Severe Air Pollution in China During Winter May Be Worsened by Global Climate Change

A new study from Georgia Institute of Technology revealed that global climate change could worsen the severe air pollution in China, especially during winters.

The study, published in the journal Science Advances, showed that the loss of sea ice in the Arctic and increased snowfall in Eurasian could create a stagnant atmospheric conditions that could trap air pollution over China's major population and industrial centers.

"Emissions in China have been decreasing over the last four years, but the severe winter haze is not getting better," said Yuhang Wang, a professor in Georgia Tech's School of Earth and Atmospheric Sciences, in a press release.

"Mostly, that's because of a very rapid change in the high polar regions where sea ice is decreasing and snowfall is increasing. This perturbation keeps cold air from getting into the eastern parts of China where it would flush out the air pollution," he added.

For the study, the researchers analyzed the historical records of China's air quality by creating a new Pollution Particle Index (PPI) using air temperature gradient anomalies and surface wind speeds. The PPI, combined with visibility measures and satellite data, showed that the winter haze over eastern China last January 2013 was well beyond anything that ever been seen in the last three decades. The severe winter haze was there despite no significant change in the emissions in the same month. This led the researchers to know that there is something else affecting China's air pollution.

Principal component and maximum covariance analyses showed a correlation between China's air condition and sea ice loss in Arctic sea and unusually high snowfall in the upper latitudes of Siberia.

Using atmospheric model simulations, the researchers found that reduction of sea ice in the Arctic and increase in snowfall in Siberia dampens the climatological pressure ridge structure over China. This flattens the temperature and pressure gradients, moving the East Asian Winter Monsoon to the east. As a result, the wind speed decreases, creating an atmospheric circulation that makes the air in China more stagnant.

With their findings, the researchers expect the winter haze in China to continue in the future, even with all the decrease in their emissions. They also cautioned that the severe air pollution over China is not all about the emission anymore, but partly to be climate-driven now.