IPCC_Managing Risks of Extreme Events.pdf - Climate Access

National Systems for Managing the Risks from Climate Extremes and DisastersChapter 6the capacity of the governments or agencies to act, the level of certaintyabout future changes, the timeframes within which these future impactsand disasters will occur, and the costs and consequences of decisionsthat play an important role in their prioritization and adoption (Heltberget al., 2008; World Bank, 2008; Wilby and Dessai, 2010).The complexity and diversity of adaptation to climate change situationsimplies that there can be no single recommended approach for assessing,planning, and implementing adaptation options (Füssel, 2007; Hammilland Tanner, 2010; Lu, 2011). When the planning horizons are short andadaptation decisions only impact the next one or two decades, adaptationto recent climate variability and observed trends may be sufficient(Hallegatte, 2009; Wilby and Dessai, 2010; Lu, 2011). For long-lastingrisks and decisions, the timing and sequencing of adaptation optionsand incorporation of climate change scenarios become increasinglyimportant (Hallegatte, 2009; OECD, 2009; Wilby and Dessai, 2010).Studies suggest that the most pragmatic adaptation and disaster riskmanagement options depend on the timeframes under consideration andthe adaptive capacity and ability of the country or sectoral agencies toeffectively integrate information on climate change and its uncertainties(McGray et al., 2007; Biesbroek et al., 2010; Krysanova et al., 2010;Wilby and Dessai, 2010; Juhola and Westerhoff, 2011). Given the variousuncertainties at decisionmaking scales, studies suggest that adaptationactions based on information on the observed climate and its trendsmay be preferable in some cases while, in other cases with long-termirreversible decisions, climate change scenario-guided adaptationactions will be required (Auld, 2008b; Hallegatte, 2009; OECD, 2009;Krysanova et al., 2010; Wilby and Dessai, 2010). Climate change scenariosprovide needed guidance for adaptation options when the direction ofthe climate change impacts are known and when the decisions involvelong-term building infrastructure, development plans, and actions toavoid catastrophic impacts from more intense extreme events(Haasnoot et al., 2009; Hallegatte, 2009; Wilby and Dessai, 2010).In dealing with climate change and disaster risk uncertainties, manynational studies identify gradations or categories of adaptation anddisaster risk management planning and policy options (Dessai and Hulme,2007; Auld, 2008b; Hallegatte, 2009; Kwadijk et al., 2010; Mastrandreaet al., 2010; Wilby and Dessai, 2010). These gradations in options rangefrom climate vulnerability or resilience approaches, sometimesdescribed as ‘bottom-up’; vulnerability, tipping point, critical threshold, orpolicy-first approaches to climate modeling, impact-based approaches,sometimes described as ‘top-down’; model or impacts-first; sciencefirst;or classical approaches (as illustrated in Figure 6-2 and outlined inthe sectoral option headings of Table 6-1 and described in Section6.3.3). Although the bottom-up and top-down terms sometimes refer toscale, subject matter, or policy (e.g., national versus local, physical tosocioeconomic systems), the terms are used here to describe thesequences or steps needed to develop adaptation and disaster riskmanagement plans and policies at the national level. When dealing withlong-term future climate change risks, the main differences between thescenarios-impacts-first and vulnerability-thresholds-first approaches liein the timing or sequencing of the stages of the analyses, as shownin Figure 6-2 (Kwadijk et al., 2010; Ranger et al., 2010). Although thisdifference appears subtle, it has significant implications for themanagement of uncertainty, the timing of adaptation options, and theefficiency of the policymaking (Dessai and Hulme, 2007; Auld, 2008b;Kwadijk et al., 2010; Wilby and Dessai, 2010; Lu, 2011). For example,“Climate Models, Scenarios, Impacts-First”“Vulnerability, Thresholds-First”Begin with the question“What if climate extremeschange according toscenarios, x, y, z?”Start with climate changemodels, scenarios,impacts, assessments,reports, etc.Structure impacts problemAssess relevant climatic changes from climatechange models, downscalingAssess relevant impacts based on projectedclimate changesBegin with the questions:“Where are thesensitivities, thresholds,and priorities consideringclimate variabilities?”“What can communitiescope with?”Input climate changeprojections and otherrelevant informationabout underlying driversIdentify development context, hazards, andvulnerability problemsIdentify vulnerabilities, sensitivities, thresholds;propose adaptation measuresAssess adaptation measures and timing foraction against climate change scenariosDesign and assess adaptation options forrelevant impactsAssess tradeoffs between adaptation optionsEvaluate outcomesEvaluate outcomesFigure 6-2 | Top-down scenario, impacts-first approach (left panel) and bottom-up vulnerability, thresholds-first approach (right panel) – comparison of stages involved in identifyingand evaluating adaptation options under changing climate conditions. Adapted from Kwadijk et al. (2010) and Ranger et al. (2010).350