IPCC_Managing Risks of Extreme Events.pdf - Climate Access

Climate Change: New Dimensions in Disaster Risk, Exposure, Vulnerability, and ResilienceChapter 1• Participatory and decentralized processes that are linked to higherlevels of territorial governance (regions, nation) are a crucial partof all the stages of risk governance that include identification,choice, and implementation of these actions (high confidence).1.3.1. Climate Change Will ComplicateManagement of Some Disaster RisksClimate change will pose added challenges in many cases for attainingdisaster risk management goals, and appropriately allocating efforts tomanage disaster risks, for at least two sets of reasons. First, as discussed inChapters 3 and 4, climate change is very likely to increase the occurrenceand vary the location of some physical events, which in turn will affectthe exposure faced by many communities, as well as their vulnerability.Increased exposure and vulnerability would contribute to an increase indisaster risk. For example, vulnerability may increase due to direct climaterelatedimpacts on the development and development potential of theaffected area, because resources otherwise available and directedtowards development goals are deflected to respond to those impacts,or because long-standing institutions for allocating resources such aswater no longer function as intended if climate change affects thescarcity and distribution of that resource. Second, climate change willmake it more difficult to anticipate, evaluate, and communicate bothprobabilities and consequences that contribute to disaster risk, inparticular that associated with extreme events. This set of issues,discussed in this subsection, will affect the management of these risksas discussed in Chapters 5, 6, 7, and 8 (high confidence).1.3.1.1. Challenge of Quantitative Estimates of Changing RisksExtreme events pose a particular set of challenges for implementingprobabilistic approaches because their relative infrequency often makesit difficult to obtain adequate data for estimating the probabilities andconsequences. Climate change exacerbates this challenge because itcontributes to potential changes in the frequency and character of suchevents (see Section 1.2.2.2).The likelihood of extreme events is most commonly described by thereturn period, the mean interval expected between one such event and itsrecurrence. For example, one might speak of a 100-year flood or a 50-yearwindstorm. More formally, these intervals are inversely proportional tothe ‘annual exceedance probability,’ the likelihood that an eventexceeding some magnitude occurs in any given year. Thus the 100-yearflood has a 1% chance of occurring in any given year (which translatesinto a 37% chance of a century passing without at least one such flood((1-0.01) 100 = 37%). Though statistical methods exist to estimatefrequencies longer than available data time series (Milly et al., 2002),the long return period of extreme events can make it difficult, if notimpossible, to reliably estimate their frequency. Paleoclimate recordsmake clear that in many regions of the world, the last few decades ofobserved climate data do not represent the full natural variability ofmany important climate variables (Jansen et al., 2003). In addition,future climate change exacerbates the challenge of non-stationarity(Milly et al., 2008), where the statistical properties of weather eventswill not remain constant over time. This complicates an already difficultestimation challenge by altering frequencies and consequences ofextremes in difficult-to-predict ways (Chapter 3; Meehl et al., 2007; TRB,2008; NRC, 2009).Estimating the likelihood of different consequences and their value is atleast as challenging as estimating the likelihood of extreme events.Projecting future vulnerability and response capacity involves predictingthe trends and changes in underlying causes of human vulnerability andthe behavior of complex human systems under potentially stressful andnovel conditions. For instance, disaster risk is endogenous in the sense thatnear-term actions to manage risk may affect future risk in unintendedways and near-term actions may affect perceptions of future risks (seeBox 1-3). Section 1.4 describes some of the challenges such systemcomplexity may pose for effective risk assessment. In addition, disastersaffect socioeconomic systems in multiple ways so that assigning aquantitative value to the consequences of a disaster proves difficult (seeSection 1.2.3.3). The literature distinguishes between direct losses,which are the immediate consequences of the disaster-related physicalevents, and indirect losses, which are the consequences that result fromthe disruption of life and activity after the immediate impacts of theevent (Pelling et al., 2002; Lindell and Prater, 2003; Cochrane, 2004; Rose,2004). Section 1.3.2 discusses some means to address these challenges.1.3.1.2. Processes that Influence Judgmentsabout Changing RisksEffective risk governance engages a wide range of stakeholder groups– such as scientists, policymakers, private firms, nongovernmentalorganizations, media, educators, and the public – in a process ofexchanging, integrating, and sharing knowledge and information. Therecently emerging field of sustainability science (Kates et al., 2001)promotes interactive co-production of knowledge between experts andother actors, based on transdisciplinarity (Jasanoff, 2004; Pohl et al.,2010) and social learning (Pelling et al., 2008; Pahl-Wostl, 2009; see alsoSection 1.4.2). The literature on judgment and decisionmaking suggeststhat various cognitive behaviors involving perceptions and judgmentsabout low-probability, high-severity events can complicate the intendedfunctioning of such stakeholder processes (see Box 1-3). Climate changecan exacerbate these challenges (high confidence).The concepts of disaster, risk, and disaster risk management have verydifferent meanings and interpretations in expert and non-expert contexts(Sjöberg, 1999a; see also Pidgeon and Fischhoff, 2011). Experts actingin formal private and public sector roles often employ quantitativeestimates of both probability and consequence in making judgmentsabout risk. In contrast, the general public, politicians, and the mediatend to focus on the concrete adverse consequences of such events,paying less attention to their likelihood (Sjöberg, 1999b). As described46