Co-benefits of CO₂ emission reduction from China's clean air actions between 2013-2020

China’s rapid economic development and urbanization have made it the world’s largest energy consumer, with heavy fossil fuel use causing severe air pollution and rising CO₂ emissions. To address air quality, China implemented the 2013 Air Pollution Prevention and Control Action Plan and the 2018 Three-Year Action Plan for Winning the Blue Sky Defense Battle, achieving large PM2.5 concentration declines by 2020. Although clean air policies target short-lived air pollutants, many measures also affect energy use, implying potential CO₂ reduction co-benefits. Despite a notable national CO₂ emissions plateau around 2013–2016 associated with reduced coal consumption, the extent to which clean air actions contributed to CO₂ mitigation, the measure-specific effects, and their role in the post-2013 deceleration of CO₂ growth had not been quantified nationally. This study aims to quantify the CO₂ reduction co-benefits of China’s clean air actions from 2013 to 2020 and attribute reductions to specific measures that alter energy use versus end-of-pipe controls.

Prior research on air quality–climate linkages has largely focused on aerosol-induced climate forcing rather than CO₂ reductions from clean air policies. Regional studies in China (e.g., Jing-Jin-Ji/Beijing-Tianjin-Hebei) have shown co-benefits, but a comprehensive national assessment attributing CO₂ reductions to individual clean air measures across the two-phase action plans was lacking. Other literature documents China’s CO₂ trends, the 2013–2016 emissions plateau, and subsequent rebound, as well as decoupling of economic growth and air pollution. The study situates itself by addressing this gap with a national, measure-specific ex-post evaluation using detailed implementation data and the MEIC model.

The study conducts an ex-post assessment of CO₂ emission reduction co-benefits from clean air measures in China (2013–2020) using the Multi-resolution Emission Inventory of China (MEIC) model. Historical CO₂ emissions (2005–2020) from fossil fuel combustion and cement production are estimated bottom-up: E_ij = A_ij × EF_i, where A_ij are sectoral activity data and EF_i are fuel/product-specific CO₂ emission factors (from Liu et al.). The analysis identifies five co-beneficial measures that alter energy use: (1) upgrades on industrial boilers; (2) phasing out small and polluting factories; (3) phasing out outdated industrial capacity (coal power, iron and steel including coking, cement, glass); (4) promoting clean fuels in the residential sector (coal-to-gas/electricity and elimination of residential coal boilers); and (5) retiring yellow-label and old vehicles. An additional category captures CO₂ increases from strengthening industrial emission standards due to wider deployment of end-of-pipe controls (e.g., FGD/denitrification), which consume energy and may generate process CO₂. Implementation rates for each measure are compiled from government inspections, provincial self-inspection/statistical reports, official news, and investigation reports. Measure-specific changes in energy end-use flows are quantified and then translated into CO₂ changes using fuel-specific emission factors. For measures that substitute technologies/fuels, the CO₂ co-benefit ΔE_k = Σ(ΔA1_i × EF_i) – Σ(ΔA2_j × EF_j), where ΔA1_i is reduced fossil energy/production and ΔA2_j is increased energy use of cleaner substitutes. Specific implementations: (a) Industrial boiler upgrades: Elimination/replacement of small coal-fired boilers based on collected eliminated capacities; assumed coal intensity 366 t coal/MW (industrial) and 377 t coal/MW (heating); of 424 GW eliminated (2013–2020), 192 GW removed, 95 GW replaced by larger boilers/central heating, 112 GW converted to natural gas, 5.9 GW to electricity, 18.5 GW to biomass. Energy savings in 2020: 63.6 Mtce coal. (b) Small/polluting factories: Complete shutdown of small furnaces (lime, brick, etc.), with coal intensity from standards/MEP databases; 2020 reductions: 22 Mtce (small furnaces) plus 4.0 Mtce (foundries, nonferrous, other processes). (c) Outdated industrial capacity: Replace outdated capacities with advanced technologies using energy intensity differences (from MEP database); 2020 coal-use reductions: 25.5 Mtce (coal power), 31.1 Mtce (iron and steel), 14.3 Mtce (cement), 0.19 Mtce (glass). (d) Residential clean fuels: Based on reported household coal-to-clean energy substitutions; among 12.7 million rural households (2013–2020), 54% switched to NG, 33% to electricity, 6% to cleaner coal, 5% to central heating, 1% eliminated coal. 2020 coal savings: 24.7 Mtce from scattered coal substitution; elimination of 198 GW residential coal boilers reduced 29.5 Mtce in 2020. Biomass treated as carbon neutral and excluded. (e) Retiring yellow-label/old vehicles: >26.8 million vehicles retired (2013–2020); energy savings E_i = VP_i × X_i × FE_i × VKT_i, with vehicle shares, fuel economies, and mileages from a vehicle emission model; 2020 energy savings: 25.2 Mtce oil. CO₂ increases from strengthened industrial emission standards: Estimated direct process CO₂ (e.g., from sorbent reactions in SO₂ control) and indirect CO₂ from additional electricity use for end-of-pipe equipment in coal power, iron and steel, cement, and industrial boilers. Baseline year 2012; changes in air pollutant emissions and control capacities from MEIC; electricity intensity of controls applied; upgrades to PM control (ESP to fabric filters) not counted due to similar electricity intensity. Regional attribution includes assessment of electricity import-related emission shifts among regions (Supplementary Note 2).

