandleontheradiativeforcingassociatedwithagiveninjection.ModelshavebeenusedtotrytoestimatetheefficiencyofinjectionofSO2(Cirisanetal,2013;English,etal.,2012.;Niemeieretal.,2011;Niemeieretal.,2013;Pierce,etal,2010).Interestingly,theefficiencyofstratosphericinjectionappearstodecreasewithincreasinginjectionratesofSO2(Niemeieretal.,2015).

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Beyondtheradiativeforcing,asnotedabove,weneedtobeabovetopredictthetemperatureresponseoftheEarth’ssurfacetoagiveninjectionstrategy.Asnotedabove,eventhisisuncertain(asistheresponseofclimatechangetoCO2).Inaddition,other“climateresponses”arenotwellknown.Theseincludetheextenttowhichprecipitationmightchange,andwherethesechangesmightoccur,theextenttowhichstratosphericO3mightchange,andwhethersuchchangesmightcauseadditionalstratosphericcirculationchanges,andtheextenttowhichvegetationmightbeaffectedbythedecreaseddirectsolarradiation(andincreaseddiffuseradiation,causedbythescatteringofthedirectbeambyparticles).Baringanothernear-termlargevolcaniceruptionthatiswell-instrumented,fieldexperimentstodetermine the radiative forcing associated with SO2 injection seem themost feasible way toadvanceourunderstandingoftheeffectivenessofagivengeoengineeringstrategy.Improvingourunderstandingof the climate response to a given radiative forcing, unfortunately, invokes theentiresuiteofissuesinvolvedinpredictingclimatechange,andthus,seemsbeyondourabilitytoadvance using field experiments. However, we may be able to test our understanding ofmicrophysicsandthesizedistributionofparticlespredictedbymodelsusingfieldexperiments.However,Ibelieveratherlargeinjectionexperimentswouldbeneededtoenablesufficientsignalto noise, and we would want to accompany these with aircraft measurements designed todeterminetheresultingparticlenumbers,sizeandlifetimeinthelowerstratosphere.Injectionofperhaps2millionmetrictonsofSulfur(asSO2)intothelowerstratospheremightbesufficienttodeterminetheparticleresponsetoinjection,toallowtestingofmodelsandtodeterminethetimehistoryofremovaloftheparticles.Butinjectionsofthissize,arelargeenoughthattheygetclosetoactualdeployment.Moreover,itisunlikelythateffectsontemperature,cirruscloudsandwatervapor,couldbedeterminedwithsufficientaccuracy.Marinecloudbrighteningisthesecondmechanismproposedtodecreaseincomingsolarradiation.Sea salt particles are naturally formed over the oceans as a result of the wind and resultingturbulencecreatedattheocean’ssurface.Oneproposalistoenhancetheproductionofseasaltaerosolparticles,throughadesigninvolvingshipscruisingovertheopenoceanandspewingupseasaltparticles(Latham,1990).Theprimaryscientificuncertaintyassociatedwithmarinecloudbrighteninghastodowiththeextenttowhichincreasedparticleconcentrationswithinthemarineboundarylayeralterclouds.This aspectbringsuponeof the largestuncertaintiesassociatedwithunderstandinghistoricalclimatechange:Howdoparticlesinteractwithcloudstochangetheirmicrophysicalnature(e.g.droporcrystalsize),theamountofwaterstoredwithinclouds(e.g.theliquidwaterpath)andtheir cover (e.g. the sky cover associatedwith clouds, or cloud fraction).While the expectedchangeindropletnumberconcentrationsisfairlywellknown(e.g.Painemaletal.,2015),themoremacroscopicchangestoclouds(i.e.watervaporpathandcloudfraction)arenotwellquantifiedandremain thesubjectof intenseresearch.All theseresponsesofclouds toparticlesmustbequantified to know how effective this solar geoengineering technique might be in reducingincomingsolarradiation.

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Therehavebeensmallship-basedfieldexperimentsperformedalreadytotrytounderstandthisphenomena (the E-PEACE mission, Russell et al., 2013). Unfortunately, some ship tracks canincreasethereflectionofsolarradiation,whileothersdecreasethereflection(Chenetal.2012).Thus, quantifying the true impact of this geoengineering strategy requires a further set ofexperiments, perhaps of larger magnitude (i.e. larger injection) and probably taking place indifferent cloud regimes, since it is thought that the response of clouds to increasing aerosolsdependsontheregime(e.g.low-levelstratocumuluscloudsoffcontinentalcoasts,andtheregimecharacterized by clouds undergoing transition from stratocumulus to cumulus clouds (e.g.WilliamsandWebb,,2009)).Moreover,importantimprovementstocurrentclimatemodelsareneeded to capture improvements to cloud parameterizations that would allow the correctpredictionoftheresponseofcloudstoaerosols(ZhouandPenner,2017).Insummary,solargeoengineeringoffersthepotentialtoshaveoffsomeofthefuturepredictedclimatechangesassociatedwithincreasingCO2.Nevertheless,wehavemuchtolearninordertobeabletoutilizesuchastrategy.Moreover,weneedanagreedupongovernancestrategytoavoidthe“slipperyslope”ofinitiatingresearchviafieldexperiments,leadingtoeverlargerexperimentsthatmightleadtofulldeploymentwithoutunderstandingtherisksassociatedwiththeresponseoftheclimatesystemtoincreasesinparticleconcentrations.References: Canty,T.,N.R.Mascioli,M.D.Smarte,andR. J.Salawitch.2013:Anempiricalmodelofglobalclimate—Part 1: A critical evaluation of volcanic cooling, Atmospheric Chemistry and Physics13(8):3997-4031.DOI:10.5194/acp-13-3997-2013.Chen,Y.C.,M.W.Christensen,L.Xue,A.Sorooshian,G.L.Stephens,R.M.Rasmussen,andJ.H.Seinfeld, 2012: Occurrence of lower cloud albedo in ship tracks, Atmospheric Chemistry andPhysics12(17):8223-8235.DOI:10.5194/acp-12-8223-2012.Cirisan,A.,Spichtinger,P.,Luo,B.P.,Weisenstein,D.K.,Wernli,H.,Lohmann,U.,andPeter,T.:2013:Microphysicalandradiativechangesincirruscloudsbygeoengineeringthestratosphere,J.Geophys.Res.-Atmos.,118,4533–4548,doi:10.1002/jgrd.50388.English,J.M.,Toon,O.B.,andMills,M.J.,2012:Microphysicalsimulationsofsulfurburdensfromstratosphericsulfurgeoengineering,Atmos.Chem.Phys.,12,4775–4793,doi:10.5194/acp-12-4775-2012.Niemeier,U.andTimmreck,C.,2015:What isthe limitofclimateengineeringbystratosphericinjectionofSO2?Atmos.Chem.Phys.,15,9129–9141,doi:10.5194/acp-15-9129-2015.Latham,J.,1990:Controlofglobalwarming,Nature347(6291),339-340,DOI:10.1038/347339b0.Niemeier,U., Schmidt,H., and Timmreck, C., 2011: Thedependencyof geoengineered sulfateaerosolontheemissionstrategy,Atmos.Sci.Lett.,12,189194,doi:10.1002/asl.304.

