Given the enormous "scale effect" for China we were somewhat sceptical of these previous studies.
Today's article from Planetark may shed some light on the matter. As always, empirical researchers are beholden to their data and this article illuminates (if indeed any additional illumination was required) that the quality of Chinese data must be considered to be on the poor side and any results derived from such data should be considered with these data issues in mind.
I suspect the following article, whilst depressing, was all too predictable.
China Says Some Officials Fake Pollution Reports
BEIJING - Some local governments in China fake pollution reports and release false statistics, state media on Thursday cited an official with the country's environment watchdog as saying.
China has promised to wage war on land, air and water pollution, the result of years of breakneck economic growth and lax enforcement of rules in the rush to get rich.
Growing public unhappiness with pollution, especially in the vast countryside, and the upcoming 2008 Olympic Games have also pushed Beijing to take the subject more seriously.
"The figures on pollution control reported by local governments dropped remarkably this year, while the real environmental situation continues to deteriorate," Xinhua news agency cited an unnamed environment official as saying.
"The inaccurate figures were caused by insufficient supervision of the local governments and possible fabrication," said the official, who works for the State Environmental Protection Administration.
According to figures reported by 26 regional governments, the goal set by Beijing of cutting main pollutants by 2 percent should have been hit, the official said.
But the level of sulphur dioxide, one of the country's main pollutants that often chokes big cities like Beijing, actually rose by 2 percent this year, according to the watchdog.
"The administration will send working groups to the provinces to check the local environmental statistics," Xinhua added.