Prioritarianism and climate change.

Summary Prioritarianism is the ethical view that gives greater weight to well-being changes affecting individuals at lower well-being levels. This view is influential both in moral philosophy, and in theoretical work on social choice-where it is captured by a social welfare function ("SWF") summing a concave transformation of individual well-being numbers. However, prioritarianism has largely been ignored by scholarship on climate change. This Article compares utilitarianism and prioritarianism as frameworks for evaluating climate policy. It reviews the distinctive normative choices that are required for the prioritarian approach: specifying a ratio scale for well-being (if the prioritarian SWF takes the standard "Atkinson" form). determining the degree of concavity of the transformation function (i.e., the degree of social inequality aversion). and choosing between "ex ante" and "ex post" prioritarianism under conditions of risk. The Article also sketches some of salient implications of a prioritarian SWF for climate policy-with respect to the social cost of carbon, the social discount rate, optimal mitigation, and the "dismal theorem." Finally, it discusses the issue of variable population.