Adaptation and the Mortality Effects of Temperature Across U.S. Climate Regions

Using 20 years of data on Medicare beneficiaries, we predict the end-of-century mortality effects of climate change among the U.S. elderly, accounting at the ZIP code level for both adaptation and regional heterogeneity in the temperature-mortality relationship. We find that this relationship varies systematically with current climate, reflecting both beneficial adaptation to frequently-experienced temperatures and harmful de-adaptation to infrequently experienced temperatures. We model adaptation to future climate using the estimated cross-sectional heterogeneity in temperature effects and combine this with projected end-of-century changes in local temperature distributions to make mortality predictions. Incorporating regional heterogeneity into these predictions reverses the conventional wisdom on the regional distribution of climate change effects: cold places bear more, not less, of the burden. Incorporating adaptation yields mortality effects of climate change that are much lower than those estimated without incorporating adaptation