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On the evidence of a trend in the CO2 airborne fraction

Nature volume 616, pages E1–E3 (2023)Cite this article

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The Original Article was published on 16 March 2022

arising from M. J. E. van Marle et al. Nature https://doi.org/10.1038/s41586-021-04376-4 (2022)

Testing the hypothesis of the presence of a trend in the airborne fraction (AF), defined as the fraction of CO2 emissions remaining in the atmosphere, has attracted much attention, with the overall consensus that there is no statistical evidence for a trend in the data1,2,3,4. In their recent publication, van Marle et al.5 introduce a new dataset for land use and land cover change CO2 emissions (LULCC), and from a Monte Carlo simulation analysis of these data, the authors conclude that there is a negative trend in the AF. We argue that the Monte Carlo design of van Marle et al. is not conducive to determine whether there is a trend in the AF and therefore presents no compelling statistical evidence. A re-examination of the data using a variety of statistical tests finds no evidence of a trend on the whole sample and some evidence of a positive trend when a break in the level of the AF is accounted for.

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Fig. 1: AF data and estimated trends.

Data availability

The data analysed in this manuscript were obtained from the original paper by van Marle et al.5 and can be downloaded at https://doi.org/10.5281/zenodo.5617953.

Code availability

MATLAB code, replicating all results in this manuscript as well as those in the Supplementary Information, is available from GitHub (https://github.com/mbennedsen/Is-there-evidence-of-a-trend-in-the-CO2-airborne-fraction).

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Acknowledgements

This research was funded by the Independent Research Fund Denmark (nos. 0219-00001B and 7015-00018B).

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Authors and Affiliations

  1. Department of Economics and Business Economics, Aarhus University, Aarhus, Denmark

    Mikkel Bennedsen & Eric Hillebrand

  2. Department of Econometrics, School of Business and Economics, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands

    Siem Jan Koopman

Authors
  1. Mikkel Bennedsen
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  2. Eric Hillebrand
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  3. Siem Jan Koopman
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Authors are listed in alphabetical order. All authors contributed equally to the manuscript.

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Correspondence to Mikkel Bennedsen.

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Supplementary Information

This file includes Supplementary Figs. 1–3, Tables 1–6 and References.

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Bennedsen, M., Hillebrand, E. & Koopman, S.J. On the evidence of a trend in the CO2 airborne fraction. Nature 616, E1–E3 (2023). https://doi.org/10.1038/s41586-023-05871-6

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