Sun, Mar 15, 2009 - Page 7 News List

Pollution dims skies as well as befouling the air


Increases in airborne pollution have dimmed the skies over most of the world during the past 30 years by blocking sunlight, researchers report in Friday’s edition of the journal Science.

While decreases in atmospheric visibility, known as global dimming, have been reported in the past, the new study compiles satellite and land-based data for a longer period than had been available.

“Creation of this database is a big step forward for researching long-term changes in air pollution and correlating these with climate change,” Kaicun Wang, assistant research scientist in the University of Maryland, said in a statement. “And it is the first time we have gotten global long-term aerosol information over land to go with information already available on aerosol measurements over the world’s oceans.”

They reported that dimming is occurring everywhere except Europe, where declines in pollution have resulted in brighter skies.

Changes in aerosols can affect weather and also may have an impact on climate, although past studies have been inconclusive.

These pollutants can result in cooling by reflecting sunlight back into space, but they also can absorb solar energy and warm the atmosphere.

Researchers at the National Oceanic and Atmospheric Administration , meanwhile, warned that suggestions for a high-atmosphere “sunshade” of particles to battle global warming could reduce energy production from solar power plants.

Those proposals are aimed at blocking sunlight that can be absorbed by so-called greenhouse gases like carbon dioxide, warming climate.

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