Sunday, July 22, 2007
One China export you can't avoid..dirty air
In today's WSJ Science Journal , there's an article on one tainted export from China to North America that has a higher cost than we might have bargained for - dirty air.
Huge plumes of dust layered with man-made sulfates, smog, industrial fumes, carbon grit and nitrates is crossing the Pacific Ocean on prevailing winds from China and other Asian economies in clouds so huge they alter the climate. These rivers of polluted air can be wider than the Amazon and deeper than the Grand Canyon.
"There are times when it covers the entire Pacific Ocean basin like a ribbon bent back and forth," said atmospheric physicist V. Ramanathan at the Scripps Institution of Oceanography in La Jolla, Calif.
On some days, almost a third of the air over Los Angeles and San Francisco can be traced directly to Asia. With it comes up to three-quarters of the black carbon particulate pollution that reaches the West Coast, Dr. Ramanathan and his colleagues recently reported in the Journal of Geophysical Research.
Over the Pacific itself, the plumes are seeding ocean clouds and spawning fiercer thunderstorms, researchers at Texas A&M University reported in the Proceedings of the National Academy of Sciences in March.
The plumes themselves may have a mixed effect on climate....warming things up in some areas because they provide a `layer' that absorbes and holds solar heat, and having a cooling effect elsewhere because the plumes block sunlight...up to ten percent, in some areas of the Pacific.
Once aloft, the plumes can circle the world in three weeks. "In a very real and immediate sense, you can look at a dust event you are breathing in China and look at this same dust as it tracks across the Pacific and reaches the United States," said climate analyst Jeff Stith at the National Center for Atmospheric Research in Colorado. "It is a remarkable mix of natural and man-made particles."
Scientists have tracked plumes that average up to 300 miles wide and six miles deep. The higher up in the atmospere the plumes were, the longer they lasted and the faster they traveled.
And the more they affected the areas they passed over.