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Global Dimming
Global dimming is a term that has been used to describe the reduction in
apparent solar radiation received at the Earth's surface in the last half
century. The magnitude of the radiation reduction varies around the globe but is
more evident in the Northern Hemisphere. Some regions have experienced as much
as 5% reduction in recent decades. This trend would counteract a part of the
global warming due to greenhouse gases, but the trend seems to have reversed in
recent years. This factor could lead to an acceleration of the observed rate of
global warming. This dimming evidently is due to particulates in the atmosphere
(atmospheric aerosol) which reflect sunlight back to space. Recent successful
efforts to reduce atmospheric concentrations of particulates have reduced this
dimming since 1990.
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