Wednesday, August 13, 2008

Beijing's Smog Experiment

Efforts to reduce pollution will let scientists see how the climate responds.

By Lauren Gravitz

Sky lab: Scientists from the University of California, San Diego, and Seoul National University will fly unmanned aerial vehicles downwind of Beijing to measure emissions reductions. The results will help climate researchers understand how pollution masks global warming.

One of the most watched projects during the run-up to the 2008 Beijing Olympics, along with the construction of the Bird's Nest Stadium and the glowing Aquatics Cube, was the Chinese government's efforts to cut emissions by 60 percent in the city. It has been a colossal undertaking in an area where air-pollution is five times higher than World Health Organization safety standards and smog can get so dense that it sometimes occludes the sun. The effort has involved ordering half of the city's cars off the roads and temporarily moving or closing dozens of steel mills, foundries, and factories across the capital.

But such a dramatic decrease in pollution could provide more than just healthier conditions for competing athletes. It may also afford scientists a rare opportunity to see how climate change responds to such a massive adjustment in emissions.

A team led by Veerabhadran Ramanathan, a climate and atmospheric scientist at the University of California, San Diego, will spend the next six weeks flying autonomous unmanned aerial vehicles (AUAVs) downwind of Beijing to measure emissions reductions. "By cutting down on the pollution over Beijing during the Olympics, the Chinese have created a huge natural laboratory for understanding how pollution impacts climate," Ramanathan says. He and collaborators at Seoul National University, in South Korea, have packed an assortment of miniature instruments into 30-kilogram, three-metre-wide AUAVs and set up a research station on South Korea's Cheju Island, about 500 kilometers south of Beijing.

Using the island as their base, the researchers are flying the small aircraft in groups of three: over, under, and through the polluted plume as it travels past the island. Because different layers of wind carry air from different regions, and because the wind currents change direction, they can also sample air from other parts of China that have not implemented emissions cutbacks. "We fly up to 12,000 feet," Ramanathan says, "so I don't have to go anywhere. The mountain comes to Mohammed."