Anthropogenic intensification of concurrent extreme hot and dry days and related vegetation fire probability

Abstract Concurrent extreme hot and dry days can induce large ecosystem disturbances and societal damages. However, they are commonly studied using indicators with inhomogeneous timescales (e.g., daily for heatwaves, monthly for droughts). This limits our capacity to accurately characterize their occurrence and attribute them to anthropogenic drivers. Here, we integrate an up-to-date daily drought index with surface air temperature and find significant increases in the number and spatial coverage of extreme hot-dry days in summer and winter, which are primarily attributed to anthropogenic forcing. By 2100, extreme hot-dry days over global land area will spatially expand 3–6 times under different warming scenarios. Vegetation fires show a stronger relationship with increased extreme hot-dry days in winter than summer, and the relationship is stronger for the concurrent extreme hot-dry days than extreme hot or dry days alone. These findings highlight the connections between anthropogenic global warming, extreme events, and vegetation fires as well as the urgency for developing adaptation and mitigation strategies.