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Abstract Extreme heat research has largely focused on dry‐heat, while humid‐heat that poses a substantial threat to human‐health remains relatively understudied. Using hourly high‐resolution ERA5 reanalysis and HadISD station data, we provide the first spatially comprehensive, global‐scale characterization of the magnitude, seasonal timing, and frequency of dry‐ and wet‐bulb temperature extremes and their trends. While the peak dry‐ and humid‐heat extreme occurrences often coincide, their timing differs in climatologically wet regions. Since 1979, dry‐ and humid‐heat extremes have become more frequent over most land regions, with the greatest increases in the tropics and Arctic. Humid‐heat extremes have increased disproportionately over populated regions (∼5.0 days per‐person per‐decade) relative to global land‐areas (∼3.6 days per‐unit‐land‐area per‐decade) and population exposure to humid‐heat has increased at a faster rate than to dry‐heat. Our study highlights the need for a multivariate approach to understand and mitigate future harm from heat stress in a warming world.
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This content will become publicly available on June 1, 2026
More Distinct Dry and Humid Heat in a Warming World
The impacts of extreme heat events depend on the concurrent humidity level. Hot and dry conditions harm crops and vegetation, while hot and humid conditions are particularly dangerous for human health. Whether a place tends to experience heat waves that are hot and dry, hot and wet, or both, depends on the local correlation between temperature and humidity. This paper uses reanalysis, observational data, and climate models to show that the global temperature‐humidity correlation has steadily declined since 1981 at a somewhat faster rate than climate models simulate. This decline in the temperature‐humidity correlation has occurred because humidity is increasing less quickly (or decreasing) on days with high dry‐bulb temperatures as compared to days with high wet‐bulb temperatures. The relative drying of hot and dry days is associated with those days warming faster than hot and humid days. Overall, the decline in the temperature‐humidity correlation has exacerbated the risk from hot and dry conditions while slightly slowing increases in hot and humid conditions.
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- Award ID(s):
- 2304953
- PAR ID:
- 10630343
- Publisher / Repository:
- American Geophysical Union
- Date Published:
- Journal Name:
- Earth's Future
- Volume:
- 13
- Issue:
- 6
- ISSN:
- 2328-4277
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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