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Niemeier,U.,Schmidt,H.,Alterskjær,K.,andKristjánsson,J.E.,2013:Solarirradiancereductionvia climate engineering – Impact of different techniques on the energy balance and thehydrologicalcycle,J.Geophys.Res.,118,11905–11917,doi:10.1002/2013JD020445.Pierce, J. R., Weisenstein, D. K., Heckendorn, P., Peter, T., and Keith, D. W., 2010: Efficientformationofstratosphericaerosolforclimateengineeringbyemissionofcondensiblevaporfromaircraft,Geophys.Res.Lett.,37,L18805,doi:10.1029/2010GL043975.Russell,L.M.,A.Sorooshian,J.H.Seinfeld,B.A.Albrecht,A.Nenes,L.Ahlm,Y.-C.Chen,M.Coggon,J.S.Craven,R.C.Flagan,A.A.Frossard,H.Jonsson,E.Jung,J.J.Lin,A.R.Metcalf,R.Modini,J.Mülmenst.dt,G.C.Roberts,T.Shingler,S.Song,Z.Wang,andA.Wonaschütz,2013:EasternPacificEmitted Aerosol Cloud Experiment (E PEACE), Bulletin of the AmericanMeterological Society,94:709-729.Williams, K.D. and Webb, M.J., 2009: A quantitative assessment of cloud regimes in climatemodels,ClimDyn,33:141-157,doi:10.1007/s00382-008-0443-1.Zhou,C.andPenner,J.E.,2017:WhydoGCMsoverestimatetheaerosolcloudlifetimeeffect?AcasestudycomparingCAM5andaCRM,Atmos.Chem.Phys.,17,21–29,doi:10.5194/acp-17-21-2017.

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The Inchoate Politics of Solar Geoengineering Research

JesseReynoldsPostdoctoralResearcher,FacultyofLaw,EconomicsandGovernance,UtrechtUniversity,TheNetherlands

Policymaylargelybeanoutcomeofpolitics,butaseconomistRobinHansonasserts,politicsis(usually)notaboutpolicy.This isparticularlytrueforsolargeoengineering,whichelicitsstrongfeelingsandrunscountertotypicalrelationsbetweenmeansandendsinenvironmentalpolicy.Here,Ioffermyperceptionsofsolargeoengineering’sinchoatepolitics,andaforecastofhowtheymightunfoldasresearchisadvanced.Suchforecasting,alwaysuncertain,isevenmoresoastheUSentersunchartedpoliticalterrain.Speaking with gross generalization, I observe three primary cohorts in solar geoengineeringpolitics. First, researchadvocateshave,almostexclusively,ahistoryof studyinganthropogenicclimate change and of calling for aggressive greenhouse gas emissions cuts (“mitigation”).However, they are pessimistic about the prospects formitigation alone to prevent dangerousclimatechange.Thiscohort isdominatedbyscientistsand,toa lesserdegree,afewmoderateenvironmentalgroups.Theyreluctantlyarguethatsolargeoengineeringappearstoofferafeasibleandeffectivemeans tocounterclimatechangeand, in turn, toprotectvulnerablepeopleandecosystems.Second,researchopponentsadvanceavarietyofarguments,themostcommonofwhich is that solar geoengineering research would undermine already insufficient mitigationefforts. They also often highlight physical risks and uncertainties, questions of control andpotential conflict,matters of justice, and the hubris ofmessingwith nature. Someopponentsaccusetheresearchadvocatesofunwittingly--orevenconsciously--aidingthevestedintereststhatbenefitfromfossilfuels’continueduse.Third,lessnoticeablearetheconservativeopponentsofmitigation who have largely remained on the sideline of solar geoengineering debates.Occasionallyaright-of-centervoicesuggeststhatsolargeoengineeringoffersasimplesolution,while a climate change denier mocks it as another unnecessary response to a nonexistentproblem.Meanwhile,thelaypublicremainsmostlyignorantand,ifasked,exhibitsawiderangeofresponsestosolargeoengineering.Initially,IwasaresearchopponentwhenIencounteredsolargeoengineering.Theassertionsthatit is simply a risky effort by fossil fuel interests to avoid mitigation both seemed logical andconfirmedbypreexistingviews.YetthecloserIlooked,themoreIsawthatsolargeoengineeringwasdrivenbydespondentenvironmentalists;thatrealisticmitigationscenarioscouldnolongerkeep global warming within the internationally agreed-upon 2� limit; that climate modelsconsistentlyindicatedthatsolargeoengineeringcouldeffectivelyreduceclimatechange;andthattheabilitytoimplementitcouldserveasatypeofinsuranceagainstfutureclimaterisks.Notably,manyotherresearchadvocatesfollowedasimilarpath.To some degree, the climate change discourse has likewise evolved with respect to solargeoengineering. As actualmitigation continues to disappoint and as the forecasts for climatechangebecomemoredire,callsforresearchhavebeenmorecommon,asseeninthe2015US

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NationalAcademiesreportsandtherecentupdatetotheNationalGlobalChangeResearchPlan.Althoughthisevolutionmaybeasourceofstrangeencouragementamongresearchadvocates,many of them are understandably cautious. Our greatest fear is that conservativeswill pivot,suddenlyembracingtheproposedtechniques.Ifthisweretohappen,thensolargeoengineeringwould be widely perceived--rightly or wrongly--as a means to perpetuate our unsustainablerelianceonfossilfuels.Ibelievethatthisconcernmaybesomewhatmisplaced.Seeingwhyrequiresdifferentiationwithintwoofthebroadpoliticalcohorts.First,althoughconservativeopponentsofmitigationareoftenlumpedtogetherandsmearedas“denialists,”theyactuallyprofessarangeofviews.Themoreextremeones indeeddeny that theclimate is changingor thathumansare theprimarycausethereof.Theyareunlikelytoembracesolargeoengineering,asdoingsowouldrequirethemtoaltertheirfoundationalbeliefs.Instead,theywillcontinuetodismissit--iftheydiscussitatall--asgrandiosenonsensefrompower-hungryscientists.However,asubstantialportionofopponentsofaggressivemitigationdoacknowledgeanthropogenicclimatechangebutarguethatitsimpactswill be moderate and that mitigation would be too expensive. In fact, some of these“lukewarmers” emphasize that theworld’s poorwould be served better by reliable access toaffordableenergy.Tothem,solargeoengineeringcouldofferameanstoreducetherealbut--intheir opinion--moderate risks of climate change without hindering development. Althoughresearchadvocatesmaybristleat theprospect,given theirdedication tomitigation, theymayneedtochoosewhethertocooperatewiththosewhohaveseriouslyconsideredclimatechangeand,inapparentgoodfaith,cometodifferentconclusionsregardingaggressivemitigation.Turning now the other direction, research opponents’ heterogeneity can be gleaned fromconsideringthemeansandendsofclimatechangepolicy.Someresearchopponents,particularlyadvocatesof“deepergreen”environmentalismandsocialjustice,havemoreambitiousgoalsthansimplypreventingclimatechange.Asevidencedbytheirrhetoricandactions,theyvariouslyaimto reduce the human footprint on nature and to redistribute power and wealth in a moreegalitarianway.Becausemitigationmightfurtherthesemoreambitiousgoals,theirsupportforithasalwaysbeenameans toanend.Andbecause solar geoengineeringwouldnotnecessarilyfurtherthesegoals--andpossiblythreatentheprioritizationofmitigationinclimatepolicy--theiropposition to solar geoengineeringwill remain fast. Yet there is another segment of researchopponents: thosewho have been calling formitigation for years, often under hostile politicalconditions. For them,mitigation has been the solemeans to a critical end for so long that itappearstohavebecometheenditself.Theyarenowreflexivelydefensivetosuggestionsofanyalternative.Solargeoengineeringdisrupts this, justasproposals toadaptsociety toachangedclimatedidtwodecadesago.Forexample,AlGoreinitiallycalledadaptation“akindoflaziness,anarrogantfaithinourabilitytoreactintimetosaveourskin.”Ittookyearsbeforeheandotherssupportedadaptation,whichnowstandsalongsidemitigationasanequallyessentialresponsetoclimatechangerisks.Manyofthesedefensiveopponentsmaywarmuptosolargeoengineering,especiallyifweresearchadvocatesengagewiththemseriouslyandproceedcautiously.Butifwefailtodoso,thentheymayhardentheirposition.Tome,thisistherealriskofadvancingsolargeoengineeringresearch.

