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The Earth's climate is not immutable. Anthropogenic factors, especially increasing atmospheric CO2 and fine particle sulfate aerosols, both produced by burning of fossil fuels, represent forces which are pushing the Earth's climate toward future change. CO2 has a warming effect, as it traps the Earth's infrared heat, while sulfate aerosols cause a cooling by reflecting incoming sunlight. It will be possible to anticipate mankind's impact on climate only if we identify and analyze all such mechanisms for climate change.
Ina Tegen, Andrew Lacis and Inez Fung have drawn attention to another climate forcing: airborne mineral dust arising from regions with distributed soils. A dramatic example of such soil dust occurred in the 1930s "dust bowl" in the U.S. Great Plains. It appears likely that poor land-use practices, at a minimum, exacerbated drought conditions. Atmospheric heating by the aerosols may have altered temperatures and atmospheric stability so as to reduce rainfall amounts.
Today mineral dust is still created in many regions, both naturally and by human activities such as overgrazing, deforestation and cultivation. The figure above shows the net radiation forcing estimated that about 50 percent of the mineral aerosols are of anthropogenic origin.
The soil dust forcing by itself is not an adequate measure of possible climate effects. Absorption of energy by the aerosols may change cloud cover and regional circulation patterns. Assessment of the dust's climate effects will require use of a fully interactive climate model.
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