GMD Geoscientific Model Development GMD Geosci. Model Dev. 1991-9603 Copernicus Publications Göttingen, Germany 10.5194/gmd-6-617-2013 Present state of global wetland extent and wetland methane modelling: methodology of a model inter-comparison project (WETCHIMP) Wania R. 1 20 Melton J. R. https://orcid.org/0000-0002-9414-064X 2 21 Hodson E. L. 3 22 Poulter B. https://orcid.org/0000-0002-9493-8600 4 Ringeval B. 4 5 6 Spahni R. https://orcid.org/0000-0002-4239-5130 7 Bohn T. 8 Avis C. A. 9 23 Chen G. 10 Eliseev A. V. https://orcid.org/0000-0001-7288-7649 11 12 Hopcroft P. O. 5 Riley W. J. https://orcid.org/0000-0002-4615-2304 13 Subin Z. M. 13 24 Tian H. https://orcid.org/0000-0002-1806-4091 10 van Bodegom P. M. 15 Kleinen T. https://orcid.org/0000-0001-9550-5164 14 Yu Z. C. https://orcid.org/0000-0003-2358-2712 16 Singarayer J. S. 5 Zürcher S. https://orcid.org/0000-0001-9566-2928 7 Lettenmaier D. P. 8 Beerling D. J. 17 Denisov S. N. https://orcid.org/0000-0001-8978-8719 11 Prigent C. 18 Papa F. 19 Kaplan J. O. https://orcid.org/0000-0001-9919-7613 2 Institut des Sciences de l'Evolution, UMR5554, CNRS – Université Montpellier 2, Place Eugène Bataillon, 34090 Montpellier, France ARVE Group, École Polytechnique Fédérale de Lausanne, Switzerland Swiss Federal Research Institute WSL, Switzerland Laboratoire des Sciences du Climat et de L'Environment, CNRS–CEA, UVSQ, Gif-sur Yvette, France BRIDGE, School of Geographical Sciences, University of Bristol, UK Department of Earth Sciences, VU University, Amsterdam, the Netherlands Climate and Environmental Physics, Physics Institute & Oeschger Centre for Climate Change Research, University of Bern, Switzerland Dept. of Civil and Environmental Engineering, University of Washington, USA School of Earth and Ocean Sciences, University of Victoria, Canada International Center for Climate and Global Change Research and School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL 36849, USA A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Russia Kazan (Volga region) Federal University, Russia Earth Sciences Division (ESD), Lawrence Berkeley National Lab, USA Max Planck Institute für Meteorologie, Hamburg, Germany Department of Ecological Sciences, VU University, Amsterdam, the Netherlands Department of Earth and Environmental Sciences, Lehigh University, USA Dept. of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK CNRS/LERMA, Observatoire de Paris, 61 Ave. de l'Observatoire, 75014 Paris, France LEGOS, IRD, 18 Ave. Edouard Belin, 31400 Toulouse, France now at: Lanser Strasse 30, 6080 Igls, Austria now at: Canadian Centre for Climate Modelling and Analysis, Environment Canada, Victoria, BC, V8W 2Y2, Canada now at: AAAS Science and Technology Policy Fellow, Office of Climate Change Policy and Technology, US Department of Energy, USA now at: Physics and Astronomy department, Camosun College, Victoria, BC, Canada now at: Princeton Environmental Institute, Princeton University, Princeton, New Jersey, USA 15 05 2013 6 3 617 641 Copyright: © 2013 R. Wania et al. 2013 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://gmd.copernicus.org/articles/6/617/2013/gmd-6-617-2013.html The full text article is available as a PDF file from https://gmd.copernicus.org/articles/6/617/2013/gmd-6-617-2013.pdf

The Wetland and Wetland CH<sub>4</sub> Intercomparison of Models Project (WETCHIMP) was created to evaluate our present ability to simulate large-scale wetland characteristics and corresponding methane (CH<sub>4</sub>) emissions. A multi-model comparison is essential to evaluate the key uncertainties in the mechanisms and parameters leading to methane emissions. Ten modelling groups joined WETCHIMP to run eight global and two regional models with a common experimental protocol using the same climate and atmospheric carbon dioxide (CO<sub>2</sub>) forcing datasets. We reported the main conclusions from the intercomparison effort in a companion paper (Melton et al., 2013). Here we provide technical details for the six experiments, which included an equilibrium, a transient, and an optimized run plus three sensitivity experiments (temperature, precipitation, and atmospheric CO<sub>2</sub> concentration). The diversity of approaches used by the models is summarized through a series of conceptual figures, and is used to evaluate the wide range of wetland extent and CH<sub>4</sub> fluxes predicted by the models in the equilibrium run. We discuss relationships among the various approaches and patterns in consistencies of these model predictions. Within this group of models, there are three broad classes of methods used to estimate wetland extent: prescribed based on wetland distribution maps, prognostic relationships between hydrological states based on satellite observations, and explicit hydrological mass balances. A larger variety of approaches was used to estimate the net CH<sub>4</sub> fluxes from wetland systems. Even though modelling of wetland extent and CH<sub>4</sub> emissions has progressed significantly over recent decades, large uncertainties still exist when estimating CH<sub>4</sub> emissions: there is little consensus on model structure or complexity due to knowledge gaps, different aims of the models, and the range of temporal and spatial resolutions of the models.

