Spatial-temporal projections of population exposure to extreme heat in China under different emission and population scenarios

Under climate warming, the recurrent incidence of extreme heat events presents a considerable challenge to human well-being, property, and sustainable development. In this century, the spatial variation and temporal trends associated with population exposure to extreme heat in China remain unclear. This study assesses the spatial changes in population exposure under different SSP-RCP (shared socioeconomic pathway-representative concentration pathway) scenarios based on climate predictions from the CMIP6 models. It identifies clustering patterns among prefecture-level cities, captures the timing and duration of when exposure exceeds 30% above baseline levels, and tracks the geographic movement of the centroid of exposure in China. The results indicate a significant increase in population exposure in China under future scenarios, with most regions stabilizing after the 2050s. During the 2030s, 2060s, and 2090s, the exposure levels under the SSP2-4.5 scenario are 1.2, 1.8, and 2.4 times higher than those of the reference period, respectively. Meanwhile, under the SSP5-8.5 scenario, they are 1.7, 1.9, and 2.6 times higher. The spatial distribution of population exposure exhibits positive correlation, but this correlation gradually decreases in the future, with low-low clustering consistently dominating the spatial distribution of exposure. The centroids of population exposure in eastern and northern China have predominantly shifted northward, whereas those in southwestern China have primarily shifted westward. Under the SSP5-8.5 scenario, these shifts in population centroids generally exhibit greater distances compared to the SSP2-4.5 scenario.