WTW-自然灾害回顾2023年7月至12月（英）

NaturalCatastrophe

Review:Expertinsights,lessonslearned

andoutlook

July–December2023

ForewordRecenteventsOutlookContactsandinformation1

TABLEOFCONTENTS

1/Foreword

4

2/Recentevents

8

2.1Analyzingtheaftermathof2023'ssevereweatherintheU.S.

9

2.2GargantuanhailinnorthernItaly:Naturalclimatevariabilityorclimatechange?

13

2.3FromHawai‘itoHellas:Naturesparks,humansfanwildfiresin2023

17

2.4Theföhn-omenalwindcrankinguptheheat

21

2.5Panamadrought:Anebbingtideliftsallboats’transitfees

25

2.6AturningpointinunderstandingNorthAtlantichurricaneactivityinachangingclimate

28

2.7RapidintensificationinthePacific:Ataleoftwotropicalcyclones

31

2.8SummerEuropeanwindstorms:Thepotentialfor€1billionEurolosses?

36

2.9StormDaniel:Acautionarytaleontheneedtomaintaininfrastructurebeforeit’stoolate

41

2.10Urbanfloodinginachangingworld:NewYorkCityandHongKong

46

2.11Fromrainfalltoresilience:Slovenia's2023record-breakingfloods

50

2.12Puttingthedevastating2023Mw6.8Moroccoearthquakeincontext

54

2.13Aworldthatspringsclimatesurprises:Antarcticseaicetrends

58

3/Outlook

62

3.1ThetropicalPacificisreadytorumble

63

3.2AcloserlookatEurope’swindstormoutlookforwinter2023/2024

67

3.3CampiFlegrei:Examiningthesciencebeyondtheheadlines

72

4/Contactsandinformation

78

ForewordRecenteventsOutlookContactsandinformation2

Foreword

Foreword

Recentevents

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Contactsandinformation

3

Welcome

InEurope,northernItalyfacedanunprecedented

hailstorm,andcertaincountries—includingPortugal,Spain,ItalyandGreece—werehitbyseverewildfires.ThePanamaCanalexperienceditsworstdroughtsinceitopenedin1914,leadingtomajorglobalshipping

disruptions.Andfloodingcauseddestructionglobally,withnotableeventsinSlovenia,NewYorkCity,HongKongandBeijing.StormDaniel,inparticular,brought

extensivefloodingtotheMediterraneanregion,culminatingincatastrophicdamfailuresin

Derna,Libya.

WelcometothelatesteditionofWTW's

NaturalCatastropheReview,abiannual

publicationthatbringsinsightsfrom

ourexperts,includingWTW’sResearch

Network,toexaminerecentnatural

disasters,lessonslearnedandemerging

trends.Offeringasmarterwaytorisk,

Secondaryperils—amisnomer?

A"secondary”perilisanaturalhazard

thatonaverageproducessmalltomidsizedamagescomparedwith“primary”

perilssuchasearthquakesorhurricanes.Commonexamplesincludesevere

convectivestorms,wildfires,floodsand

droughts.However,lossesfromsecondaryperilshaveriseninrecentyears.This

increasehasledmanyinsurerstocall

foralternativelabels,suchas"earnings”perils,1toacknowledgethatwhatmight

besecondaryintermsofindividualeventlossescanstillhaveaprimaryeffecton

theirprofitabilityinaggregate.

thisreportgoesbeyondthenumbersto

providenewperspectivestohelpwith

naturalcatastropheriskmanagement

andresilienceacrossmultiplesectors.

Thiseditiondelvesintothephysical,vulnerabilityand

socioeconomicfactorsthatcontributedtothelargest

naturaldisastersinthesecondhalfof2023(Figure

1)andexaminestheoverarchingthemesoftheyear.

Italsoprovidesanoutlookforearly2024,focusing

ontheongoingElNiñointhePacificandwinter

windstormforecastsfortheEuropeanNorth

Atlanticregion.

