Reduced Urban Heat Island with Warmer Climate

How will urban climate, and in particular urban-rural thermal differences or the Urban Heat Island effect, change in response to background climate as the climate warms? This question has important implications in an urbanizing world, as heat-related fatalities represent one of the deadliest forms of climate hazard. Previous studies indicate that the UHI increases with temperature, either with a warming climate, or in response to heatwaves. We show here that this is not the case. Using 30 years of observation data from more fifty than cities, we find that summertime urban-rural temperature differences are negatively correlated with temperature, meaning that the urban heat island effect (UHI) decreases for every degree in rural warming. Furthermore, during heatwaves, UHI is further reduced, though it does not completely go away.