Large humidity effects on urban heat exposure and cooling challenges under climate change

The two trends have contrasting effects on human-perceived heat stress. However, their combined impact on urban humid heat and adaptation has remained largely unclear.

Here, we use simulations from an earth system model to investigate how urbanization coupled with climate change affects urban humid heat stress, exposure, and adaptation. Our results show that urban humid heat will increase substantially across the globe by 3.1 degrees C by the end of the century under a high emission scenario. This projected trend is largely attributed to climate change-driven increases in specific humidity (1.8 degrees C), followed by air temperature (1.4 degrees C)-with urbanization impacts varying by location and of a smaller magnitude.