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Benefits, Risks, and/or Opportunities of U.S. Solar Geoengineering Research

KateRicke

AssistantProfessor,SchoolofGlobalPolicyandStrategyandScrippsInstitutionofOceanography,

UniversityofCalifornia-SanDiego

Research has demonstrated that, in climate models at least, solar geoengineering has atremendouspotentialtoreducetheamountsandratesofregionalclimatechangecausedbyrisingatmosphericgreenhousegasconcentrations1,2.Solargeoengineeringisfarfrombeingaperfectsubstitute for emissions reductions – it has different effects counteracting temperature andhydrologicalchanges,doesnothingtoreduceoceanacidification,andmayintroduceitsownriskssuchasincreasedamountsofstratosphericozonedestruction3.Nonetheless,withglobalwarmingcontinuingapaceandhighlevelsofuncertaintyabouttheextenttowhichmitigationpoliciescanlimitglobaltemperaturesto1.5°Cor2°Cabovepre-industrial,solargeoengineeringresearchcan’tbeignored.There are a few areas where I think the current state of the geoengineering literature isproblematicandwherethereareopportunitiestoimprovethediscussion.Scenarios Climatemodeling always requires choosing between transparency and realismwhen decidingwhatscenariostosimulate.Thefirstgenerationofgeoengineeringmodelingexperimentssensiblyfocusedonidealizedscenariosthatprovidedasoundbasisforunderstandingphysicalmechanismsassociatedwithgeoengineeringforcings,butconclusionsaboutimpactsthatsolargeoengineeringimplementationmighthavetherealworldwerethenextrapolatedfromtheseresults(oftenbasedonintuition).Idon’tknowanyonewhobelievessolargeoengineeringisapanacea,butitisoftenimplementedasone in idealizedsimulations.As solargeoengineering researchbecomesmoremainstream,thisresearchcommunityshouldtrytocatchupwiththebroaderclimatemodelingcommunity in terms of formulating geoengineering scenarios based on sound socioeconomicassumptionsandinterdisciplinaryexpertise.Impacts Assessment There’sbeenanexplosionofresearchonsocioeconomicimpactsofclimatechangeinthepastdecade based on econometric analysis4. Temperature shocks (and sometimes precipitationshocks) have been robustly linked to awhole host ofmicro- andmacroeconomic effects. Butapplicationofthisworkisproblematicinasolargeoengineeringcontextbecausecompensatingforgreenhousegasforcingswithsolaronesdivorcestemperaturefromhydrology.Thesignalofprecipitation effects on impacts is often not statistically discernable because at the levels ofanalysisused,temperatureandprecipitationstronglycovary.Weneedtofindbetterwaystoteaseoutparticular impactscontributionsdirectlyattributabletotemperatureversusfactorssuchasprecipitationandsoilmoisture.There’snowaytomakeagoodcaseeitherfororagainsttheuse

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ofsolargeoengineeringwithouthavingamoresolidgraspontheimpactsoftheparticularclimateconditionssolargeoengineeringcreates.Behavior, Economics and Societal Transitions18Becausedecarbonizationofenergysystems,negativeemissionstechnology,adaptationandsolargeoengineeringareall tools tomitigateclimate risks,aneconomy inwhichallareviablemustexhibit some substitution effects between solar geoengineering and othermore conventionalapproaches.Manyscholarshavealsoraisedthepossibilityofamoralhazardeffectassociatedwithsolar geoengineering, whereby people under-account for risks from CO2 once learning of thepotential of solar geoengineering to cheaplymitigate its effects. There is also some empiricalevidencethatanoppositeeffectexists inwhichpeoplewantmoreemissionsreductions inthepresence of a geoengineering option. Understanding how solar geoengineering decisions willinteractdecisionsaboutimplementationofmitigationandadaptationisamajorchallenge.Support formajor policy initiative is always going to depend on tradeoffs between costs andbenefits. One could imagine a situation in which the threshold for implementing solargeoengineering is lower than that for a major overhaul of the energy system. Under suchcircumstances, it’spossiblethatsolargeoengineeringdesignedtoreducesuffering intheshorttermcouldultimatelyincreasenetsuffering.Thefigurebelowillustratesahighlysimplifiedthoughtexerciseonhowthiscouldhappen,basedontheassumptionthatthethresholdfordeployingsolargeoengineeringis lowerthanthatforreducinggreenhousegasemissionsbecausesolargeoengineeringdeploymentis:1)cheaperthangreenhouse gas reductions and 2) requires less international coordination (from a technicalperspective).PanelAshowsimpactsfromclimatechangeovertimeasillustratedinaworldwherethere is no solar geoengineering. As climate changes, impacts (and suffering) increase. At thethreshold point, impacts become so intolerable that strong and lasting actions are taken toeliminate greenhouse gas emissions. Because of carbon inertia, even after such a policy shift,impactswouldlikelycontinuetoriseuntilCO2concentrationsandrateofclimatechangecanbestabilized.PanelB showshow impacts/suffering fromclimatechangeover timemight change inaworldwheresolargeoengineeringisapossiblemeansofreducingsufferingatalowercostthanGHGreductions.Geoengineeringslowstherateofimpactincreases(orcouldperhapsevenreverseitforatime),butbecauseitisanimperfectsubstituteforGHGreductions,eventuallyundersuchascenario,totalimpacts--asillustratedbytheareaunderthecurve–couldbemuchgreaterthaninaworldwithoutsolargeoengineering.Ofcourse,evenwithdifferential thresholds for interventionforsolargeoengineeringandGHGemissionsreductions,solargeoengineeringmaynotnecessarilyincreasenetimpactsasinPanelB.Forexample,theimpactsthresholdforreducingemissionscoulddiminishovertimeduetothedevelopmentofcheapermitigationtechnologiesorchangingsocialtolerancesforsuffering(panel

18PortionsofthissectionareadaptedfromChapter5ofRicke(2011)5.

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C). Or the rate at which impacts could bereducedmaybegreater if the threshold foraction is passed later (panelD). Evenundersuch scenarios, though, when solargeoengineering is implemented, someimpacts are likely being pushedonto futuregenerations.Thewaysuchdynamicsplayoutissubjecttohugeuncertainties,butitwouldbe helpful to start thinking about theconditionsunderwhich itwouldbe“sociallyrisky” to implement solar geoengineering(e.g., rapidly rising emissions, no strongmitigationpolicies)versusthoseunderwhichit is unlikely to result in indefinite delay inreducing GHG emissions (e.g., afterrenewable energy has become cost-competitive with fossil fuel based energy).Thiswouldaid intheformulationofpoliciesand institutions that can facilitate solargeoengineeringimplementationifitturnsoutit’surgentlyneeded,andalsorestrictitsuseunder conditions that may lead to acatastrophicendgames.Characterizationsofgeoengineeringas“highrisk” are contingent upon implementationapproachesthataren’tnecessarilyconsistentwithreasonableobjectivesforuse.Hopefully,asthefieldmatures,discussionsaboutsolargeoengineeringcanshift towardevaluationsfocused on more realistic scenarios forimpacts, objectives and constraints onimplementation.

