Aerosols are small particles or droplets that float in the air. They are emitted by both natural events and human activities. Some aerosols cool the climate, and others have a warming effect. Image credits, left to right: Saiho/Pixabay, olegkamenskij20120/Pixabay, USGS. Image design: NASA/JPL-Caltech

Both! In general, light-colored particles in the atmosphere will reflect incoming sunlight and cause a cooling effect. Dark-colored particles absorb sunlight and make the atmosphere warmer. Because different types of particles have different effects, aerosols are a hot topic in climate research.

Learn more about the climate effects of aerosols.