Divergent humidity-driven growth in urban air-conditioning energy demand under climate change

Abstract Rapid urbanization and climate change are intensifying humid heat in cities, making air conditioning (AC) increasingly essential for both cooling and dehumidification. However, the evolving and spatially varied contribution of humidity to urban AC energy demand remains poorly understood, posing risks to climate-sensitive urban energy planning and building thermal design. Here, by coupling an updated urban building energy model with a global Earth system model, we project that urban dehumidification energy demand will rise by 47% globally under a high-emission scenario. Its contribution to total urban AC demand diverges markedly across regions owing to interacting changes in temperature and humidity that reshape city-specific building thermal design conditions. We further show that humidity amplifies the temperature sensitivity of urban AC demand across climate zones, leading to AC energy demand two to three times higher on humid days. These findings highlight the critical need to incorporate humidity dynamics into urban energy and infrastructure planning, particularly in rapidly urbanizing regions of the global south.