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References 1.Ricke,K.L.,Rowlands,D.J.,Ingram,W.J.,Keith,D.W.&GrangerMorgan,M.Effectivenessof

stratosphericsolar-radiationmanagementasafunctionofclimatesensitivity.Nat.Clim.Change2,92–96(2012).

2. Kravitz, B. et al. A multi-model assessment of regional climate disparities caused by solargeoengineering.Environ.Res.Lett.9,74013(2014).

3.Board,O.S.,Council,N.R.&others.Climate Intervention:ReflectingSunlight toCoolEarth.(NationalAcademiesPress,2015).

4.Carleton,T.A.&Hsiang,S.M.Socialandeconomicimpactsofclimate.Science353,aad9837(2016).

5. Ricke, K. L. Characterizing Impacts and Implications of Proposals for Solar RadiationManagement,aFormofClimateEngineering.(2011).

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The Benefits of U.S. Solar Geoengineering Research

AlanRobockDistinguishedProfessor,DepartmentofEnvironmentalSciences,RutgersUniversity

Thispaperdrawsheavilyonmyrecentessayonthesametopic[Robock,2016].Summary: Research on albedo enhancement by stratospheric sulfur injection inspired by Paul Crutzen’spaper a decade agohasmade clear that itmaypresent serious risks and concerns aswell asbenefitsifusedtoaddresstheglobalwarmingproblem.Whilevolcaniceruptionsweresuggestedasinnocuousexamplesofstratosphericaerosolscoolingtheplanet,thevolcanoanalogalsoarguesagainst stratospheric geoengineering because of ozone depletion and regional hydrologicresponses.ContinuousinjectionofSO2intothelowerstratospherewouldreduceglobalwarmingandsomeofitsnegativeimpacts,andwouldincreasingtheuptakeofCO2byplants,butresearchin the past decade has pointed out a number of potential negative impacts of stratosphericgeoengineering.Moreresearchisneeded,andshouldbefundedbytheU.S.government,tobetterquantifythepotentialbenefitsandriskssothatifsocietyistemptedtoimplementgeoengineeringinthefutureitwillbeabletomakeaninformeddecision.Atmyfirstmeetingongeoengineering,theManagingSolarRadiationWorkshopatNASAAmesResearchCenter,MoffettField,California,November18-19,2006,Iwasamazedandshockedtofind somany engineers and physicists enamored of this idea, and ended upwriting down 20reasonswhyitmightbeabadidea[Robock,2008].Thehubrisofsome,whothoughtthatthiswasjustamechanicalorphysicalproblemtosolve,andtheirlackofawarenessofthescienceofclimatechangeandthenaturalchaoticvariabilityofclimate,wasveryscary.Anumberofthosepotentialriskswerealreadyunderstood10yearsago,andwerediscussedbyCrutzen [2006]and in theaccompanying essays, particularly byMacCracken [2006], but work in the past decade hasproduced much better understanding and identification of those risks, in particular thattemperatureandprecipitationcannotbothbecontrolledatthesametime[e.g.,Jonesetal.,2013],thatsummermonsoonprecipitationwouldbereduced[Tilmesetal.,2013],thatevenifglobalaverage temperature could be kept from increasing, there would be cooling and warming indifferent places [Kravitz et al., 2013a], that ice sheets melt from the bottom, and changinginsolationwouldnotbeveryeffectiveatslowingtheirmelting[McCuskeretal.,2015],andthatabrupt implementation or termination of geoengineering would produce serious impacts onecosystems[Trisosetal.,2017].Thehistoryofpastweatherandclimatemodificationattemptsprovidesstronglessonsaboutthedifficultyofgovernanceandthedangersofmilitaryapplications[Fleming,2010].Table1ofRobock[2016]givesalistoffivepotentialbenefitsofstratosphericgeoengineeringand27 risks or concerns. Number 1 on the benefits side, that stratospheric geoengineering couldreduceglobalwarmingandmanyofitsnegativeimpacts,maybesoimportantthatsocietyinthefuture may decide to implement stratospheric geoengineering to reduce some amount of

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warming and livewith and adapt to the negative consequences of geoengineering. (The onlyrationalwaytodothiswouldbeforalimitedamountoftimewhilemitigationandcarbondioxideremovalfromtheatmospherereducetheradiativeforcingfromgreenhousegases.)Eachofthepotentialbenefitsandrisksneedstobequantifiedsothatsocietycanmakeinformeddecisionsinthefutureabouthowmuchandwhattypeofgeoengineeringtoimplementandforhowlong.Someofthepotentialbenefitsandriskscanbeaddressedbyclimatemodeling.WithBenKravitzand others, I have started the Geoengineering Model Intercomparison Project [GeoMIP,http://climate.envsci.rutgers.edu/GeoMIP/; Kravitz et al., 2011, 2013b, 2013c, 2015a, 2015b;Tilmesetal.,2015], inwhichvariousscenariosofanthropogenicstratosphericaerosols,marinecloudbrightening,andcirrusthinningarebeingevaluatedwithclimatemodelexperimentsasaresponsetoglobalwarming.Inadditiontothestandardexperiments,GeoMIPalsoestablishesaGeoMIP Testbed for new experiments to be conducted by one or a few climate models asdemonstrationprojectsforfuturepossiblemodelintercomparisons.Some of the potential benefits and risks can be studied by looking at the analog of volcaniceruptions[Robocketal.,2013],butsomecannotbeaddressedatallbyscientificinvestigation.In2012, I thought that thegovernanceproblems, someofwhichwerediscussedbyMacCracken[2006],wouldbeinsolubleandthatstratosphericgeoengineeringwillneverbeimplementedbyinternationalagreement[Robock,2012a],andhaveyettochangemymind.Infactthemorewelookatstratosphericgeoengineering,themoreunlikelyimplementationbecomesbecauseoftheassociatedrisks.Inparticular,risksassociatedwithunknowns,governance,andethicswillbeverydifficulttoaddress.Nevertheless,muchisstillunknown,andwehaveanobligationtocontinuetheresearch.Theethicsofdoinggeoengineeringresearchalsoneedstobeaddressed.BothLawrence[2006]and Cicerone [2006]made a clear case that we have an obligation to better understand thebenefits and risks of potential geoengineeringdeployment so that policymakers in the future,should theybe tempted,wouldbeable tomake informeddecisions. I agree [Robock, 2012b],provided that outdoor small-scale experiments are subject to environmental regulation andgovernance.However,asdiscussedbyRobocketal.[2010],large-scaleexperimentswouldhavetobeconductedfordecadestodistinguishthesignalofsmallinjectionsfromthenoiseofweatherandclimatevariations.Thiswouldbenodifferentfromactualgeoengineeringimplementation.Furthermore, only by injecting SO2 into an existing sulfate aerosol cloud could the growth ofaerosolsbestudied.Perhaps,afterthenextlargevolcaniceruption,thiscouldbetestedonpartofthecloud,butthatwouldrequiredevelopmentofmonitoringequipmentthatcouldfollowtheairparcel.TheAmericanMeteorologicalSocietypolicystatementongeoengineering[AMS,2009],whichwassubsequentlyadoptedbytheAmericanGeophysicalUnion[AGU,2009],recommends“Enhancedresearch on the scientific and technological potential for geoengineering the climate system,including research on intended and unintended environmental responses.” Strongrecommendations for geoengineering research have also come from Keith et al. [2010], Betz[2012],andGAO[2011].TherecentU.S.NationalAcademyofSciencesreport[McNuttetal.,2015]

