Ultrafine aerosols—minute particles from urban (e.g., vehicles) and industrial air pollution—fuel powerful storms and influence weather much more than has been appreciated, according to a study published in the journal Science . Scientists have known that aerosols may play an important role in shaping weather and climate; the new study shows that the smallest of particles have an outsize effect. Ultrafine aerosol particles smaller than 50 nanometers (UAP<50) can cause storms to intensify, clouds to grow and more rain to fall. Deep convective cloud (DCC) systems in the tropics produce copious precipitation and drive the global-scale circulation. Precipitation, latent heating, and cloud radiative forcing associated with DCCs are strongly modulated by cloud microphysical processes. These processes in tropical DCCs are initiated from droplet nucleation (which is determined by vapor supersaturation in updrafts and aerosol properties such as composition and size distribution. Aerosol impacts on cloud processes via this pathway […]