 References Aselman,&nbsp;I. and Crutzen,&nbsp;P.&nbsp;J.: Global distribution of natural freshwater wetlands and rice paddies, and their net primary productivity, seasonality and possible methane emissions,&nbsp;J. Atmos. Chem., 8, 307–358, 1989. Avis,&nbsp;C.&nbsp;A., Weaver,&nbsp;A.&nbsp;J., and Meissner,&nbsp;K.&nbsp;J.: Reduction in areal extent of high-latitude wetlands in response to permafrost thaw, Nat. Geosci., 4, 444–448, 2011. Bartalev,&nbsp;S.&nbsp;A., Belward,&nbsp;A.&nbsp;S., Erchov,&nbsp;D.&nbsp;V., and Isaev,&nbsp;A.&nbsp;S.: A new SPOT4-VEGETATION derived land cover map of Northern Eurasia, Int.&nbsp;J. Remote Sens., 24, 1977–1982, 2003. Batjes,&nbsp;N.&nbsp;H.: A world dataset of derived soil properties by FAO-UNESCO soil unit for global modelling, Soil Use Manage., 13, 9–16, 1997. Beerling,&nbsp;D.&nbsp;J. and Woodward,&nbsp;F.&nbsp;I.: Vegetation and the Terrestrial Carbon Cycle: Modelling the first 400 Million Years, Cambridge University Press, Cambridge, 2001. Beerling,&nbsp;D.&nbsp;J., Fox,&nbsp;A., Stevenson,&nbsp;D.&nbsp;S., and Valdes,&nbsp;P.&nbsp;J.: Enhanced chemistry-climate feedbacks in past greenhouse worlds, P. Natl. Acad. Sci. USA, 108, 9770–9775, https://doi.org/<a href="http://dx.doi.org/10.1073/pnas.1102409108">10.1073/pnas.1102409108</a>, 2011. Berendse,&nbsp;F., Breemen,&nbsp;N.&nbsp;V., Rydin,&nbsp;H., Buttler,&nbsp;A., Heijmans,&nbsp;M., Hoosbeek,&nbsp;M.&nbsp;R., Lee,&nbsp;J.&nbsp;A., Mitchell,&nbsp;E., Saarinen,&nbsp;T., Vasander,&nbsp;H., and Wallen,&nbsp;B.: Raised atmospheric CO<sub>2</sub> levels and increased N deposition cause shifts in plant species composition and production in <i>Sphagnum</i> bogs, Glob. Change Biol., 7, 591–598, 2001. Beven,&nbsp;K.&nbsp;J. and Kirkby,&nbsp;M.&nbsp;J.: A physically based, variable contributing area model of basin hydrology, Hydrol. Sci.&nbsp;J., 24, 43–69, 1979. Boardman,&nbsp;C.&nbsp;P., Gauci,&nbsp;V., Watson,&nbsp;J.&nbsp;S., Blake,&nbsp;S., and Beerling,&nbsp;D.&nbsp;J.: Contrasting wetland CH<sub>4</sub> emission responses to simulated glacial atmospheric CO<sub>2</sub> in temperate bogs and fens, New Phytol., 192, 898–911, 2011. Bohn,&nbsp;T.&nbsp;J. and Lettenmaier,&nbsp;D.&nbsp;P.: Systematic biases in large-scale estimates of wetland methane emissions arising from water table formulations, Geophys. Res. Lett., 37, L22401, https://doi.org/<a href="http://dx.doi.org/10.1029/ 2010GL045450">10.1029/ 2010GL045450</a> 2010. Bohn,&nbsp;T.&nbsp;J., Lettenmaier,&nbsp;D.&nbsp;P., Sathulur,&nbsp;K., Bowling,&nbsp;L.&nbsp;C., Podest,&nbsp;E., McDonald,&nbsp;K.&nbsp;C., and Friborg,&nbsp;T.: Methane emissions from western {S}iberian wetlands: heterogeneity and sensitivity to climate change, Environ. Res. Lett., 2, 259–268, 2007. Bowling,&nbsp;L.&nbsp;C. and Lettenmaier,&nbsp;D.&nbsp;P.: Modeling the effects of lakes and wetlands on the water balance of {A}rctic environments,&nbsp;J. Hydrometeorol., 11, 276–295, 2010. Cao,&nbsp;M.&nbsp;K., Marshall,&nbsp;S., and Gregson,&nbsp;K.: Global carbon exchange and methane emissions from natural wetlands: application of a process-based model,&nbsp;J. Geophys. Res., 101, 14399–14414, 1996. Chen,&nbsp;G., Tian,&nbsp;H., Zhang,&nbsp;C., Liu,&nbsp;M., Ren,&nbsp;W., Zhu,&nbsp;W., Chappelka,&nbsp;A., Prior,&nbsp;S.&nbsp;A., and Lockaby,&nbsp;G.: Drought in the southern {U}nited {S}tates over the last century: variability and its impacts on terrestrial ecosystem productivity and carbon storage, Clim. Change, 114, 379–397, https://doi.org/<a href="http://dx.doi.org/10.1007/s10584-012-0410-z">10.1007/s10584-012-0410-z</a>, 2012. Cherkauer,&nbsp;K.&nbsp;A. and Lettenmaier,&nbsp;D.&nbsp;P.: Hydrologic effects of frozen soils in the upper Mississippi River basin,&nbsp;J. Geophys. Res.-Atmos., 104, 19599–19610, 1999. Christensen,&nbsp;T.&nbsp;R. and Cox,&nbsp;P.: Response of methane emission from arctic tundra to climatic change: results from a model simulation, Tellus B, 47, 301–309, 1995. Christensen,&nbsp;T.&nbsp;R., Prentice,&nbsp;I.&nbsp;C., Kaplan,&nbsp;J., Haxeltine,&nbsp;A., and Sitch,&nbsp;S.: Methane flux from northern wetlands and tundra – an ecosystem source modelling approach, Tellus B, 48, 652–661, 1996. Coe,&nbsp;M.&nbsp;T.: Simulating continental surface waters: an application to {H}olocene northern {A}frica,&nbsp;J. Clim., 10, 1680–1689, https://doi.org/<a href="http://dx.doi.org/10.1175/1520-0442(1997)010\3E2.0.CO;2">10.1175/1520-0442(1997)010\3E2.0.CO;2</a>, 1997. Coe,&nbsp;M.&nbsp;T.: A linked global model of terrestrial hydrologic processes: simulation of modern rivers, lakes, and wetlands,&nbsp;J. Geophys. Res., 103, 8885–8899, 1998. Cox,&nbsp;P.: Description of the TRIFFID dynamic global vegetation model, Hadley Centre, Met Office, Technical Note 24, 2001. Curry,&nbsp;C.&nbsp;L.: Modelling the soil consumption of atmospheric methane at the global scale, Global Biogeochem. Cy., 21, gB4012, https://doi.org/<a href="http://dx.doi.org/10.1029/2006GB002818">10.1029/2006GB002818</a>, 2007. Curry,&nbsp;C.