Increases in atmospheric aerosol abundance are associated with an intensification of rainfall over the land and oceans, reports a study published online in Nature Geoscience this week. The influence of aerosols on clouds and, in particular, precipitation, is uncertain. Ilan Koren and colleagues examined the relationship between aerosols and rain, using satellite and meteorological data. They find that increases in aerosol abundance are associated with a rise in the intensity of rainfall in the tropics, subtropics and mid-latitudes.