As2023drewtoaclose,theeconomicandsocietal

impactsof"secondary"perilsbecameafocalpoint

forriskmanagersfollowingayeardominatedby

severeconvectivestorms(SCSs),wildfires,droughts

andfloods.IntheU.S.,insurerssawthecostliest

SCSyearonrecord,withtotalclaimsexceeding$50

billion.Meanwhile,inthesecondhalfof2023,Hawai‘i

witnesseditsdeadliestwildfireinrecenthistory,

claimingover100lives.

1Moody'sRMS.EarningsPerils:RedefiningtheRisksThatMatter.(2023).

Foreword

Recentevents

OutlookContactsandinformation4

Figure1.ProminentnaturalcatastrophesJuly–December2023

HurricaneIdalia

(August)

WindstormCiarán

(November)

Sloveniaflooding

(August)

NorthernItaly

gargantuanhail

(July)

U.S.severe

convectivestorms

Europeanwildfires,Mediterraneanregion

(July—October)

(January—December)

HurricaneOtis

(October)

TyphoonDoksuri

(July)

Hawai'iwildfires

(August)

HongKongflooding

(September)

Moroccoearthquake

(September)

PanamaCanaldrought

(May—December)

StormDaniel,

NewYorkCityflooding

(September)

Mediterraneanregion

(September)

5

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Foreword

Recentevents

Beyondeconomicdamages,numerousdisastersin

2023highlightedtheneedforaproactiveapproach

toriskidentification,mitigationandadaptation.Ina

worldincreasinglyshapedbyaginginfrastructure,

climatechangeandurbangrowthintorisk-prone

areas,wearenowfacingdisastersthatwereeither

notanticipatedordeemedunlikelyjustafewdecadesago.Thisevolvingsituationnecessitatesapivot

towardnotjustrecognizingbutactivelypreparingforawiderarrayofrisks,someofwhichmighthavebeenpreviouslydismissedorunderplayed.

Onewayriskmanagerscantacklethischallenge

isbyexamininghowhistoricaleventscouldhave

resultedinworseoutcomes,alsoknownasdownwardcounterfactualanalysis.2Forexample,in2018,Hawai‘iexperiencedwildfiresverysimilartothosein2023

affectingWestMaui(Section2.3).Althoughthe2018fireswerelesssevere,exploringhowtheymighthaveescalatedcouldhavebetterpreparedriskmanagers

forthesignificantlymoredestructivewildfiresin2023.Similarly,a2022researchpaperonhistoricalfloodinginLibyawarnedthatarecurrenceofamajorevent,

suchasthedevastating1959floods,couldresultindamfailuresinDerna.3Despitethisprediction,thewarningswentunheeded,andtheanticipatedrisk

materializedfollowingstormDanielin2023(Section2.9).

Theimportanceofsuchforesightcannotbe

overstated,especiallygiventhatthehistoricalrecordalonedoesnotcapturethefullrangeofpotential

risksfromrarenaturalhazards.Byexaminingwhat-ifscenarios,organizationsandgovernmentscangaininsightsintopotentialvulnerabilitiesanddevelop

strategiesforamoreresilientfuture.

Ayearofclimaterecords

AccordingtotheEU’sCopernicusClimateChange

Service,theglobalmeantemperaturerosetoa

remarkable1.48°Cabovethepre-industrial(1850

–1900)averagein2023,4surpassingtheprevious

recordof1.25°Cjointlyheldby2016and2020.The

scaleofthewarmingwasevidentassevenmonthsoftheyearmarkedtheirhighesttemperaturesonrecord.Theoceansalsosawexceptionalwarmth,withglobalsea-surfacetemperatures(SSTs)atrecordmonthly

highsfromAprilthroughDecember,notablyinthe

easternNorthAtlantic,GulfofMexico,Caribbean

andlargepartsoftheSouthernOcean.Meanwhile,

Antarcticseaiceendureditssmallestmaximumextentinthesatelliteera(Section2.13).