&nbsp;L.: The consumption of atmospheric methane by soil in a simulated future climate, Biogeosciences, 6, 2355–2367, https://doi.org/<a href="http://dx.doi.org/10.5194/bg-6-2355-2009">10.5194/bg-6-2355-2009</a>, 2009. Dentener,&nbsp;F., Drevet,&nbsp;J., Lamarque,&nbsp;J., Bey,&nbsp;I., Eickhout,&nbsp;B., Fiore,&nbsp;A., Hauglustaine,&nbsp;D., Horowitz,&nbsp;L., Krol,&nbsp;M., and Kulshrestha,&nbsp;U.: Nitrogen and sulfur deposition on regional and global scales: a multimodel evaluation, Global Biogeochem. Cy., 20, gB4003, https://doi.org/<a href="http://dx.doi.org/10.1029/2005GB002672">10.1029/2005GB002672</a>, 2006. ETOPO: 2-minute gridded global relief data ({ETOPO2v2}), US {D}epartment of Commerce, National Oceanic and Atmospheric Administration, National Geophysical Data Center, available at: <a href="http://www.ngdc.noaa.gov/mgg/fliers/06mgg01.html">http://www.ngdc.noaa.gov/mgg/fliers/06mgg01.html</a> (last access:&nbsp;14&nbsp;August&nbsp;2012), 2006. FAO/IIASA/ISRIC/ISSCAS/JRC: Harmonized W}orld {S}oil {D}atabase (version 1.1), Tech. rep., FAO, Rome, Italy and {IIASA, Laxenburg, Austria, 2009. Farouki,&nbsp;O.&nbsp;T.: The thermal-properties of soils in cold regions, Cold Reg. Sci. Technol., 5, 67–75, 1981. Farr,&nbsp;T.&nbsp;G. and Kobrick,&nbsp;M.: Shuttle radar topography mission produces a wealth of data, EOS Trans. Am. Geophys. Union, 81, 583–585, 2000. Fries,&nbsp;R.&nbsp;D., Hansen,&nbsp;M., Townshend,&nbsp;J., and Sohlberg,&nbsp;R.: Global land cover classifications at 8 <abbr>km</abbr> spatial resolution: the use of training data derived from Landsat imagery in decision tree classifiers, Int.&nbsp;J. Remote Sens., 19, 3141–3168, 1998. Frolking,&nbsp;S., Roulet,&nbsp;N.&nbsp;T., Moore,&nbsp;T.&nbsp;R., Lafleur,&nbsp;P.&nbsp;M., Bubier,&nbsp;J.&nbsp;L., and Crill,&nbsp;P.&nbsp;M.: Modeling seasonal to annual carbon balance of {M}er {B}leue {B}og, {O}ntario, {C}anada, Global Biogeochem. Cy., 16, 4-1–4-21, https://doi.org/<a href="http://dx.doi.org/10.1029/2001GB001457">10.1029/2001GB001457</a> 2002. Fung,&nbsp;I.&nbsp;Y., John,&nbsp;J., Lerner,&nbsp;J., Matthews,&nbsp;E., Prather,&nbsp;M., Steele,&nbsp;L.&nbsp;P., and Fraser,&nbsp;P.&nbsp;J.: Three-dimensional model synthesis of the global methane cycle,&nbsp;J. Geophys. Res., 96, 13033–13065, 1991. Gedney,&nbsp;N., Cox,&nbsp;P.&nbsp;M., and Huntingford,&nbsp;C.: Climate feedback from wetland methane emissions, Geophys. Res. Lett., 31, L20503, https://doi.org/<a href="http://dx.doi.org/10.1029/2004GL020919">10.1029/2004GL020919</a>, 2004. Gerber,&nbsp;S., Joos,&nbsp;F., Brugger,&nbsp;P., Stocker,&nbsp;T., Mann,&nbsp;M., Sitch,&nbsp;S., and Scholze,&nbsp;M.: Constraining temperature variations over the last millennium by comparing simulated and observed atmospheric CO<sub>2</sub>, Clim. Dynam., 20, 281–299, https://doi.org/<a href="http://dx.doi.org/10.1007/s00382-002-0270-8">10.1007/s00382-002-0270-8</a>, 2003. Gerten,&nbsp;D., Schaphoff,&nbsp;S., Haberlandt,&nbsp;U., Lucht,&nbsp;W., and Sitch,&nbsp;S.: Terrestrial vegetation and water balance – hydrological evaluation of a dynamic global vegetation model,&nbsp;J. Hydrol., 286, 249–270, 2004. Glagolev,&nbsp;M.&nbsp;V., Kleptsova,&nbsp;I.&nbsp;E., Filippov,&nbsp;I.&nbsp;V., Kazantsev,&nbsp;V.&nbsp;S., Machida,&nbsp;T., and Maksyutov,&nbsp;S.: Methane emissions from subtaiga mires of {W}estern {S}iberia: the {S}tandard {M}odel {B}c5, Moscow Univ. Soil Sci. Bull., 65, 86–93, 2010. Global Soil Data Task Group: Global gridded surfaces of selected soil characteristics ({IGBP-DIS}), Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, USA, available at: <a href="http://www.daac.ornl.gov">http://www.daac.ornl.gov</a> (last access:&nbsp;14&nbsp;August&nbsp;2012), 2000. Hayakawa,&nbsp;Y.&nbsp;S., Oguchi,&nbsp;T., and Lin,&nbsp;Z.: Comparison of new and existing global digital elevation models: ASTER G-DEM and SRTM-3, Geophys. Res. Lett., 35, 19599–19610, 2008. Heijmans,&nbsp;M.&nbsp;M.&nbsp;P.&nbsp;D., Arp,&nbsp;W.&nbsp;J., and Berendse,&nbsp;F.: Effects of elevated CO<sub>2</sub> and vascular plants on evapotranspiration in bog vegetation, Glob. Change Biol., 7, 817–827, 2001. Heijmans,&nbsp;M.&nbsp;M.&nbsp;P.&nbsp;D., Klees,&nbsp;H., and Berendse,&nbsp;F.: Competition between <i>Sphagnum magellanicum</i> and <i>Eriophorum angustifolium</i> as affected by raised CO<sub>2</sub> and increased N deposition, Oikos, 97, 415–425, 2002{a}. Heijmans,&nbsp;M.&nbsp;M.&nbsp;P.&nbsp;D., Klees,&nbsp;H., de&nbsp;Visser,&nbsp;W., and Berendse,&nbsp;F.: Response of a <i>Sphagnum</i> bog plant community to elevated CO<sub>2</sub> and N supply, Plant Ecol., 162, 123–134, 2002{b}. Hodson,&nbsp;E.&nbsp;L., Poulter,&nbsp;B., Zimmermann,&nbsp;N.&nbsp;E., Prigent,&nbsp;C., and Kaplan,&nbsp;J.&nbsp;O.: The {E}l {N}i{ñ}o-{S}outhern {O}scillation and wetland methane interannual variability, Geophys. Res. Lett., 38, L08810, https://doi.org/<a href="http://dx.doi.org/10.1029/2011GL046861">10.1029/2011GL046861</a>, 2011. Hopcroft,&nbsp;P.&nbsp;O., Valdes,&nbsp;P.&nbsp;J., and Beerling,&nbsp;D.&nbsp;J.: Simulating idealized Dansgaard-Oeschger events and their potential impacts on the global methane cycle, Quaternary Sci. Rev., 30, 3258–3268, 2011. Hungate,&nbsp;B.&nbsp;A., Dukes,&nbsp;J.&nbsp;S., Shaw,&nbsp;M.&nbsp;R., Luo,&nbsp;Y.&nbsp;Q., and Field,&nbsp;C.&nbsp;B.: Nitrogen and climate change, Science, 302, 1512–1513, 2003. IPCC: Emissions {S}cenarios, {S}pecial {R}eport of the {I}ntergovernmental {P}anel on {C}limate {C}hange, Tech. Rep., Cambridge University Press, Cambridge UK, 2000. ISLSCP-II: Global Gridded Surfaces of Selected Soil Characteristics for the International Satellite Land Surface Climatology Project ({ISLSCP}) Initiative II Data Collection, Global Soil Data Task Group, Oak Ridge, Tennessee, USA, available at:&nbsp;<a href="https://daac.ornl.gov">https://daac.ornl.gov</a> (last access:&nbsp;14&nbsp;August&nbsp;2012), 2009. Jones,&nbsp;P.