The Hadley circulation plays a key role in transporting atmospheric heat from the tropics to the subtropics, shaping the climate in low latitudes. While its projected weakening has been largely attributed to rising greenhouse gas concentrations, the long-term impact of future anthropogenic aerosol concentrations remains underexplored. Here, we show that the projected changes in anthropogenic aerosol concentrations can account for about one-third of the Northern Hemisphere Hadley circulation weakening between 1980 and 2080, emerging as a major driver of tropical circulation change throughout the 21st century. This impact is linked to altered diabatic heating patterns in the northern tropics, driven by precipitation changes under reduced aerosol forcing. These results highlight a critical trade-off of aerosol mitigation: while improving air quality, it may amplify tropical atmospheric circulation changes driven by greenhouse gases.
Kim et al. (Mon,) studied this question.