Rapid urbanization and climate change significantly contribute to worsening urban human thermal comfort: A national 183-city, 26-year study in China

Urban residents are gradually being exposed to increasing urban high temperatures and extreme heatwave events under rapid urbanization and global warming. Although there is an increase in air and surface temperatures observed, spatiotemporal changes in urban human thermal comfort and their drivers are rarely considered when assessing the urban thermal environment, especially at a national scale in China. Based on weather stations, we combined daily meteorological data, including air temperature, solar radiation, wind speed, and humidity, to comprehensively assess the annual dynamics of urban thermal comfort and their relationship with rapid urbanization and climate change in 183 Chinese cities from 1990 to 2016. Our results show that urban air temperature and solar radiation have increased, and urban humidity and wind speed have decreased at the national scale. Following these changes, urban residents' thermal comfort is deteriorating, with physiological equivalent temperature and uncomfortable days increasing in 68% and 59% of cities, respectively, during summer in China, predominantly located in temperate monsoon and continental climatic zones. The worsening of urban thermal comfort was largely explained by climate change, and rapid urbanization contributed 10.9% in our study. Climate change (e.g., global warming, precipitation, and wind speed decrease) and rapid urbanization had positive effects (P < 0.05) on the deteriorative urban thermal environment. Our findings could enrich the knowledge on spatiotemporal changes in the urban thermal environment under climate change and rapid urbanization.