- Air pollutant reductions: From 2013 to 2020, SO₂, NOx, and primary PM2.5 emissions declined by 69%, 28%, and 44%, respectively. Average PM2.5 in 74 key cities fell from 72 to 34 µg/m³ by 2020. - CO₂ trend: National CO₂ emissions plateaued during 2013–2016 due to reduced coal use, then rebounded after 2016 led by the power sector. Despite COVID-19, CO₂ did not drop notably in 2020 due to rapid economic recovery. - 2020 co-benefits: Clean air measures avoided 0.57 Gt CO₂ in 2020 (5.5% of actual 2020 emissions). Net energy savings were 0.25 Gtce in 2020; cumulative 1.06 Gtce saved (2013–2020). - Measure-specific 2020 CO₂ reductions: 0.20 Gt (phasing out outdated industrial capacities), 0.17 Gt (industrial boiler upgrades), 0.12 Gt (residential clean fuels), 0.07 Gt (phasing out small/polluting factories), 0.06 Gt (retiring yellow-label/old vehicles). End-of-pipe controls added ~0.05 Gt CO₂ in 2020 (mainly power and iron & steel). - Cumulative effects (2013–2020): 2.66 Gt CO₂ reduced from five co-beneficial measures vs. 0.23 Gt increase from end-of-pipe controls; net cumulative reduction 2.43 Gt CO₂ (≈3.1% of China’s 2013–2020 CO₂), exceeding the accumulated national CO₂ increase (2.03 Gt) in the same period. - Temporal pattern: Rapid growth of co-benefits through 2017 aligned with first Action Plan deadlines; slower growth post-2017 as policies shifted toward end-of-pipe and VOC controls. - Regional distribution (2020): Four key regions (BTH, YRD, PRD, FW) accounted for 53.2% of net co-benefits. BTH largest, then YRD, FW, PRD. Measure rankings varied: BTH emphasized outdated capacity phase-out, residential clean fuels, and boiler upgrades; YRD emphasized boiler upgrades; PRD had lowest co-benefits among the four; FW’s largest contributor was residential clean fuels. - Interregional electricity effects: Additional CO₂ in exporting regions due to increased electricity use in BTH, YRD, PRD were 7.9, 1.4, and 0.2 Mt in 2020—smaller than local reductions. - Provincial outcomes: Provinces with stricter policies saw larger PM2.5 and CO₂ reductions. Hebei, Shandong, Zhejiang, Shanxi, and Henan reduced local CO₂ by 5.9%–13.2% in 2020.

The analysis shows that China’s clean air actions, though designed to abate short-lived air pollutants, significantly transformed energy and industrial systems by phasing out carbon-intensive, inefficient infrastructure and promoting cleaner, more efficient alternatives. These transformations yielded substantial CO₂ co-benefits, helping to drive the 2013–2016 national CO₂ plateau and contributing to the global carbon budget by offsetting growth elsewhere. The findings underscore the value of integrating air quality and climate objectives: while end-of-pipe controls are effective for rapid air quality gains, their energy demands can increase CO₂, and their standalone potential is diminishing relative to structural and efficiency measures. Economic assessment indicates higher average abatement costs for these co-beneficial measures (~$95.6 per ton CO₂) than for traditional CO₂ measures (e.g., renewables), but the health and economic gains from cleaner air can compensate or offset these costs, enhancing overall societal benefits. The study also highlights the role of renewables: although excluded from the clean air action co-benefit scope, increased renewable generation since 2013 likely avoided an additional 3.78 Gt CO₂ if otherwise replaced by thermal power, emphasizing the necessity of sustained low-carbon power sector transitions. Regionally, heterogeneous policy intensities and sectoral profiles shape measure effectiveness; however, even accounting for electricity import emissions, key regions achieved substantial net reductions. The results inform policy design in China and provide a template for other developing countries to leverage air quality imperatives for near-term climate co-benefits when rapid low-carbon transitions face financial or infrastructural constraints.

China’s stringent clean air actions between 2013 and 2020 generated major CO₂ reduction co-benefits by accelerating energy efficiency improvements, phasing out outdated industrial capacity, upgrading industrial boilers, promoting clean residential fuels, and retiring high-emitting vehicles. Net cumulative reductions of 2.43 Gt CO₂ (2013–2020) exceeded the period’s national CO₂ increase, demonstrating that air quality policies can materially contribute to climate mitigation. Future policy should prioritize co-beneficial measures, coordinate air quality and climate strategies, and continue structural shifts toward cleaner energy—particularly renewables—to achieve air quality standards by 2035 and carbon neutrality by 2060. Further work should refine measure-specific cost-effectiveness, expand integration with renewable deployment and electrification, and improve regional coordination to maximize co-benefits while managing interregional emission shifts.

- Scope limitations: Renewable energy expansion since 2005 was excluded from the co-benefit attribution because it was not deemed a consequence of the clean air action; hence total climate benefits associated with broader policy environments may be underestimated. - Data sources: Measure implementation rates rely on provincial self-inspection reports, official news, and other government reports (including unpublished data), which may introduce reporting uncertainties. - End-of-pipe estimation: Additional CO₂ from particulate control upgrades was not calculated due to similar electricity intensities across technologies; this simplification may omit minor increments. - Meteorology: While PM2.5 improvements are attributed primarily to emissions reductions, meteorological variability can influence concentrations and is not fully disentangled here. - Biomass accounting: Biomass fuels were treated as carbon neutral and excluded from CO₂ estimates, which may overlook lifecycle emissions depending on context.