Planetary Radiation Balance as a Function of Atmospheric Dust: Climatological Consequences

Abstract

An analysis of several atmospheric dust-loading events at Phoenix, Arizona, under background cloudless sky conditions, allowed determination of dust-induced changes in both the net solar and net thermal radiation received at the earth's surface. The resultant climatological forcing function for surface temperature change was plotted against the ratio of diffuse to normal-incidence solar radiation. It was found that initial increases in atmospheric dust concentration tend to warm the planet's surface. After a certain critical concentration has been reached, continued dust buildup reduces this warming effect until at a second critical dust concentration a cooling trend begins. This second critical dust concentration is so great, however, that any particulate pollution of the lower atmosphere by man will have a tendency to increase surface temperatures. Thus, anthropogenically produced tropospheric aerosols cannot be looked on as offsetting the warming tendency of increased carbon dioxide: their concurrent buildups must inexorably tend to warm the planet's surface.