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Published January 10, 2020 | Published + Supplemental Material
Journal Article Open

Physical and virtual carbon metabolism of global cities

Abstract

Urban activities have profound and lasting effects on the global carbon balance. Here we develop a consistent metabolic approach that combines two complementary carbon accounts, the physical carbon balance and the fossil fuel-derived gaseous carbon footprint, to track carbon coming into, being added to urban stocks, and eventually leaving the city. We find that over 88% of the physical carbon in 16 global cities is imported from outside their urban boundaries, and this outsourcing of carbon is notably amplified by virtual emissions from upstream activities that contribute 33–68% to their total carbon inflows. While 13–33% of the carbon appropriated by cities is immediately combusted and released as CO₂, between 8 and 24% is stored in durable household goods or becomes part of other urban stocks. Inventorying carbon consumed and stored for urban metabolism should be given more credit for the role it can play in stabilizing future global climate.

Additional Information

© 2020 The Author(s). This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Received 06 November 2018; Accepted 30 October 2019; Published 10 January 2020. This work was supported by the National Science Fund for Distinguished Young Scholars of China (71725005), Natural Science Funds for Distinguished Young Scholar of Guangdong Province, China (2018B030306032), Beijing Outstanding Young Scientist Program (BJJWZYJH01201910027031), the National Natural Science Foundation of China (71704015, 71874097, and 71961137009), Strategic Priority Research Program of Chinese Academy of Sciences (No. XDA20100104), and the National Key Research & Development Program (2016YFA0602304). Z.L. and N.F. acknowledge support from the Resnick Sustainability Institute at California Institute of Technology. Z.L. acknowledges Beijing Natural Science Foundation (JQ19032) and the Qiu Shi Science & Technologies Foundation. K.H was partly supported by the Czech Science Foundation under the project VEENEX (GA ČR no. 16-17978S). The authors would like to thank Prof. Laixiang Sun, Prof. John Crittenden and Prof. Karen Seto for their constructive comments on the idea of this study. S. Chen wants to give special thanks to the selfless support from his loving family, especially his better half X. Li during the writing of this paper. Data availability: The sources of energy and material flow data for the 16 global cities are provided in Supplementary Table 3. Other supporting urban socioeconomic and metabolic data have been linked to the literature or websites cited in the paper. Code availability: Programming code for carbon flow model is available from the corresponding author on request. Author Contributions: S.C., B.C., and K.H. designed the research; S.C., K.F., and Z.L. compiled the carbon data; S.C., K.H., and Z.L. developed the model and performed global analyses; S.C., B.C., K.F., Z.L., N.F., X.T., A. A., T.H., H.W., H.J.S., and K.H. contributed to results interpretation and paper writing. The authors declare no competing interests.

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Created:
August 22, 2023
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October 18, 2023