Liquid or solid particles suspended in the atmosphere, but not including water droplets or ice crystals.
Climate change and aerosols
A substantial part of the warming during the past 30 years has been driven by “dark” aerosols rather than by CO2.
Man-made aerosols are certainly important players in the Earth's energy budget. But it is not clear whether the “white” aerosols (largely sulphuric acid generated from sulfur dioxide released when coal is burned) or the “black” aerosols (largely carbon black associated with coal and biomass burning) are the more important. As incoming sunlight is reflected by “white” aerosols and outgoing earth light is captured and reradiated by “black” aerosols, their impacts work against each other. The “whites” tend to cool the Earth and the “blacks” tend to warm it.
Two points must be kept in mind. First, unlike CO2, the atmospheric lifetime of aerosols is only days to weeks. Second, as both SO2 and fine particulates constitute serious health hazards, efforts to reduce them have a high priority. Hence, even if aerosols are currently a significant player in the Earth's energy budget, as time passes, their role compared to that of CO2 will surely be greatly diminished." (Source: Wallace Broecker)
1. A world-wide network of sensors called Aeronet has been set up to monitor and measure atmospheric aerosols.
2. Click here to read an excellent Real Climate post on how aerosols affect climate.
Example Usages -
1. "The uncertainties listed for aerosols are quite large, particularly for the indirect effects of aerosols in providing condensation centers for cloud formation. [IPCC-AR4 2007, Fig. TS-5, p.32]. In addition, aerosols come in different flavors, ranging from reflecting sulfates to absorbing soot particles. Unlike well-mixed GH gases, like CO2, aerosols show particular geographic and temporal distributions, which also affect climate projections significantly. Given the realistic range of aerosol compositions used here, it is not possible for global models to correctly calculate the cloud albedo effect if composition is ignored" .
(Source: Roesler and Penner 2010 as quoted by Fred Singer inUncertainty in Climate Modeling )