Beijing Temporary Traffic Restrictions Cut NOx By 40%
30 April 2007
The Chinese government’s restrictions on Beijing motorists during a three-day conference last November succeeded in cutting the city’s NOx emissions by 40%.
Harvard University researchers Michael B. McElroy, Yuxuan Wang, and K. Folkert Boersma used data from the Dutch-Finnish Ozone Monitoring Instrument (OMI) to assess the drop in emissions. The scientists detail their work this week in the journal Geophysical Research Letters.
China’s restrictions on Beijing drivers coincided with the Summit of the Forum on China-Africa Cooperation from 4-6 November 2006, during which an estimated 800,000 of Beijing’s 2.82 million vehicles—about 28%—were taken off the road. The OMI—aboard NASA’s Aura satellite, launched in 2004—documented a 40% reduction in NOx while the restrictions were in place.
I don’t think a proper analysis has ever been made before of such a remarkable shift of environmental policy in such a short period of time.—Michael McElroy
The measured reduction may also imply a more effective regulatory strategy than has been presented by the Chinese media. Recent estimates say that during non-heating seasons, nearly 70% of all NOx emissions in the Beijing area are from vehicular emissions. Using this as a standard, McElroy, Wang, and Boersma calculated that there would need to be a 50% reduction in vehicular use in Beijing to account for the observed 40% reduction in NOx. This stands in contrast to the 30% reduction reported by China.
We’re not sure what this means, and there will definitely need to be more detailed data on vehicle energy usage, like gasoline sales data, to develop a more precise value.—Yuxuan Wang
Last November’s driving restrictions ranged from regulating access to specific roads to restricting use of both private and government vehicles. China, the world’s second largest producer of greenhouse gases behind the United States and a major source of atmospheric NOx, is expected to duplicate these traffic restrictions during the 2008 Summer Olympic Games.
I think the real value here is that these kinds of restrictions can really bring about significant change.—Michael McElroy
McElroy, Wang, and Boersma worked in collaboration with NASA and Henk J. Estes and J. Pepijn Veefkind of the Royal Dutch Meteorological Institute. Boersma worked on the OMI satellite instrument in the Netherlands before joining Professor Daniel Jacob’s atmospheric research group at Harvard. The research was supported by the National Science Foundation.
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