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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Preprints
https://doi.org/10.5194/bg-2020-33
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2020-33
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 10 Feb 2020

Submitted as: research article | 10 Feb 2020

Review status
A revised version of this preprint was accepted for the journal BG and is expected to appear here in due course.

Historical CO2 emissions from land-use and land-cover change and their uncertainty

Thomas Gasser1, Léa Crepin1,2, Yann Quilcaille1, Richard A. Houghton3, Philippe Ciais4, and Michael Obersteiner1,5 Thomas Gasser et al.
  • 1International Institute for Applied Systems Analysis (IIASA), 2361 Laxenburg, Austria
  • 2AgroParisTech, 75231 Paris, France
  • 3Woods Hole Research Center, 02540 Falmouth, Massachusetts, USA
  • 4Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, Université Paris-Saclay, CEA – CNRS – UVSQ, 91191 Gif-sur-Yvette, France
  • 5Environmental Change Institute, University of Oxford, OX1 3QY Oxford, UK

Abstract. Emissions from land-use and land-cover change are a key component of the global carbon cycle. Models are required to disentangle these emissions and the land carbon sink, however, because only the sum of both can be physically observed. Their assessment within the yearly community-wide effort known as the Global Carbon Budget remains a major difficulty, because it combines two lines of evidence that are inherently inconsistent: bookkeeping models and dynamic global vegetation models. Here, we propose a unifying approach relying on a bookkeeping model that embeds processes and parameters calibrated on dynamic global vegetation models, and the use of an empirical constraint. We estimate global CO2 emissions from land-use and land-cover change were 1.36 ± 0.42 Pg C yr−1 (1-σ range) on average over 2009–2018, and 206 ± 57 Pg C cumulated over 1750–2018. We also estimate that land-cover change induced a global loss of additional sink capacity – that is, a foregone carbon removal, not part of the emissions – of 0.68 ± 0.57 Pg C yr−1 and 32 ± 23 Pg C over the same periods, respectively. Additionally, we provide a breakdown of our results' uncertainty following aspects that include the land-use and land-cover change data sets used as input, and the model's biogeochemical parameters. We find the biogeochemical uncertainty dominates our global and regional estimates, with the exception of tropical regions in which the input data dominates. Our analysis further identifies key sources of uncertainty, and suggests ways to strengthen the robustness of future Global Carbon Budgets.

Thomas Gasser et al.

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Interactive discussion

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Thomas Gasser et al.

Thomas Gasser et al.

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Latest update: 07 Jul 2020
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Short summary
We combine several lines of evidence to provide a robust estimate of historical CO2 emissions from land-use change. Our novel approach leads to reduced uncertainty, and identifies key remaining sources of uncertainty and discrepancy. We also quantify the carbon removal by natural ecosystems that would have happened if these ecosystems had not been destroyed (mostly through deforestation). Over the last decade, this foregone carbon sink amounted to about 50 % of the actual emissions.
We combine several lines of evidence to provide a robust estimate of historical CO2 emissions...
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