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recommends “an albedomodification research program be developed and implemented thatemphasizesmultiple-benefitresearchthatalsofurthersbasicunderstandingoftheclimatesystemand its human dimensions.” Yet a U.S. national geoengineering research program has yet tomaterialize.Nowthat thestigmaofdoing theresearch isover, itwouldberelativelycheaptoevaluatethemanysuggestedtechniques,bycontinuedcomputermodelingandstudyofanalogs,andalsobyconductingsmalloutdoorexperiments,asrecommendedbyCrutzen.Crutzenstartedaninternationalresearcheffortongeoengineering,yetmuchmoreremainstobelearned.AllscientistsworkingongeoengineeringthatIknowofmakeastrongcallformitigationand adaptation to address global warming, and this is also the recommendation of the U.S.NationalAcademyofSciencesreport[McNuttetal.,2015].Infact,arapidtransitiontosolarandwindpowercankeepglobalwarmingclosetothe2015Parisgoalof2°Cabovepre-industriallevels[e.g.,InternationalEnergyAgency,2016].Sofargeoengineeringresearchconcludesthatthereisno safe “Plan B,” and provides enhanced support for mitigation and adaptation. Additionalresearch support for these effortswillmake clear over the next decadewhether this currentunderstandingisrobust,anditwouldbeirresponsiblefortheU.S.andothernationsnottomakethisinvestmentinresearch.Acknowledgments SupportedbyNSFgrantsAGS-1157525,GEO-1240507,andAGS-1617844.References AmericanGeophysicalUnion(AGU)(2009),AGUPositionStatement,GeoengineeringSolutionsto

ClimateChangeRequireEnhancedResearch,ConsiderationofSocietalImpacts,andPolicy

Development,http://sciencepolicy.agu.org/files/2013/07/AGU-Geoengineering-Position-Statement_March-20121.pdf.

AmericanMeteorologicalSociety(AMS)(2009),GeoengineeringtheClimateSystem;APolicyStatementoftheAmericanMeteorologicalSociety,https://www2.ametsoc.org/ams/index.cfm/about-ams/ams-statements/statements-of-the-ams-in-force/geoengineering-the-climate-system/

Betz,G. (2012),Thecaseforclimateengineeringresearch:Ananalysisofthe“armthefuture”argument,ClimaticChange,111,473-485,doi:10.1007/s10584-011-0207-5.

Cicerone, R. (2006), Geoengineering: Encouraging research and overseeing implementation,ClimaticChange,77,221-226,doi:10.1007/s10584-006-9102-x.

Crutzen, P. (2006), Albedo enhancement by stratospheric sulfur injections: A contribution toresolveapolicydilemma?ClimaticChange,77,211-220,doi:10.1007/s10584-006-9101-y.

Fleming, J. R. (2010), Fixing the Sky: The Checkered History of Weather and Climate Control,ColumbiaUniversityPress,NewYork,344pp.

GAO (2011),ClimateEngineering:Technical Status,FutureDirections,andPotentialResponses.Report GAO-11-71 (Government Accountability Office, Washington, DC), 135 pp.http://www.gao.gov/new.items/d1171.pdf

InternationalEnergyAgency(2016),EnergyTechnologyPerspectives2016, InternationalEnergyAgency,Paris,France,418pp.

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Jones, A., et al. (2013), The impact of abrupt suspension of solar radiation management(terminationeffect)inexperimentG2oftheGeoengineeringModelIntercomparisonProject(GeoMIP),J.Geophys.Res.Atmos.,118,9743-9752,doi:10.1002/jgrd.50762.

Keith, D.W., E. Parson andM.G.Morgan (2010), Research on global sun block needed now,Nature,463,426–427,doi:10.1038/463426a.

Kravitz,B.,A.Robock,O.Boucher,H.Schmidt,K.Taylor,G.Stenchikov,andM.Schulz(2011),TheGeoengineering Model Intercomparison Project (GeoMIP). Atmos. Sci. Lett., 12, 162-167,doi:10.1002/asl.316.

Kravitz, B., et al. (2013a), Climate model response from the Geoengineering ModelIntercomparison Project (GeoMIP), J. Geophys. Res. Atmos., 118, 8320-8332,doi:10.1002/jgrd.50646.

Kravitz,B.,etal. (2013b),Seaspraygeoengineeringexperiments in theGeoengineeringModelIntercomparisonProject(GeoMIP):Experimentaldesignandpreliminaryresults.J.Geophys.Res.Atmos.,118,11,175-11,186,doi:10.1002/jgrd.50856.

Kravitz,B.,A.Robock,P.M.Forster,J.M.Haywood,M.G.Lawrence,andH.Schmidt(2013c),Anoverviewof theGeoengineeringModel IntercomparisonProject (GeoMIP). J.Geophys.Res.Atmos.,118,13,103-13,107,doi:10.1029/2013JD020569.

Kravitz,B.etal.(2015),TheGeoengineeringModelIntercomparisonProjectPhase6(GeoMIP6):Simulation design and preliminary results. Geosci. Model Dev., 8, 3379–3392,doi:10.5194/gmd-8-3379-2015.

Lawrence,M.(2006),Thegeoengineeringdilemma:Tospeakornottospeak,ClimaticChange,77,245-248,doi:0.1007/s10584-006-9131-5.

MacCracken,M. (2006),Geoengineering:Worthyof cautiousevaluation?ClimaticChange,77,235-243,doi:10.1007/s10584-006-9130-6.

McCusker,K.E.,D.S.BattistiandC.M.Bitz(2015),StratosphericsulfateaerosolinjectionscannotpreservetheWestAntarcticIceSheet,Geophys.Res.Lett.,42,4989-4997.

McNutt,M.K.(Chair),CommitteeonGeoengineeringClimate:TechnicalEvaluationandDiscussionof Impacts (2015), Climate Intervention: Reflecting Sunlight to Cool Earth, (U.S. NationalAcademyofSciences,Washington,DC),234pp.

Robock,A.,M.Bunzl,B.Kravitz,andG.Stenchikov(2010),Atestforgeoengineering?Science,327,530-531,doi:10.1126/science.1186237.

Robock,A.(2012a),Willgeoengineeringwithsolarradiationmanagementeverbeused?Ethics,Policy&Environment,15,202-205.

Robock,A.(2012b),Isgeoengineeringresearchethical?PeaceandSecurity,4,226-229.Robock,A.,D.G.MacMartin,R.Duren,andM.W.Christensen(2013),Studyinggeoengineering

withnaturalandanthropogenicanalogs,ClimaticChange,121,445-458,doi:10.1007/s10584-013-0777-5.

