Effect on Man
Before 1970, atmospheric dust was generally thought to have a cooling effect on world climate because of a supposed greater reflection to space of solar radiation with increased atmospheric dust concentrations. Since then, however, the opposite opinion has gradually gained ascendency for two reasons. First, it has been shown that if the ratio of the absorbing to backscattering coefficients of the dust particles for solar radiation is great enough (and it often appears to be so), less solar radiation will actually be returned to space, and a warming will result. Second, recent studies, including several of my own, have indicated that atmospheric dust may have a “thermal blanketing” effect in that it may act to reduce the loss of terrestrial thermal radiation to space by somewhat “closing” the so-called atmospheric window, thereby also creating a net warming effect. Thus, all of the major effects of man upon the climate of the Earth appear to contribute to the increase of the Earth’s surface temperature.