Climate Change and Disparities in Extreme Heat Exposure for Socially Vulnerable Areas in the Contiguous United States

Socially vulnerable communities within the contiguous United States (CONUS) face disproportionate heat exposure, yet how these disparities will change under future warming remains unclear. Although socially vulnerable communities already experience higher air temperatures, high-resolution downscaled climate projections have not been used to assess future exposure disparities under different Global Warming Levels (GWLs). Here, we evaluate past and future daily maximum air temperature exposure across CONUS for high- and low-vulnerability locations using the Social Vulnerability Index. We find the disparity in air temperature exposure for high-SVI areas increased from ∼1.3°C (∼2.3°F) 1951–1980 to ∼1.6°C (∼2.9°F) 1994–2023. Using an ensemble of downscaled climate models, we assess future impacts at GWLs of 1.5°C, 2°C, and 3°C (2.7°F, 3.6°F, and 5.4°F). We compare the number of days/year that exceed air temperature thresholds recommended for safe fan use (35°C, 39°C, or 95°F, 102.2°F) in high-SVI and low-SVI areas. We find that for exposure to a 35°C air temperature threshold, at 1.5°C global warming there is an average annual exposure difference of ∼16 days, at 2°C ∼18 days, and at 3°C ∼22 days. For exposure to a 39°C threshold, at 1.5°C global warming there is an exposure difference of ∼5 days, at 2°C ∼6 days, and at 3°C ∼9 days. These results highlight that future warming will disproportionately increase the number of days exceeding adaptation-relevant air temperature thresholds in high-SVI areas. These findings support the need to slow global warming and direct adaptation efforts toward more vulnerable communities.