The consolidated European synthesis of CO2 emissions and removals for the European Union and United Kingdom: 1990–2020

McGrath, Matthew J., Petrescu, Ana Maria Roxana, Peylin, Philippe, Andrew, Robbie M., Matthews, Bradley, Dentener, Frank, Balkovič, Juraj, Bastrikov, Vladislav, Becker, Meike, Broquet, Gregoire, Ciais, Philippe, Fortems-Cheiney, Audrey, Ganzenmüller, Raphael, Grassi, Giacomo, Harris, Ian, Jones, Matthew ORCID:, Knauer, Jürgen, Kuhnert, Matthias, Monteil, Guillaume, Munassar, Saqr, Palmer, Paul I., Peters, Glen P., Qiu, Chunjing, Schelhaas, Mart-Jan, Tarasova, Oksana, Vizzarri, Matteo, Winkler, Karina, Balsamo, Gianpaolo, Berchet, Antoine, Briggs, Peter, Brockmann, Patrick, Chevallier, Frédéric, Conchedda, Giulia, Crippa, Monica, Dellaert, Stijn N. C., Denier van der Gon, Hugo A. C., Filipek, Sara, Friedlingstein, Pierre, Fuchs, Richard, Gauss, Michael, Gerbig, Christoph, Guizzardi, Diego, Günther, Dirk, Houghton, Richard A., Janssens-Maenhout, Greet, Lauerwald, Ronny, Lerink, Bas, Luijkx, Ingrid T., Moulas, Géraud, Muntean, Marilena, Nabuurs, Gert-jan, Paquirissamy, Aurélie, Perugini, Lucia, Peters, Wouter, Pilli, Roberto, Pongratz, Julia, Regnier, Pierre, Scholze, Marko, Serengil, Yusuf, Smith, Pete, Solazzo, Efisio, Thompson, Rona L., Tubiello, Francesco N., Vesala, Timo and Walther, Sophia (2023) The consolidated European synthesis of CO2 emissions and removals for the European Union and United Kingdom: 1990–2020. Earth System Science Data, 15 (10). pp. 4295-4370. ISSN 1866-3508

