 Published December 16, 2010 08:14 AM  EarthTalk: What is Global
Dimming?  Global dimming is a less well-known but real
phenomenon resulting from atmospheric pollution. The burning of
fossil fuels by industry and internal combustion engines, in
addition to releasing the carbon dioxide that collects and traps
the sun's heat within our atmosphere, causes the emission of so-
called particulate pollution—composed primarily of sulphur
dioxide, soot and ash. When these particulates enter the
atmosphere they absorb solar energy and reflect sunlight
otherwise bound for the Earth's surface back into space.
Particulate pollution also changes the properties of clouds—so-
called "brown clouds" are more reflective and produce less
rainfall than their more pristine counterparts. The reduction in
heat reaching the Earth's surface as a result of both of these
processes is what researchers have dubbed global dimming.  "At
first, it sounds like an ironic savior to climate change
problems," reports Anup Shah of the website Glob