Theserecordsprovidedabackdroptothe28th

ConferenceoftheParties(COP)inDubai,whereanewglobalagreementlaidthegroundforatransitionawayfromfossilfuelsandincludedsignificantcommitments

totriplerenewableenergycapacityanddouble

energyefficiencyby2030.Despitetheseefforts,theInternationalEnergyAgencynotedthatthecurrenttrajectorysuggeststhe1.5°CParisAgreementtargetwillbechallengingtoachieve.5

2WooG.,MaynardT.,SeriaJ.Reimagininghistory:counterfactualriskanalysis.Lloyd’sofLondonReport.(2017).

3Ashoor,A.A.R.EstimationofthesurfacerunoffdepthofWadiDernaBasinbyintegratingthegeographicinformationsystemsand

SoilConservationService(SCS-CN)model.JOPAS21,90–100(2022).

4Copernicus.

2023isthehottestyearonrecord,withglobaltemperaturesclosetothe1.5°Climit

.(2023).5Reuters.

COP28pledgessofarnotenoughtolimitwarmingto1.5C-IEA

.(2023).

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6

Insuredlossestop$100billion

In2023,globalinsuredlossesexceeded$100billionforthefourthconsecutiveyear,afteradjustingfor

inflation.Echoingpreviousyears,theworldfacedaconsiderableprotectiongap,withtotaleconomiclossessurpassing$350billion.Ayearrecording

morethan$100billionininsureddamagesisnowmoreofanormthananaberration,reflecting

growthinexposuresandinflation.Secondaryperillosses,primarilysevereconvectivestormsinthe

U.S.andEurope,contributedsubstantiallytothe

year'sinsuranceclaims,underscoringtheirgrowing

influence.InSection2.1,WTW’sCameronRye

reviewstherecord-breakingSCSdamagesintheU.S.,emphasizingtheneedforriskmanagerstoredefine

expectationsofan“average”yearforthisperilinthe2020s.Meanwhile,inSection2.2,anarticleledby

MichaelKunzandJannickFischerfromtheKarlsruheInstituteofTechnologyexaminesJuly'sgargantuan

hailinnorthernItalythroughaclimatechangelens.

Warmseasdriveanunusualyearfor

tropicalcyclones

TheNorthAtlanticbecameafocalpointofdiscussionin2023duetoaclashbetweenexceptionally

warmSSTs—typicallyacatalystforheightened

hurricaneactivity—andthepresenceofElNiño,

whichishistoricallyassociatedwiththesuppressionofstorminess.InSection2.6,JamesDoneofthe

NationalCenterforAtmosphericResearchanalyzestheseason,markedbymanystormsbutfewlandfalls.

HedelvesintothereasonsforthewarmSSTsandquestionswhetherclimatechangeisalteringthehistoricalElNiñoSouthernOscillation-tropical

cyclonerelationship.

InSection2.7,thefocusshiftstothenorthernPacific,whereWTW’sJessicaBoyddiscussestheocean’s

tropicalcycloneactivityin2023,markedbytwo

particularlydamagingstorms,DoksuriandOtis,thatunderwentrapidintensificationbeforelandfall.

Preparednessandresilience

Asinpreviousyears,2023sparkeddiscussionsondisasterpreparedness,emergencyresponseand

resilience.InSection2.3,WTW’sDanielBannisterreviewstheyear’smajorwildfires,highlightinghowhumanactionsandsocietaldecisionsplayeda

significantroleintheseverityofseveraldisasters,

includingthedeadlyHawai‘ifires.Floodingalsoraisedquestions,particularlyinrelationtothereadinessof

urbanareastomanageflashfloodrisksinawarmerworld.InSection2.10,anarticleledbyWTW’s

NeilGunnandNewcastleUniversity’sChrisKilby

examinesthefloodeventsinNewYorkCityandHongKong,showcasingthebenefitsofresilienturban

designandhigh-resolutionmodeling.

