Urban Shrinkage and Surface Urban Heat Islands: Does Population Decline Lead to Cooling? A Spatiotemporal Analysis of China's 89 Shrinking Cities (2001–2019)

Abstract Numerous studies have examined how urban expansion exacerbates Surface Urban Heat Island intensity (SUHII), yet limited attention has been paid to whether and how urban shrinkage mitigates SUHII. This study employed multiple models to analyze the spatiotemporal evolution of surface urban heat island (SUHI) and its driving factors in 89 shrinking cities in China from 2001 to 2019 across interannual, seasonal, and diurnal scales. The results show that (a) From 2001 to 2019, the average SUHII of shrinking cities in China experienced a slight overall decrease, falling by 0.150 K during the daytime and 0.128 K at nighttime. However, at the individual city level, the dominant change types were non‐significant decrease and non‐significant increase. (b) During the daytime and nighttime, 66.292% and 57.303% of shrinking cities, respectively, exhibited declining SUHII trends, with pronounced differences across climate zones. Shrinking cities located in the North Subtropical climate zone showed the most significant magnitude of SUHII reduction. (c) The driving mechanisms of SUHII in shrinking cities revealed pronounced diurnal asymmetry and climate zone dependence. Daytime SUHII was primarily driven by meteorological factors such as relative humidity, sunshine duration, and surface pressure, whereas nighttime SUHII reflected the combined effects of both meteorological and anthropogenic factors. Moreover, the cooling effect associated with population loss partially offset the enhancement of SUHII caused by urban expansion. This study provides new empirical evidence for understanding the spatiotemporal dynamics and driving mechanisms of SUHI in shrinking cities.