Variability and quasi-decadal changes in the methane budget over
the period 2000–2012
Marielle Saunois1, Philippe Bousquet1, Benjamin Poulter2, Anna Peregon1, Philippe Ciais1, Josep G. Canadell3, Edward J. Dlugokencky4, Giuseppe Etiope5,6, David Bastviken7, Sander Houweling8,9, Greet Janssens-Maenhout10, Francesco N. Tubiello11, Simona Castaldi12,13,14, Robert B. Jackson15, Mihai Alexe10, Vivek K. Arora16, David J. Beerling17, Peter Bergamaschi10, Donald R. Blake18, Gordon Brailsford19, Lori Bruhwiler4, Cyril Crevoisier20, Patrick Crill21, Kristofer Covey22, Christian Frankenberg23,24, Nicola Gedney25, Lena Höglund-Isaksson26, Misa Ishizawa27, Akihiko Ito27, Fortunat Joos28, Heon-Sook Kim27, Thomas Kleinen29, Paul Krummel30, Jean-François Lamarque31, Ray Langenfelds30, Robin Locatelli1, Toshinobu Machida27, Shamil Maksyutov27, Joe R. Melton32, Isamu Morino33, Vaishali Naik34, Simon O'Doherty35, Frans-Jan W. Parmentier36, Prabir K. Patra37, Changhui Peng38,39, Shushi Peng1,40, Glen P. Peters41, Isabelle Pison1, Ronald Prinn42, Michel Ramonet1, William J. Riley43, Makoto Saito27, Monia Santini14, Ronny Schroeder44, Isobel J. Simpson18, Renato Spahni28, Atsushi Takizawa45, Brett F. Thornton22, Hanqin Tian46, Yasunori Tohjima27, Nicolas Viovy1, Apostolos Voulgarakis47, Ray Weiss48, David J. Wilton17, Andy Wiltshire49, Doug Worthy50, Debra Wunch51, Xiyan Xu43,52, Yukio Yoshida27, Bowen Zhang46, Zhen Zhang2,53, and Qiuan Zhu391Laboratoire des Sciences du Climat et de l’Environnement, LSCE-IPSL (CEA-CNRS-UVSQ), Université Paris-Saclay 91191 Gif-sur-Yvette, France 2NASA Goddard Space Flight Center, Biospheric Science Laboratory, Greenbelt, MD 20771, USA 3Global Carbon Project, CSIRO Oceans and Atmosphere, Canberra, ACT 2601, Australia 4NOAA ESRL, 325 Broadway, Boulder, Colorado 80305, USA 5Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma 2, via V. Murata 605 00143, Roma 6Faculty of Environmental Science and Engineering, Babes Bolyai University, Cluj-Napoca, Romania 7Department of Thematic Studies – Environmental Change, Linköping University, SE-581 83 Linköping, Sweden 8Netherlands Institute for Space Research (SRON), Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands 9Institute for Marine and Atmospheric Research Sorbonnelaan 2, 3584 CA, Utrecht, The Netherlands 10European Commission Joint Research Centre, Ispra (Va), Italy 11Statistics Division, Food and Agriculture Organization of the United Nations (FAO), Viale delle Terme di Caracalla, Rome 00153, Italy 12Dipartimento di Scienze Ambientali, Biologiche e Farmaceutiche, Seconda Universita di Napoli, via Vivaldi 43, 81100 Caserta, Italy 13Far East Federal University (FEFU), Vladivostok, Russky Island, Russia 14Euro-Mediterranean Center on Climate Change, Via Augusto Imperatore 16, 73100 Lecce, Italy 15School of Earth, Energy & Environmental Sciences, Stanford University, Stanford, CA 94305-2210, USA 16Canadian Centre for Climate Modelling and Analysis, Climate Research Division, Environment and Climate Change Canada, Victoria, BC, V8W 2Y2, Canada 17Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK 18University of California Irvine, 570 Rowland Hall, Irvine, California 92697, USA 19National Institute of Water and Atmospheric Research, 301 Evans Bay Parade, Wellington, New Zealand 20Laboratoire de Météorologie Dynamique, LMD/IPSL, CNRS Ecole polytechnique, Université Paris-Saclay, 91120 Palaiseau, France 21Department of Geological Sciences and Bolin Centre for Climate Research, Svante Arrhenius väg 8, SE-106 91 Stockholm, Sweden 22School of Forestry and Environmental Studies, Yale University New Haven, CT 06511, USA 23California Institute of Technology, Geological and Planetary