Seite - 70 - in Loss and Damage from Climate Change - Concepts, Methods and Policy Options

70 L.M.Bouwer of the studies that applied loss normalisation also refer to “attribution of changes in impacts.”This is however different from the formal detection and attribution as approachedbytheclimateresearchcommunity,whichusuallyreferstothedetection5 of statistically significant changes in climate variables, and attribution6 of these changestonaturalforcingandanthropogenicgreenhousegasemissions.Inthecaseof studiesondisaster losses,attributiontakestwosteps:firstattributionof theobserved changeindisasterlossestosocioeconomicdrivers(exposure,vulnerability),andnext establish whether there is a remaining trend, that could be attributed to changing weather hazard conditions, usually regardless of human causes (e.g. Huggel et al. 2013).Other linesofresearch, includeso-calledeventattributionstudiesputadirect link between the occurrence of individual extreme events and increased likelihood of theseevents that isdue toanthropogenic forcing. Ina fewcases, also the impacts or losses fromtheseeventsare included in themodels (e.g.Pall et al. 2011),butnot changes inother variables beside climate, such as changes in catchment hydrology or flooddefences thatwould also influenceflood risk (Schaller et al. 2016). These event attributionstudiesare furtherdiscussed in thechapterbyJameset al. (2018). 3.3.2 AnalysisofLossTrends Anumber of assessments is available of the current understanding of disaster loss recordsonthebasisofindividualstudies,mostnotablytheIPCCSREXreport(IPCC 2012), including the chapter on human and ecosystem impacts byHandmer et al. (2012), and in the contribution fromWorking Group II to the Fifth Assessment report, including the chapters on attribution by Cramer et al. (2014), and on the insurance sector in thechapterbyArent et al. (2014).Throughout thesechapters, it is acknowledged that losses fromnaturalhazardshave increased, regardlessofcau- sationoftheincrease.Inaddition,it isnotedthatlossesfromweather-relatedhazards have increasedmore rapidly thanfromgeophysical events suchasearthquakes (e.g. Handmer et al. 2012). The assessments of IPCChave concluded the following on thecausesof theupward trends in losses fromextremeweather events: Long-term trends in economicdisaster losses adjusted forwealth andpopulation increases havenotbeenattributedtoclimatechange,butaroleforclimatechangehasnotbeenexcluded (SREXSPM, IPCC2012). Economic losses due to extreme weather events have increased globally, mostly due to increase inwealthandexposure,withapossible influenceofclimatechange (Crameret al. 2014). 5Detection:“Detectionofchangeisdefinedastheprocessofdemonstratingthatclimateorasystem affected by climate has changed in somedefined statistical sense,without providing a reason for that change” (IPCC2013:Annex IIIGlossary). 6Attribution:“Attributionisdefinedastheprocessofevaluatingtherelativecontributionsofmultiple causalfactorstoachangeoreventwithanassignmentofstatisticalconfidence”(IPCC2013:Annex IIIGlossary).