Robock,A.(2016),Albedoenhancementbystratosphericsulfurinjections:Moreresearchneeded,Earth’sFuture,4,644-648,doi:10.1002/2016EF000407.

Tilmes,S.,etal.(2013),ThehydrologicalimpactofgeoengineeringintheGeoengineeringModelIntercomparison Project (GeoMIP), J. Geophys. Res. Atmos., 118, 11,036-11,058,doi:10.1002/jgrd.50868.

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Tilmes, S., et al. (2015), A new Geoengineering Model Intercomparison Project (GeoMIP)experiment designed for climate and chemistry models. Geosci. Model Dev., 8, 43-49,doi:10.5194/gmd-8-43-2015.

Trisos, C. H., G. Amatulli, J. Gurevitch, A. Robock, L. Xia, and B. Zambri (2017), Dangerousconsequences of geoengineering implementation and termination for natural systems.SubmittedtoScience.

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Some Informal Comments on Solar Geoengineering

DanielP.SchragSturgisHooperProfessorofGeology,ProfessorofEnvironmentalScienceandEngineering,Harvard

University;Director,HarvardUniversityCenterfortheEnvironment;

Director,HarvardKennedySchoolProgramonScience,Technology,andPublicPolicy

Inthediscussionofappropriateactionstomitigateglobalclimatechange,solargeoengineeringhas often been described as an emergency option, if perhaps the rate of climate changeacceleratedoverthenextfewdecades,or iftheconsequencesofclimatechangelookedmuchworsethananticipated.Ifindthisframingtobealittletroubling,as itmakesitseemlikesolargeoengineeringshouldonlybeusediftherearesurprises,failingtoacceptourownclimatestudiesthatshowtrulycatastrophic impactsfromevery-increasingatmosphericCO2 levels inthemostlikelyemissionsscenarios.Perhapsitcomesfromapsychologicaldesiretoclingtovisionsofanon-fossilenergysystemthatcouldbeachieved(oratleastlargelyimplemented)bymid-century(nowonlythreedecadesaway),regardlessofhowunlikelythisscenariois.

Whatseemstobemissingistherealizationbytheclimatesciencecommunitythatdeepemissionsreductionsareextremelyunlikely–stillworthfightingfor,asemissionsreductionsmustoccuratsomepoint,evenifhopefultargetsaremissed–butextremelyunlikely.Forexample,inarecentstudyofclimaterisk(Kingetal.,2015),welookedatthelikelihoodoftheworldachievingalow-carbonemissionspathway,andfoundthatamoderateemissionspathway(CO2reaching600to700ppmbytheendofthe21stcentury)wasthemostlikely,andemissionspathwaysthatkeptCO2 below 550 ppm were extremely improbable, as they require multiple technologicalinnovations,wellbeyondcurrentcapabilities(includingambitiousreductionsincost)inmultiplesectorsoverthenextfewdecades.Thus, I suspect that there will be a transition in the way our community thinks about solargeoengineeringoverthecomingdecades,as the impactsofclimatechangebecomemoreandmoreapparent.Isuspectthatwewillstopframingsolargeoengineeringasanemergencyoption,butacceptthatwealreadyareexperiencingaplanetaryemergency(albeit,onewithalongtimeconstant),andthatsolargeoengineeringislikelytobeanecessarycomponentofaclimatechangeresponse–thatincludesinvestmentsinadaptationandemissionsreductions.Thequestionsthatremainwillbehowandwhentoimplementdifferentsolargeoengineeringstrategies,andhowtocontrol it. This means that the linkage between the science and engineering of solargeoengineeringandthegovernanceofsolargeoengineeringaredeeplyentwined,inpartbecauseofthepotentialforcomplexgeoengineeringschemesthataredrivenbydivergentnationalandregionalinterests.Manystudiesemphasizethatsolargeoengineeringisnotasubstituteforemissionsreductions,andthatemissionsreductionsmustinevitablyoccur.Somehaveusedthisasanargumentagainstsolargeoengineering.Forexample,ArcherandBrovkin (2008)argue that,becauseof the longlifetimeofCO2,sustainingsuchanengineeringsystemfortensofthousandsofyearsormoreis

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not feasible. This fails to consider that engineering the climate for a few centuries could becombinedwithavarietyofwaysofremovingCO2fromtheatmosphere,albeitatrelativelyhighcost,sothattheproblemwascompletelyabatedbytheendofafewcenturiesorso.Idonotmeantoimplythatwecurrentlyunderstandenoughofwhatsolargeoengineeringwilldoto theEarthsystemtostateconfidently that itwillbesafeandeffective. Just theopposite– Ibelievewe are in the infancy of our understanding. Inmy ownwork, I haveworkedwithmygraduatestudent(KatieDagon)onhowsolargeoengineeringinteractswithterrestrialecosystemsintermsofeffectsonevapotranspiration.WehavefoundthatthecouplingofphysiologicaleffectsofhigherCO2 levels (throughwateruseefficiencyand stomatal conductance)with impactsofradiationandtemperatureeffectsareextremelysensitivetodifferentparametersusedinclimatemodels, and can lead to a wide range of effects including increases in soil moisture andtemperature stability in some regions and extreme deficits in others.Manymore studies areneededtounderstandhowsolargeoengineeringinteractswithweathersystems,andnotsimplytheaverageclimateresponsethathasbeenthesubjectofthevastmajorityofmodelingstudiesthusfar.Butatthesametime,itisimportanttoacknowledgethatthereisnostudyIhaveseenthatlooksatpotentialeffectsofsolargeoengineeringthatshowsthatimpactsofsolargeoengineeringareworsethanaworldwithhigherCO2withoutsolargeoengineering.Inotherwords,everythingweknowtodaypointstothefactthatincludingsolargeoengineeringasacomponentofourresponsetoclimatechangeisfarbetterthannot.Again,thisisnottosaythatweunderstandhowtodosolargeoengineering,orthatweunderstandallofthewaysthatsolargeoengineeringmaycreatevariousclimateimpactsthatareharmful.Weclearlydonotunderstandthisverywell.Butwhatwedoknowsuggeststhatminimizingthemostcatastrophicimpactsofclimatechangewilllikelyinvolve some investment in solar geoengineering. Thus, there is an imperative to accelerate aresearchefforttounderstandwhatitmightdo,andhowtomakeitaseffectiveaspossible.Whatformofgeoengineeringshouldwestudy?Thisisaplacewhereourinitialapproachtotheproblemhasbeentoosimplistic.Moststudiesthatuseclimatemodelstounderstandtheimpactsof solargeoengineeringusevery simple representationsof solargeoengineering.Many simplyturndownthesolarluminosityinthemodel–averyusefulwaytolookatthetradeoffsofreducingshortwaveradiationtocompensateforhighergreenhousegases,butthisobviouslyignoresthecomplexityofstratospherictransportofaerosolsandthepotentialforlargeregionalvariationsinalbedo.Otherstudieshaveusedchemical transportmodels, coupledwithclimatemodels,buthaveusedarelativelysimplescenarioinwhichthereisasinglesolargeoengineeringapproach,withtheaimofreducingtheimpactsofclimatechangefromaglobalperspective.The truth is that any real solar geoengineering system will almost certainly have regionaldifferencesineffectiveness.Differentcountriesanddifferentregions,quiterationally,willtrytoensure that the solar geoengineering approaches are done with their interests in mind. Forexample,wecannotimaginetheU.S.allowingasolargeoengineeringsystemtobedeployedthatmay have a strong net benefit to most countries, but has a detrimental effect to rainfall insummertimeintheU.S.Midwest.Similarly,itisdifficulttoseehowageoengineeringsystemthat

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isintendedtoslowdownorstopthemeltingoficeinGreenlandwouldavoidhavinganegativeimpact on Russian investment in ports along its northern coastline, opened up by the rapidwarmingintheArcticinrecentdecades.Isuspectthepotentialformultiplesolargeoengineeringsystems to be deployed simultaneously is quite likely – and this makes coordination andgovernanceanevenmoreimportantissue.Perhapssomescientificstudiesofsolargeoengineeringshouldlookatthepotentialforharmfulconsequencesfromduelingsystems,withoutcoordinationorcontrol,wherelocalbenefitsarevaluedoverbroad,globalstability.