RenewableenergyinElNiño'swake

ElNiñoisexpectedtocontinueinto2024.InSection3.1,WTW'sScottSt.Georgeexploresitsimplicationsforglobalweatherpatterns,focusingonregional

watersuppliesandrenewableenergyproduction.Thisphenomenoncansignificantlyalterrainfall,potentiallycausingdroughtsorfloods,therebyimpacting

wateravailability.Atthesametime,renewable

energysourcesmaybeaffected.Forinstance,

shiftingweatherpatternscouldreducewindenergygenerationinsomepartsoftheworld.Recognizing

andadaptingtothesechangesiscrucialforeffective

waterresourcemanagementandensuring

consistentrenewableenergyproductionduringElNiño'sinfluence.

Geologicalrisks

Amid2023’sweatherandclimaterecords,wemustnotforgetthedevastatingKahramanmaraşearthquakesinTürkiyeinFebruary(see

WTW’sH1NaturalCatastrophe

Review

)andtheMw6.8earthquakeinMarrakech,

Morocco,inSeptember.InSection2.12,RossStein

andco-authorsfromTemblorreviewtheMorrocco

earthquake,highlightingtherarityoftheevent,whichstruckinaremotepartoftheAtlasMountains.Anothergeologicalriskthatmadeheadlinesin2023wasthe

volcanicunrestatCampiFlegreinearNaples,Italy.

InSection3.3,WTW’sJamesDalzielexploresthe

sciencebehindtheheadlines,includingthelikelihoodandconsequencesofaneruptionofthissupervolcano.

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Recentevents

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Foreword

Recentevents

2.1Analyzingtheaftermathof2023'ssevereweatherintheU.S.

ByCameronRye

Withsevereconvectivestormshavingcausedarecord-breaking$50billionplusininsuranceclaimsin2023,thereisagrowingneedfor

insurersandotherriskmanagerstoredefineexpectationsofan"average"yearforthisperilinthe2020s.

In2023,insurerssawthecostliestyearonrecordfor

U.S.severeconvectivestorms(SCSs),withtotalclaimsexceeding$50billionforthefirsttime.Thisfigure,

whichincludesdamagefromtornadoes,hailand

straight-linewind,representedamajorshareofglobalinsuredlosses—whichhavenowexceeded$100

billionforthefourthconsecutiveyearafteradjustingforinflation.Inrecenttimes,insurershaveviewed

annualizedlossesintheregionof$20billionto$30billionfromU.S.convectivestormsasindicativeofa

challengingyear.Butthisthresholdshouldnowbe

reevaluatedaftertheunprecedenteddamageseenin2023andthecontinuedgrowthofpropertyexposures.

In

WTW’sH1NaturalCatastropheReview

,we

highlightedthefirstquarterof2023asbeingunusually

activefortornadoes,withthehighestnumberof

eventsonrecordbetweenJanuaryandMarch.This

rapidstartwasfollowedbyseveralsevereoutbreaksinthesecondhalfoftheyear,includingasequence

of13tornadoesinnortheasternIllinoisonJuly12thatcausedover$1billionindamage.Anothernotable

outbreakoccurredAugust4to8,with40tornadoesacrosstheEasternU.S.,PlainsandMidwest,includingtwoEF3-ratedstormsthattoucheddowninthestatesofNewYorkandColorado.

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Atthetimeofwriting,thepreliminarytotalnumberoftornadoesfor2023standsat1,423,whichis13%abovethe1990–2022averageof1,260(Table1).

Haildamageisusuallytheprimarylossdriverfrom

SCSevents,and2023hasbeennoexceptionwith

1,077preliminarylargehailreports—aremarkable77%abovethelong-termaverage(Table1).Thishasonly

beenexceededinrecentyearsby2011whenthere

were1,079reportsoflargehail,resultinginthelargestinsuredlossyearonrecordatthetime.Someofthe

mostsevereoutbreaksin2023occurredinColoradoinJunewhereover90concertgoersweretreated

forhail-relatedinjuries,1andinMinnesota,which

experiencedhailovertwoinchesindiameterinboth

JulyandAugust,2causingsubstantial

propertydamage.

Table1.PreliminarycountsofU.S.tornadoesandlargehailfor2023.Alsoshownisthelong-term(1990–2022)average.

Tornadoes

Largehail(>2inches)

2023

1,423

1,077

1990–2022average

1,260

607

Datasource:

U.S.StormPredictionCenter.