&nbsp;D. and Harris,&nbsp;I.: CRU {T}ime {S}eries ({TS}) high resolution gridded datasets, University of East Anglia Climatic Research Unit (CRU), available at: <a href="http://badc.nerc.ac.uk/view/badc.nerc.ac.uk_ATOM_dataent_1256223773328276">http://badc.nerc.ac.uk/view/badc.nerc.ac.uk_ATOM_dataent_1256223773328276</a> (last access:&nbsp;28&nbsp;August&nbsp;2012), 2008. Joos,&nbsp;F., Gerber,&nbsp;S., Prentice,&nbsp;I.&nbsp;C., Otto-Bliesner,&nbsp;B.&nbsp;L., and Valdes,&nbsp;P.&nbsp;J.: Transient simulations of {H}olocene atmospheric carbon dioxide and terrestrial carbon since the {L}ast {G}lacial {M}aximum, Global Biogeochem. Cy., 18, GB2002, https://doi.org/<a href="http://dx.doi.org/10.1029/2003GB002156">10.1029/2003GB002156</a>, 2004. Kaplan,&nbsp;J.&nbsp;O.: Wetlands at the {L}ast {G}lacial {M}aximum: Distribution and methane emissions, Geophys. Res. Lett., 29, 1079, https://doi.org/<a href="http://dx.doi.org/10.1029/2001GL013366">10.1029/2001GL013366</a>, 2002. Knorr,&nbsp;W.: Annual and interannual CO<sub>2</sub> exchanges of the terrestrial biosphere: process-based simulations and uncertainties, Global Ecol. Biogeogr., 9, 225–252, 2000. Koven,&nbsp;C.&nbsp;D., Ringeval,&nbsp;B., Friedlingstein,&nbsp;P., Ciais,&nbsp;P., Cadule,&nbsp;P., Khvorostyanov,&nbsp;D., Krinner,&nbsp;G., and Tarnocai,&nbsp;C.: Permafrost carbon-climate feedbacks accelerate global warming,&nbsp;P. Natl. Acad. Sci., 108, 14769–14774, 2011. Krinner,&nbsp;G.: Impact of lakes and wetlands on boreal climate,&nbsp;J. Geophys. Res., 108, 4520,https://doi.org/<a href="http://dx.doi.org/10.1029/2002JD002597">10.1029/2002JD002597</a>, 2003. Krinner,&nbsp;G., Viovy,&nbsp;N., de&nbsp;Noblet-Ducoudre,&nbsp;N., Ogee,&nbsp;J., Polcher,&nbsp;J., Friedlingstein,&nbsp;P., Ciais,&nbsp;P., Sitch,&nbsp;S., and Prentice,&nbsp;I.&nbsp;C.: A dynamic global vegetation model for studies of the coupled atmosphere-biosphere system, Global Biogeochem. Cy., 19, 941–962, 2005. Kudryavtsev,&nbsp;V.&nbsp;A., Garagula,&nbsp;L.&nbsp;S., Kondratiyeva,&nbsp;K.&nbsp;A., and Melamed,&nbsp;V.&nbsp;E.: Frost Forecasting in Geological Engineering Investigations, CRREL, Hanover, NH, 1977. Lawrence,&nbsp;D.&nbsp;M., Oleson,&nbsp;K.&nbsp;W., Flanner,&nbsp;M.&nbsp;G., Thornton,&nbsp;P.&nbsp;E., Swenson,&nbsp;S.&nbsp;C., Lawrence,&nbsp;P.&nbsp;J., Zeng,&nbsp;X., Yang,&nbsp;Z.-L., Levis,&nbsp;S., Sakaguchi,&nbsp;K., Bonan,&nbsp;G.&nbsp;B., and Slate,&nbsp;A.&nbsp;G.: Parameterization improvements and functional and structural advances in version 4 of the {C}ommunity {L}and {M}odel,&nbsp;J. Adv. Model. Earth. Sys., 3, M03001, https://doi.org/<a href="http://dx.doi.org/10.1029/2011MS000045">10.1029/2011MS000045</a>, 2011. DOI is taken directly from journal website... Lawrence,&nbsp;P.&nbsp;J. and Chase,&nbsp;T.&nbsp;N.: Representing a new MODIS consistent land surface in the C}ommunity {L}and {M}odel ({CLM 3.0),&nbsp;J. Geophys. Res., 112, G01023, https://doi.org/<a href="http://dx.doi.org/10.1029/2006JG000168">10.1029/2006JG000168</a>, 2007. Leff,&nbsp;B., Ramankutty,&nbsp;N., and Foley,&nbsp;J.: Geographic distribution of major crops across the world, Global. Biogeochem. Cy., 18, GB1009, https://doi.org/<a href="http://dx.doi.org/10.1029/2003GB002108">10.1029/2003GB002108</a>, 2004. Lehner,&nbsp;B. and D{ö}ll,&nbsp;P.: Development and validation of a global database of lakes, reservoirs and wetlands,&nbsp;J. Hydrol., 296, 1–22, 2004. Letts,&nbsp;M.&nbsp;G., Roulet,&nbsp;N.&nbsp;T., Comer,&nbsp;N.&nbsp;T., Skarupa,&nbsp;M.&nbsp;R., and Verseghy,&nbsp;D.&nbsp;L.: Parametrization of peatland hydraulic properties for the {C}anadian {L}and {S}urface {S}cheme, Atmos. Ocean, 38, 141–160, 2000. Liang,&nbsp;X., Lettenmaier,&nbsp;D.&nbsp;P., Wood,&nbsp;E.&nbsp;F., and Burges,&nbsp;S.&nbsp;J.: A simple hydrologically based model of land-surface water and energy fluxes for general-circulation models,&nbsp;J. Geophys. Res., 99, 14415–14428, 1994. Liu,&nbsp;M., Tian,&nbsp;H., Yang,&nbsp;Q., Yang,&nbsp;J., Song,&nbsp;X., Lohrenz,&nbsp;S.&nbsp;E., and Cai,&nbsp;W.: Long-term trends in evapotranspiration and runoff over the drainage basins of the {G}ulf of {M}exico during 1901–2008, Water Resour. Res., 49, 1–25, <a href="http://dx.doi.org/10.1002/wrcr.20180">10.1002/wrcr.20180</a>, 2013. Matthews,&nbsp;E. and Fung,&nbsp;I.&nbsp;Y.: Methane emission from natural wetlands: Global distribution, area, and environmental characteristics of sources, Global Biogeochem. Cy., 1, 61–86, 1987. Meehl,&nbsp;G.&nbsp;A., Stocker,&nbsp;T.&nbsp;F., Collins,&nbsp;W.&nbsp;D., Friedlingstein,&nbsp;P., Gaye,&nbsp;A.&nbsp;T., Gregory,&nbsp;J.&nbsp;M., Kitoh,&nbsp;A., Knutti,&nbsp;R., Murphy,&nbsp;J.&nbsp;M., Noda,&nbsp;A., Raper,&nbsp;S.&nbsp;C.&nbsp;B., Watterson,&nbsp;I.&nbsp;G., Weaver,&nbsp;A.&nbsp;J., and Zhao,&nbsp;Z.-C.: Global climate projections, in: Climate change 2007: T}he physical science basis. Contribution of {W}orking {G}roup {I to the {F}ourth {A}ssessment {R}eport of the {I}ntergovernmental {P}anel on {C}limate {C}hange, edited by: Solomon,&nbsp;S., Qin,&nbsp;D., Manning,&nbsp;M., Chen,&nbsp;Z., Marquis,&nbsp;M., Averyt,&nbsp;K.&nbsp;B., Tignor,&nbsp;M., and Miller,&nbsp;H.&nbsp;L., chap.&nbsp;10, Cambridge University Press, Cambridge, UK and New York, NY, USA, 747–846, 2007. Meissner,&nbsp;K.