Climate effects of future aerosol reductions for achieving carbon neutrality in China

 Newswise — Prof. Yang Yang from Nanjing University of Information Science and Technology is heading this research project. In light of China's commitment to achieving carbon neutrality and improving long-term air quality, the study suggests that reducing aerosol emissions will lead to a temperature rise across eastern China and amplify precipitation over southern China. Additionally, the study highlights that specifically targeting the reduction of black carbon (BC) emissions can effectively counteract the warming effects resulting from other aerosol emission reductions, aligning with the goal of carbon neutrality.

China, being the largest developing nation and a substantial emitter of carbon dioxide (CO2), has unveiled its ambitious climate agenda, aiming to reach its carbon peak by 2030 and attain carbon neutrality by 2060. Aerosols, which can disrupt the Earth's radiation balance and influence climate by interacting with radiation and clouds, assume significant importance in the pursuit of carbon neutrality in China. As such, the reduction of aerosols resulting from air pollution control policies is highly likely to exert a substantial impact on the climate.

This study examines the climate impact of reducing aerosols through China's clean air initiatives, employing the Community Earth System Model version 1 (CESM1) to explore localized future emission scenarios. In the near-term future, under a carbon neutrality scenario, aerosol reductions are projected to result in a temperature increase of 0.2-0.5 K over eastern China by 2030. Looking ahead to the long-term future, the implementation of clean air actions is anticipated to raise air temperatures by over 0.5 K in eastern China by 2060. Concurrently, as temperatures rise and aerosol levels decrease, there will be an augmentation in annual mean precipitation over southern China and the downwind northwestern Pacific. The maximum increases are estimated to reach 0.2-0.3 mm per day in 2030 and exceed 0.3 mm per day by 2060, as a consequence of China's clean air efforts under the carbon neutrality scenario, in comparison to the conditions in 2015.

While carbon neutrality efforts directly contribute to mitigating climate change by reducing greenhouse gas emissions, it's important to note that the reduction of aerosols and their precursors as part of China's future clean air initiatives could partially counterbalance the radiative cooling effect of CO2 emission reductions. In China's carbon peak year of 2030, the cooling and warming effects at the surface resulting from the decline in black carbon (BC) and other scattering aerosol emissions nearly offset each other in East Asia. By the carbon neutral year of 2060, the substantial reduction in scattering aerosol emissions in China is projected to cause an average temperature increase of 0.36 K in East Asia. However, approximately half of this increase could be mitigated by the reduction in BC emissions in China under the carbon neutrality scenario. Prof. Yang emphasizes that although BC represents only a small fraction of aerosols in China, the future clean air actions targeting BC emission reductions hold significant potential for achieving co-benefits in terms of air quality improvement and climate mitigation under the carbon neutrality agenda.

This study offers valuable scientific insights that can serve as a reference for China in developing carbon neutral pathways, targets, and policies. It also provides essential theoretical support for achieving the co-benefits of air quality improvement and climate mitigation within the framework of carbon neutrality. The findings of this study contribute to the knowledge base necessary for informed decision-making and effective implementation of measures that align with China's goals of carbon neutrality while simultaneously addressing air quality and climate challenges.