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DRAFT

STATEOFCALIFORNIASEA-LEVELRISEGUIDANCE:2018Update

November2017

Photocredit:AldaronLairdPhotocredit:KeithWillis

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TABLEOFCONTENTSEXECUTIVESUMMARY............................................................................................................3

INTRODUCTION.......................................................................................................................7PurposeandIntendedUse...................................................................................................................10FrequencyofFutureUpdates................................................................................................................11

BESTAVAILABLESCIENCETOSUPPORTPLANNINGFORSEA-LEVELRISEINCALIFORNIA.12RisingSeasinCalifornia:AnUpdateonSea-LevelRiseScience.............................................................12GlobalGreenhouseGasEmissionsScenarios........................................................................................14AdvancesinSea-LevelRiseModeling....................................................................................................15

SEA-LEVELRISEPROJECTIONSFORCALIFORNIA.....................................................................17

GUIDANCEONHOWTOSELECTSEA-LEVELRISEPROJECTIONS..............................................20

RECOMMENDATIONSFORSEA-LEVELRISEPLANNINGANDADAPTATION.............................27

TOOLSAVAILABLETOVISUALIZESEA-LEVELRISESPATIALLY..................................................31

CONCLUSION.........................................................................................................................34

GLOSSARY.............................................................................................................................36

APPENDIX1:GUIDANCEDOCUMENTDEVELOPMENT............................................................40

APPENDIX2:MAPOFTIDEGAUGELOCATIONS.....................................................................42

APPENDIX3:SEA-LEVELRISEPROJECTIONSFORALL12TIDEGAUGES...................................43

APPDENDIX4:RISKDECISIONFRAMEWORK.........................................................................67

APPDENDIX5:QUESTIONSFROMTHEPOLICYADVISORYCOMMITTEE..................................68

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EXECUTIVESUMMARY

TheclimateacrossCaliforniaischanging,andtheeffectssuchasrisingaveragetemperatures,shrinkingmountainsnowpack,moreintensestorms,andhighersealevelsareexpectedtocontinueandworseninthecomingdecades.Sea-levelrisecausedbythethermalexpansionofwarmingoceanandmeltingoflandiceastheEarthwarms,isoneofthemostobviousmanifestationsofthetrendofclimatechangeandisanimmediateandrealthreattolives,livelihoods,transportation,economies,andtheenvironmentinCalifornia.

InApril2017,catalyzedbydirectionfromGovernorBrownandtheneedtoensurethebestavailablesciencewasinformingsea-levelriseplanningdecisionsinCalifornia,aWorkingGroupoftheCaliforniaOceanProtectionCouncilsScienceAdvisoryTeamreleasedareport,entitledRisingSeasinCalifornia:AnUpdateonSea-LevelRise.Thereportsynthesizedthecurrentstateofsea-levelrisescience,includingadvancesinmodelingandimprovedunderstandingoftheprocessesthatcoulddriveextremeglobalsea-levelriseasaresultoficelossfromtheGreenlandandAntarcticicesheets.Thereportfoundthat:

Scientificunderstandingofsea-levelriseisadvancingatarapidpace. Thedirectionofsea-levelchangeisclear;sealevelsarerising. TherateoficelossfromtheGreenlandandAntarcticicesheetsisincreasing,andCaliforniais

particularlyvulnerabletosea-levelrisecausedbyicelossfromWestAntarctica. Newscientificevidencehashighlightedthepotentialforextremesea-levelrise. Probabilitiesofspecificsea-levelincreasescaninformdecisions. Currentpolicydecisionsareshapingourcoastalfuture. Waitingforscientificcertaintyisneitherasafenorprudentoption.

Theincreasedunderstandingofsea-levelriseprojectionsandpolaricesheetlosswarrantedanupdatetotheStatessea-levelriseguidancedocumenttoensuredecisionswerebasedonthebestavailablescience.Additionally,anincreasedpolicyfocusrequiringstateandlocalgovernmentstoincorporateclimatechangeintodecisionmakingmeritedanupdatetoaddresstheneedsofbothstateandlocalaudiences.

Thisupdateddocument,theStateofCaliforniaSea-LevelRiseGuidance(Guidance),providesaboldscience-basedmethodologyforstateandlocalgovernmentstoanalyzeandassesstherisksassociatedwithsea-levelriseandincorporatesea-levelriseintotheirplanning,permitting,andinvestmentdecisions.ThisGuidanceprovides:

1. Asynthesisofthebestavailablescienceonsea-levelriseprojectionsandratesforCalifornia;2. Astep-by-stepapproachforstateagenciesandlocalgovernmentstoevaluatethose

projectionsandrelatedhazardinformationindecisionmaking;and3. Preferredcoastaladaptationapproaches.

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WhatHasChangedSincethe2013UpdatetotheGuidance?

Newpolicycontextandexpandedaudience.StateagencieswerethetargetaudiencefortheearlierversionsofthisGuidance,whichwasinitiallyadoptedin2010andupdatedin2013.However,overthepastfiveyears,therehasbeenamultitudeofpolicyandlegislativedirectivesandmandatesfocusedonimprovingclimateadaptationandresiliencyinCaliforniaatboththestateandlocallevel,including:

GovernorBrownsExecutiveOrderB-30-15directingstateagenciestofactorclimatechangeintotheirplanningandinvestmentdecisions;

SenateBill379(Jackson)requiringlocalgovernmentstoincorporateclimateadaptationandresiliencystrategiesintotheirGeneralPlans;and

SenateBill264(Wieckowski),whichestablishedtheGovernorsOfficeofPlanningandResearchsIntegratedClimateAdaptationandResiliencyProgramtocoordinatelocalandstateclimateadaptationstrategies.

