Future patterns and drivers of socioeconomic exposure to hot extremes in coastal China: Insights for coastal sustainability

Coastal China, characterized by complex climate dynamics and concentrated socioeconomic activity, faces heightened risks from escalating extreme heat events. This study aims to systematically assess future socioeconomic exposure to hot extremes in this vulnerable yet vital zone. Based on CMIP6 multi-model simulations under SSP1–2.6, SSP2–4.5, and SSP5–8.5 scenarios, we project multiple extreme heat indices and couple them with spatially explicit population and GDP projections to quantify exposure risks and attribute their drivers. The findings reveal a widespread intensification of hot extremes across coastal China, with risks increasing markedly under higher emission pathways. Importantly, different types of hot extremes exhibit divergent changes, indicating that future heat risks cannot be adequately characterized by a single index. Socioeconomic exposure demonstrates pronounced spatial heterogeneity. Population exposure decreases for most heat indices across broad coastal areas but increases within major economic agglomerations, while GDP exposure rises consistently across all scenarios, with the strongest intensification also concentrated in these major economic agglomerations. This contrast highlights that population and GDP exposure respond differently to changes in hot extremes, with major economic centers emerging as persistent hotspots of future heat exposure risks. Attribution analysis indicates that population exposure is primarily driven by population change, whereas GDP exposure is dominated by economic growth. However, for warm spell duration (WSDI) and tropical nights (TR20), climate change and interaction contributions become important drivers under higher emission pathways, highlighting that exposure drivers are dynamic and vary across indices and scenarios. Overall, this study provides new insight into the coupled mechanisms shaping future heat-related socioeconomic risks by integrating multiple heat indices, exposure assessment, and attribution analysis. The findings underscore the need for integrated and regionally differentiated adaptation strategies that jointly address climate change and socioeconomic development to enhance sustainability and resilience in coastal China.