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Inverse modelling of European CH4 emissions during 2006-2012 using different inverse models and reassessed atmospheric observations

Bergamaschi, P., Karstens, U., Manning, A. J., Saunois, M., Tsuruta, A., Berchet, A., Vermeulen, A. T., Arnold, T., Janssens-Maenhout, G., Hammer, S., Levin, I., Ramonet, M., Lopez, M., Lavric, J., Aalto, T., Chen, H., Feist, D. G., Gerbig, C., Haszpra, L., Hermansen, O., Manca, G., Moncrieff, J., Meinhardt, F., Necki, J., Galkowski, M., O'Doherty, S., Paramonova, N., Scheeren, H. A., Steinbacher, M. & Dlugokencky, E., 25-Jan-2018, In : Atmospheric Chemistry and Physics. 18, 2, p. 901-920 20 p.

Research output: Contribution to journalArticleAcademicpeer-review

  • Peter Bergamaschi
  • Ute Karstens
  • Alistair J. Manning
  • Marielle Saunois
  • Aki Tsuruta
  • Antoine Berchet
  • Alexander T. Vermeulen
  • Tim Arnold
  • Greet Janssens-Maenhout
  • Samuel Hammer
  • Ingeborg Levin
  • Michel Ramonet
  • Morgan Lopez
  • Jost Lavric
  • Tuula Aalto
  • Huilin Chen
  • Dietrich G. Feist
  • Christoph Gerbig
  • Laszlo Haszpra
  • Ove Hermansen
  • Giovanni Manca
  • John Moncrieff
  • Frank Meinhardt
  • Jaroslaw Necki
  • Michal Galkowski
  • Simon O'Doherty
  • Nina Paramonova
  • Hubertus A. Scheeren
  • Martin Steinbacher
  • Ed Dlugokencky

We present inverse modelling (top down) estimates of European methane (CH4) emissions for 2006-2012 based on a new quality-controlled and harmonised in situ data set from 18 European atmospheric monitoring stations. We applied an ensemble of seven inverse models and performed four inversion experiments, investigating the impact of different sets of stations and the use of a priori information on emissions.

The inverse models infer total CH4 emissions of 26.8 (20.2-29.7) TgCH(4) yr(-1) (mean, 10th and 90th percentiles from all inversions) for the EU-28 for 2006-2012 from the four inversion experiments. For comparison, total anthropogenic CH4 emissions reported to UNFCCC (bottom up, based on statistical data and emissions factors) amount to only 21.3 TgCH(4) yr(-1) (2006) to 18.8 TgCH(4) yr(-1) (2012). A potential explanation for the higher range of top-down estimates compared to bottom-up inventories could be the contribution from natural sources, such as peatlands, wetlands, and wet soils. Based on seven different wetland inventories from the Wetland and Wetland CH4 Inter-comparison of Models Project (WETCHIMP), total wetland emissions of 4.3 (2.3-8.2) TgCH(4) yr(-1) from the EU-28 are estimated. The hypothesis of significant natural emissions is supported by the finding that several inverse models yield significant seasonal cycles of derived CH4 emissions with maxima in summer, while anthropogenic CH4 emissions are assumed to have much lower seasonal variability. Taking into account the wetland emissions from the WETCHIMP ensemble, the top-down estimates are broadly consistent with the sum of anthropogenic and natural bottom-up inventories. However, the contribution of natural sources and their regional distribution remain rather uncertain.

Furthermore, we investigate potential biases in the inverse models by comparison with regular aircraft profiles at four European sites and with vertical profiles obtained during the Infrastructure for Measurement of the European Carbon Cycle (IMECC) aircraft campaign. We present a novel approach to estimate the biases in the derived emissions, based on the comparison of simulated and measured enhancements of CH4 compared to the background, integrated over the entire boundary layer and over the lower troposphere. The estimated average regional biases range between -40 and 20% at the aircraft profile sites in France, Hungary and Poland.

Original languageEnglish
Pages (from-to)901-920
Number of pages20
JournalAtmospheric Chemistry and Physics
Volume18
Issue number2
Publication statusPublished - 25-Jan-2018

    Keywords

  • GREENHOUSE-GAS MEASUREMENTS, COMPARISON PROJECT WETCHIMP, C-13/C-12 ISOTOPIC-RATIOS, DATA ASSIMILATION SYSTEM, GLOBAL WETLAND EXTENT, IN-SITU MEASUREMENTS, METHANE EMISSIONS, PRESENT STATE, LOS-ANGELES, TOP-DOWN

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