On November 29, Zhang Qiang’s Research Group and Tong Dan’s Research Group of the Department of Earth System Science (DESS), Tsinghua University jointly published a paper titled “Health co-benefits of climate change mitigation on strategic power plant retirements and pollution controls” online in Nature Climate Change, revealing that the health co-benefits of carbon emission reduction in the thermal power sector not only depends on pathways to carbon emission reduction, but also highly depends on the retirements of power plants and pollution control strategies. On this basis, a new co-benefits pathway of pollution and carbon reduction in the global thermal power sector is proposed.
Carbon dioxide, sharing the same origin as air pollutants, mainly comes from the combustion and utilization process of fossil fuels. Therefore, the carbon emission reduction policy committed to mitigating climate change will also bring about the reduction of air pollutants, which in turn will improve air quality and yield health benefits, that is, “co-benefits.” Some related studies, generally holding that the co-benefits are mainly related to the carbon emission reduction pathways (that is, the carbon emission reduction intensity), pay more attention to the comparative analysis of the co-benefits of different carbon emission reduction pathways, and accordingly urge decision makers to step up efforts to reduce carbon emissions. However, the air pollutant emissions and health losses caused by pollution sources are also affected by many other factors, such as pollution control level, atmospheric diffusion conditions and surrounding population density. The health losses per unit carbon emissions of different pollution sources vary greatly. In recent years, researchers have noticed this problem and started to explore how to maximize the co-benefits into the carbon emission reduction policy design. However, no comprehensive research has been conducted on how to fully release the co-benefits of global carbon emission reduction pathways.
In light of the above problems, the research team has, with the global thermal power sector as the research object, based on the energy consumption and emission database of more than 90,000 thermal power units in service around the world previously built, and by coupling the comprehensive evaluation model, atmospheric chemistry model and health effect model, developed the first global thermal power sector unit scale emission and air pollution health impact prediction model system, which has been used to evaluate the co-benefits of emission reduction in the global thermal power sector. It has been found that the pathways of carbon emission reduction are not the only determinant of co-benefits. Only by implementing targeted governance strategies such as early retirement of super-polluting units and gradually tightening pollution control level, which are coordinated with the pathways of carbon emission reduction, and vigorously releasing the co-benefits potential of the pathways of carbon emission reduction, can the health co-benefits be maximized.
It is found that the health impact of carbon emission per unit of super-polluting units in the thermal power sector (that is, the emission level of pollutants being much higher than the local average level) is more than three times that of the average level, and premature deaths caused by emissions of super-polluting coal-fired units accounting for less than 15% of the installed capacity in the world account for 50% of premature deaths caused by total emissions in the global power sector. Under the global carbon emission reduction pathways to achieve the 2℃ and 1.5℃ targets, if no tailored control strategy is adopted, the global carbon emissions of the thermal power sector will increase by 14% and decrease by 7% respectively in 2030 compared with 2010, while the premature deaths caused by emissions from the thermal power sector will increase by 38% (330,000 people /year) and 8% (70,000 people /year) respectively compared with 2010. This is due to the limited promotion potential of renewable power in the world before 2030, and the population growth and aging in the future will expose more people to pollution, which will offset the co-benefits of carbon emission reduction. By 2050, with the substantial increase in the proportion of renewable power, the carbon emissions of the thermal power sector around the world under the carbon emission reduction pathways to achieve the 2℃ and 1.5℃ targets will be reduced by 66% and 77% respectively compared with 2010, and the corresponding premature deaths will be reduced by 33% (290,000 people/year) and 66% (570,000 people/year) respectively compared with 2010.
However, if the pollution control level is tightened under the same pathways of carbon emission reduction, the number of premature deaths caused by emissions from the global thermal power sector in 2030 and 2050 will be reduced by 310,000 people/year and 620,000 people/year respectively compared with 2010 under the pathways of 1.5℃. On this basis, we will further promote the accelerated retirements of super-polluting units in advance, and the premature deaths in 2030 and 2050 will be reduced by 560,000 people/year and 680,000 people/year respectively compared with 2010. The research shows that the targeted pollution control policy coordinated with the carbon emission reduction policy can greatly improve health co-benefits, especially with regards to the short-term and medium-term benefits. Due to the low energy efficiency and serious health impact of super-polluting units, early retirement of these units can simultaneously increase carbon emission reduction and health co-benefits. Compared with the natural retirement scenario, the early retirement of super-polluting units under the 1.5℃ pathways can cumulatively reduce 43 billion tons of carbon emissions during the period of 2010-2050, and cumulatively avoid the premature death of nearly 6 million people, thus realizing large co-benefits of pollution reduction and carbon reduction.
The research reveals a new way for the global thermal power sector to realize the co-benefits of reducing pollution and carbon, and demonstrates that accelerating the retirements of the global high-pollution emission units is of great significance for reducing air pollution and protecting people’s health. The research draws a universal conclusion in the field of climate change mitigation and response, that is, climate change policy does not automatically bring health co-benefits, and targeted pollution control strategies must be implemented together with carbon emission reduction to maximize co-benefits. For developing countries subject to both climate and environmental problems, health protection should be taken as the starting point of coordinated control of climate change and air pollution. In the design and implementation of policies to deal with climate change, we should consider minimizing public health risks, promoting co-benefits of pollution and carbon reduction, and protecting public health.
Tong Dan, assistant professor of the Department of Earth System Science, Tsinghua University, and Geng Guannan, assistant researcher of the School of Environment, Tsinghua University, are co-first authors of the paper, and Professor Zhang Qiang of the Department of Earth System Science and Professor Steven J. Davis of the University of California, Irvine are correspondence authors of the paper. Co-authors of this paper include Cheng Jing and Qin Xinying, doctoral students in the Department of Earth System Science of Tsinghua University, Hong Chaopeng, a former postdoctoral researcher at the University of California, Irvine, and currently assistant professor at Shenzhen International Graduate School, Tsinghua University, and He Kebin, a professor at Tsinghua University School of Environment and president of the Institute for Carbon Neutrality. The research is supported by the National Natural Science Foundation of China and the Energy Foundation China.
Paper link: https://www.nature.com/articles/s41558-021-01216-1
Fig. 1 Changes of future carbon emissions and health impacts of the global power sector under different emission reduction pathways
Written by Zhang Qiang
Edited by Wang Jiayin
Checked by Huang Xiaomeng