There is also an interesting NOVA program on this subject. Here is a link to that NOVA . There is a lot of info and you can even read the transcripts.
And here is an excerpt from the wiki link.
QUOTE
"Some scientists now consider that the effects of global dimming have masked the effect of global warming to some extent and that resolving global dimming may therefore lead to increases in predictions of future temperature rise.[14] According to Beate Liebert, "We lived in a global warming plus a global dimming world and now we are taking out global dimming. So we end up with the global warming world, which will be much worse than we thought it will be, much hotter."[36] The magnitude of this masking effect is one of the central problems in climate change with significant implications for future climate changes and policy responses to global warming.[37]
But it's much more complicated than an either warming or dimming issue. Global warming and global dimming are not mutually exclusive or contradictory. In a paper published March 8 in the American Geophysical Union's Geophysical Research Letters, a research team led by Anastasia Romanou of Columbia University's Department of Applied Physics and Mathematics, New York, also showed that the apparently opposing forces of global warming and global dimming can occur at the same time.[38] Global dimming interacts with global warming by blocking sunlight that would otherwise cause evaporation and the particulates bind to water droplets. Water vapor is one of the greenhouse gases. On the other hand, global dimming is affected by evaporation and rain. Rain has the effect of clearing out polluted skies.
Climatologists are stressing that the roots of both global dimming causing pollutants and global warming causing greenhouse gases have to be dealt with together and soon.[39]"
But it's much more complicated than an either warming or dimming issue. Global warming and global dimming are not mutually exclusive or contradictory. In a paper published March 8 in the American Geophysical Union's Geophysical Research Letters, a research team led by Anastasia Romanou of Columbia University's Department of Applied Physics and Mathematics, New York, also showed that the apparently opposing forces of global warming and global dimming can occur at the same time.[38] Global dimming interacts with global warming by blocking sunlight that would otherwise cause evaporation and the particulates bind to water droplets. Water vapor is one of the greenhouse gases. On the other hand, global dimming is affected by evaporation and rain. Rain has the effect of clearing out polluted skies.
Climatologists are stressing that the roots of both global dimming causing pollutants and global warming causing greenhouse gases have to be dealt with together and soon.[39]"
Global dimming basically means that there is an increase in particulates due to pollution entering the atmosphere, evaporated water droplets bind to them, creating lighter particles of evaporated globules of water in cloud formation. This in turn leads to an increase in cloud cover, without a release because the combined water droplets aren't heavy enough to form rain. That really doesn't cover the issue totally, but it's kind of an intro to dimming.
There is a great deal of evidence to support this from data of normal rain cycles being affected in Africa, as well as data gathered after the grounding of all air traffic on 9/11 in the US (which means less particulate pollution) that clearly showed an increase in daytime temperatures and a decrease in nightime temperatures, suggesting greater variation overall in day to night levels from a reduction in cloud cover and water vapor overall.
