A Foggy Notion: Particulate Pollution

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Particulate pollution reflects the sun’s light and heat instead of trapping the warm air in the atmosphere like carbon dioxide.

The Rust Belt is notorious for its poor air quality. For decades, coal plants, steel production, and auto emissions have pumped particulates like sulfate into the atmosphere over the eastern U.S. Especially before air quality laws began appearing in the 1970s, particulate pollution was behind acid rain, respiratory disease, ozone depletion, and a host of other problems. But a new study from Harvard suggests that the Rust Belt’s thick particulate fog may have helped slow down the effects of climate change, particularly when it was thickest.

Throughout the 20th century, global temperatures have gone up by just under one degree Celsius. But in the U.S., eastern and central states haven’t seen the same rise. In fact, temps there actually decreased over the same period. The reason seems to be particulate pollution, reports E Magazine (May 7, 2012). Instead of trapping warm air in the atmosphere like carbon dioxide, fine particles like sulfate reflect the sun’s light and heat. They may even group with watery cloud droplets, which do the same thing. The effect is a net cooling across entire regions.

Today, with cleaner air over the Midwest and East Coast, particulates have much less impact. But other countries still face the same problem. As places like China begin to get serious about air quality, climate change may become more of an issue.

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