&nbsp;J., Weaver,&nbsp;A.&nbsp;J., Matthews,&nbsp;H.&nbsp;D., and Cox,&nbsp;P.&nbsp;M.: The role of land surface dynamics in glacial inception: a study with the UVic Earth System Model, Clim. Dynam., 21, 515–537, 2003. Melton, J. R., Wania, R., Hodson, E. L., Poulter, B., Ringeval, B., Spahni, R., Bohn, T., Avis, C. A., Beerling, D. J., Chen, G., Eliseev, A. V., Denisov, S. N., Hopcroft, P. O., Lettenmaier, D. P., Riley, W. J., Singarayer, J. S., Subin, Z. M., Tian, H., Zürcher, S., Brovkin, V., van Bodegom, P. M., Kleinen, T., Yu, Z. C., and Kaplan, J. O.: Present state of global wetland extent and wetland methane modelling: conclusions from a model inter-comparison project (WETCHIMP), Biogeosciences, 10, 753–788, <a href="http://dx.doi.org/10.5194/bg-10-753-2013">https://doi.org/10.5194/bg-10-753-2013</a>, 2013. Mitchell,&nbsp;T.&nbsp;D. and Jones,&nbsp;P.&nbsp;D.: An improved method of constructing a database of monthly climate observations and associated high-resolution grids, Int.&nbsp;J. Climatol., 25, 693–712, 2005. Mokhov,&nbsp;I.&nbsp;I., Eliseev,&nbsp;A.&nbsp;V., and Denisov,&nbsp;S.&nbsp;N.: Model diagnostics of variations in methane emissions by wetlands in the second half of the 20th century based on reanalysis data, Doklady Earth Sci., 417, 1293–1297, https://doi.org/<a href="http://dx.doi.org/10.1134/S1028334X07080375">10.1134/S1028334X07080375</a>, 2007. Myneni,&nbsp;R.&nbsp;B., Hoffman,&nbsp;S., Knyazikhin,&nbsp;Y., Privette,&nbsp;J.&nbsp;L., Glassy,&nbsp;J., Tian,&nbsp;Y., Wang,&nbsp;Y., Song,&nbsp;X., Zhang,&nbsp;Y., Smith,&nbsp;G.&nbsp;R., Lotsch,&nbsp;A., Friedl,&nbsp;M., Morisette,&nbsp;J.&nbsp;T., Votava,&nbsp;P., Nemani,&nbsp;R.&nbsp;R., and Running,&nbsp;S.&nbsp;W.: Global products of vegetation leaf area and fraction absorbed PAR from year one of MODIS data, Remote Sens. Environ., 83, 214–231, 2002. Niu, &nbsp;G., Yang, &nbsp;Z., Dickinson, &nbsp;R.&nbsp;E., and Gulden, &nbsp;L.&nbsp;E.: A simple TOPMODEL-based runoff parameterization ({SIMTOP}) for use in global climate models, &nbsp;J. Geophys. Res., 110, D21106, <a href="http://dx.doi.org/10.1029/2005JD006111">https://doi.org/10.1029/2005JD006111</a>, 2005. Oleson, &nbsp;K. &nbsp;W., Niu, &nbsp;G.&nbsp;-Y., Yang, &nbsp;Z.&nbsp;-L., Lawrence, &nbsp;D. &nbsp;M., Thornton, &nbsp;P. &nbsp;E., Lawrence, &nbsp;P. &nbsp;J., Stöckli, &nbsp;R., Dickinson, &nbsp;R. &nbsp;E., Bonan, &nbsp;G. &nbsp;B., Levis, &nbsp;S., Dai, &nbsp;A., and Qian, &nbsp;T.: Improvements to the {C}ommunity {L}and {M}odel and their impact on the hydrological cycle, &nbsp;J. Geophys. Res. Biogeosci., 113, 2156–2202, <a href="http://dx.doi.org/10.1029/2007JG000563">https://doi.org/10.1029/2007JG000563</a>, 2008. Papa,&nbsp;F., Prigent,&nbsp;C., Durand,&nbsp;F., and Rossow,&nbsp;W.&nbsp;B.: Wetland dynamics using a suite of satellite observations: a case study of application and evaluation for the {I}ndian {S}ubcontinent, Geophys. Res. Lett., 33, L08401, https://doi.org/<a href="http://dx.doi.org/10.1029/2006GL025767">10.1029/2006GL025767</a>, 2006. Papa,&nbsp;F., Prigent,&nbsp;C., and Rossow,&nbsp;W.&nbsp;B.: Monitoring flood and discharge variations in the large {S}iberian rivers from a multi-satellite technique, Surv. Geophys., 29, 297–317, https://doi.org/<a href="http://dx.doi.org/10.1007/s10712-008-9036-0">10.1007/s10712-008-9036-0</a>, 2008. Papa,&nbsp;F., Prigent,&nbsp;C., Aires,&nbsp;F., Jimenez,&nbsp;C., Rossow,&nbsp;W.&nbsp;B., and Matthews,&nbsp;E.: Interannual variability of surface water extent at the global scale, 1993–2004,&nbsp;J. Geophys. Res., 115, D12111, https://doi.org/<a href="http://dx.doi.org/10.1029/2009JD012674">10.1029/2009JD012674</a>, 2010. Parton,&nbsp;W.&nbsp;J., Scurlock,&nbsp;J.&nbsp;M.&nbsp;O., Ojima,&nbsp;D.&nbsp;S., Gilmanov,&nbsp;T.&nbsp;G., Scholes,&nbsp;R.&nbsp;J., Schimel,&nbsp;D.&nbsp;S., Kirchner,&nbsp;T., Menaut,&nbsp;J.&nbsp;C., Seastedt,&nbsp;T., Moya,&nbsp;E.&nbsp;G., Kamnalrut,&nbsp;A., and Kinyamario,&nbsp;J.&nbsp;I.: Observations and modeling of biomass and soil organic-matter dynamics for the grassland biome worldwide, Global Biogeochem. Cy., 7, 785–809, 1993. Pickett-Heaps,&nbsp;C.&nbsp;A., Jacob,&nbsp;D.&nbsp;J., Wecht,&nbsp;K.&nbsp;J., Kort,&nbsp;E.&nbsp;A., Wofsy,&nbsp;S.&nbsp;C., Diskin,&nbsp;G.&nbsp;S., Worthy,&nbsp;D.&nbsp;E.&nbsp;J., Kaplan,&nbsp;J.&nbsp;O., Bey,&nbsp;I., and Drevet,&nbsp;J.: Magnitude and seasonality of wetland methane emissions from the Hudson Bay Lowlands (Canada), Atmos. Chem. Phys., 11, 3773–3779, https://doi.org/<a href="http://dx.doi.org/10.5194/acp-11-3773-2011">10.5194/acp-11-3773-2011</a>, 2011. Pison, I., Ringeval, B., Bousquet, P., Prigent, C., and Papa, F.: Stable atmospheric methane in the 2000s: key-role of emissions from natural wetlands, Atmos. Chem. Phys. Discuss., 13, 9017–9049, <a href="http://dx.doi.org/10.5194/acpd-13-9017-2013">https://doi.org/10.5194/acpd-13-9017-2013</a>, 2013. Potter,&nbsp;C.&nbsp;S.: An ecosystem simulation model for methane production and emission from wetlands, Global Biogeochem. Cy., 11, 495–506, 1997. Prentice,&nbsp;I.&nbsp;C., Farquhar,&nbsp;G.&nbsp;D., Fasham,&nbsp;M.&nbsp;J.&nbsp;R., Goulden,&nbsp;M., Heimann,&nbsp;M., Jaramillo,&nbsp;V., Kheshgi,&nbsp;H., Qu{é}r{é},&nbsp;C.