Sciences, Pasadena, USA 24Jet Propulsion Laboratory, M/S 183-601, 4800 Oak Grove Drive, Pasadena, CA 91109, USA 25Met Office Hadley Centre, Joint Centre for Hydrometeorological Research, Maclean Building, Wallingford OX10 8BB, UK 26Air Quality and Greenhouse Gases program (AIR), International Institute for Applied Systems Analysis (IIASA), A-2361 Laxenburg, Austria 27Center for Global Environmental Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan 28Climate and Environmental Physics, Physics Institute and Oeschger Center for Climate Change Research, University of Bern, Sidlerstr. 5, CH-3012 Bern, Switzerland 29Max Planck Institute for Meteorology, Bundesstrasse 53, 20146 Hamburg, Germany 30CSIRO Oceans and Atmosphere, Aspendale, Victoria 3195 Australia 31NCAR, PO Box 3000, Boulder, Colorado 80307-3000, USA 32Climate Research Division, Environment and Climate Change Canada, Victoria, BC, V8W 2Y2, Canada 33Center for Global Environmental Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan 34NOAA, GFDL, 201 Forrestal Rd., Princeton, NJ 08540 35School of Chemistry, University of Bristol, Cantock's Close, Clifton, Bristol BS8 1TS 36Department of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and Economics, UiT: The Arctic University of Norway, NO-9037, Tromsø, Norway 37Department of Environmental Geochemical Cycle Research and Institute of Arctic Climate and Environment Research, JAMSTEC, 3173-25 Showa-machi, Kanazawa-ku, Yokohama, 236-0001, Japan 38Department of Biology Sciences, Institute of Environment Science, University of Quebec at Montreal, Montreal, QC H3C 3P8, Canada 39State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling, Shaanxi 712100, China 40Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China 41CICERO Center for International Climate Research, Pb. 1129 Blindern, 0318 Oslo, Norway 42Massachusetts Institute of Technology (MIT), Building 54-1312, Cambridge, MA 02139, USA 43Earth Sciences Division, Lawrence Berkeley National Lab, 1 Cyclotron Road, Berkeley, CA 94720, USA 44Department of Civil & Environmental Engineering, University of New Hampshire, Durham, NH 03824, USA 45Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan 46International Center for Climate and Global Change Research, School of Forestry and Wildlife Sciences, Auburn University, 602 Duncan Drive, Auburn, AL 36849, USA 47Space & Atmospheric Physics, The Blackett Laboratory, Imperial College London, London SW7 2AZ, UK 48Scripps Institution of Oceanography (SIO), University of California San Diego, La Jolla, CA 92093, USA 49Met Office Hadley Centre, FitzRoy Road, Exeter, EX1 3PB, United Kingdom 50Environnement Canada, 4905, rue Dufferin, Toronto, Canada 51Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario, Canada 52CAS Key Laboratory of Regional Climate-Environment for Temperate East Asia, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China 53Swiss Federal Research Institute WSL, Birmensdorf 8059, Switzerland
Received: 30 Mar 2017 – Accepted for review: 08 Apr 2017 – Discussion started: 18 Apr 2017
Abstract. Following the recent Global Carbon project (GCP) synthesis of the decadal methane (CH4) budget over 2000–2012 (Saunois et al., 2016), we analyse here the same dataset with a focus on quasi-decadal and inter-annual variability in CH4 emissions. The GCP dataset integrates results from top-down studies (exploiting atmospheric observations within an atmospheric inverse-modelling frameworks) and bottom-up models, inventories, and data-driven approaches (including process-based models for estimating land surface emissions and atmospheric chemistry, inventories of anthropogenic emissions, and data-driven extrapolations).
