1. Key Points

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In a recent observational study, it was found that during spring in East Asia, approximately 90% of black carbon (BC), a short-lived climate pollutant with a crucial impact upon global warming, originates from fossil fuel combustion.

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The observed evidence provides a scientific basis for reducing BC emissions, which is believed to be an effective means of mitigating global warming in East Asia, where massive amounts of anthropogenic air pollutants are released into the atmosphere, as compared with other regions worldwide.

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The results of this study may be useful for the next Intergovernmental Panel on Climate Change (IPCC) report.

2．Overview

The Environmental Geochemical Cycle Research Group at the Research Institute for Global Change (RIGC) of the Japan Agency for Marine–Earth Science and Technology (JAMSTEC) recently conducted a study of black carbon (BC). Black carbon promotes global warming along with major greenhouse gases, such as carbon dioxide and methane; in contrast, organic carbon (OC), can cool the atmosphere (Figure 1). The source of BC was estimated (i.e., fossil fuel vs. non-fossil fuel sources) in downstream areas of East Asia via analyses of the chemical compositions of samples of atmospheric particulate matter with diameters of less than 2.5 micrometers (PM_2.5 aerosol) collected in the spring of 2015 on Fukue Island in Nagasaki Prefecture, Japan (Figure 2).

The results showed that fossil fuels accounted for an average of approximately 90% of BC emission sources during the observation period (Figures 3 and 4). This indicates that an emphasis on reducing the emissions of BC from fossil fuels in East Asia, which is a source of massive amounts of anthropogenic air pollutants, would be effective in lessening the impact of global warming. However, it was also found that, in addition to fossil fuels, natural sources, such as terrestrial vegetation and the ocean can contribute approximately half of the OC in the atmosphere. (Figure 4). This result suggests that the mitigating effect of OC against global warming may continue even if the use of fossil fuels is suppressed because such a measure would not affect natural sources of OC. These findings serve as foundational knowledge for developing new measures of mitigating global warming in East Asia, where warming continues to progress, and they could be used in the next report by the Intergovernmental Panel on Climate Change (IPCC).

This work was conducted as a part of the Arctic Challenge for Sustainability (ArCS) project, funded by the Environment Research and Technology Development Fund (grant numbers S-7 and 2-1403) of the Ministry of Environment of Japan, and by the Japan Society for the Promotion of Science (JSPS) Kakenhi (grant number JP26550021). The study was published in Atmospheric Environment, volume 214 on October 1, 2019 (JST).

Title: Characterization of carbonaceous aerosols in Asian outflow in the spring of 2015: importance of non-fossil fuel sources
Authors: T. Miyakawa¹, Y. Komazaki², C. Zhu¹, F. Taketani¹, X. Pan^1,3, Z. Wang³, and Y. Kanaya¹
Affiliations: 1.　Earth Surface System Research Center, Research Institute for Global Changes,　JAMSTEC 2. (Previous affiliation) JAMSTEC 3. Institute for Atmospheric Physics, Chinese Academy of Science
https://doi.org/10.1016/j.atmosenv.2019.116858