Implications of RCP emissions on future PM2.5 air quality and direct radiative forcing over China
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 (PM2.5). To protect human health and meet the newly implemented annual PM2.5 target (less than 35 μg m-3), great efforts are needed to reduce emissions effectively. It is, therefore, essential to understand how future PM2.5 concentrations are affected by changes in anthropogenic emissions.
By using a global chemical transport and future emission scenarios (the representative concentration pathways, RCPs), researchers from Institute of Atmospheric Physics and their co-authors, projected that by 2030 wintertime (summertime) PM2.5 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 PM2.5 concentrations obtained on the basis of the four RCPs.
"In consideration of annual PM2.5 target, controlling PM2.5 pollution in Beijing-Tianjin-Hebei and Sichuan Basin will be challenging." said Hong Liao, who is the corresponding author of the research published in Journal of Geophysical Research: Atmospheres. "In these two regions, it will take at least two decades to achieve the annual PM2.5 target under the RCP2.6, RCP4.5, and RCP8.5 scenarios, and PM2.5 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 PM2.5 pollution in China based on the emission scenarios." Concluded Liao. "At the same time, the consequent warming from reduced aerosols is also significant and inevitable."
The study has been published in Journal of Geophysical Research: Atmospheres.