Abstract

Methane is an important greenhouse gas, responsible for about 20% of the warming induced by long-lived greenhouse gases since pre-industrial times. By reacting with hydroxyl radicals, methane reduces the oxidizing capacity of the atmosphere and generates ozone in the troposphere. Although most sources and sinks of methane have been identified, their relative contributions to atmospheric methane levels are highly uncertain. As such, the factors responsible for the observed stabilization of atmospheric methane levels in the early 2000s, and the renewed rise after 2006, remain unclear. Here, we construct decadal budgets for methane sources and sinks between 1980 and 2010, using a combination of atmospheric measurements and results from chemical transport models, ecosystem models, climate chemistry models and inventories of anthropogenic emissions. The resultant budgets suggest that data-driven approaches and ecosystem models overestimate total natural emissions. We build three contrasting emission scenarios — which differ in fossil fuel and microbial emissions — to explain the decadal variability in atmospheric methane levels detected, here and in previous studies, since 1985. Although uncertainties in emission trends do not allow definitive conclusions to be drawn, we show that the observed stabilization of methane levels between 1999 and 2006 can potentially be explained by decreasing-to-stable fossil fuel emissions, combined with stable-to-increasing microbial emissions. We show that a rise in natural wetland emissions and fossil fuel emissions probably accounts for the renewed increase in global methane levels after 2006, although the relative contribution of these two sources remains uncertain.

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Acknowledgements

This paper is the result of an international collaboration of scientists organized by the Global Carbon Project, a joint project of the Earth System Science Partnership. This work was supported by: the UK NERC National Centre for Earth Observation; the European Commission's 7th Framework Programme (FP7/2007-2013) projects MACC (grant agreement no. 218793) and GEOCARBON (grant agreement no. 283080); contract DE-AC52-07NA27344 with different parts supported by the US DOE IMPACTS and SciDAC Climate Consortium projects; computing resources of NERSC, which is supported by the US DOE under contract DE-AC02-05CH11231; NOAA flask data for CH3CCl3 (made available by S. Montzka); the Australian Climate Change Science Program, and ERC grant 247349. Simulations from LSCE were performed using HPC resources from DSM-CCRT and CCRT/CINES/IDRIS under the allocation 2012-t2012012201 made by GENCI (Grand Equipement National de Calcul Intensif). We thank the EDGAR group at JRC (Italy) and US-EPA for providing estimates of anthropogenic emissions.

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Affiliations

  1. LSCE-CEA-UVSQ-CNRS, Orme des Merisiers, 91190 Gif-sur-Yvette, France

    • Stefanie Kirschke
    • , Philippe Bousquet
    • , Philippe Ciais
    • , Marielle Saunois
    • , Frédéric Chevallier
    • , Isabelle Pison
    • , Benjamin Poulter
    • , Martina Schmidt
    •  & Sophie Szopa
  2. Global Carbon Project, CSIRO Marine and Atmospheric Research, GPO Box 3023, Canberra, ACT 2601, Australia

    • Josep G. Canadell
  3. NOAA ESRL, 325 Broadway, Boulder, Colorado 80305, USA

    • Edward J. Dlugokencky
    •  & Lori Bruhwiler
  4. Institute for Environment and Sustainability, Joint Research Centre, TP290, I-21027 Ispra (Va), Italy

    • Peter Bergamaschi
  5. Lawrence Livermore National Laboratory, PO Box 808, Livermore, California 94551-0808, USA

    • Daniel Bergmann
    •  & Philip Cameron-Smith
  6. University of California Irvine, 570 Rowland Hall, Irvine, California 92697, USA

    • Donald R. Blake
    •  & Isobel J. Simpson
  7. Department of Environmental Sciences, Second University of Naples, via Vivaldi 43, 81100 Caserta, Italy

    • Simona Castaldi
  8. Centro Euro-Mediterraneo sui Cambiamenti Climatici (CMCC), via Augusto Imperatore 16, 73100 Lecce, Italy

    • Simona Castaldi
    •  & Monia Santini
  9. School of Geosciences, University of Edinburgh, Crew Building, West Mains Road, Edinburgh, EH9 3JN, UK

    • Liang Feng
    • , Annemarie Fraser
    •  & Paul I. Palmer
  10. Max Planck Institute for Biogeochemistry, PF 100164, D-07701 Jena, Germany

    • Martin Heimann
  11. Swiss Federal Research Institute WSL, Zuercherstrasse 111, 8903 Mensdorf, Switzerland

