With rapid industrialization and urbanization over the past decades, China has experienced widespread air pollution induced by fine particulate matter with a diameter of 2.5 µm or less (PM_2.5). To protect human health and meet the newly implemented annual PM_2.5 target (less than 35 µg m^-3), great efforts are needed to reduce emissions effectively. It is, therefore, essential to understand how future PM_2.5 concentrations are affected by changes in anthropogenic emissions. 

The photo shows a panoramic view of the Beijing Olympic Park Zone, taken from HD cameras placed at the 280-meter platform of the 325-meter high meteorological observation tower of the Institute of Atmospheric Physics, Chinese Academy Sciences http://view.iap.ac.cn:8080/imageview/ (Image by IAP)

Researchers from Institute of Atmospheric Physics and their co-authors, by using a global chemical transport and future emission scenarios (the representative concentration pathways, RCPs), projected that by 2030 wintertime (summertime) PM_2.5 concentrations averaged over Beijing-Tianjin-Hebei, Yangtze River Delta, Pearl River Delta, and Sichuan Basin will be 49–56 (31–40), 40–50 (23–29), 22–27 (8–11), and 56–68 (19–24) µg m^-3, respectively, with the ranges of PM_2.5 concentrations obtained on the basis of the four RCPs.  

“In consideration of annual PM_2.5 target, controlling PM_2.5 pollution in Beijing-Tianjin-Hebei and Sichuan Basin will be challenging.” said LIAO Hong, corresponding author of this research published in Journal of Geophysical Research: Atmospheres . “In these two regions, it will take at least two decades to achieve the annual PM_2.5 target under the RCP2.6, RCP4.5, and RCP8.5 scenarios, and PM_2.5 concentrations will keep increasing under RCP6.0.” 

In the meantime of improving air quality, policymakers are suggested considering the impacts on climate induced by decreases in aerosol concentrations, as experienced in the US and Europe. The IPCC has estimated that the global mean surface temperature exhibited a warming of 0.85°C (0.65−1.06°C) from 1880 to 2012, and the associated radiative forcings by greenhouse gases and aerosols were +2.83 and −0.90 W m⁻², respectively. “Thus, the predicted positive aerosol direct radiative forcing of 0.7−1.9 W m⁻² over eastern China (20°–45°N, 100°–125°E) in 2050 relative to 2000 under all RCPs except for RCP6.0 have important implications for regional climate.” said LIAO. 

“There is a long way to go to mitigate future PM_2.5 pollution in China based on the emission scenarios.” said LIAO. “At the same time, the consequent warming from reduced aerosols is also significant and inevitable.”