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Volume 18, issue 5
Atmos. Chem. Phys., 18, 3779-3798, 2018
https://doi.org/10.5194/acp-18-3779-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Atmos. Chem. Phys., 18, 3779-3798, 2018
https://doi.org/10.5194/acp-18-3779-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 15 Mar 2018

Research article | 15 Mar 2018

How a European network may help with estimating methane emissions on the French national scale

Isabelle Pison1, Antoine Berchet2,1, Marielle Saunois1, Philippe Bousquet1, Grégoire Broquet1, Sébastien Conil3, Marc Delmotte1, Anita Ganesan5, Olivier Laurent1, Damien Martin4, Simon O'Doherty5, Michel Ramonet1, T. Gerard Spain6, Alex Vermeulen7,a, and Camille Yver Kwok1 Isabelle Pison et al.
  • 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, Petten, the Netherlands
  • anow at: ICOS ERIC – Carbon Portal, Lund, Sweden

Abstract. Methane emissions on 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 on 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 in 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) make it difficult to attribute maximum emissions to a specific sector. On the yearly and national scales, the two inversions range from 3835 to 4050GgCH4 and from 3570 to 4190GgCH4 for the regional and sectorial runs, 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 underestimated 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 the UNFCCC. Uncertainties in the total annual national budget are 108 and 312GgCH4, i.e, 3 to 8%, for the regional and sectorial runs 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 us to fully constrain all regions in France accurately, a regional inversion set-up makes it possible to provide estimates of French methane fluxes with an uncertainty in the total budget of less than 10% on the yearly timescale. Additional sites deployed since 2012 would help to constrain French emissions on finer spatial and temporal scales and attributing missing emissions to specific sectors.

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Methane emissions on 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 on the national scale. The results are compared with existing inventories and other regional inversions.
Methane emissions on the national scale in France in 2012 are inferred by assimilating...
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