Climate Feedback

Clouding the Blue Skies

ChinaPollution.jpg The recent Summer Olympics in Beijing has drawn international attention to China’s efforts to improve air quality and reduce pollution, both during the Olympics and in the long term. According to Chinese officials, they have made tremendous strides in raising air quality levels since 1998, reporting ever increasing numbers of ’Blue Sky Days’.

However, a new study by Steven Q. Andrews of Princeton University in Environmental Research Letters suggests this may have more to do with reporting than actual increases in air quality. Andrews reanalyzed air quality data and found that much of the improvement reported for Beijing can be attributed to changes in the locations of monitoring stations and revisions to the air quality standards, rather than changes in the level of pollutants. Using the 1996 air quality standards and the original monitoring stations, Andrews finds 55 fewer ‘Blue Sky Days’ in 2007 than the official reports.


Particulate matter makes up the bulk of the pollution, but NO2 and SO2, powerful greenhouse gases, are also included in this assessment. The revised Chinese Ambient Air Quality Standards for 2000 actually allow for higher levels of these gases (as well as particulates) than the previous standards. Andrews finds that these gases seem to be under-reported as well.

Aside from the obvious effects on human health (these Chinese standards are less rigorous than those set by the World Health Organization), these gases can affect climate globally. While every country certainly has the right to set their own standards by which to measure air quality, there is also a duty for each country to provide accurate reporting of emissions of greenhouse gases to the international community. Although the results of this study are specific to Beijing, they do raise questions about the reliability of self-reporting of greenhouse gases.

Alicia Newton

Photo: SeaWIFS image showing air pollution over China (copyright NASA)

Vote or comment on the importance of this paper in the Journal Club at Nature Reports Climate Change.

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