-L., Scholes,&nbsp;R., and Wallace,&nbsp;D.: The C}arbon {C}ycle and {A}tmospheric {C}arbon {D}ioxide, in: Climate Change 2001: The scientific basis, Contributions of {W}orking {G}roup {I to the {T}hird {A}ssessment {R}eport of the {I}ntergovernmental {P}anel on {C}limate {C}hange, edited by: Pitelka,&nbsp;L.&nbsp;F. and Rojas,&nbsp;A.&nbsp;R., Cambridge University Press, Cambridge, 183–237, 2001. Prigent,&nbsp;C., Papa,&nbsp;F., Aires,&nbsp;F., Rossow,&nbsp;W.&nbsp;B., and Matthews,&nbsp;E.: Global inundation dynamics inferred from multiple satellite observations, 1993–2000,&nbsp;J. Geophys. Res., 112, 305–317, https://doi.org/<a href="http://dx.doi.org/10.1029/2006JD007847">10.1029/2006JD007847</a>, 2007. Prigent,&nbsp;C., Papa,&nbsp;F., Aires,&nbsp;F., Jimenez,&nbsp;C., Rossow,&nbsp;W.&nbsp;B., and Matthews,&nbsp;E.: Changes in land surface water dynamics since the 1990s and relation to population pressure, Geophys. Res. Lett., 39, L08403, https://doi.org/<a href="http://dx.doi.org/10.1029/2012GL051276">10.1029/2012GL051276</a>, 2012. Qian,&nbsp;T.&nbsp;T., Dai,&nbsp;A., Trenberth,&nbsp;K.&nbsp;E., and Oleson,&nbsp;K.&nbsp;W.: Simulation of global land surface conditions from 1948 to 2004, part I: forcing data and evaluations,&nbsp;J. Hydrometeorol., 7, 953–975, 2006. Ridgwell,&nbsp;A., Marshall,&nbsp;S.&nbsp;J., and Gregson,&nbsp;K.: Consumption of atmospheric methane by soils: a process-based model, Global Biogeochem. Cy., 13, 59–70, 1999. Riley, W. J., Subin, Z. M., Lawrence, D. M., Swenson, S. C., Torn, M. S., Meng, L., Mahowald, N. M., and Hess, P.: Barriers to predicting changes in global terrestrial methane fluxes: analyses using CLM4Me, a methane biogeochemistry model integrated in CESM, Biogeosciences, 8, 1925–1953, <a href="http://dx.doi.org/10.5194/bg-8-1925-2011">https://doi.org/10.5194/bg-8-1925-2011</a>, 2011. Ringeval,&nbsp;B.: Interactions entre climat et é}missions de m{é}thane par les zones humides {à l'{é}chelle global, Ph.&nbsp;D. thesis, Universit{é} Pierre & Marie Curie, Paris, France, 2011. Ringeval,&nbsp;B., de&nbsp;Noblet-Ducoudre,&nbsp;N., Ciais,&nbsp;P., Bousquet,&nbsp;P., Prigent,&nbsp;C., Papa,&nbsp;F., and Rossow,&nbsp;W.&nbsp;B.: An attempt to quantify the impact of changes in wetland extent on methane emissions on the seasonal and interannual time scales, Global Biogeochem. Cy., 24, 611–617, 2010. Ringeval, B., Friedlingstein, P., Koven, C., Ciais, P., de Noblet-Ducoudré, N., Decharme, B., and Cadule, P.: Climate-CH<sub>4</sub> feedback from wetlands and its interaction with the climate-CO<sub>2</sub> feedback, Biogeosciences, 8, 2137–2157, <a href="http://dx.doi.org/10.5194/bg-8-2137-2011">https://doi.org/10.5194/bg-8-2137-2011</a>, 2011. Ringeval, B., Decharme, B., Piao, S. L., Ciais, P., Papa, F., de Noblet-Ducoudré, N., Prigent, C., Friedlingstein, P., Gouttevin, I., Koven, C., and Ducharne, A.: Modelling sub-grid wetland in the ORCHIDEE global land surface model: evaluation against river discharges and remotely sensed data, Geosci. Model Dev., 5, 941–962, <a href="http://dx.doi.org/10.5194/gmd-5-941-2012">https://doi.org/10.5194/gmd-5-941-2012</a>, 2012. Ringeval,&nbsp;B., Hopcroft,&nbsp;P.&nbsp;O., Valdes,&nbsp;P.&nbsp;J., Ciais,&nbsp;P., Ramstein,&nbsp;G., Dolman,&nbsp;A.&nbsp;J., and Kageyama,&nbsp;M.: Response of methane emissions from wetlands to the Last Glacial Maximum and an idealized Dansgaard-Oeschger climate event: insights from two models of different complexity, Clim. Past, 9, 149–171, https://doi.org/<a href="http://dx.doi.org/10.5194/cp-9-149-2013">10.5194/cp-9-149-2013</a>, 2013. Roulet,&nbsp;N.&nbsp;T., Moore,&nbsp;T.&nbsp;R., Bubier,&nbsp;J., and Lafleur,&nbsp;P.: Northern fens: methane flux and climate change, Tellus, 44B, 100–106, 1992. Schroeder,&nbsp;R., Rawlins,&nbsp;M.&nbsp;A., McDonald,&nbsp;K.&nbsp;C., Podest,&nbsp;E., Zimmermann,&nbsp;R., and Kueppers,&nbsp;M.: Satellite microwave remote sensing of North Eurasian inundation dynamics: development of coarse-resolution products and comparison with high-resolution synthetic aperture radar data, Environ. Res. Lett., 5, 14415–14428, 2010. Segers,&nbsp;R. and Leffelaar,&nbsp;P.&nbsp;A.: Modeling methane fluxes in wetlands with gas-transporting plants 3, plot scale,&nbsp;J. Geophys. Res., 106, 3541–3558, 2001. Sellers,&nbsp;P.&nbsp;J., Meeson,&nbsp;B.&nbsp;W., Closs,&nbsp;J., Corprew,&nbsp;F., Dazlich,&nbsp;D., Hall,&nbsp;F.&nbsp;G., Kerr,&nbsp;Y., Koster,&nbsp;R., Los,&nbsp;S., Mitchell,&nbsp;K., McManus,&nbsp;J., Myers,&nbsp;D., Sun,&nbsp;K.-J., and National Aeronautics and Space Administration and Goddard Space Flight Center,&nbsp;P.&nbsp;J.&nbsp;T.: I}nternational {S}atellite {L}and {S}urface {C}limatology {P}roject – {I}nitiative {I data collection ({ISLSCP I}), available at: <a href="http://badc.nerc.ac.uk/view/badc.nerc.ac.uk__ATOM__dataent_ISLSCP">http://badc.nerc.ac.uk/view/badc.nerc.ac.uk__ATOM__dataent_ISLSCP</a> (last access:&nbsp;1&nbsp;September&nbsp;2012), 1996. Citation Sheng,&nbsp;Y.&nbsp;W., Smith,&nbsp;L.&nbsp;C., MacDonald,&nbsp;G.&nbsp;M., Kremenetski,&nbsp;K.&nbsp;V., Frey,&nbsp;K.&nbsp;E., elichko,&nbsp;A.&nbsp;A., Lee,&nbsp;M., Beilman,&nbsp;D.&nbsp;W., and Dubinin,&nbsp;P.: A high-resolution {GIS}-based inventory of the west {S}iberian peat carbon pool, Global Biogeochem. Cy., 18, 14415–14428, 2004. Shindell,&nbsp;D.&nbsp;T., Walter,&nbsp;B.&nbsp;P., and Faluvegi,&nbsp;G.: Impacts of climate change on methane emissions from wetlands, Geophys. Res. Lett., 31, L21202, https://doi.org/<a href="http://dx.doi.org/10.1029/2004GL021009">10.1029/2004GL021009</a>, 2004. Singarayer,&nbsp;J.