China’s future greenhouse gas and air pollutant emission scenario database

2020-08-12 | Dan Tong, Jing Cheng

Air quality improvement, carbon mitigation, and economic growth are three major development goals in China. Along with the effective progress of air pollution control, the PM2.5 air quality over China has significantly improved. However, the annual average PM2.5 concentration in most parts of China are still higher than the national ambient air quality standard (i.e., 35 μg/m3), and the ecological environment is still under great pressure. Meanwhile, China is at a critical stage of industrialization and urbanization, that the extensive economic development and high fossil fuel consumption have made China the largest carbon emitter in the world. To better realize the short-term environmental goals of building of a beautiful China and carbon mitigation goals of meeting peak carbon, as well as the long-term fundamental air quality improvement and carbon-neutral emissions, it is urgent to establish China’s future dynamic emission scenarios and explore the coordinated governance pathways of reducing air pollutants and GHG emissions, which could provide decision support for sustainable development.

Therefore, the Dynamic Projection model for Emissions in China (DPEC) is built to dynamically project China’s future air pollutants and GHG emissions under a series of climate, environmental policies, and social-economic development assumptions. DPEC is constructed on the Multi-resolution emission inventory for China (MEIC) model framework and consists of a series of innovative technology-based turnover models on power, industry (including detailed industry sectors, such as industrial boilers, iron and steel, nonferrous metals, cement, petrochemical industry), transportation, residential, solvent use, and agriculture sectors. DPEC is fully coupled with two models from multiple perspectives such as driving force, technology distribution, and emission structure: China’s provincial energy system model in the global integrated assessment model context (GCAM-China, developed by the PNNL team) and the sectoral technology-based turnover models; contains the energy, socioeconomic projection module, and the combustion/production technology, end-of-pipe control technology turnover module, which could dynamically multi-resolution track the evolution of China’s air pollutants and CO2 emissions under the global socioeconomic and energy scenarios and China’s local clean air policies (Fig1).

Fig1. The methodology framework of DPEC model

With an integrated consideration of the global climate change, socio-economic development, and domestic air pollution control policies, the MEIC team further established China’s future air emissions scenario database through the DPEC model. The DEPC future emission database currently contains six emission scenarios, namely SSP1-26-BHE, SSP1-26-ECP, SSP2-45-ECP, SSP3-70-BAU, SSP4-60-BAU, and SSP5-85-BHE. These scenarios are combined from five global CMIP6 scenarios (including SSP1-26, SSP2-45, SSP3-70, SSP4-60, and SSP5-85) and three local pollution control scenarios (including Business-As-Usual (BAU), Enhanced-control-policy (ECP), Best-Health-Effect (BHE)). Compared with the global future socioeconomic and emission scenarios designed by Intergovernmental Panel on Climate Change (IPCC), the DPEC emission scenarios incorporated more detailed China’s local pollution control actions, which can better describe China’s clean air process and well capture the near-term rapid emission decrement (Fig2).

Fig 2. Comparison of future emissions estimated in DPEC emission scenarios and the harmonized CMIP6 emissions dataset

The methodology of DPEC model, as well as the relevant emission scenario database, were published online in the well-known academic journal of Atmospheric Chemistry and Physics (Tong et al., 2020). With those scenarios, this research presented a wide range of China’s future emissions to 2050 under different development and policy pathways. We found that, with a combination of strong low-carbon policy and air pollution control policy (i.e. SSP1-26-BHE scenario), emissions of major air pollutants (i.e. SO2, NOx, PM2.5, and non-methane volatile organic compounds – NMVOCs) in China will be reduced by 34 %–66 % in 2030 and 58 %–87 % in 2050 compared to 2015. End-of-pipe control measures are more effective for reducing air pollutant emissions before 2030, while low-carbon policy will play a more important role in continuous emission reduction until 2050.

With the DPEC model and future emission scenarios, the MEIC team further analyzed the air quality and health benefits of China’s current and upcoming clean air policies till 2030, which was published online in the academic journal of Faraday Discussions (Cheng et al., 2021). This research indicated that China’s current and upcoming clean air policies could decrease the national population-weighted PM2.5 concentrations from 61.6 μg m−3 in 2010 to 26.4 μg m−3 in 2030 (57.2% reduction). These air quality improvements will ensure that over 80% of the population lives in areas with PM2.5 levels below the current annual PM2.5 air quality standard (i.e., 35 μg m−3) and will avoid 95.0 (95% CI, 76.3, 104.2) thousand premature deaths in 2030 (Fig. 3). The research also suggests that more ambitious control actions are needed to better protect public health with an increasing ageing population.

Fig 3. Air quality and health benefits of China’s current and upcoming clean air policies during 2010-2030

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