Formanyyears,insurershavereferredtoconvectivestormsasa“secondaryperil”becausetheseeventshavehistoricallyproducedsmalltomidsizelosses.

However,claimsfromsecondaryperils—whichalsoincludefloodsandwildfires—haveriseninrecent

years,leadingmanyintheindustrytoquestion

whetherthislabelisallthatuseful.WhenanalyzingtheaftermathoftherecentsevereweatherintheU.S.,it

isimportanttocontextualizethisincreaseinlossesbyexamininghowpropertyexposuresarechangingwhilealsonotforgettingabouttheimportantrolesofnaturalvariabilityandclimatechangeinshapingthehazard.

Detailedinsightsintoexposuretrends

Itiswidelyrecognizedthatoneofthekeyinfluences

behindincreasingU.S.naturalcatastrophelossesisthegrowthinvalueatrisk—drivenbyincreasesinwealth,

populationandthenumberofassetsinexposed

areas.Disentanglingtherelationshipbetweenthese

factorsandinsuranceclaimshastraditionallyrelied

onanalyzingtemporaltrendsinnationwideorstate-

levelsocioeconomicvariablessuchasGDP.3Whilethisapproachoffersahigh-levelviewofexposuregrowthovertime,itcannotprovidedetailedinsightsintohowpropertynumbershavechangedinhigh-riskareas,

whichisarguablyofgreatervaluetoinsurerswhenitcomestounderstandinghowtheriskisevolving.

NewresearchfromtheUniversityofColoradohasnowgonesomewaytoaddressingthisgap,byproducinganovelhigh-resolution(250meter)datasetonpropertytrendsincatastrophe-exposedareas.4

Thedatasetcoverstheperiod1945–2015and

includesfiveU.S.perils:tornados,hurricanes,floods,wildfiresandearthquakes.Inthecaseoftornados,

theauthorsidentifiedhazardhotspotsusinghistoricalstormpathsfromtheNationalWeatherServiceStormPredictionCenter.Thesepathswerethenoverlaidwith

landuseinformationfromtheHistoricalSettlementDataCompilationfortheU.S.(HISDAC-US).

1Kaufman,G.

FreakHailStormDuringLouisTomlinson’sRedRocksShowHospitalizes7,InjuresDozens.

Billboard.(2023).

2NWSDuluth[@NWSduluth].

ThethunderstormcurrentlymovingeastofBowstringandMarcellMNproducedtennissizedhailasitpassedoverLittleJessieLake

.Twitter.(2023).3e.g.Barthel,F.&Neumayer,E.Atrendanalysisofnormalizedinsureddamagefromnaturaldisasters.ClimaticChange113,215–237(2012).

4Iglesias,V.etal.RiskyDevelopment:IncreasingExposuretoNaturalHazardsintheUnitedStates.Earth’sFuture9,e2020EF001795(2021).

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Theresultsshowthatoverthepasteightdecades,

thenumberofstructureslocatedwithintornado

hotspotsintheU.S.increasedby7.8million(Figure1).Outofthisfigure,22%havebeenbuiltsince

theturnofthecentury.Priortotheyear2000,the

growthinstructureswasprimarilyduetoexpansionintoundevelopedareas.However,post-2000urbanconsolidationhasplayedagreaterrole,withtherate

ofdensificationbeing2.3timesthenationalaverage.

Thisdensificationhasbeenlargelydrivenbyeconomicgrowthintornado-susceptiblecitiessuchasAtlanta.

Thisresearchclearlyhighlightsthepressuresonthe

insuranceindustry:Bybuildingmorestructuresin

tornadohotspots,wearecreatingthepotentialfor

progressivelylargerlosses.Itshouldbenotedthatthedatabaseonlygoesupto2015,andexposureshave

alreadyincreasedfurthersincethen—atrendthatis

likelytocontinueoverthecomingdecades.AseparatestudyledbyVillanovaUniversitysuggeststhateven

attheendofthe21stcentury,exposuregrowthcouldstillhavealargereffectontornadolossesthanclimatechange.5Theauthorsofthisstudyprojectthatthe

combinedeffectsofexposureandclimatecould

leadtoathreefoldincreaseinthemediannumberofhousingunitsaffectedbytornadosby2100.

