On September 6th, An international collaborative study led by Peking University, Tsinghua University and McGill University was published as an Article in Nature Geoscience, which revealed the complex impacts of international trade on global climate forcing of aerosol pollution. Professor Jintai Lin in the Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Professor Qiang Zhang at Tsinghua University and Professor Yi Huang at McGill University are the corresponding authors of the paper, and Jintai Lin and Dan Tong, a graduate student at Tsinghua University, are the first authors.

Production of goods for consumption and associated economic processes (transportation, power generation, etc.) result in tremendous amounts of air pollutant emissions with a profound impact on regional air quality and global atmospheric pollution transport. Aerosol (a.k.a. PM) pollution affects the climate system by scattering and absorption of solar radiative and by interactions with the cloud-precipitation processes. In the current globalized economy, international trade separates regions consuming goods and services from regions where goods and related aerosol pollution are produced. This has enormous consequences not only on regional pollution but also on radiative forcing of pollutants.

In their previous PNAS paper published in 2014, Jintai Lin et al. revealed for the first time the coupled mechanism for global pollution transfer through economic trade and atmospheric processes. Through an integration of economic input-output analysis, emission calculation and atmospheric chemical transport modeling, Lin et al. showed that for 2006 alone, 23-34% of sulfate particulate concentrations, 10-23% of black carbon and 12-23% of carbon monoxide in the surface atmosphere of East China were caused by the country’s export-related emissions, and that certain portions of China’s export-related pollutants are further transported by weather systems to the western United States and other downwind regions of China. The paper won the prestigious PNAS Cozzarelli Prize, as one of the 6 papers “of outstanding scientific excellence and originality” out of ~ 3500 PNAS papers published in 2014. This award-winning paper has been downloaded by over 150,000 times.

In this Nature Geoscience study, Jintai Lin et al. further revealed the impacts of global multi-lateral economic trade and atmospheric processes together on global air pollution, geographic transfer, and, for the first time, the top-of-atmosphere direct radiative forcing of aerosol pollution. The work was done by integrating a series of calculations on trade-related emissions, pollution transport and radiative processes. As shown in Fig. 1, Lin et al. revealed that East Asia (mostly China) is the largest net exporter of goods, and in 2007 the aerosol radiative forcing due to East Asian consumption of goods (RFc) was smaller than the forcing due to its production (RFp) by 18% for secondary inorganic aerosols (SIOA) and primary organic aerosol (POA) together and by 10% for black carbon. By contrast, Western Europe is a giant net importer of goods, and its RFc in 2007 was twice as much as its RFp for SIOA+POA and was 1.7 times its RFp for black carbon. Overall, the developed countries are net importers of goods, and their RFc exceeded RFp, with an opposite story for the developing countries – in other words, there is net transfer of radiative forcing from the developed to the developing countries. Due to the short lifetime of aerosol pollutants, the difference between any region’s RFc and RFp has substantial spatial variability (Fig. 2), with important impactions for climate responses.

The studies of Lin et al. revealed strong yet previously hardly-recognized linkage between consumption, trade, and environmental and climate consequences, which calls for improved international efforts to reduce emissions in the exporting countries that will help alleviate trade-related climate and health impacts of air pollution while lowering global emissions.

The Nature Geoscience research was funded by NSFC, 973 Project, and WWF.

References:

Lin, J.-T. *, Tong, D., Davis, S., Ni, R.-J., Tan, X., Pan, D., Zhao, H., Lu, Z., Streets, D., Feng, T., Zhang, Q. *, Yan, Y.-Y., Hu, Y., Li, J., Liu, Z., Jiang, X., Geng, G., He, K., Huang, Y. *, and Guan, D.: Global climate forcing of aerosols embodied in international trade, Nature Geoscience, doi: 10.1038/NGEO2798, 2016 (link: http://dx.doi.org/10.1038/ngeo2798)

Lin, J.-T. *, Pan, D., Davis, S. J., Zhang, Q. *, He, K. *, Wang, C., Streets, D. G., Wuebbles, D. J., and Guan, D.: China’s international trade and air pollution in the United States, PNAS, 111, 1736-1741, doi:10.1073/pnas.1312860111, 2014 (link: http://www.pnas.org/content/111/5/1736?tab=metrics)

PNAS Cozzerelli Prize News: http://www.nasonline.org/news-and-multimedia/news/2014-cozzarelli-prize-recipients.html

Jintai Lin’s group: http://www.atmos.pku.edu.cn/acm/index.html