Several types of atmospheric aerosol have a significant effect on Earth's climate: volcanic, desert dust, sea-salt, that originating from biogenic sources and human-made. Volcanic aerosol forms in the stratosphere after an eruption as droplets of sulfuric acid that can prevail for up to two years, and reflect sunlight, lowering temperature. Desert dust, mineral particles blown to high altitudes, absorb heat and may be responsible for inhibiting storm cloud formation. Human-made sulfate aerosols, primarily from burning oil and coal, affect the behavior of clouds.
Although all hydrometeors, solid and liquid, can be described as aerosols, a distinction is commonly made between such dispersions (i.e. clouds) containing activated drops and crystals, and aerosol particles. The atmosphere of Earth contains aerosols of various types and concentrations, including quantities of:
* natural inorganic materials: fine dust, sea salt, or water droplets
* natural organic materials: smoke, pollen, spores, or bacteria
* anthropogenic products of combustion such as: smoke, ashes or dusts
Aerosols can be found in urban ecosystems in various forms, for example:
* Dust
* Cigarette smoke
* Mist from aerosol spray cans
* Soot or fumes in car exhaust
The presence of aerosols in the Earth's atmosphere can influence its climate, as well as human health.