Impact of Climate Warming on All-Causes Mortality in China: The Role of Non-Optimal Temperature Exposure and Multi-Scenario Projections to 2050.

Global warming intensifies non-optimal temperature exposure (consisting of high and low temperature), which poses severe threats to human health. As the world's most populous country located in temperate and subtropical zones, China is highly vulnerable to temperature-related mortality, with distinct yearly and population disparities in health risks. To investigate the impact of non-optimal temperature exposure on China's all-causes mortality during 1990-2023 and project future trends (2024-2050) under different climate change scenarios. Integrated CN05.1 gridded observational data, CMIP6 climate data (SSP2-4.5 and SSP5-8.5 scenarios), SimmEX extreme temperature indices data, and GBD 2023 disease burden data. We applied Spearman's correlation analysis, Joinpoint regression, Age-Period-Cohort analysis, and restricted cubic spline models for trend quantification and future projections. Non-optimal temperature-related deaths increased, while age-standardized mortality rate declined significantly. Low-temperature exposure remained the primary risk, but high-temperature-related health impacts intensified notably. The elderly (≥80 years) and individuals with cardio-cerebrovascular or respiratory diseases were the most susceptible. Climate warming showed significant correlations with most cause-specific mortalities. Future projections revealed divergent disease risk trends under the two emission scenarios, with some diseases facing elevated risks. Non-optimal temperature exposure exerts heterogeneous impacts on China's all-causes mortality, with high-temperature risks becoming increasingly prominent amid global warming. Targeted prevention and control strategies tailored to age, disease types, and emission scenarios are crucial to mitigate temperature-related health burdens.