A group of experts, for instance climate scientists, is to choose among two policies f and g. Consider the following decision rule. If all experts agree that the expected utility of f is higher than the expected utility of g, the unanimity rule applies, and f is chosen. Otherwise, the precautionary principle is implemented and the policy yielding the highest minimal expected utility is chosen.
This decision rule may lead to time inconsistencies when an intermediate period of partial resolution of uncertainty is added. We propose two axioms that enlarge the initial group of experts with veto power, making it the smallest “rectangular set” that contains the original one. As a result, the decision rule becomes dynamically consistent. Our analysis offers a novel behavioral characterization of rectangularity and a prescriptive way to aggregate opinions in order to avoid sure regret.