Climate change may have mitigated winter air pollution in north China over the past two decades, according to new research.
Researchers, analyzing data from 1996 to 2016, found that the Arctic has become warmer, accompanied by a rapid decline of sea ice cover, while Eurasia has cooled, causing the intensity of Siberian high atmospheric pressure to increase.
The Siberian high atmospheric pressure, called the Siberian High, is the main weather system that affects China in winter. Model calculation revealed that the enhanced Siberian High could bring about strengthened northerly winds, which have been the main driving force in dispersing smog on the North China Plain.
In January 2016, PM_2.5 density during a strong Siberian High period was 100 to 200? micrograms per cubic meter of air lower than during a weaker period in January 2013.
They also found that the decrease in PM_2.5 density caused by emission reduction was comparable to that caused by strong Siberian high atmospheric pressure, suggesting that climate change in the past few years might have mitigated air pollution.
Air quality usually worsens in winter in northern China due to increased emissions from heating sources and decreased wind.
The research, led by the Institute of Earth Environment under the Chinese Academy of Sciences, was recently published in the Journal "Earth's Future." (Xinhua)

 The decreased PM_2.5 mass concentration (μg m^-3) and enhanced surface northerly winds (m s-1) from Jan. 2016 (a strong SiH) to Jan. 2013 (a weak SiH). The contour and shading represent PM_2.5 mass concentration, and the arrows represent horizontal winds.(Image by ZHAO, et al.) 

Contact: Bai Jie, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China. Email:baijie@ieecas.cn