Global Dimming

Greenhouse gases disappearing, helping solar power continue

Global dimming is a phenomenon that can be defined as the gradual reduction of global direct irradiance. Basically, less sun reaching the surface of the earth because of pollutants in the air that reflect sun back into space. This phenomenon was observed for several decades after they started measuring it in the 1950's. It varied by location, but overall there was nearly a 4% reduction during the decades of 1960-1990.

Since 1990, the trend seems to be reversing. It is believed that it was caused by particulates in the atmosphere, including aerosols, which were being "dumped" into the atmosphere by humans. When these chemicals were reduced and eliminated, the trend was reversed. There now seems to be a "global brightening" occurring.

Global dimming seems to have interfered with the hydrological cycle. This means it has reduced evaporation, and thus reduced rainfall in many areas of the world. It also creates a cooling effect that may be masking the effect of greenhouse gases on global warming trends.



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