TheUKCP18projectbuildsuponUKCP09currentsetofprojectionstoprovidethemostup-todateassessmentofhowtheclimateoftheUKmaychangeoverthe21stCentury.

1

ThebestnewscienceTheprojectionsarebasedonthelatestdevelopmentsinclimatescienceandweresubjecttoanindependentpeerreview,fromthecommencementoftheproject,toassessthescienceandmethodsthatunderpinUKCP18DevelopedwithusersBuildingonthelearningfromUKCP09,usergroupsforgovernmentandwidersociety,alongwiththepeerreviewpanel,havehelpedtoshapeUKCP18,co-designingtoolsandcapabilitiestobettermeetuserneeds.Forexample,(i)changingtheformatofthedatathatisprovidedtothewidely-usedOrdnanceSurvey’scoordinatesystem,(ii)anenhanceduserinterfacethatusesthelatestwebdesignand(iii)providingdatasetsthatrepresentUKclimateinscenariosof2°Cand4°CofglobalwarmingFromclimatetrendstofutureweather•  TheinstallationoftheMetOffice’snewsupercomputerhasenabledacrediblerangeofclimateprojections

2

UKCP18movesbeyondclimatetrends–buildingupontheconclusionsofUKCP09,thesenewresultstranslateglobalclimatechangestatisticsintochangingseasonalweathercharacteristicsfortheUKObservations•  InthemostrecentStateoftheUKClimate2017report,trendsshowthattheUKclimateiscontinuingtowarm

andthatsealevelscontinuetorise.•  Thelongestrunninginstrumentalrecordoftemperatureintheworld,theCentralEnglandTemperaturedataset,

showsthatthemostrecentdecade(2008-2017)wasaround1°Cwarmerthanthepre-industrialperiod(1850-1900).ThistemperatureriseintheUKisconsistentwithwarmingthathasbeenobservedataglobalscale,ofaround1°Csincepre-industrial.

MarineProjections•  AnewsetofmarineprojectionsshowthatsealevelaroundtheUKwillcontinuetoriseto2100underall

emissionpathways.

3

GeneralclimatechangetrendsprojectedoverUKlandforthe21stcenturyarebroadlyconsistentwithearlierprojections(UKCP09)showinganincreasedchanceofmilder,wetterwintersandhotter,driersummersalongwithanincreaseinthefrequencyandintensityofextremes.��Bytheendofthe21stcentury,allareasoftheUKareprojectedtobewarmer,moresoinsummerthaninwinter.��Thefigureshowsregionalprojectionsforlowest,centralandhighestUKmeanforthehighemissionsscenario,RCP8.5,for2061-2080.Theyretainspatialcoherenceandthespatialdistributionofthewarmingfordifferentpossiblefutures,showingthatsouthernEnglandwarmsmorethannorthernregionsoftheUK.��WhenwecomparethefullrangeofpossibleoutcomesfromUKCP09andUKCP18thereisagreatdealofoverlap,althoughusersmaywanttoinvestigatedifferences,forexample,intheextremeendsoftheranges.��

4

ProbabilisticProjectionsInUKCP18,theprobabilisticprojectionsprovidelocallow,centralandhighchangesacrosstheUK,correspondingtoe.g.10%,50%and90%probabilitylevels.ThefullsetofRCPscenariosareavailablefortheprobabilisticprojections,allowingustolookatthefullrangeoffutureemissionsscenarios.WecanalsolookatSRESA1BusingtheprobabilisticprojectionstocomparewithUKCP09

5

Hotsummersareexpectedtobecomemorecommon.Intherecentpast(1981-2000)thechanceofseeingasummerashotas2018waslow(<10%).Thechanceasalreadyincreasedduetoclimatechangeandisnowbetween10-20%.Withfuturewarming,hotsummersbymid-centurycouldbecomeevenmorecommon(~50%).

•  Summer2018wasoneofthehottestonrecordfortheUK,tiedwith1976,2003and2006.UKCP18showshowthechancesofextremeevents,likethatofsummer2018,maychangeinthefuturebyamountsthatdependonfutureemissionsofgreenhousegases.

•  TheUKwasoftenundertheinfluenceofhighpressure,particularlyduringJuneandJuly.ThiswastheUK’swarmestsummersince2006,thedriestsince2003andthesunniestsince1995.

•  AverageUKtemperaturewas15.8C•  Studyofchangingriskandattributiontohumaninfluenceongoing:

•  Summer2018heatwavewasatleastpartlydrivenbytheunusualhighpressureoverScandinaviaandthepatternofheatintheAtlanticOcean.

