Climate-specific trends in urban land surface temperature: A global analysis of 432 cities (2014-2024)

This study investigates 2014-2024 trends in urban land surface temperature (ULST) across 432 cities spanning Arid, Cold, Temperate, and Tropical climates. Using MODIS observations and Mann-Kendall tests, we identify distinct climate-specific and diurnal patterns. Results show significant daytime warming in Temperate (τ = 0.636, p = 0.008) and Cold (τ = 0.491, p = 0.043) regions. At night, Arid (τ = 0.782, p = 0.001), Temperate (τ = 0.636, p = 0.008), and Cold (τ = 0.527, p = 0.029) climates warm significantly; Tropical cities show no significant decadal trend. These results indicate that Cold and Temperate cities exhibit the strongest and most consistent diurnal warming, Arid cities display minimal daytime change but pronounced nocturnal intensification, and Tropical cities remain comparatively stable with daytime cooling offset by weak nighttime warming. Warm-season and phase-indexed analyses further reveal that nocturnal heat extends into pre- and post-summer months, lengthening seasonal exposure and thereby amplifying urban heat risks. The contrasted diurnal responses across climates demonstrate that background climate exerts a first-order control on urban thermal trajectories. Our findings suggest that effective urban resilience strategies should consider both climate regime and time of day, such as targeting nighttime heat in Arid and Temperate zones, accounting for accelerated warming in high-latitude Cold regions, and addressing daytime-nighttime asymmetries in the Tropics.