Black carbon aerosols can contribute to global warming by absorbing the Sun's radiation and re-radiating the Sun's energy as infrared radiation that is trapped by the earth's atmosphere in much the same way that the windshield of an automobile contributes to a parked automobile heating up in the summer's sun.
Sulfate aerosols, produced from the sulfur dioxide gas that spews out of a volcano or from the burning of sulfur-bearing fossil fuels, reflects the Sun's radiation out into space and typically cause cooling. Aerosols, unlike greenhouse gases, have a short lifetime in the atmosphere. After they are produced they may interact with other atmospheric constituents including gases, particularly water vapor, other aerosols, and cloud particles, and are transported by the winds before being removed from the atmosphere by sedimentation or rainout over periods of order a week. Because of both natural and anthropogenic events, aerosols are constantly being replenished and the anthropogenic aerosols, since the beginning of the industrial age, have been increasing.
Aerosol can also play a critical role in precipitation but again some species of aerosols may increase precipitation, while others may inhibit precipitation. While it is recognized that aerosols play a key role, because of the uncertainty of the composition of the aerosols in the atmosphere there remains great uncertainty in the effect that atmospheric aerosols have on climate - hotter or cooler, more rain or less.