PNNL

Abstract

Future trends in air pollution and greenhouse gas (GHG) emissions for China are of great concern to the community. A set of global scenarios regarding future socioeconomic and climate developments, combining shared socioeconomic pathways (SSPs) with climate forcing outcomes as described by the representative concentration pathways (RCPs), were created by the Intergovernmental Panel on Climate Change (IPCC). Chinese researchers have also developed various emission scenarios by considering detailed local environmental and climate policies. However, a comprehensive scenario set connecting SSP-RCP scenarios with local policies and representing dynamic emission changes under local policies is still missing. In this work, to fill this gap, we developed a dynamic projection model, the Dynamic Projection model for Emissions in China (DPEC), to explore China’s future anthropogenic emission pathways. The DPEC model is designed to integrate the energy system model, emission inventory model, dynamic projection model, and parameterized scheme of Chinese policies. The model contains two main modules, an energy-model-driven activity rate projection module and a sector-based emission projection module. The activity rate projection module provides the standardized and unified future energy scenarios after reorganizing and refining the outputs from the energy system model. Here we use a new China-focused version of the Global Change Assessment Model (GCAM-China) to project future energy demand and supply in China under different SSP-RCP scenarios at the provincial level. The emission projection module links a bottom-up emission inventory model, the Multi-resolution Emission Inventory for China (MEIC), to GCAM-China, and accurately tracks the evolution of future combustion/production technologies and control measures under different environmental policies. We developed technology-based turnover models for several key emitting sectors (e.g., coal-fired power plants, key industries, and on-road transportation sectors), which can simulate the dynamic changes in the unit/vehicle fleet turnover process by tracking the lifespan of each unit/vehicle on an annual basis. With the integrated modelling framework, we connected five SSP scenarios (SSP1-5), five RCP scenarios (RCP 8.5, 7.0, 6.0, 4.5, and 2.6), and three pollution control scenarios (business as usual (BAU), enhanced control policy (ECP), and best health effect (BHE)) to produce six combined emission scenarios. With those scenarios, we 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 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 more important role for continuous emission reduction until 2050. On contrast, China's emissions will remain high level until 2050 under a reference scenario without active action (i.e., SSP3-70-BAU). Compared to similar scenarios set in the CMIP6 (Coupled Model Intercomparison Project Phase 6), our estimates of emission ranges are much lower than the estimates from the CMIP6 in 2020/2030, but their emission ranges become similar in the year 2050