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Solar Climate Engineering Research: A Whole-Systems Approach

KellyWanser

PrincipalDirector,MarineCloudBrighteningProject

SeniorAdvisor,OceanConservancy

Climate changeposes grave risks tohumanwelfare and the stability of theearth system thatsustains human life. Changes are occurring rapidly, andmay outpace efforts to address theircauses.Increasing the reflection of sunlight from the atmosphere to reduce warming, ‘solar climateengineering’,may reducedamageandstabilize theearth systemwhilewe reducegreenhousegases in theatmosphere.But,climaterisksgrowaschangesoccur,andtimemaybeshort forassessinganddevelopingsolarclimateengineeringoptionstoreducetheserisks.The Mission of Solar Climate Engineering Research Inthiscontext,whatdoweneedfromsolarclimateengineeringresearch,inwhattimescale?Indefiningtheaimsofresearch,onemightstartwiththequestionsuchas:For solar climate engineering, what questions do wewant to have the answers to, andwhat

capabilitieswouldweliketohaveavailable,within10years?

Questionswewouldlikeanswerstowithintenyearsmightinclude:

• Dowehaveanyviablealternatives?• Ifso,whataretheirenvironmentaleffectsandrisks?• Whataretheirsocietaleffectsandrisks?• Whataretherequirementsforasystem(orsystems)todeliversolarclimateengineering

capabilities?• Whatinformationisrequiredtomanageandgovernsolarclimateengineeringactivities?• Whatarethecosts,benefitsandrisksofsolarclimateengineeringversusunabated

climatechange?High-levelcapabilitieswemightseektohaveavailableintenyearsmightinclude:

• Multipleviableapproaches,withreasonableunderstandingoftheireffectsandrisks• Coretechnologyforeachapproach• Systemdesignandoperatingmodelforeachapproachand/orapproachesintandem• Governancemodelsfordifferentgeopoliticalconditionsanddifferentsolarclimate

engineeringapproaches(ormultipleapproachesintandem)

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• Actionableinformation(observationalandanalyticalsystems)formanagingclimateWhilethesearesomeamongmanypossibilities,thedialogueaboutwhatwewanttoknow,andwhatcapabilitieswewould liketohaveavailable, inwhattimescale, iscriticaltodefiningsolarclimateengineeringresearchprograms.Indeterminingthese,weestablishamissionforresearch.Oncewehaveagreedonthemission,wecandevelopresearchprogramsdesignedtomeet itsobjectives.Whole-Systems Approach Toassessanddevelopoptionsforsolarclimateengineering,itiscriticaltomovefromdiscussionscenteredon isolatedpartsof theproblem, suchas radiative forcingefficacyor governanceofmature systems, to thinking about the entirety of what we need from a climate engineeringsystem,acrossphysicalandsocietaldimensions,or“wholesystems”.Inawhole-systemsapproach,wewouldfirstdescribeatthehighestlevel,thepurpose,or‘end-uservision’,ofasystem.Forsolarclimateengineering,thismightbe:“managedreductionofsolar

radiativeforcing”,where“managed”includesallthephysicalandsocietalconditionsrequiredtosuccessfullyengineerreductioninradiativeforcingintheatmosphereinacontrolledway.With a shared end-user vision, we could then proceed to define, at the highest level, therequirementsforsuchasystem.Forthephysicalaspects,high-levelrequirementsmightinclude:

• materialoftherightcharacteristics(non-polluting,nanoscale,etc.)• manageddeliveryofmaterialintotheatmosphere(platforms,operations,etc.)• actionableinformationformanagingdelivery(dataandanalysisplatforms)

Forthesocietalaspects,high-levelrequirementsmightinclude:

• governanceandlegalframework• publicacceptance

Foreachofthesehigh-levelrequirementsthereareabroadersub-setofrequirementsthatwillbe iterativelyadaptedasnew findingsaremade.These requirementswill driveassessmentoffeasibility, risks, costs and benefits, and surface, at every stage of progress, disqualifyingconditions.Mission-Driven Interdisciplinary Collaboration Todeliveragainstthemission,inawholesystemsapproach,researchprogramsmustencompassallofthedisciplinesrequiredtoassessanddevelopanentiresolution,withcollaboratorsworkingtoasharedsetofobjectivesalongasharedtimeline.Forsolarclimateengineering,thisincludesengineering,atmosphericandenvironmentalsciences,computeranddatasciences,economics

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andriskanalysis,policy,lawandbehavioralsciences–witharenasoffocusrangingfromnanoscaleparticleinteractionstoglobaldeliveryandgovernance.

Figure 1.Parallelresearcheffortsinamission-drivensolarclimateengineeringprogram

Withineachdiscipline,thereisasetofresearchquestionsandgoals(withemphasisonidentifyingrisks and disqualifiers) and a timeline that corresponds to interdisciplinarymilestones for theprogram.Thiselevatestheimportanceofprogramstrategyandmanagement,toalignresearchefforts,evaluatenewinformationandadaptplans,andensurethesuccessofthemission.The importance of portfolios Inawhole-systemsapproach,toincreasetheoddsofsuccessandminimizepointsoffailure,itisimportanttopursueaportfolioofpromisingsolutions,preferablywithdifferingriskandbenefitprofiles.Giventhehigh-stakesandnumerousrisksofsolarclimateengineering,itiscriticaltoresearchanddevelop multiple methods for generating reflectivity in the atmosphere. A research portfoliowouldoptimallyincludeapproacheswithdifferentdeploymentcharacteristics(e.g.localizedandtemporary versus global and sustained), differing side effect risks (e.g. precipitation impacts,agricultural and biological productivity) and different societal risk profiles (governance, publicacceptance,etc.).Itmayalsobecriticaltounderstandanddevelopmultiplegovernancemodelsthatmap to different possible geopolitical constraints and different levels of information andcontrol.Within each research sub-specialty, until a definitive answer is reached, parallel study ofreasonablealternatives(e.g.differentdesignsforaerosolgeneration)willhelpminimizetheriskoffailuretodeliver,andensuretheabilitydeliveragainstthemilestonesofthelargereffort.Engagement and decision-making Whole-systemsthinkingshouldalsohelpshifthigh-leveldiscourseaboutsolarclimateengineeringresearchfromthearenaofacademicspecialiststobroaderengagement.

