Precaution and proportionality in the management of global environmental change

► Suggest analytical tools to communicate ex ante trade-offs when probabilities are unavailable. ► These are used to implement a version of the precautionary principle that guards disproportionately against false-negative mistakes. ► Applied to climate policy using the integrated assessment model DICE. ► Also situate decision-making within the broader context of implementing a precautionary response at the international level.