Seite - 271 - in Loss and Damage from Climate Change - Concepts, Methods and Policy Options

11 TheRoleof thePhysicalSciences inLossandDamage… 271 Theability tomakeL&Ddecisionsdependson skills andknow-howfor assess- ing the risks, and institutional capacity as well as funding to address those risks (UNFCCC2012a). But given the large uncertainties inherent to the estimation of risk, the use of a decision-making framework that can make the best use of the available information to develop strategies to reduceL&Dis also key.Twowidely recogniseddecision-makingframeworkshavebeendiscussedinthecontextofCCA: the ‘topdownor science-driven’ and the ‘bottomuporpolicy-driven’ frameworks. In the first framework, the process startswith the generation of climate projec- tions, often downscaled and corrected for possible biases, followed by an analysis of their physical impacts that, combinedwith vulnerability assessments, are used to designpolicies and adaptation options tomitigate those impacts.Application of the ‘science-driven’ approach include, for instance, theSternReviewand the IPCC risk assessments. This approach has been criticised for its heavy reliance on cli- mateprojections that are limited in their ability to represent keydrivers of extreme events and not generally fit for purpose for decision support (IPCC 2012; Smith andStern 2011; Stainforth et al. 2007), and for the potential lack of robustness of theprojected impactsdue todifferentmethodological issues (Hall2007;Merzetal. 2010; Tebaldi andKnutti 2007). Uncertainty is clearly one of the key challenges for decision-makers, especially when competing with concerns about daily lives. But theuncertainty that comeswith this approachdoesnot only stemfromclimate change; in fact the climate dimension just adds to the uncertainty derived from the wide rangeof socio-economicandenvironmental factors considered,often referred to as the ‘cascade of uncertainty’ (Schneider 1983) or the ‘uncertainty explosion’ (Henderson-Sellers1993).Fewscience-firstassessmentshavebeenusedtoevaluate realadaptationoptions, since the‘uncertaintyexplosion’oftenrenders theappraisal of adaptation options impracticable (Dessai and Hulme 2007;Wilby and Dessai 2010). The second framework startswith the adaptationproblem itself rather thanwith climateprojections. It isbasedonriskmanagementapproaches thatbeginbydefin- ing the policy or adaptation goal to be addressed (Ranger et al. 2010a, b;Willows et al. 2003).This includesdelineating theobjectiveor decision criteria, identifying presentandfutureclimatic5 andnon-climatic risks thatmakethesystemvulnerable, identifying institutionalandregulatoryconstraints, identifying thepossibleoptions, 5Modellingcapabilitiescanbeusedtogenerateclimateprojectionsthat, incombinationwithsocio- economic scenarios, result in suitable tools to assessvulnerabilities indifferent regions including, wherepossible, thestudyofvulnerability tochanges infrequencyofoccurrenceofextremeevents. In the framework of scenario planning as an approach to support strategic decision-making, sce- narios are intended to be challengingdescriptions of awide range of possible futures. Therefore, the combination of climate and socio-economic scenarioswe refer to cannot be, by construction, representative of the full range of possible futures. On the climatemodelling side for example, missing feedbacks and unknown uncertainties in climatemodels limit the ability to represent all plausible futures.Notwithstandingtheseconstraints, scenarioscanstillbeusedas tools toconsider a range of possible futures, and their associated consequences. Then, an analysis of the options available couldbecarriedout, and feedbackcanbeprovidedonwhat informationabout the likely futureswouldbemostvaluable fordecisionmakers.