    • Elke L. Hodson
  12. SRON, Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands

    • Sander Houweling
  13. Institue for Marine and Atmospheric Research Utrecht, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands

    • Sander Houweling
    •  & Bruno Ringeval
  14. Météo France, CNRM/GMGEC/CARMA, 42 av G. Coriolis, 31057 Toulouse, France

    • Béatrice Josse
  15. Centre for Australian Weather and Climate Research/CSIRO Marine and Atmospheric Research, Aspendale, Victoria 3195, Australia

    • Paul J. Fraser
    • , Paul B. Krummel
    • , Ray L. Langenfelds
    •  & L. Paul Steele
  16. NCAR, PO Box 3000, Boulder, Colorado 80307-3000, USA

    • Jean-François Lamarque
  17. Tyndall Centre for Climate Change Research, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK

    • Corinne Le Quéré
  18. UCAR/NOAA Geophysical Fluid Dynamics Laboratory, 201 Forrestal Road, Princeton, New Jersey 08540, USA

    • Vaishali Naik
  19. University of Bristol, Office Old Park Hill, Cantock's Close, Clifton, Bristol BS8 1TS, UK

    • Simon O'Doherty
  20. Canadian Centre for Climate Modelling and Analysis, Environment Canada, 550 Sherbrooke Street West, West Tower, Montréal, Quebec, H3A 1B9, Canada

    • David Plummer
  21. Massachusetts Institute of Technology, Building 54-1312, Cambridge, Massachusetts 02139-2307, USA

    • Ronald G. Prinn
  22. School of Chemistry, University of Bristol, Cantocks Close, Bristol BS8 1TS, UK

    • Matt Rigby
  23. IMAU, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands

    • Bruno Ringeval
  24. Department of Systems Ecology, VU University Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands

    • Bruno Ringeval
  25. NASA Goddard Institute for Space Studies, 2880 Broadway, New York, New York 10025, USA

    • Drew T. Shindell
    •  & Apostolos Voulgarakis
  26. University of Bern, Physics Institute, Climate and Environmental Physics, Sidlerstrasse 5, CH-3012 Bern, Switzerland

    • Renato Spahni
  27. NASA Goddard Space Flight Centre, Greenbelt, Maryland 20771, USA

    • Sarah A. Strode
  28. Universities Space Research Association, NASA Goddard Space Flight Centre, Greenbelt, Maryland 20771, USA

    • Sarah A. Strode
  29. Graduate School of Environmental Studies, Nagoya University Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan

    • Kengo Sudo
  30. VU University, Faculty of Earth and Life Sciences, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands

    • Guido R. van der Werf
  31. Department of Physics, Imperial College London, London SW7 2AZ, UK

    • Apostolos Voulgarakis
  32. Royal Netherlands Meteorological Institute (KNMI), PO Box 201, 3730 AE De Bilt, The Netherlands

    • Michiel van Weele
    •  & Jason E. Williams
  33. Scripps Institution of Oceanography, UCSD, La Jolla, California 92093-0244, USA

    • Ray F. Weiss
  34. National Institute of Water and Atmospheric Research, Private Bag 50061, Omakau, Central Otago 9352, New Zealand

    • Guang Zeng

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Contributions

S.K., P. Bousquet, P.C., J.G.C. and C.L.Q. designed the study and provided conceptual advice. S.K., P. Bousquet and M. Saunois processed data sets, developed figures and wrote the manuscript. E.J.D., M. Schmidt, P.J.F., P.B.K., L.P.S., R.L.L., R.G.P., M.R., R.F.W., D.R.B. and I.J.S. provided atmospheric in situ data. P.Bousquet, P.Bergamaschi, L.B., F.C., L.F., A.F., S.H., P.I.P. and I.P. provided top-down inversion results (all five emission categories). S.C., E.L.H., B.P., B.R., M.Santini, R.S. and G.R.v.d.W provided bottom-up modelling and inventory data sets for wetland, biomass burning and termite emissions. D.B., P.C.-S., B.J., J.-F.L., V.N., D.P., D.T.S., S.A.S., K.S., S.S., A.V., M.v.W., J.E.W. and G.Z. provided bottom-up estimates of CH4 loss due to OH. All authors contributed extensively to the work presented in this paper, and to revisions of the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Philippe Bousquet.

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https://doi.org/10.1038/ngeo1955

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