Anthropogenic Warming and Population Growth May Double US Heat Stress by the Late 21st Century

Globally, heat stress (HS) is nearly certain to increase rapidly over the coming decades, characterized by increased frequency, severity, and spatiotemporal extent of extreme temperature and humidity. While these characteristics have been investigated independently, a holistic analysis integrating them is potentially more informative. Using observations, climate projections from the CMIP5 model ensemble, and historical and future population estimates, we apply the IPCC risk framework to examine present and projected future potential impact (PI) of summer heat stress for the contiguous United States (CONUS) as a function of non-stationary HS characteristics and population exposure. We find that the PI of short-to-medium duration (1-7 days) HS events is likely to increase more than three-fold across densely populated regions of the U.S. including the Northeast, Southeast Piedmont, Midwest, and parts of the Desert Southwest by late this century (2060-2099) under the highest emissions scenario. The contribution from climate change alone more than doubles the impact in the coastal Pacific Northwest, central California, and the Great Lakes region, implying a substantial increase in HS risk without aggressive mitigation efforts.

Automated summary

Globally, heat stress is expected to increase rapidly in the coming decades, with extreme temperature and humidity becoming more frequent and severe. In the contiguous United States, the potential impact of summer heat stress is likely to more than triple in densely populated regions by the end of this century, particularly under high emissions scenarios. Climate change will exacerbate this impact, doubling the risk in certain coastal and lakeside regions, highlighting the need for aggressive mitigation efforts.