Expanding compound heat and ultraviolet radiation stress amplifies exposure risks for elderly populations

Extreme heat and heightened ultraviolet radiation are both projected to intensify under climate change, posing increasing risks to public health. Individual differences and demographic trends further complicate the concurrent heat and high ultraviolet stress, leaving global patterns of the compound event underexplored. Here we merged global climate data with the Ultraviolet Index and demographic characteristics for 1960–2100. Our analysis shows Central Asia, North Africa, and India have historically experienced frequent combined stress, with future projections indicating intensification. By the end of this century, population exposure is expected to increase 1.98- to 3.69-fold across emission scenarios relative to the 1960–2022 baseline, with India, China, and Pakistan facing the highest risks. The elderly population (≥ 65 years) is projected to experience a marked increase in exposure. Our findings identify regions and populations most at risk, laying the groundwork for strategies to reduce health risks in a warming world. Central Asia, North Africa, and India have historically experienced frequent combined heat and high ultraviolet radiation stress, and by the end of this century, population exposure is expected to increase across emission scenarios, according to climate, ultraviolet index, and demographic data.