A Detailed Look at Beijing's "Blue Sky" Days

Earlier this year we mentioned some serious questions raised about Beijing's air pollution statistics. Steven Andrews' argued in the Wall Street Journal that improvements in the city's air quality statistics were the result of gaming the numbers, not actual reductions in pollution. Beijing environmental officials have denied Andrews' claims. Now he has published a report in Environmental Research Letters that adds a significant amount of detail. His key assertion remains the same:

Although nine continuous years of air quality improvement has been reported in Beijing between 1998 and 2007, my analysis finds that these improvements, as indicated by the annual number of `Blue Sky' days, are due to irregularities in the monitoring and reporting of air quality and not to less polluted air. Reported variations in air quality that occur as a result of changes in monitoring station locations or air quality standards, should be considered as inconsistencies in the metrics and not as actual changes in air quality.