Contrasting Trends and Drivers of Global Surface and Canopy Urban Heat Islands

Abstract

Abstract A comprehensive comparison of the trends and drivers of global surface and canopy urban heat islands (termed I s and I c trends, respectively) is critical for better designing urban heat mitigation strategies. However, such a global comparison remains largely absent. Using spatially continuous land surface temperatures and surface air temperatures (2003–2020), here we find that the magnitude of the global mean I s trend (0.19 ± 0.006°C/decade, mean ± SE) for 5,643 cities worldwide is nearly six‐times the corresponding I c trend (0.03 ± 0.002°C/decade) during the day, while the former (0.06 ± 0.004°C/decade) is double the latter (0.03 ± 0.002°C/decade) at night. Variable importance scores indicate that global daytime I s trend is slightly more controlled by surface property, while background climate plays a more dominant role in regulating global daytime I c trend. At night, both global I s and I c trends are mainly controlled by background climate.