&nbsp;S., Valdes,&nbsp;P.&nbsp;J., Friedlingstein,&nbsp;P., Nelson,&nbsp;S., and Beerling,&nbsp;D.&nbsp;J.: Late Holocene methane rise caused by orbitally controlled increase in tropical sources, Nature, 470, 82–91, 2011. Sitch,&nbsp;S., Smith,&nbsp;B., Prentice,&nbsp;I.&nbsp;C., Arneth,&nbsp;A., Bondeau,&nbsp;A., Cramer,&nbsp;W., Kaplan,&nbsp;J.&nbsp;O., Levis,&nbsp;S., Lucht,&nbsp;W., Sykes,&nbsp;M.&nbsp;T., Thonicke,&nbsp;K., and Venevsky,&nbsp;S.: Evaluation of ecosystem dynamics, plant geography and terrestrial carbon cycling in the LPJ dynamic global vegetation model, Glob. Change Biol., 9, 161–185, 2003. Spahni,&nbsp;R., Wania,&nbsp;R., Neef,&nbsp;L., van Weele,&nbsp;M., Pison,&nbsp;I., Bousquet,&nbsp;P., Frankenberg,&nbsp;C., Foster,&nbsp;P.&nbsp;N., Joos,&nbsp;F., Prentice,&nbsp;I.&nbsp;C., and van Velthoven,&nbsp;P.: Constraining global methane emissions and uptake by ecosystems, Biogeosciences, 8, 1643–1665, https://doi.org/<a href="http://dx.doi.org/10.5194/bg-8-1643-2011">10.5194/bg-8-1643-2011</a>, 2011. Stillwell-Soller,&nbsp;L.&nbsp;M., Klinger,&nbsp;L.&nbsp;F., Pollard,&nbsp;D., and Thompson,&nbsp;S.&nbsp;L.: The Global Distribution of Freshwater Wetlands, Tech. Rep. NCAR/TN-416+STR, NCAR, available at: <a href="http://www.cisl.ucar.edu/ess/services/dbst/wetlands/">http://www.cisl.ucar.edu/ess/services/dbst/wetlands/</a> (last access:&nbsp;11&nbsp;September&nbsp;2012), 1995. Stocker,&nbsp;B.&nbsp;D., Strassmann,&nbsp;K., and Joos,&nbsp;F.: Sensitivity of Holocene atmospheric CO<sub>2</sub> and the modern carbon budget to early human land use: analyses with a process-based model, Biogeosciences, 8, 69–88, https://doi.org/<a href="http://dx.doi.org/10.5194/bg-8-69-2011">10.5194/bg-8-69-2011</a>, 2011. Strassmann,&nbsp;K.&nbsp;M., Joos,&nbsp;F., and Fischer,&nbsp;G.: Simulating effects of land use changes on carbon fluxes: past contributions to atmospheric CO<sub>2</sub> increases and future commitments due to losses of terrestrial sink capacity, Tellus B, 60, 583–603, https://doi.org/<a href="http://dx.doi.org/10.1111/j.1600-0889.2008.00340.x">10.1111/j.1600-0889.2008.00340.x</a>, 2008. DOI is copied directly from journal website. Tarnocai,&nbsp;C., Swanson,&nbsp;D., Kimble,&nbsp;J., and Broll,&nbsp;J.: Northern Circumpolar Soil Carbon Database, Tech. Rep. Version 1, Research Branch, Agriculture and Agri-Food Canada,, available at: <a href="http://wms1.agr.gc.ca/NortherCircumpolar/northercircumpolar.zip">http://wms1.agr.gc.ca/NortherCircumpolar/northercircumpolar.zip</a> (last access:&nbsp;1&nbsp;October&nbsp;2012), 2007. Tarnocai,&nbsp;C., Canadell,&nbsp;J.&nbsp;G., Schuur,&nbsp;E.&nbsp;A.&nbsp;G., Kuhry,&nbsp;P., Mazhitova,&nbsp;G., and Zimov,&nbsp;S.: Soil organic carbon pools in the northern circumpolar permafrost region, Global Biogeochem. Cy., 23, GB2023, https://doi.org/<a href="http://dx.doi.org/10.1029/2008GB003327">10.1029/2008GB003327</a>, 2009. Tian,&nbsp;H., Xu,&nbsp;X., Liu,&nbsp;M., Ren,&nbsp;W., Zhang,&nbsp;C., Chen,&nbsp;G., and Lu,&nbsp;C.: Spatial and temporal patterns of CH<sub>4</sub> and N<sub>2O</sub> fluxes in terrestrial ecosystems of North America during 1979–2008: application of a global biogeochemistry model, Biogeosciences, 7, 2673–2694, https://doi.org/<a href="http://dx.doi.org/10.5194/bg-7-2673-2010">10.5194/bg-7-2673-2010</a>, 2010. Tian,&nbsp;H.&nbsp;Q., Melillo,&nbsp;J., Lu,&nbsp;C.&nbsp;Q., Kicklighter,&nbsp;D., Liu,&nbsp;M.&nbsp;L., Ren,&nbsp;W., Xu,&nbsp;X.&nbsp;F., Chen,&nbsp;G.&nbsp;S., Zhang,&nbsp;C., Pan,&nbsp;S.&nbsp;F., Liu,&nbsp;J.&nbsp;Y., and Running,&nbsp;S.: China's terrestrial carbon balance: contributions from multiple global change factors, Global Biogeochem. Cy., 25, 222–240, 2011{a}. Tian,&nbsp;H.&nbsp;Q., Xu,&nbsp;X.&nbsp;F., Lu,&nbsp;C.&nbsp;Q., Liu,&nbsp;M.&nbsp;L., Ren,&nbsp;W., Chen,&nbsp;G.&nbsp;S., Melillo,&nbsp;J., and Liu,&nbsp;J.&nbsp;Y.: Net exchanges of CO<sub>2</sub>, CH<sub>4</sub>, and N<sub>2O</sub> between C}hina's terrestrial ecosystems and the atmosphere and their contributions to global climate warming,&nbsp;J. Geophys. Res., 116, G02011, https://doi.org/<a href="http://dx.doi.org/10.1029/2010JG001393">10.1029/2010JG001393</a>, 2011{b. %Tian,~H Q., Chen,~G S., Zhang,~C., Liu,~M L., Sun,~G., %Chappelka,~A., Ren,~W., Xu,~X F., Lu,~C Q., Pan,~S F., Chen,~H., %Hui,~D F., McNulty,~S., Lockaby,~G., and Vance,~E.: Century-scale responses of ecosystem carbon % storage and flux to multiple environmental changes in the southern United % States, Ecosystems, 15, 674–694, 2012. Tian,&nbsp;H.&nbsp;Q., Lu,&nbsp;G., Chen,&nbsp;G.&nbsp;S., Tao,&nbsp;S., Pan,&nbsp;S.&nbsp;F., Del Grosso,&nbsp;S.&nbsp;J., Xu,&nbsp;X.&nbsp;F., Bruhwiler,&nbsp;L., Wofsy,&nbsp;S.&nbsp;C., Kort,&nbsp;E.&nbsp;A., and Prior,&nbsp;S.&nbsp;A.: Contemporary and projected biogenic fluxes of methane and nitrous oxide in terrestrial ecosystems of {N}orth {A}merica, Frontiers in Ecology and the Environment, 10, 528–536, https://doi.org/<a href="http://dx.doi.org/10.1890/120057">10.1890/120057</a>, 2012. Valdes,&nbsp;P.&nbsp;J., Beerling,&nbsp;D.&nbsp;J., and Johnson,&nbsp;C.