Long‒term trends in surface thermal environment and its potential drivers along the urban development gradients in rapidly urbanizing regions of China

Urban areas are experiencing extensive expansion and intensive warming, accompanied by the deterioration of environmental quality and increased health risks. However, the complex effect of global climate change and human activity on the thermal environment evolution under different stages of urbanization remains unclear. In this study, land surface temperature (LST) and a newly-proposed surface urban heat island intensity (SUHII) were used to reveal the thermal environment and its evolution during 2002‒2020 in the Yangtze River Delta (YRD), a rapidly urbanizing region in eastern China. The potential drivers of LST evolution were detected with random forest algorithm. We found that the thermal environment in the YRD had undergone deterioration trends, with the fastest warming trend observed in urban new towns (2.30 °C/decade). Although the urban cores had the highest LST, 15.91% of urban cores exhibited a cooling trend, especially in cities with higher urbanization levels, which was caused by restored vegetation through urban renewal. Population density had the highest positive contributions in urban cores (21.08%), while anthropogenic heat emissions accounted 21.87% of the warming trend in urban new towns. Appropriate urban renewal and green infrastructure construction are effective strategies to alleviate the thermal environmental risks in highly urbanized areas.