Interannual variability and spatial diversification of global urban tree cooling effects.

While widespread urban greening is documented, how these efforts translate into changes in a city's cooling potential remains unanswered. Here, we employed multi-satellite observations to assess the spatial dynamics and temporal variations in tree cooling efficiency (TCE) over 550 cities worldwide from 2002 to 2020. Our study identified substantial interannual variability of TCE across cities, especially in developing regions like Africa, Asia, and South America. Conversely, cities in Europe and the United States, characterized by a larger share of urban trees, exhibited a markedly lower degree of year-to-year fluctuations. Despite the prevalent urban vegetation expansion, which may not considerably enhance the cooling capability, we revealed a significant association between the tree cover level and the magnitude of temporal dynamics in TCE. This study highlights that tree cover improvement may play a crucial role in contributing to the stability of tree cooling potential under a changing climate.