The annual global methane emissions from top-down studies, which by construction match the observed methane growth rate within their uncertainties, all show an increase in total methane emissions over the period 2000–2012, but this increase is not linear over the 13 years. Despite differences between individual studies, the mean emission anomaly of the top-down ensemble shows no significant trend in total methane emissions over the period 2000–2006, during the plateau of atmospheric methane mole fractions, and also over the period 2008–2012, during the renewed atmospheric methane increase. However, the top-down ensemble mean produces an emission shift between 2006 and 2008, leading to 22 [16–32] Tg CH4 yr−1 higher methane emissions over the period 2008–2012 compared to 2002–2006. This emission increase mostly originated from the tropics with a smaller contribution from mid-latitudes and no significant change from boreal regions.
The regional contributions remain uncertain in top-down studies. Tropical South America and South and East Asia seems to contribute the most to the emission increase in the tropics. However, these two regions have only limited atmospheric measurements and remain therefore poorly constrained.
The sectorial partitioning of this emission increase between the periods 2002–2006 and 2008–2012 differs from one atmospheric inversion study to another. However, all top-down studies suggest smaller changes in fossil fuel emissions (from oil, gas, and coal industries) compared to the mean of the bottom-up inventories included in this study. This difference is partly driven by a smaller emission change in China from the top-down studies compared to the estimate in the EDGARv4.2 inventory, which should be revised to smaller values in a near future. Though the sectorial partitioning of six individual top-down studies out of eight are not consistent with the observed change in atmospheric 13CH4, the partitioning derived from the ensemble mean is consistent with this isotopic constraint. At the global scale, the top-down ensemble mean suggests that, the dominant contribution to the resumed atmospheric CH4 growth after 2006 comes from microbial sources (more from agriculture and waste sectors than from natural wetlands), with an uncertain but smaller contribution from fossil CH4 emissions. Besides, a decrease in biomass burning emissions (in agreement with the biomass burning emission databases) makes the balance of sources consistent with atmospheric 13CH4 observations.
The methane loss (in particular through OH oxidation) has not been investigated in detail in this study, although it may play a significant role in the recent atmospheric methane changes.
Saunois, M., Bousquet, P., Poulter, B., Peregon, A., Ciais, P., Canadell, J. G., Dlugokencky, E. J., Etiope, G., Bastviken, D., Houweling, S., Janssens-Maenhout, G., Tubiello, F. N., Castaldi, S., Jackson, R. B., Alexe, M., Arora, V. K., Beerling, D. J., Bergamaschi, P., Blake, D. R., Brailsford, G., Bruhwiler, L., Crevoisier, C., Crill, P., Covey, K., Frankenberg, C., Gedney, N., Höglund-Isaksson, L., Ishizawa, M., Ito, A., Joos, F., Kim, H.-S., Kleinen, T., Krummel, P., Lamarque, J.-F., Langenfelds, R., Locatelli, R., Machida, T., Maksyutov, S., Melton, J. R., Morino, I., Naik, V., O'Doherty, S., Parmentier, F.-J. W., Patra, P. K., Peng, C., Peng, S., Peters, G. P., Pison, I., Prinn, R., Ramonet, M., Riley, W. J., Saito, M., Santini, M., Schroeder, R., Simpson, I. J., Spahni, R., Takizawa, A., Thornton, B. F., Tian, H., Tohjima, Y., Viovy, N., Voulgarakis, A., Weiss, R., Wilton, D. J., Wiltshire, A., Worthy, D., Wunch, D., Xu, X., Yoshida, Y., Zhang, B., Zhang, Z., and Zhu, Q.: Variability and quasi-decadal changes in the methane budget over
the period 2000–2012, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-296, in review, 2017.