This article examines the economic basis for what is termed "rational discounting," which entails full recognition of policy effects over time and exponential discounting at a riskless rate of return. Policies often cannot be ranked unambiguously in terms of their present or future orientation....

A formula is derived for the social cost of carbon (SCC) that takes account of intragenerational income inequality and its evolution with economic growth. The social discount rate (SDR) should be adjusted to account for intragenerational and intergenerational inequality aversion and for risk...