Future exposure to moist heat extremes linked to soil dryness

Abstract

Soil moisture critically modulates moist heat via surface energy fluxes, impacting human health and ecosystems under climate change. Using CMIP6 models with or without interactive soil moisture, we dissect its global role. Moist heat is most severe in tropical and extra-tropical regions, with mid-latitudes showing >2.4 °C increases significantly amplified by soil moisture. Soil moisture dynamics intensify moist heat across most land regions, exhibiting strong negative correlations, especially in eastern South America and Central America. Conversely, diverse moist heat responses to soil moisture variations are found in the Arabian Peninsula and northern Africa. High moist heat generally coincides with high Bowen ratio and low soil moisture while low moist heat is generally found with low Bowen ratio and high moisture. Our findings also highlight exceptions exist where moist heat is not directly influenced by these factors. Critically, soil moisture changes are increasing global population exposure to wet-hot extremes in most regions.