6

ObservationsTotalrainfallfromextremelywetdays(daysexceedingthe99thpercentileofthe1961-1990rainfall)hasincreasedbyaround17%inthemostrecentdecade(2008-2017),fortheUKoverall.However,changesarelargestforScotlandandnotsignificantformostofsouthernandeasternEngland.ProjectionsConsistentwithearlierprojections,UKCP18showsanincreasedchanceofwarmer,wetterwintersintheUKButvariabilityinrainfallisincreasing:wetwinterswillgetwetter,butwecanstillexpecttoseedrywinters.Thismeansthatwewillneedtoberesilienttowiderrangeofconditionsthanweareusedto.

7

ProbabilisticProjectionsforHighEmissionsScenarioPrecipitationchangesaredependentonseasonandonceagainconsistentwithearlierprojections,UKCP18showsanincreasedchanceofwarmer,wetterwintersintheUKAlsoconsistentwiththeglobalprojections,variabilityinrainfallisincreasing:wetwinterswillgetwetter,butwecanstillexpecttoseedrywinters.Thismeansthatwewillneedtoberesilienttowiderrangeofconditionsthanweareusedto.

8

RainfallpatternsacrosstheUKarenotuniformandvaryonseasonalandregionalscalesandwillcontinuetovaryinthefuture.NextsummerwillseethelaunchofafurthersetofresultsfromUKCP18whichwillprovideveryhigh-resolutionprojectionsofrainfallovertheUK,fineenoughtobeabletoresolveindividualconvectivestorms.Thiswillallowustoprovidemoredetailaroundprojectionsoflocalisedheavyrainfallforfloodriskassessments.

9

ThepatternofsealevelriseisnotuniformacrosstheUK.Sealevelriseislessinthenorthandmoreinthesouth,thisismainlyduetothemovementofland,upanddown.Wecancontinuetoexpectincreasestoextremecoastalwaterlevelsdrivenmainlybyincreasesinmeansealevelrise,althoughwecannotruleoutadditionalchangesinstormsurges.UKCP18includesexploratoryestimatesofsealevelriseoutto2300,whichshowcontinuedrisebeyond2100.Sealevelriseisalong-termchallengethatinitialresultssuggestvariessubstantiallydependingonhowsuccessfulweareatcurbingglobalgreenhousegasemissionsinthecomingyears.

10

ForLondon,sealevelrisebytheendofthecentury(whencomparedto1981-2000),forthelowemissionscenarioisverylikelytobeintherange0.29mto0.70m.Forahighemissionscenario,therangeisverylikelytobe0.53mto1.15m.ForEdinburgh,sealevelrisebytheendofthecentury(whencomparedto1981-2000),forthelowemissionscenarioisverylikelytobeintherange0.08mto0.49m.Forahighemissionscenariothisrangeisverylikelytobe0.30mto0.90m.UKCP18sealevelriseisprojectedtobehigherthaninUKCP09,butthisincreasehasalreadybeenfactoredintocurrentadaptationplanning.Duetothenewtreatmentoflandicecontributiontosealevelrise,UKCP18ishigherthanUKCP09.Forexample,theupperendoftherangeofsealevelriseinUKCP18,forthehighemissionscenarioforLondon,isaround25cmhigherthaninUKCP09at2100.Thisisnotunexpectedandhasbeenfactoredintoadaptationplanning.

11

UKCP18productsandserviceshavebeendesigned,reviewedandtestedbytheUKCP18usergroupsandhaveresultedin:

•  Webpagestoenablequickaccessinformationdependingonwhatpeoplewanttouseitfor,aswellasbeingabletovisualisetheresults.Guidancematerialsdescribethedifferentcomponentsoftheprojectindetailandexplainhowtousethem.

•  Auserinterfacewhichallowsdownloadingandtailoringmapsandgraphs,i.e.easieraccesstotheunderlyingdata

•  CEDAArchiveforthosewhoarefamiliarwithusingclimatedatafiles(netCDF).

12

TheUKCP18informationresourcessupportawiderangeoftasksfrombriefingmaterialsthroughourkeyfindingsdocumentsandinfographics,thosewhorequiremoreinformationtoinformtheirsustainabilityandadaptationplans,tothosewhorequirerawdatatoperformtheirownclimateanalysisand/orclimateimpactsanalysis,ThelaunchofUKCP18isthereforejustthebeginningandtheworkisongoing.Weareproviding24/7onlinesupportandareeffortsarenowfocusedonmakingthehighresolution2.2kmdatasetin2019.FeedbackisbeingcollatedthroughourinteractionwithourusergroupsandwebformwhichwillinformhowtoimprovetheuserinterfaceandproductsaswellasadditionalanalysisthatwecarryouttosupporttheuseofUKCP18.

13

14