Chinese Dust and Climate Change

"One tainted export from China can't be avoided in North America -- air", says a July 20 report in the Wall Street Journal.  Huge plumes of dust originating in China and Mongolia cross the Pacific Ocean and bring with them sulfates, smog, industrial fumes, carbon grit and nitrates. These "rivers of polluted air" affect the climate in different ways.  300 miles wide and six miles deep, they can have both a warming and cooling effect: soot in the plumes absorbs solar heat and warms the planet, but cooling sulfate particles block more than 10% of the sunlight over the Pacific.  

The report says that on some days almost a third of the air over Los Angeles and San Francisco can be traced directly to Asia. The article has photographs of the plumes and describes how they form:

Asia is the world’s largest source of aerosols, man-made and natural.  Every spring and summer, storms whip up silt from the Gobi desert of Mongolia and the hardpan of the Taklamakan desert of western China, where, for centuries, dust has shaped a way of life.  From the dunes of Dunhuang, where vendors hawk gauze face masks alongside braided leather camel whips, to the oasis of Kashgar at the feet of the Tian Shan Mountains 1,500 miles to the west, there is no escaping it....In an instant, billows of grit can envelope the landscape in a mist so fine that it never completely settles.  Moving east, the dust sweeps up pollutants from heavily industrialized regions that turn the yellow plumes a bruised brown. In Beijing, where authorities estimate a million tons of this dust settle every year, the level of microscopic aerosols is seven times the public-health standard set by the World Health Organization.

The plumes can circle the world in three weeks. Scientists see "a dust event" in China and observe the same polluted dust moving across the Pacific and reaching the United States. Although NASA satellites have been monitoring the plumes for several years, this spring for the first time, an international research team in a Gulfstream V jet tracked and sampled the plumes for six weeks across the Pacific.  They detected a new "high altitude plume" every three or four days.

The findings to be released this year involve NASA, the National Oceanic and Atmospheric Administration, nine U.S. universities, and the National Institute for Environmental Studies in Japan, Seoul National University in Korea, and Lanzhou University and Peking University in China.

The article concludes that Asian pollution thus far may have "tempered the pace of global warming," but when China reduces its sulfate emissions, global warming may accelerate.