Climate change impact assessment and adaptation under uncertainty

Abstract

Expected impacts of climate change are associated with large uncertainties, particularly at the local level. Adaptation scientists, practitioners, and decision-makers will need to find ways to cope with these uncertainties. Several approaches have been suggested as ‘uncertainty-proof’ to some degree, but their suitability depends on the specific situation. For instance, some approaches work well under deep uncertainty, while others perform better under lower levels of uncertainty. This thesis presents several empirical studies on climate change impacts & adaptation under uncertainty in actual adaptation decision-situations. Methods used include expert elicitation, document analysis, empirical workshops, discourse analysis, literature review, and case-study analysis. The case-study on health impacts revealed large knowledge gaps; many potential impacts cannot yet be quantified, although an expected direction of change can often be indicated. In several cases, even this is not possible; changes could go either way. A few other potential impacts could be quantified, although they should be interpreted as rough ‘order-of-magnitude’ estimates. Another case-study, on impacts and adaptation in Rotterdam, indicated that quantification was easier for effects such as sea level rise and river discharge, although the range of potential outcomes is wide, and a suite of imaginable surprises can be identified. In situations with large uncertainties and knowledge gaps, traditional ‘predict & control’ adaptation strategies are insufficient. To cope with such deep uncertainties, measures are required that enhance resilience, flexibility, and adaptive capacity. For relatively quantifiable impacts, the concept of robust decision-making may prove useful. For impacts that are both highly uncertain and highly relevant, precautionary measures could be considered. Impact assessments should communicate uncertainties in a concise and policy-relevant way. Uncertainty communication should be tailored to the assessment’s audience and the decision-situation which this audience faces. Reflection on the implications and qualitative aspects of uncertainty is also important. This thesis discusses several aspects that influence policy-relevance of uncertainties, and investigates several ways of presenting them. Decision-makers face societal uncertainties in addition to the scientific ones. Societal groups may hold different views of how the world works or what the ‘ideal’ approach to manage societal issues is. As a case-study in public discourse on ethics and climate change in the US shows, such worldviews and values can lead to differing interpretations of the problems, goals, solutions, and uncertainties surrounding climate change. Different framings of climate adaptation also influence which knowledge, governance structures, and decision-making tools are seen as appropriate and relevant; e.g. is climate adaptation described in terms of promotion or prevention; in narrow or broad terms; and as a matter of computation, judgement, compromise, or inspiration? The latter relates to the perceived levels of scientific and societal uncertainty. Based on this thesis, it seems that relying solely on ‘predict & control’ approaches to climate change adaptation will not adequately address the challenges and complexities involved. As decision-makers face multiple levels of uncertainty and multiple goals/interests, a combination of approaches should be employed that explicitly takes into account the relevant uncertainties, societal needs & desires, and benefits & drawbacks of various approaches