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October 1, 2019

90% of Black Carbon during Spring in East Asia Originates from Fossil Fuels

1. Key Points

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


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 (PM2.5 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. Pan1,3, 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

Figure 1

Fig 1. Radiative forcing (RF) from 1970–2010 for several atmospheric components. Positive RF values indicate the potential to contribute to atmospheric warming, while negative values indicate potential cooling effects. “Aerosol direct effect” includes the direct RF induced by all of the atmospheric aerosols.

Figure 2

Fig 2.
[Left] Study region; star indicates the observation site (Fukue Island).
[Right] View from the observatory rooftop on April 9, 2015.

Figure 3

Fig 3. [Upper] Temporal variation in the percentage fraction of non-fossil fuel carbon (derived from 14C concentration). The horizontal dashed line depicts the mean fraction of non-fossil fuel carbon throughout the observation period. [Bottom] Temporal variations in the concentrations of PM2.5 aerosols (red line), carbonaceous (BC + OC) aerosols (green lines and markers), and carbon monoxide (CO, black line). The fraction of non-fossil fuel carbon decreased with increases in the concentrations of CO and carbonaceous aerosols. (Source: Miyakawa et al.).

Figure 4

Fig 4. Mean contributions of classified BC [left] and OC [right]. Abbreviations: FF (fossil fuel), BB (biomass burning). Percentages were determined using the datasets of Miyakawa et al.


(For this study)
Takuma Miyakawa, Environmental Geochemical Cycle Research Group, Research Institute for Global Change, Earth Surface System Research Center
(For press release)
Public Relations Section, Marine Science and Technology Strategy Department
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