Chinese government regulators had clearer skies and easier breathing in mind in the summer of 2008 when they temporarily shuttered some factories and banished many cars in a pre-Olympic sprint to clean up Beijing's air. And that's what they got.
They were not necessarily planning for something else: an unprecedented experiment using satellites to measure the impact of air pollution controls. Taking advantage of the opportunity, NASA researchers have since analyzed data from NASA's Aura and Terra satellites that show how key pollutants responded to the Olympic restrictions.
According to atmospheric scientist Jacquelyn Witte and colleagues from NASA's Goddard Space Flight Center in Greenbelt, Md., the emission restrictions had an unmistakable impact. During the two months when restrictions were in place, the levels of nitrogen dioxide (NO2)a noxious gas resulting from fossil fuel combustion (primarily in cars, trucks, and power plants)plunged nearly 50 percent. Likewise, levels of carbon monoxide (CO) fell about 20 percent.
Witte presented the results on behalf of the team on Dec. 16 at the fall meeting of the American Geophysical Union in San Francisco.
Some scientists have questioned whether Beijing's highly publicized air quality restrictions actually had an impact. This new data shows clearly that they did. "After the authorities lifted the traffic restrictions, the levels of these pollutants shot right back up," Witte noted.
The steep decline in certain pollutants surprised the researchers. In a preliminary analysis of the data, the effect seemed to be minimal, explained Mark Schoeberl, project scientist for the Aura mission and a contributor to the study. The reductions only became noticeable when the investigators focused tightly on the Beijing area.
"If you take a wide view, you start to pick up long distance transport of pollutants," Schoeberl said. That seemed to be the case with
|Contact: Michael Carlowicz|
NASA/Goddard Space Flight Center