11 - Anthropogenic aerosol emissions
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Aerosols (solid or liquid particles suspended in the air) have natural or human causes. Examples of natural causes: volcanic eruptions, pollen, sandstorms. Examples of human causes: industrial activities / combustion of fossil fuels, transport (diesel, tire wear and brakes), agriculture. Aerosols are bad for your health and are part of what we call “fine particles”.
1Cause
The imperfect combustion of fossil fuels leads to aerosol emissions into the atmosphere.
2Consequences
Some aerosols have a cooling effect, and others a warming effect (depending on their composition, their altitudes, and even the seasons), but overall, the radiative forcing of aerosols is negative and therefore has a cooling effect. In fact, aerosols will (1) reflect the sun's rays directly and (2) contribute to the formation of clouds which will also reflect the sun's rays.
Even though they have a shorter lifespan than GHGs, the continuous emission of aerosols increases the aerosol load in the atmosphere.
2Other possible causes
Agriculture is responsible for ammonia emissions, via fertilizer use and livestock. Ammonia then plays a role in the formation of aerosols.
Concerning transport, there are emissions of aerosols through the wear of the braking systems. For the use of buildings, a major source of aerosol emissions is wood heating, especially with low-efficiency fireplaces.
1Wrong consequence
Aerosols are small particles suspended in the air (fine particles, soot from volcanoes, etc.) and have no impact on the ozone layer. They should not be confused with aerosol bombs which used chlorine gases (CFCs), which were responsible for the hole in the ozone layer.