Re-examining Mortality Impacts of Urban Heat Islands in United States Cities

Recent research has suggested that in many cities, mitigation of urban heat islands (UHI) would result in net increases in temperature-related mortality, as the additional cold temperature deaths surpass the expected lives saved. Given the profound policy implications of these conclusions, we re-examined the predicted impact of UHI removal on mortality in 49 major United States cities using observed temperature data to estimate the UHI intensity and Bayesian inference to recreate published temperature and mortality models with high precision. Half of the 49 cities showed no change in net mortality following UHI removal. Among the remainder, increases in net mortality were < 1% of total mortality and < 5% of temperature-related mortality, changes several-fold smaller than those previously reported. While temperature-related mortality is a critical metric, it provides an incomplete assessment of urban climate health impacts: there is more to living than not dying. To safeguard vulnerable populations from both hot and cold thermal extremes, comprehensive urban climate policies must move towards approaches that integrate exposure metrics, vulnerabilities, and the feasibility of transformative infrastructure modifications.