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Themission,end-uservisionandhigh-levelrequirementsofawhole-systemssolutionforsolarclimateengineeringcan,andshould,bedebatedandagreedbyexperts,policymakers,affectedcommunitiesandsocietyatlarge.Theyoperateabovethelevelofcategoryexpertise,allowingforwidespreadinputandparticipation,andthepossibilityofbroadconsensus.Once agreed, themission, vision and requirements serve as guidelines for experts to deliversolutions of shared importance to society. As research surfaces information, and innovationsemerge, they are also framework for assessing progress andmaking decisions, in a way thatsupportstransparency.It is critically important that we rapidly begin to define a whole-systems framework for solarclimateengineeringresearch.Wecouldbeginbyasking,“Whatquestionswouldweliketohavetheanswersto,andwhatcapabilitieswouldweliketohaveavailable,within10years?”

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Practical Needs for Geoengineering Policy

JanieWiseThompsonVicePresident,Cassidy&Associates

Sciencepolicymakershaveatrickyjob.First,scientificfindingsandinnovationsthatinitiallybogglethemindactuallycomealongfairlyoften,andpolicymakersareusuallymadeawarebeforethegeneralpublic.Atthesetimes,theymustbefar-sightedandflextheirimaginationstoanticipatetheimplicationsforperhapsbillionsofpeopleacrosscurrentandfuturegenerations.Butastheyseektochartapolicycourseinordertobalancetechnologicalpromisewithhumansafety,thesepolicymakersmustberelentlesslypractical.Theyhavetoeducatetheirpeersandshepherdtheirpolicyvisionthroughthesamearcanepoliticalprocessaseveryoneelse.Solar geoengineering and even geoengineering research may be among the most profound,consequential “science ideas” to confront American policymakers yet. If deployed at scale,geoengineeringwouldnecessarilyhaveenormousconsequences.Theremaybenosuchthingaspilot scale solar geoengineering. (It is worth noting that the climate course we have alreadychartedforourselves isequallyconsequential).While IwillnotendeavortomakethecaseforresearchmoreeloquentlythantheothercontributorstothisForum,Ibelievethatthetimehascometoinitiatemoreseriousdiscussionsonsolargeoengineeringwithinthefederalgovernment.Boththeresearchandthegovernanceaspectsofthisfieldneedtomaturequickly,withfederalparticipationformingthebedrock.Givensuchdauntingimplications,whatactionsandtoolsareneededforsciencepolicymakersandregulatorstonavigatethepracticalpoliticalpathwaystoenablesafegeoengineeringresearch?How can researchers, climate advocates and civil society helpwrestle this challenging subjectmatterintosomethingmoreconcrete,moremanageable?First,wemustatlastrallyaroundacommonvocabularyforsolargeoengineering.Manyscholarshave pointed out that the word “geoengineering” is both loaded and perhaps inaccurate,indicatingaleveloftechnicalcontroloverearthsystemsthatcouldlikelyneverbeachieved.Inits2015report,TheNationalAcademieselectedtousetheterm“ClimateIntervention”asamoreappropriate designation for the scope of its inquiry, which considered both solar and carbonremoval approaches. In the 2009-2010 Congressional hearings, theHouse Science Committeeused“climateengineering.”Nonetheless,“geoengineering”seemstobethebuzzwordadoptedbythemedia,anditiswellestablishedasatermofart.Continueddisputeaboutnomenclatureonlytakesawayfromthemoreimportantpolicyquestions.

By the same token, “geoengineering” should refer to solar geoengineeringonly.While carbonremovalhaslongbeenlumpedtogetherwithsolarradiationmanagementasa‘PlanB’approachtoclimateeffects,theyarenotsimilaroneithertechnicalorgovernanceterms.Carbonremovalultimately seeks to address the cause of climate change – by reducing concentrations ofgreenhousegasesintheatmosphere–whilesolargeoengineeringseekstoaddressonlysomeof

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theeffects.Inasense,carbonremovalbelongsinthemitigationfamily,whilesolargeoengineeringisatypeofadaptation.Whilemanycarbonremovalproposalsarenotfreeofrisk,theygenerallyseektoharnessnaturalcarboncyclingprocessesandexpandingthescopeofcapabilitiesthatarealreadywell-establishedintheglobalindustrialgasessector.

Second, in its February 2015 report, the National Academies recommended that the federalgovernmentallocateseriousresearchdollarstogeoengineering.Thepoliticalwilltoactuallydosowillfollowmorereadilyifresearchersandtheclimatecommunitycandrawoutandcommunicatewithpolicymakersaboutthespecificsciencetopicswithinthebroaderfieldthatneedattention.Agenericcallfor“geoengineeringresearch”withoutadditionaldetailisnotactionable.Identifyingthefinitetopicswithincloudphysics,systemsengineering,etc.,andrecommendingthetoolsandfundinglevelsneededintheneartermwillgivelawmakerssomethingtheycanworkwith.Itisworthnotingthatfederalsupportforgeoengineeringresearchdoesnothavetobeginwithanew, independentprogram. There aremanyways theexisting science capabilities at researchagencies, especially DOE, NSF and NASA, can be expanded and directed to unpack themanyremainingtechnicalquestions.Forexample,someNASAsatellitesystemsaremoreeffectivethanever at recording and evaluating the enigmatic cloud-aerosol effect. Enhancing theseobservationaltoolswilltellusmoreaboutthelevelof“accidentalgeoengineering”alreadytakingplacefromglobalsulfateemissions,whichwill inturnhelpresearchersconsiderhow– if -thiseffectcanbeharnessedanduseddeliberately.Third, a most successful research venture should begin quietly, without political fanfare andwithoutanycommitments in themediaorbudget justificationsas towhat the researchcouldpotentiallyyield.Geoengineeringresearchatthistimeisafringefieldofstudywithinthebroaderpartisanquagmirethatisclimatepolicy.Ifadedicatedefforttocommitmoreresourcesistomoveforward,itmustbeasustainedeffortthattakesplaceacrossmanysessionsofCongress,andanyassociationwithaparticularpoliticalideologyorpartywillonlyunderminethequestforunbiasedscientificunderstanding.Fourth,legalexpertsmustbegintofocustheirgeoengineeringthoughtexercisetoamorefinitesetofconceptscenteredaroundthemostmatureproposalsbeingofferedtoday.Theuniverseoftheoreticalgeoengineeringproposalsisvast,andthustheirpolicyandlegalimplications–andsideeffects – are never ending. As long as the policy discourse around geoengineering remainstheoretical,stakeholderswillthinkfirstofthefurthest-reachingscenariosandwillformopinionsaccordingly.Butthereareonlyahandfulofseriousresearcheffortsthatmightsoonseektoplanfor fieldstudies.Theirplanswillbespecific inscopeandduration. Itwillbepossibleandtrulyuseful toput theseconceptsunder the lensof thevariousenvironmentalpolicy lawswehavetoday–theNationalEnvironmentalPolicyAct,theCleanAirAct,theCleanWaterAct,andsoon–andseehowadaptabletheyaretothesenewapplicationsandwherewemightseeregulatorygaps. Projects like the Carnegie Climate Geoengineering Governance Initiative and theEnvironmental Defense Fund’s SRM Governance Initiative will be important forums for theseactivities.

Thank you

We would like to thank the Alfred P. Sloan

Foundation for supporting this Forum.

We would also like to thank our speakers

for participating in the Forum and for

contributing to this report.

Emmett Center on Climate Change and the Environment at the University of California, Los Angeles:

law.ucla.edu/centers/environmental-law/emmett-institute-on-climate-change-and-the-environment

Harvard’s Solar Geoengineering Research Program:

geoengineering.environment.harvard.edu