Home > Aerosol

Some occur naturally, originating from volcanoes, dust storms, forest and grassland fire s, 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.

1 Radiative forcing from aerosols

Aerosols, natural and anthropogenic, can affect the climate by changing the way radiation is transmitted through the atmosphere. Direct observations of the effects of aerosols are quite limited so any attempt to estimate their global effect necessarily involves the use of models. The IPCC say: While the radiative forcing due to greenhouse gases may be determined to a reasonably high degree of accuracy... the uncertainties relating to aerosol radiative forcings remain large, and rely to a large extent on the estimates from global modelling studies that are difficult to verify at the present time [1].

1.1 Sulphate aerosol

Sulphate aerosol has two main effects, direct and indirect. The direct effect, via albedo, is to cool the planet: the IPCC best estimate of the radiative forcing is -0.4 Wm-2 with a range of -0.2 to -0.8 Wm-2 [2] but there are substantial uncertainties. The effect varies strongly geographically, with most cooling believed to be at and downwind of major industrial centres. Modern climate models attempting to deal with the attribution of recent climate change need to inclued sulphate forcing, which appears to account (at least partly) for the slight drop in global temperature in the middle of the 20th century. The indirect effect (via the aerosol acting as CCNs and thereby modifying the cloud properties) is more uncertain.

1.2 Black carbon

Black carbon from fossil fuels is estimated by the IPCC in the TAR to contribute a global mean radiative forcing of +0.2 Wm-2 (was +0.1 Wm-2 in the SAR) with a range +0.1 to +0.4 Wm-2.

2 Aerosol spray

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.

3 References

• Article at earthobservatory.nasa.gov describing the possible influence of aerosols on the climate

4 See also

• Aerosol propellants
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• Global warmingGlobal warming is an increase over time of the average temperature of Earth's atmosphere and oceans. Global warming theories attempt to account for the documented rise in average global temperatures since the late 19th century and assess the extent to whi
• Radiological weaponA radiological weapon (or radiological dispersion device, RDD is any weapon that is designed to spread radioactive contamination, either to kill, or to deny the use of an area (a modern version of salting the earth) and consists of a device (such as a nuc