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There is a growing focus on the economics of adaptation as policy moves from theory to practice. However, the techniques commonly used in economic appraisal have limitations in coping with climate change uncertainty. While decision making under uncertainty has gained prominence, economic appraisal of adaptation still uses approaches such as deterministic cost-benefit analysis. Against this background, this paper provides a critical review and assessment of existing economic decision support tools (cost-benefit analysis and cost-effectiveness analysis) an uncertainty framework (iterative risk management) and alternative tools that more fully incorporate uncertainty (real options analysis, robust decision making and portfolio analysis). The paper summarises each method, provides examples, and assesses their strengths and weaknesses for adaptation. The tools are then compared to identify key differences, and to identify when these approaches might be appropriate for specific applications in adaptation decision making. [ABSTRACT FROM AUTHOR]

Public fear over environmental and health impacts of CO storage, or over potential leakage of CO from geological reservoirs, is among the reasons why over the past decade CCS has not yet been deployed on a scale large enough so as to meaningfully contribute to mitigate climate change. Storage of CO under the seabed moves this climate mitigation option away from inhabited areas and could thereby take away some of the opposition towards this technology. Given that in the event of CO leakage through the overburden in the case of sub-seabed CCS, the ocean could function as buffer for receiving this greenhouse gas, instead of it directly being emitted into the atmosphere, offshore CCS could also address concerns over the climatic impacts of CO seepage. We point out that recent geological studies provide evidence that to date CO has been safely stored under the seabed. Leakage for individual offshore CCS operations could thus be unlikely from a technical point of view, if storage sites are well chosen, well managed and well monitored. But we argue that on a global longterm scale, for an ensemble of thousands or millions of storage sites, leakage of CO could take place in certain cases and/or countries for e.g. economic, institutional, legal or safety-cultural reasons. In this paper we investigate what the impact could be in terms of temperature increase and ocean acidification if leakage occurs at a global level, and address the question what the relative roles could be of on- and offshore CCS if mankind desires to divert the damages resulting from climate change. For this purpose, we constructed a top-down energy-environment-economy model, with which we performed a probabilistic Monte-Carlo cost-benefit analysis of climate change mitigation with on- and offshore CCS as specific CO abatement options. One of our main conclusions is that, even under conditions with non-zero (permille/year) leakage for CCS activity globally, both onshore and offshore CCS should probably - on economic grounds at least - still account for anywhere between 20 % and 80 % of all future CO abatement efforts under a broad range of CCS cost assumptions. [ABSTRACT FROM AUTHOR]