Cautionary tales on air-quality improvement in Beijing

The official air-quality statistic reported that Beijing had a 9.9% decline in the annual concentration of PM_2.5 in 2016. While this statistic offered some relief for the inhabitants of the capital, we present several analyses based on Beijing's PM_2.5 data of the past 4 years at 36 monitoring sites along with meteorological data of the past 7 years. The analyses reveal the air pollution situation in 2016 was not as rosy as the 9.9% decline would convey, and improvement if any was rather uncertain. The paper also provides an assessment on the city's PM_2.5 situation in the past 4 years.