Figure1.EvolutionofthebuiltenvironmentinU.S.tornadohotspotssince1945.

Source:Iglesiasetal.(2021).

106,000

Thenumberofstructures

addedperyear2000–2015

450%

Growthinthetotalbuilt-uparea1945–2015

7.8million

Increaseinthenumberofstructures1945–2015

Table2.Thelikelihoodofanunfavorableyearaccordingtoa

U.S.severeconvectivestormcatastrophemodelusedbyWTW.Themodelcontains100,000yearsoflosses,whichwereusedtocalculatethelong-termaverageannualloss(AALLT).The

likelihoodofselectingayearatrandomthatis(a)aboveAALLTand(b)1.5xaboveAALLTwascalculated.Thiswasrepeated

usingfive-yearand10-yearsamples.

Likelihood

1-yearsamples:

SampleyearaboveAALLT

44%

Sampleyear1.5xaboveAALLT

10%

5-yearsamples:

Atleast1sampleyearaboveAALLT

93%

Atleast1sampleyear1.5xaboveAALLT

42%

10-yearsamples:

Atleast1sampleyearaboveAALLT

99.5%

Atleast1sampleyear50%aboveAALLT

67%

5Strader,S.M.,Ashley,W.S.,Pingel,T.J.&Krmenec,A.J.Projected21stcenturychangesintornadoexposure,risk,anddisasterpotential.ClimaticChange141,301–313(2017).

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Assessingtheodds

Althoughtheincreasednumberofpropertiesinhigh-

riskareasisakeyfactorinexplainingthesubstantiallossesfromlastyear'sstorms,itisimportantto

rememberthat,evendecadesago,SCSeventscouldproducesignificantlosses.Agoodexampleofthis

isthe1965PalmSundaytornadooutbreak,whichwasoneoftheworstsevereweatherepisodesin

U.S.history(Figure2).SpanningacrossMidwesternandSoutheasternstates,theoutbreakspawned55tornadoesinasingledayandproducedestimateddamagesof$200million6($2billionin2023U.S.

dollars).Devastatingoutbreakslikethiswill

continuetohappenduetonaturalvariability,whichremainsasignificantcontributorto

weather-relatedcatastrophes.

Insurerscanbetterunderstandlossvolatilitythroughcatastrophemodels,whichsimulatetensofthousandsofyearsofhypotheticaleventsforpresent-day

exposures.Thelikelihoodofanunfavorableyearcouldbehigherthanyoumightinitiallythink.InaU.S.SCS

modelusedbyWTW,thereisa42%chanceofhavingatleastoneyearwithinafive-yearperiodthathasa

loss1.5timesabovethelong-termaverage,andina

10-yearperiod,thisnumberincreasesto67%(Table2).Therefore,weshouldnotbesurprisedifweexperienceoutsizedlossesormultipleabove-averageyearsin

arow.

Lastyear'ssevereweathermayhavebeendueto

naturalvariability.Evenifthisiscorrect,westillshouldnotoverlookthepotentialimpactofclimatechange

onthisperil.

TheIntergovernmentalPanelonClimateChangenoteswithhighconfidencethatclimatemodelsconsistentlyprojectenvironmentalchangesconducivetomore

frequentandintensesevereconvectivestormsinthefuture.7Thisisbecauseawarmeratmospherethat

holdsmorewaterprovidesstormswithmoreenergyforformationandintensification.Detectingthese

changestodayischallengingduetotheinherent

rarityofconvectivestormsintheU.S.,whichmeansthattrendsinobservationsoftendonotmeetthe

conventionalthresholdsforstatisticalsignificance.Thereissomeevidencethatthefrequencyof

severeweatheroutbreakswithmanytornadoesis

increasing,butthishasnotyetbeenlinkedtoclimatechange.8Thisuncertainty,however,shouldnotlead

tocomplacencyaboutthebroaderimplicationsandrisksofclimatechangeforthisperil.Thistopicis

furtherexploredinSection2.2,whichexaminestheunprecedentedItalianhailstorminJuly2023.