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Quantification of land surface–atmosphere fluxes of carbon dioxide (CO2) and their trends and uncertainties is essential for monitoring progress of the EU27+UK bloc as it strives to meet ambitious targets determined by both international agreements and internal regulation. This study provides a consolidated synthesis of fossil sources (CO2 fossil) and natural (including formally managed ecosystems) sources and sinks over land (CO2 land) using bottom-up (BU) and top-down (TD) approaches for the European Union and United Kingdom (EU27+UK), updating earlier syntheses (Petrescu et al., 2020, 2021). Given the wide scope of the work and the variety of approaches involved, this study aims to answer essential questions identified in the previous syntheses and understand the differences between datasets, particularly for poorly characterized fluxes from managed and unmanaged ecosystems. The work integrates updated emission inventory data, process-based model results, data-driven categorical model results, and inverse modeling estimates, extending the previous period 1990–2018 to the year 2020 to the extent possible. BU and TD products are compared with the European national greenhouse gas inventory (NGHGI) reported by parties including the year 2019 under the United Nations Framework Convention on Climate Change (UNFCCC). The uncertainties of the EU27+UK NGHGI were evaluated using the standard deviation reported by the EU member states following the guidelines of the Intergovernmental Panel on Climate Change (IPCC) and harmonized by gap-filling procedures. Variation in estimates produced with other methods, such as atmospheric inversion models (TD) or spatially disaggregated inventory datasets (BU), originate from within-model uncertainty related to parameterization as well as structural differences between models. By comparing the NGHGI with other approaches, key sources of differences between estimates arise primarily in activities. System boundaries and emission categories create differences in CO2 fossil datasets, while different land use definitions for reporting emissions from land use, land use change, and forestry (LULUCF) activities result in differences for CO2 land. The latter has important consequences for atmospheric inversions, leading to inversions reporting stronger sinks in vegetation and soils than are reported by the NGHGI. For CO2 fossil emissions, after harmonizing estimates based on common activities and selecting the most recent year available for all datasets, the UNFCCC NGHGI for the EU27+UK accounts for 926 ± 13 Tg C yr−1, while eight other BU sources report a mean value of 948 [937,961] Tg C yr−1 (25th, 75th percentiles). The sole top-down inversion of fossil emissions currently available accounts for 875 Tg C in this same year, a value outside the uncertainty of both the NGHGI and bottom-up ensemble estimates and for which uncertainty estimates are not currently available. For the net CO2 land fluxes, during the most recent 5-year period including the NGHGI estimates, the NGHGI accounted for −91 ± 32 Tg C yr−1, while six other BU approaches reported a mean sink of −62 [] Tg C yr−1, and a 15-member ensemble of dynamic global vegetation models (DGVMs) reported −69 [] Tg C yr−1. The 5-year mean of three TD regional ensembles combined with one non-ensemble inversion of −73 Tg C yr−1 has a slightly smaller spread (0th–100th percentiles of [] Tg C yr−1), and it was calculated after removing net land–atmosphere CO2 fluxes caused by lateral transport of carbon (crop trade, wood trade, river transport, and net uptake from inland water bodies), resulting in increased agreement with the NGHGI and bottom-up approaches. Results at the category level (Forest Land, Cropland, Grassland) generally show good agreement between the NGHGI and category-specific models, but results for DGVMs are mixed. Overall, for both CO2 fossil and net CO2 land fluxes, we find that current independent approaches are consistent with the NGHGI at the scale of the EU27+UK. We conclude that CO2 emissions from fossil sources have decreased over the past 30 years in the EU27+UK, while land fluxes are relatively stable: positive or negative trends larger (smaller) than 0.07 (−0.61) Tg C yr−2 can be ruled out for the NGHGI. In addition, a gap on the order of 1000 Tg C yr−1 between CO2 fossil emissions and net CO2 uptake by the land exists regardless of the type of approach (NGHGI, TD, BU), falling well outside all available estimates of uncertainties. However, uncertainties in top-down approaches to estimate CO2 fossil emissions remain uncharacterized and are likely substantial, in addition to known uncertainties in top-down estimates of the land fluxes. The data used to plot the figures are available at (McGrath et al., 2023).

Item Type: Article
Additional Information: Funding Information: This research has been supported by the European Commission, Horizon 2020 Framework Programme (VERIFY, grant no. 776810, for Antoine Berchet, Audrey Fortems-Cheiney, Ana Maria Roxana Petrescu, Aurélie Paquirissamy, Christoph Gerbig, Gregoire Broquet, Greet Janssens-Maenhout, Gert-Jan Nabuurs, Guillaume Monteil, Glen P. Peters, Hugo A. C. Denier van der Gon, Juraj Balkovič, Lucia Perugini, Matthew Jones, Matthew Joseph McGrath, Matthias Kuhnert, Matteo Vizzarri, Philippe Peylin, Pierre Regnier, Pete Smith, Raphael Ganzenmüller, Robbie M. Andrew, Stijn Dellaert). Matthew Joseph McGrath, Greet Janssens-Maenhout, Glen P. Peters, and Robbie M. Andrew also acknowledge funding from the European Union's Horizon 2020 research and innovation program under grant agreement no. 958927 (CoCO2). Philippe Ciais acknowledges the support of European Research Council Synergy project SyG-2013-610028 IMBALANCE-P and from the ANR CLand Convergence Institute.
Uncontrolled Keywords: earth and planetary sciences(all),sdg 15 - life on land,sdg 13 - climate action ,/dk/atira/pure/subjectarea/asjc/1900
Faculty \ School: Faculty of Science > School of Environmental Sciences
University of East Anglia Research Groups/Centres > Theme - ClimateUEA
UEA Research Groups: Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences
Faculty of Science > Research Groups > Climatic Research Unit
University of East Anglia Schools > Faculty of Science > Tyndall Centre for Climate Change Research
Faculty of Science > Research Centres > Tyndall Centre for Climate Change Research
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Depositing User: LivePure Connector
Date Deposited: 07 Oct 2023 01:25
Last Modified: 19 Dec 2023 04:49
DOI: 10.5194/essd-15-4295-2023


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