I develop an asset-pricing framework in which climate premia depend on the price of risk and on how firm characteristics map into cash-flow exposure. Which characteristics are priced is therefore a question about economic mechanisms, not proxy selection. The framework characterizes when a scalar characteristic is sufficient for priced exposure: normalized exposure must be measurable with respect to that characteristic. Applying this criterion to emission intensity yields two testable implications, spanning and scale invariance. Both are rejected in international firm-level data: the intensity premium varies with firm size, and emission levels carry independent information conditional on firm value.