Tuesday, June 30, 2009

china daily questions official air quality statistics

The story about the US Embassy's BeijingAir air quality twitter feed (whose subscribers now top 2,200) was picked up by the China Daily today. Perhaps surprisingly, the China Daily article uses the embassy data to question whether the Beijing EPB's official data present an accurate view of Beijing's air quality:
China Daily calculated that only five days were above "moderate" level in May on BeijingAir, but the local environment bureau said on its website on May 31 that the capital's air quality was the clearest during the same period since 2000, with 25 blue-sky days.
However, the article goes on to quote both an embassy official and a Chinese expert cautioning that the single station is not representative of Beijing's overall air quality:
"This is a single site," [US Embassy spokesperson Susan] Stevenson said. "It cannot be used to measure the air quality across the city. They can't be compared."
"The embassy is located in the central business district, which has heavy traffic, and its monitoring station cannot represent the overall picture," Zhu Tong, an environment professor with Peking University, said yesterday.
Signficantly, the China Daily article does not question whether or not the embassy data is valid for that area, only whether the single data point can be extrapolated out to the rest of the city. To me, this is an important distinction, because collective agreement that the embassy data is valid should ultimately help pressure the Beijing EPB to set up their own real-time PM2.5 monitors across the city (which is the direction we should be driving in).

The article closes with this comment, noteworthy for its open questioning of air quality data. Such questioning is rare in the Chinese state-run media:
Some residents expressed doubts about the official air quality data.

Wang Haiyan, a 36-year-old Beijinger living in Chaoyang district, said that even under a different measuring system, there is still no reason to get such different air quality results.
Within Chinese-language media, Xinhua's International Herald Leader (国际先驱导报) published a story two days ago (also printed with a different title in the Hong Kong-based Phoenix magazine (凤凰) here) on the US Embassy's air quality reporting; the story included this photo that is apparently of the monitor:

As one would expect, the tone of the Xinhua piece is much more defensive of the official data and critical of the embassy. Unfortunately, I don't have time now to write more on this; stay tuned tomorrow for some translation and commentary.

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