Humidity-driven divergence and extremes in global air-conditioning energy response under climate change

As climate change causes more frequent and intense humid heat extremes worldwide, air conditioning (AC) is quickly becoming a necessity for cooling as well as dehumidification. However, humidity’s evolving and spatially varied contribution to AC energy demand is poorly understood or accounted for. This puts climate-sensitive energy planning and future-conscious building thermal design at risk. Here, we dynamically model the dehumidification energy of urban buildings in the urban building energy model of the Community Earth System Model to quantify the AC energy demand for maintaining indoor comfort and health under climate change. We show latent heat load is projected to increase by 47% globally under a high emission scenario, but its relative contribution to total AC energy demand diverges spatially. Such divergent shifts result from the interplay between climate-driven temperature and humidity changes and uniquely alter individual cities’ building energy design conditions. Dehumidification makes AC energy demand exponentially more sensitive to temperature under higher humidity across diverse climate zones. Humid days may see unanticipated demand spikes three times that of the non-humid days, and this effect is further amplified by climate change. These results have critical implications for infrastructure planning in preparation for rapid urbanization in the Global South. Our study underscores the importance of accounting for the evolving and spatially diverging humidity effect on building energy to support climate-resilient buildings and energy infrastructure.