Withthisincreasedpolicydirectionandimprovedunderstandingofpossibleimpacts,the2018Guidanceaimstorespondtotheneedsforguidancethatcanhelpcities,countiesandtheStatepreparefor,andadaptto,sea-levelrise.

Significantadvancesinthescientificunderstandingofsea-levelrise.

Scenario-basedversusprobabilisticsea-levelriseprojections.The2013versionoftheStatessea-levelriseguidanceprovidedscenario-basedsea-levelriseprojectionsbasedona2012NationalResearchCouncilreport;thesescenario-basedprojectionswerenottiedtoaspecificgreenhousegasemissionsscenarioorlikelihoodofoccurrence.ThisupdatedGuidanceincorporatesprobabilisticsea-levelriseprojections,whichassociatealikelihoodofoccurrence(orprobability)withsea-levelriseheightsandrates,andaredirectlytiedtoarangeofemissionsscenarios.Usingprobabilisticsea-levelriseprojectionsiscurrentlythemostappropriatescientificapproachforpolicysettinginCalifornia,providingdecisionmakerswithincreasedunderstandingofpotentialsea-levelriseimpactsandconsequences.

H++scenario.Theprobabilisticprojectionsmayunderestimatethelikelihoodofextremesea-levelrise(resultingfromlossoftheWestAntarcticicesheet),particularlyunderhighemissionsscenarios.Therefore,the2018updatetotheGuidancealsoincludesanextremescenariocalledtheH++scenario.Theprobabilityofthisscenarioiscurrentlyunknown,butitsconsiderationisimportant,particularlyforhigh-stakes,long-termdecisions.

Thescienceonsea-levelrisewillcontinuetoevolve,possiblysignificantly,incomingyears.Continualupdatestoourscientificunderstandingmustbeexpectedasobservationsandmodelsimprove,andastheenvironmentcontinuestochange.ThisGuidanceisbasedontherecognitionthatitisnolongerappropriatetoassumeastaticenvironmentinplanninganddecisionmaking.

ExtendedstakeholderengagementinGuidancedevelopment.The2018updatetotheGuidancewasdevelopedbytheOceanProtectionCouncil(OPC),inclosecoordinationwithaPolicyAdvisory

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CommitteewithrepresentationfromtheCaliforniaNaturalResourcesAgency,theGovernorsOfficeofPlanningandResearch,andtheCaliforniaEnergyCommission.Toimprovecoordinationandconsistencyinsea-levelriseplanning,OPCalsocollaboratedcloselywithstatecoastalmanagementagenciesandothermemberagenciesoftheStatesCoastalandOceanWorkingGroupofCaliforniasClimateActionTeam(CO-CAT).Inaddition,OPC,withassistancefromtheOceanScienceTrustandengagementexperts,solicitedinputfromcoastalstakeholders(localgovernments,regionalagencies,federalagencies,coastalconsultants,environmentalgroups,Tribes,andothers)tobetterunderstandtheneedsandconcernsrelatedtoplanningforsea-levelriseandrelatedrisksacrossthestate.

Sea-levelriseriskanalysisanddecisionframework.ThisGuidanceprovidesastep-wiseapproachtohelpdecisionmakersassessriskbyevaluatingarangeofsea-levelriseprojectionsandtheimpactsorconsequencesassociatedwiththeseprojections.Dependingonthefinitefactorsofaproposedprojectslocationandlifespan,decisionmakerscanevaluatethepotentialimpactsandadaptivecapacityoftheprojectacrossaspectrumofsea-levelriseprojections.Thisanalysiswillenablestateagenciesandlocalgovernmentstodeterminewhichsea-levelriseprojectionsandrelatedhazardinformationtoconsiderindifferenttypesofdecisionsacrossCalifornia.

Thefollowingstepsprovideadecisionframeworktoevaluatetheconsequencesandrisktoleranceofvariousplanningdecisionsandshouldbeusedtoguideselectionofappropriatesea-levelriseprojections:

PreferredCoastalAdaptationPlanningApproaches.ThisGuidanceexpandsthepreferredcoastaladaptationplanningapproachesidentifiedinOPCspreviousguidance,incorporatingexistinglaw,expressedpolicypreferencesbytheGovernorandLegislature,andthegoaloffosteringconsistencyacrosscoastalandoceangovernmentagencies.Theserecommendationsinclude:

Adaptationstrategiesshouldprioritizeprotectionofvulnerablecommunitiesandtakeintoconsiderationsocialequityandenvironmentaljustice.

Coastalhabitatsandpublicaccessshouldbeprotectedandpreserved. Acuteincreasesinsea-levelrisecausedbystormsurges,ElNioevents,kingtides,orlarge

wavesshouldbeconsidered.Theseeventscouldproducesignificantlyhigherwaterlevels

Step1:

Idengfythenearestgdegauge

Step2:

Evaluateprojectlifespan

Step3:

Idengfyarangeofsea-levelriseprojecgons

Step4:

Evaluatepotengalimpactsandadapgve