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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-666
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
06 Oct 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
How a European network may help estimating methane emissions at the French national scale
Isabelle Pison1, Antoine Berchet2, Marielle Saunois1, Philippe Bousquet1, Grégoire Broquet1, Sébastien Conil3, Marc Delmotte1, Anita L. Ganesan5, Olivier Laurent1, Damien Martin4, Simon O'Doherty5, Michel Ramonet1, T. Gerard Spain6, Alex Vermeulen7,a, and Camille Yver Kwok1 1Laboratoire des Sciences du Climat et de l’Environnement, LSCE-IPSL (CEA-CNRS-UVSQ), Université Paris-Saclay, 91191 Gif-sur-Yvette, France
2Laboratory for Air Pollution/Environmental Technology, Empa - Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
3Agence Nationale pour la gestion des Déchets RadioActifs, Châtenay-Malabry, France
4Centre for Climate and Air Pollution Studies, School of Physics, National University of Ireland Galway, Galway, Ireland
5Atmospheric Chemistry Research Group, School of Chemistry, University of Bristol, Cantocks Close, Bristol, UK
6National University of Ireland Galway, Galway, Ireland
7Energy Research Centre of the Netherlands, Heerhugowaard, The Netherlands
anow at: Dept. Phys. Geography and Ecosystem Science, Lund, Sweden
Abstract. Methane emissions at the national scale in France in 2012 are inferred by assimilating continuous atmospheric mixing ratio measurements from nine stations of the European network ICOS located in France and surrounding countries. To assess the robustness of the fluxes deduced by our inversion system based on an objectified quantification of uncertainties, two complementary inversion set-ups are computed and analysed: i) a regional run correcting for the spatial distribution of fluxes in France, and ii) a sectorial run correcting fluxes for activity sectors at the national scale. In addition, our results for the two set-ups are compared with fluxes produced in the framework of the inversion inter-comparison exercise of the InGOS project. The seasonal variability of fluxes is consistent between different set-ups, with maximum emissions in summer, likely due to agricultural activity. However, very high monthly posterior uncertainties (up to ≈ 65 % to 74 % in the sectorial run in May and June) makes it difficult to attribute maximum emissions to a specific sector. At the yearly national scale, the two inversions range to 3835–4050 Gg CH4 and 3570–4190 Gg CH4 for the regional and sectorial run, respectively, consistently with the InGOS products. These estimates are 25 to 55 % higher than the total national emissions from bottom-up approaches (biogeochemical models from natural emissions, plus inventories for anthropogenic ones), consistently pointing at missing or under-estimated sources in the inventories and/or in natural sources. More specifically, in the sectorial set-up, agricultural emissions are inferred as 66 % larger than estimates reported to UNFCCC. Uncertainties on the total annual national budget are 108 Gg CH4 and 312 Gg CH4, i.e, 3 to 8 %, for the regional and sectorial run respectively, smaller than uncertainties in available bottom-up products, proving the added value of top-down atmospheric inversions. Therefore, even though the surface network used in 2012 does not allow to fully constrain all regions in France accurately, a regional inversion set-ups makes it possible to provide estimates of French methane fluxes with an uncertainty on the total budget less than 10 % at the yearly scale. Additional sites deployed since 2012 would help to constrain French emissions at finer spatial and temporal scales and attributing missing emissions to specific sectors.

Citation: Pison, I., Berchet, A., Saunois, M., Bousquet, P., Broquet, G., Conil, S., Delmotte, M., Ganesan, A. L., Laurent, O., Martin, D., O'Doherty, S., Ramonet, M., Spain, T. G., Vermeulen, A., and Yver Kwok, C.: How a European network may help estimating methane emissions at the French national scale, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-666, in review, 2017.
Isabelle Pison et al.
Isabelle Pison et al.
Isabelle Pison et al.

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Short summary
Methane emissions at the national scale in France in 2012 are inferred by assimilating continuous atmospheric mixing ratio measurements from nine stations of the European network ICOS. Two complementary inversion set-ups are computed and analysed: i) a regional run correcting for the spatial distribution of fluxes in France, and ii) a sectorial run correcting fluxes for activity sectors at the national scale. The results are compared with existing inventories and other regional inversions.
Methane emissions at the national scale in France in 2012 are inferred by assimilating...
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