Characterizing Climate-Change Uncertainties for Decision-Makers

Climate-change policy-making confronts a wide range of significant scientific and socioeconomic uncertainties. How experts should best characterize such uncertainties for decision-makers has emerged as an important debate within the Intergovernmental Panel on Climate Change (IPCC). Advocates assert that good decisions under uncertainty are contingent on well-defined probabilities and, lacking experts judgements, decision-makers will make their own politically motivated estimates of likelihood. Probability-based estimates are a powerful risk-management tool, but can have serious limitations when applied to a problem such as climate change. To avoid the pitfalls of probability-based methods, the IPCC should also consider approaches to decision-making under conditions of uncertainty that do not depend on expert consensus on probabilities.