LightSail writes "In a startling study, NASA adds another possible cause for global warming: Clean Air. Read at http://www.spaceflightnow.com/news/n0703/26sunscr
Aerosol dust has dropped 20% since 1991, leading to a significant increase of in sunlight reaching the ground. Even more interesting is that the sunlight decreased steadily from 1960 to 1990. This Global Dimming would have helped temperatures to stay stable despite increased green house gas levels. Then the increased sunlight would add to the slight increase due to green house gases and elevate the global tempters.
The failure to account for the increased sunlight in global warming computer models has lead to the hysterical over-reaction by environmentalists. They over-state the effects of green house gases: they missed what may the most important climate changing factor- clean air and sunshine"