Implications of RCP emissions on future PM_2.5 air quality and direct radiative forcing over China

Abstract

Severe PM2.5 air pollution in China and the First Grand National Standard (FGNS), implemented in 2016 (annual PM2.5 concentration target of less than 35 µg m−3), necessitate urgent reduction strategies. This study applied the nested‐grid version of the Goddard Earth Observing System (GEOS) chemical transport model (GEOS‐Chem) to quantify 2000–2050 changes in PM2.5 air quality and related direct radiative forcing (DRF) in China, based on future emission changes under the representative concentration pathway (RCP) scenarios of RCP2.6, RCP4.5, RCP6.0, and RCP8.5. In the near term (2000–2030), a projected maximum increase in PM2.5 concentrations of 10–15 µg m−3 is found over east China under RCP6.0 and RCP8.5 and less than 5 µg m−3 under RCP2.6 and RCP4.5. In the long term (2000–2050), PM2.5 pollution clearly improves, and the largest decrease in PM2.5 concentrations of 15–30 µg m−3 is over east China under all RCPs except RCP6.0. Focusing particularly on highly polluted regions, we find that Beijing‐Tianjin‐Hebei (BTH) wintertime PM2.5 concentrations meeting the FGNS occur after 2040 under RCP2.6, RCP4.5, and RCP8.5, and summertime PM2.5 concentrations reach this goal by 2030 under RCP2.6 and RCP4.5. In Sichuan Basin (SCB), wintertime PM2.5 concentrations below the FGNS occur only in 2050 under RCP2.6 and RCP4.5, although future summertime PM2.5 will be well controlled. The difficulty in controlling future PM2.5 concentrations relates to unmitigated high levels of nitrate, although NOx and SO2 emissions show substantial reductions during 2020–2040. The changes in aerosol concentrations lead to positive aerosol DRF over east China (20°–45°N, 100°–125°E) by 1.22, 1.88, and 0.66 W m−2 in 2050 relative to 2000 under RCP2.6, RCP4.5, and RCP8.5, respectively. When considering both health and climate effects of PM2.5 over China, for example, PM2.5 concentrations averaged over east China under RCP4.5 (RCP2.6) decrease by 54% (43%) in 2050 relative to 2000, but at the cost of warming with DRF of 1.88 (1.22) W m−2. Our results indicate that it will be possible to mitigate future PM2.5 pollution in China, but it will likely take two decades for polluted regions such as BTH and SCB to meet the FGNS, based on all RCP scenarios. At the same time, the consequent warming effects from reduced aerosols are also significant and inevitable.

Radiative Forcing and Health Impact of Aerosols and Ozone in China as the Consequence of Clean Air Actions over 2012–2017

“…The aerosol DRF averaged over eastern China was −7.80 W/m 2 in 2012, which was slightly larger than the values (−4.8 to −6.08 W/m 2 ) estimated by previous studies J. W. Li et al, 2013;K. Li et al, 2016;Qian et al, Table S1.…”

“…Li et al, ; K . Li et al, ; Qian et al, ) as listed in Table S1. These differences in estimated aerosol DRF can be caused by discrepancies in anthropogenic emissions, chemical mechanisms of the models as well as the treatment of aerosol optical properties.…”

Simulated impacts of direct radiative effects of scattering and absorbing aerosols on surface layer aerosol concentrations in China during a heavily polluted event in February 2014

“…Previous studies found that MODIS retrievals tended to overestimate AOD in the NCP during polluted events compared with AERONET AOD [Gao et al, 2015;Li et al, 2016;Miao et al, 2016]. Therefore, we are mainly focused on the comparisons between simulated AOD values and AERONET observations in this work.…”

MICS-Asia III: Multi-model comparison and evaluation of aerosol over East Asia

“…In order to better understand the properties of atmospheric aerosols and their impacts, chemical transport models (CTMs) can be a critical tool, and they have been drawn up and applied to study various air pollution issues all over the world. For example, a fully coupled online Weather Research and Forecasting/Chemistry (WRF/Chem) model was developed by Grell et al (2005) and was used to study the aerosol-radiation-cloud feedbacks on meteorology and air quality (Gao et al, 2014;Zhang et al, 2015a;Qiu et al, 2017); a Models-3 Community Multi-scale Air Quality (CMAQ) modeling system was designed by the US Environmental Protection Agency (Byun and Ching, 1999) and was carried out to address acid deposition, visibility and haze pollution issues (Zhang et al, 2006;Han et al, 2014;Fan et al, 2015); a nested air quality prediction model system (NAQPMS) was developed by the Institute of Atmospheric Physics, Chinese Academy of Science (IAP/CAS) (Wang et al, 2001) for targeting at reproducing the transport and evolution of atmospheric pollutants in Asia (Li et al, 2012a;Wang et al, 2013c;Li et al, 2017a); a global three-dimensional chemical transport model (GEOS-CHEM) was first presented by Bey et al (2001) and was applied to study the source sector contribution, long-range transport and the prediction of future change in ozone and aerosol concentrations (Liao et al, 2006;Li et al, 2016b;.…”