BenedictSt Johns University United States Department of Geosciences and Woodrow Wilson School of Public and International Affairs Princeton University United States 1 Introduction Over the past two decades skeptics of the reality and signi64257cance ID: 84498
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).Theresultsofthethree-yearstudy,commissionedbytheU.S.ClimateChangeScienceProgram(CCSP)andpublishedin Knutsonetal.,2010,pp.157Ð161).ThelatterclaimissomewhatweakerthanIPCCÕs.ThusweÞndthatwithregardtooneofthemostpotentiallyalarmingconclusionsofclimatescienceÑthatdeadlyhurricaneseventuallywouldgetstrongerÑIPCCÕsclaimsdonotdivergewidelyfromatleastoneotherattemptatassessmentbytherelevantexpertcommunity.Takentogether,thecomparisonofIPCCÕsjudgmentsandthoseofKnutsonandcolleaguesshowsthattherangeofplausiblejudgmentsfromtheexpertcommunityonthistopicisrathernarrow,providinglittlesupportfortheargumentthatIPCCexaggeratesrisk.2.6.PredictionsofpermafrostmeltingOnemoretopicwillhelptounderscorethepoint.Itiswellacceptedthatcertainfeedbacksintheclimatesystem,suchasincreasedcloudcoverortheArcticice-albedofeedback,couldworktoaccelerateordecelerateglobalwarming.Onepotentiallylarge,positivefeedbackinvolvespermafrostmelting,whichcouldreleaseincreasingamountsofgreenhousegases.Thetotalcarboncontainedinpermafrosthasbeenestimatedat1672gigatons,morethantwicetheamountofcarbonintheatmosphere(Tarnocaietal.,2009).Thismeansthatthepotentialamplifyingeffectofgreenhousegasreleasefrompermafrostmeltingisenormous.YetthisfeedbackÔÔhasnotbeenaccountedforinanyoftheIPCCprojectionsÕÕ(Allisonetal.,2009,p.21).ThisomissionintroducesapotentiallyprofoundbiasintheclimateprojectionsÑnottowardoverestimationofclimatechange,buttowarditsunderestimation.2.7.Previousanalysis:Risbey(2008)In2008,climatologistJamesRisbeyconductedananalysisofqualitativetermsusedinrecentclimatechangeliterature,examin-ingtheuseofpotentiallyalarmistwordssuchasÔÔcatastrophicÕÕ,ÔÔurgentÕÕ,ÔÔirreversibleÕÕ,andÔÔrapidÕÕ(Risbey,2008).WhencomparedtothescientiÞcclaimsandobservationsthosetermswereusedtocharacterize,hefoundthattheiruseappearedtobeboth SupplementaryOnlineMaterialformoredetails,andforsomesampleinterviewquestions.)4.1.ÔCryingwolfÕaboutozonedepletionThehistoryofozonedepletionresearchoffersanexampleofhowscientistshavebeenattackedwhentheyover-predictedapotentiallyalarmingoutcome.InFebruaryof1992,NASAscientistsstudyingtheArcticstratosphereissuedapressreleasewarningthatamajorArcticozonehole,liketheoneoverAntarctica,coulddevelopthatspring(seee.g.,Perlman,1992).NASAÕssecondAirborneArcticStratosphericExperiment(AASE-II)hadfoundgreatlyelevatedlevelsofchlorinemonoxideintheArcticstratosphereinJanuary1992,indicatingthepotentialforsevereozonelosswiththereturnofsunlightinthespring.ItwasonthebasisofthisinformationthatscientistswarnedofpotentiallysevereArcticozonedepletioninthecomingmonths.However,whilethesciencebehindthispredictionwasnotincorrect,thelatewintermonthsturnedouttobewarmerthanexpected,preventingtheformationofthepolarstratosphericcloudparticlesthatprovidethesurfacesonwhichsomeofthekeychemicalreactionsnecessaryforpolarozonedepletionwouldtypicallyoccur.Asaresult,Arcticozonedepletioninthespringof1992waslessthanscientistshadfeared,andnoArcticozoneÔholeÕappearedthatyear(Lambright,2005;Conway,2008;OreskesandConway,2010).MoresevereArcticozonedepletionoccurredinotheryears,however.Inthewinterof2010/2011,Arcticozonelevelsreachedtheirlowestrecordedlevels,followinganunusuallyprolongedperiodofextremelylowstratospherictemperatures,andcreatinganozoneholeÔÔcomparabletothatseeninsomeyearsintheAntarcticÕÕ(NASA,2011).Intheaftermathoftheunrealized1992Arcticozoneholeprediction,NASAscientistswereseverelycriticizedintheconservativepressforcryingwolf,causingunnecessarypanic,andactingaccordingtoemotionalimperativesoranenvironmen-talagendainsteadofaccordingtothedictatesofscientiÞcobjectivity.AneditorialintheWashingtonTimes,forexample,denigratedtheoriginal3February1992NASAwarningofapotentialArcticozonehole,sayingÔÔThisisnotthedisinterested,objective,just-the-factstoneoneordinarilyexpectsfromscien-tists.Norisitthestuffofpeer-reviewedscience,theconsensus-settingstandardthathelpsestablishwhatisorisnotÔscience.ÕThisisthecryoftheapocalyptic,layingthegroundworkforadecidedlynon-scientiÞcend:publicpolicy.ÕÕThearticleconcludedthatÔÔsomepeopleintheagency[NASA]apparentlywereeagertocreatethepanicofFebruary3,forreasonshavingnothingtodowithscienceandeverythingtodowiththeirideologicalenvironmentalism.Asitis,itwouldbeniceifthenexttimeNASAcriesÔwolf,Õfewerjournalists,politiciansandcitizensheedthewarninglikesheepÕÕ( sizedineach[IPCC]reportÕÕ(Harris,2009).Hesuggestedthatthisphenomenoncouldbeexplainedatleastpartiallybysociologicalreasons,citingthereactionofthefossilfuelindustrytothe1995IPCCreportwhichwastheÞrstassessmenttodeÞnitivelyattributeglobalwarmingtoanthropogenicactivity.TheleadauthoroftherelevantIPCCchapter,climatescientistBenSanter,wasÔÔabsolute-lyviliÞedÕÕbyindustry(documentedinOreskesandConway,2010).Thisexample,hesuggests,hasmadeotherscientistsinvolvedwithlaterassessmentsmuchmorecautiouswiththeirownstatements.Whatisperhapsmostimportantaboutthisstoryisthatthisforcingfunctionwouldtendtooperateinthesamedirectionastheinternalvaluesofscientiststhemselves.Afterall,manyscientistsarecourageous,andhistoryprovidesmanyexamplesofscientistswillingtostandupfortheirÞndingsinthefaceofexternalpressure.ButiftheexternalpressurestendtotrackinthesamedirectionasscientistsÕowninstincts,thatisadifferentmatter.Weargueherethatthesepressuresoftendoalign.ScientistsÕdesiretoavoidexternalattack,andnotbeaccusedofcryingwolf,isreinforcedbytheirinternalvaluesysteminwhichobjectivityisofteninterpretedtomeandownplayingpotentiallydramaticresults.Indeed,sometimesthedesiretobeobjectiveleadsscientiststorefusetoprovideestimatesatall,whichmightbeconsideredtheultimateversionofunder-prediction.Considerthe community(Oppenheimeretal.,2007;Overpeck,2009;Vaughan,2009;Rahmstorf,2010)assettingapoorprecedent,inadequatelyrepresentingtheavailablescientiÞcmaterial,refusingtogivesufÞcientweighttonon-model-basedresearchasameansforprovidinganumericalestimate,andgivingtheimpressionthatexpectedsealevelriseismoremodestthanislikelytobethecase.Ataboutthesametime,researchonmethodsforroughlyestimatingthiscontributionevenabsentfull-scalemodels(Rahmstorf,2007;Pfefferetal.,2008)wasunderway.WhilethesepublicationsdidnotmeetthedeadlineforinclusioninAR4,someoftheresultingmethodsandÞndingsweremadeavailabletotheIPCCwritingteam.Sowhydidtheauthorsdecidetoomitanestimateforthedynamicicelosscontribution?Ininterviews,severalauthorshavestatedthattheirdecisionwasthebestjudgmentpossibleatthattime,giventheinformationavailable(Alley,2009;Gregory,2009;Solomon,2010).Thismaywellbethecase;dealingwithemergingscienceisclearlyadifÞcultissuefortheIPCC(InterAcademyCouncil,2010).However,inretrospect,andparticularlygiventhenewresearchpublishedsince2007,theviewthatitwasanoverlycautiousapproachisequallyplausible(althoughonlytimewilltellwhetheritwillresultinunder-prediction).TwofactorsinteractedtodetermineIPCCÕsapproachinthiscase:(1)thewayIPCCgenerallymanagesuncertainty,and(2)thesocialcompositionandinteractionsoftheassessmentgroupinthisparticularcase,whichinßuencetheoutcomeofitsdeliberations(OÕReillyetal.,2011,2012).Withregardtouncertaintymanagement,structural,model-baseduncertaintiesthatdominatetheWAIScaseremaininadequatelyrepresented(oraltogetheromitted),despitecontinuingreÞne-mentbyIPCCofitsmethodforjudginguncertainty.Thegeneralissueofuncertaintyhasbeenthesubjectofintensestudyinrecent