According to the Earth Observatory at NASA, "aerosols are tiny particles suspended in the air. Some occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as the burning of fossil fuels and the alteration of natural surface cover, also generate aerosols. Averaged over the globe, aerosols made by human activities currently account for about 10 percent of the total amount of aerosols in our atmosphere."
Scientists have much to learn about the way aerosols affect regional and global climate. They are unsure whether aerosols are warming or cooling our planet.
Colloquially, an aerosol (short for aerosol spray) is a canister holding a liquid under pressure from a compressed gas. When a valve is opened, the liquid is forced out of a small hole and emerges as a mist. Typical liquids dispensed in this way are deodorants[?] and paints. An atomiser[?] is a similar device that is pressurised by a hand-operated pump rather than by stored gas.