The IPCC Uncertainty Framework: What Decision Makers Want (and Why They Shouldn't)

In “Combining probability with qualitative degree-of-certainty metrics in assessment,” Helgeson et al. present a mathematical model of the confidence-likelihood relationship in the IPCC uncertainty framework. Their goal is to resolve ambiguities in the framework and clarify the roles of “confidence” and “likelihood” in decision-making. In this paper, I provide a conceptual evaluation of their proposal. I argue that the IPCC cannot implement the model coherently and that adopting it could result in unclear and potentially misleading communication of uncertainty.