inthe1960s;hecalledit(inuncharacteristicallyprosaicterms)ÔÔresistancetochangeÕÕ(Kuhn,1962,pp.151Ð152).Establishedknowledgeisthedefaultposition,untilsufÞcientevidenceisdevelopedtodislodgeit.Thus,anyonewithanewclaimÑsuchastheideathattherecouldbeanozoneholeorthathumanactivitiesarechangingtheclimatesystemÑfacestheburdenofproof.Indeed,anynewlydiscoveredphenomenonÑwhetheritbetherelativityoftimeandspace,themotionofcontinents,orthehumanimpactontheglobalclimatesystemÑwillfaceanuphillbattle.Inscience,thenullhypothesisisthatexistingknowledgeiscorrect;theburdenofproofisonthemanorwomanwhowishestodislodgethestatusquo(Kuhn,1962).Overall,thisisprobablyagoodthing,helpingtoprotectsciencefromfashionsandfads.Iftheissueatstakehasnoparticularpublicpolicyimplications,thenscientistsarenodoubtrighttoproceedcautiously,takingtheirtimetomakesuretheevidenceisbeyondreproachbeforecastingoffhard-wonpriorknowledge.ButifthereisapolicyconsequencetothescientiÞcresults,andparticularlyifthereisanegativeconsequenceassociatedwithinactionordelay,thenscientiÞcconservatismmayhavenegativesocialconsequences.AversionoferringonthesideofleastdramacanbefoundinwhatstatisticianscallType1andType2errors.Asmostscientistsknow,aType1errorinvolvesthinkinganeffectisrealwhenitisnot;aType2errormeansmissingeffectsthatareactuallythere.MakingaType1errorcanbethoughtofasbeingnaõ¬ve,credulous,orgullible;makingaType2errorcanbeinterpretedasbeingexcessivelyskepticaloroverlycautious.Interestingly,convention-alstatisticsissetuptobedeeplyskepticalandtoavoidType1errors,byplacingaveryhighstatisticalbaronclaimsforstatisticalsigniÞcance.Theuseofa95%oreven99%conÞdencelimitinmanyscientiÞcexperimentsreßectsascientiÞcworldviewinwhichskepticismisavirtueandcredulityisnot.Infact,somestatisticiansclaimthatType2errorsarenÕtreallyerrorsatall,justmissedopportunities(Lane,2007;seealsoZiliakandMcCloskey,2008;OreskesandConway,2010.)ItistellingthatprofessionalstatisticiansgenerallyregardType1errorsasmoreimportanttoavoidthanType2;socialscientistswouldarguethateachcaseshouldbejudgedonitsownmerits:whichisworsedependsuponwhatkindofdamageensuesfromtheType1versustheType2errorinthatparticularcase.ThataprofessionalstatisticiancouldpubliclyclaimthatthataType2errorisnÕtreallyanerroratallisremarkable;italsoÞtswithourhypothesisofESLD:skepticismisgood;credulityisbad.Therefore,scientistsoftensetaveryhighbar.Inthesecases,theywouldwillinglyerronthesideofdisbelievingsomethingthatis,ratherthanbelievingsomethingthatisnot(IPCCÕsapproachtouncertaintyismorenuanced;seedescriptionsandapplications inscienceforpolicy:thecaseofconsensusaroundclimatesensitivity.SocialStudiesofScience28(2),291Ð323.vanderSluijs,J.P.,vanEst,R.,Riphagen,M.,2010.Beyondconsensus:reßectionsfromademocraticperspectiveontheinteractionbetweenclimatepoliticsandscience.CurrentOpinioninEnvironmentalSustainability2(5Ð6),409Ð415.Vaughan,D.,2009.RecordedinterviewwithJ.OÕReilly.17July.Cambridge,England.Watts,A.,2011.Hurricanesandglobalwarming:stillnoconnection.(5January)WattsUpWithThat?CommentaryonPuzzlingThingsinLife,Nature,Science,Weather,ClimateChange,TechnologyandRecentNews.