Wednesday March 14, 2007

I saw a very sobering and well-made Nova documentary this past weekend. Called Dimming the Sun, it's about a phenomenon that has been dubbed global dimming. Did you know the amount of sunlight reaching the ground has dropped 10-20% worldwide since the 1950s? 10-20%

The particulate matter in polution is the primary culprit., e.g. car and airplane exhaust, power plant emissions, waste incineration. The very large number of very small particles causes an increase in cloud cover and a consequent increase in the amount of solar energy reflected away from the Earth. With less solar energy reaching the ground, one would expect to see a cooling effect. And we would--except for the presence of global warming, which acts as an opposing force on the environment.

Ironically, as we work to reduce global dimming through reductions in particulate matter via catalytic converters, smokestack scrubbers, etc., we are making global warming worse. Dimming has been masking warming. It is likely that current global warming models, which do not take either dimming or a reduction in dimming into effect, are significantly under-predicting the magnitude and timing of global temperature increases. In other words, we are in even more trouble than we thought.

Yet another inconvenient truth.