&nbsp;E.: The ice age methane budget, Geophys. Res. Lett., 32, 941–962, 2005. van Bodegom,&nbsp;P., Goudriaan,&nbsp;J., and Leffelaar,&nbsp;P.: A mechanistic model on methane oxidation in a rice rhizosphere, Biogeochem., 55, 145–177, 2001{a}. van Bodegom,&nbsp;P., Wassmann,&nbsp;R., and Metra-Corton,&nbsp;T.: A process-based model for methane emission predictions from flooded rice paddies, Global Biogeochem. Cy., 15, 247–263, 2001{b}. Viovy,&nbsp;N. and Ciais,&nbsp;P.: CRUNCEP data set for 1901–2008, Tech. Rep. Version 4, Laboratoire des Sciences du Climat et de l'Environnement, available at: <a href="http://dods.extra.cea.fr/data/p529viov/cruncep/">http://dods.extra.cea.fr/data/p529viov/cruncep/</a>, last access:&nbsp;1&nbsp;September 2011. Walter,&nbsp;B.&nbsp;P. and Heimann,&nbsp;M.: A process-based, climate-sensitive model to derive methane emissions from natural wetlands: application to five wetland sites, sensitivity to model parameters, and climate, Global Biogeochem. Cy., 14, 745–765, 2000. Walter,&nbsp;B.&nbsp;P., Heimann,&nbsp;M., Shannon,&nbsp;R.&nbsp;D., and White,&nbsp;J.&nbsp;R.: A process-based model to derive methane emissions from natural wetlands, Geophys. Res. Lett., 23, 3731–3734, 1996. Walter,&nbsp;B.&nbsp;P., Heimann,&nbsp;M., and Matthews,&nbsp;E.: Modeling modern methane emissions from natural wetlands 1, model description and results,&nbsp;J. Geophys. Res., 106, 34189–34206, 2001{a}. Walter,&nbsp;B.&nbsp;P., Heimann,&nbsp;M., and Matthews,&nbsp;E.: Modeling modern methane emissions from natural wetlands 2, interannual variations 1982–1993,&nbsp;J. Geophys. Res., 106, 34207–34219, 2001{b}. Wania,&nbsp;R., Ross,&nbsp;I., and Prentice,&nbsp;I.&nbsp;C.: Integrating peatlands and permafrost into a dynamic global vegetation model, I: evaluation and sensitivity of physical land surface processes, Global Biogeochem. Cy., 23, GB3014, https://doi.org/<a href="http://dx.doi.org/10.1029/2008GB003412">10.1029/2008GB003412</a>, 2009{a}. Wania,&nbsp;R., Ross,&nbsp;I., and Prentice,&nbsp;I.&nbsp;C.: Integrating peatlands and permafrost into a dynamic global vegetation model, II: evaluation and sensitivity of vegetation and carbon cycle processes, Global Biogeochem. Cy., 23, GB3015, https://doi.org/<a href="http://dx.doi.org/10.1029/2008GB003413">10.1029/2008GB003413</a>, 2009{b}. Wania,&nbsp;R., Ross,&nbsp;I., and Prentice,&nbsp;I.&nbsp;C.: Implementation and evaluation of a new methane model within a dynamic global vegetation model: LPJ-WHyMe v1.3.1, Geosci. Model Dev., 3, 565–584, https://doi.org/<a href="http://dx.doi.org/10.5194/gmd-3-565-2010">10.5194/gmd-3-565-2010</a>, 2010. Weaver,&nbsp;A.&nbsp;J., Eby,&nbsp;M., Wiebe,&nbsp;E.&nbsp;C., Bitz,&nbsp;C.&nbsp;M., Duffy,&nbsp;P.&nbsp;B., Ewen,&nbsp;T.&nbsp;L., Fanning,&nbsp;A.&nbsp;F., Holland,&nbsp;M.&nbsp;M., MacFadyen,&nbsp;A., Matthews,&nbsp;H.&nbsp;D., Meissner,&nbsp;K.&nbsp;J., Saenko,&nbsp;O., Schmittner,&nbsp;A., Wang,&nbsp;H.&nbsp;X., and Yoshimori,&nbsp;M.: The UVic Earth System Climate Model: model description, climatology, and applications to past, present and future climates, Atmos. Ocean, 39, 361–428, 2001. Weber,&nbsp;S.&nbsp;L., Drury,&nbsp;A.&nbsp;J., Toonen,&nbsp;W.&nbsp;H.&nbsp;J., and van Weele,&nbsp;M.: Wetland methane emissions during the L}ast {G}lacial {M}aximum estimated from {PMIP2 simulations: {C}limate, vegetation, and geographic controls,&nbsp;J. Geophys. Res., 115, D06111, https://doi.org/<a href="http://dx.doi.org/10.1029/2009JD012110">10.1029/2009JD012110</a>, 2010. Woodward,&nbsp;F.&nbsp;I., Smith,&nbsp;T.&nbsp;M., and Emanuel,&nbsp;W.&nbsp;R.: A global land primary productivity and phytogeography model, Global Biogeochem. Cy., 9, 471–490, 1995. Xu,&nbsp;X.&nbsp;F., Tian,&nbsp;H.&nbsp;Q., Zhang,&nbsp;C., Liu,&nbsp;M.&nbsp;L., Ren,&nbsp;W., Chen,&nbsp;G.&nbsp;S., Lu,&nbsp;C.&nbsp;Q., and Bruhwiler,&nbsp;L.: Attribution of spatial and temporal variations in terrestrial methane flux over North America, Biogeosciences, 7, 3637–3655, https://doi.org/<a href="http://dx.doi.org/10.5194/bg-7-3637-2010">10.5194/bg-7-3637-2010</a>, 2010. Zhuang,&nbsp;Q., Melillo,&nbsp;J.&nbsp;M., Kicklighter,&nbsp;D.&nbsp;W., Prinn,&nbsp;R.&nbsp;G., McGuire,&nbsp;A.&nbsp;D., Steudler,&nbsp;P.&nbsp;A., Felzer,&nbsp;B.&nbsp;S., and Hu,&nbsp;S.: Methane fluxes between terrestrial ecosystems and the atmosphere at northern high latitudes during the past century: A retrospective analysis with a process-based biogeochemistry model, Global Biogeochem. Cy., 18, GB3010, https://doi.org/<a href="http://dx.doi.org/10.1029/2004GB002239">10.1029/2004GB002239</a>, 2004. Zhuang,&nbsp;Q., Melillo,&nbsp;J.&nbsp;M., Sarofim,&nbsp;M.&nbsp;C., Kicklighter,&nbsp;D.&nbsp;W., Mc{G}uire,&nbsp;A.&nbsp;D., Felzer,&nbsp;B.&nbsp;S., Sokolov,&nbsp;A., Prinn,&nbsp;R.&nbsp;G., Steudler,&nbsp;P.&nbsp;A., and Hu,&nbsp;S.: CO<sub>2</sub> and CH<sub>4</sub> exchanges between land ecosystems and the atmosphere in northern high latitudes over the 21st century, Geophys. Res. Lett., 33, L17403, https://doi.org/<a href="http://dx.doi.org/10.1029/2006GL026972">10.1029/2006GL026972</a>, 2006. Zobler,&nbsp;L.: A world soil file for global climate modelling, Technical Memorandum 87802, 32, NASA, 1986. Z{ü}rcher,&nbsp;S., Spahni,&nbsp;R., Joos,&nbsp;F., Steinacher,&nbsp;M., and Fischer,&nbsp;H.: Impact of an abrupt cooling event on interglacial methane emissions in northern peatlands, Biogeosciences, 10, 1963–1981, https://doi.org/<a href="http://dx.doi.org/10.5194/bg-10-1963-2013">10.5194/bg-10-1963-2013</a>, 2013.