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

Isabelle Pison*, Antoine Berchet, Marielle Saunois, Philippe Bousquet, Grégoire Broquet, Sébastien Conil, Marc Delmotte, Anita Ganesan, Olivier Laurent, Damien Martin, Simon O'Doherty, Michel Ramonet, T. Gerard Spain, Alex Vermeulen, Camille Yver Kwok

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)

4 Citations (Scopus)
353 Downloads (Pure)

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 intercomparison 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 4050 GgCH4 and from 3570 to 4190 GgCH4 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 312 GgCH4, 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.

Original languageEnglish
Pages (from-to)3779-3798
Number of pages20
JournalAtmospheric Chemistry and Physics
Volume18
Issue number5
Early online date15 Mar 2018
DOIs
Publication statusPublished - 15 Mar 2018

Fingerprint Dive into the research topics of 'How a European network may help with estimating methane emissions on the French national scale'. Together they form a unique fingerprint.

  • Projects

    Cite this

    Pison, I., Berchet, A., Saunois, M., Bousquet, P., Broquet, G., Conil, S., Delmotte, M., Ganesan, A., Laurent, O., Martin, D., O'Doherty, S., Ramonet, M., Spain, T. G., Vermeulen, A., & Kwok, C. Y. (2018). How a European network may help with estimating methane emissions on the French national scale. Atmospheric Chemistry and Physics, 18(5), 3779-3798. https://doi.org/10.5194/acp-18-3779-2018