Makinguptheaverage

Finally,weshouldbearinmindthatasexposuresgrow,theexpected(oraverageannual)lossalsoincreases.

Whatwasconsideredanaverageloss10or20years

agoislikelynolongerareliableguidetofuturelosses.

ArecentreportbyVeriskputsthelatestglobal

modeledaverageannuallossfromallperilsat$133

billion.9Fromanactuarialperspective,smalltomidsizelosses(orsecondaryperils)makeupmostofthistotal.Largedisasters,suchasaCategory5hurricanehittingMiami,areinfrequent,whichmeansthatinaggregatethesmallerbutmorecommonperilsdominateour

viewofexpectedtotaldamages.

Figure2.1965Elkhart,Indiana,doubletornadoonPalmSundaytakenbyPaulHuffman.

Source:NOAAPhotoLibrary.

Therefore,aswealthandexposurecontinuetogrow,

weshouldexpectan“averageyear”tobecomposedofincreasinglylargerclaimsfromcommonperilssuchasconvectivestorms,wildfiresandfloods.

Overall,thismeansthatinsurersandotherrisk

managersshouldregularlyrecalibratetheirviewofrisk.AnnuallossesintheregionoftensofbillionsofdollarsfromSCSshouldnolongerbeasurprise

inthe2020s,particularlywhenthedicerolled

bynaturalvariabilitygeneratesayearwith

above-averagestorminess.

6NationalWeatherService.

50thAnniversaryofthe1965PalmSundayOutbreak

.(2023).

7IntergovernmentalPanelOnClimateChange.ClimateChange2021–ThePhysicalScienceBasis:WorkingGroupIContributiontotheSixthAssessmentReportoftheIntergovernmentalPanelonClimateChange.(CambridgeUniversityPress,2023).

8Tippett,M.K.,Lepore,C.&Cohen,J.E.MoretornadoesinthemostextremeU.S.tornadooutbreaks.Science354,1419–1423(2016).

9Verisk.

2023GlobalModeledCatastropheLosses.

(2023).

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2.2GargantuanhailinnorthernItaly:

Naturalclimatevariabilityorclimatechange?

ByMichaelKunz,JannickFischerandDanielBannister

InJuly2023,northernItalywitnessedtwo

unprecedentedEuropeanhailstonerecords:first,a16centimeterhailstonewasfound,

followedbya19centimeterstonejustfivedayslater.Theseoccurrencesprompt

questionsabouttheinfluenceofclimate

changeonsuchextremeeventsandthe

potentialforincreasedseverityinthefuture.

Record-breakinghailstonesinnorthernItaly

NorthernItalyisnostrangertothedamagingeffects

ofenormoushailstones,but2023witnessedan

alarmingincreaseinthesizeofhailstones.The

previousEuropeanhailsizerecordof15centimeters

wasbrokentwicewithinoneweekinJuly2023.

OnJuly19,largehailwithamaximumsizeof16

centimetersfellinCarmignanodiBrentainnorthern

Italy,provinceofVeneto(Figure1).Thehailstoneshad

atypicalspheroidalshapewithlonglobes(Figure2,

top).Incontrast,thelargesthailstonethatshattered

therecordonJuly24,nearAzzanoDecimo,Friuli-

VeneziaGiulia,withasizeof19centimeters,hada

ratherunusualshape(Figure2,bottom)butwasstill

acceptedtobeagenuinehailstonebyexpertsofthe

EuropeanSevereStormsLaboratory(ESSL).Suchlarge

hailstonescanseverelydamagebuildings,carsand

criticalinfrastructure(e.g.,photovoltaicpanels)and

cancompletelydestroyharvests.

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Therecordhailonbothdayswasnoisolated

phenomenonbutoccurredwithinhailswathscoveringlargeregionsofnorthernItaly.Onbothdays,the

atmosphericconditionsenabledseveral