Geosci. Model Dev. Discuss., 5, 4071-4136, 2012
www.geosci-model-dev-discuss.net/5/4071/2012/
doi:10.5194/gmdd-5-4071-2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review Status
This discussion paper has been under review for the journal Geoscientific Model Development (GMD). Please refer to the corresponding final paper in GMD.
Present state of global wetland extent and wetland methane modelling: methodology of a model intercomparison project (WETCHIMP)
R. Wania1,*, J. R. Melton2,**, E. L. Hodson3,***, B. Poulter4, B. Ringeval4,5,6, R. Spahni7, T. Bohn8, C. A. Avis9,****, G. Chen10, A. V. Eliseev11,12, P. O. Hopcroft5, W. J. Riley13, Z. M. Subin13,*****, H. Tian10, V. Brovkin14, P. M. van Bodegom15, T. Kleinen14, Z. C. Yu16, J. S. Singarayer5, S. Zürcher7, D. P. Lettenmaier8, D. J. Beerling17, S. N. Denisov11, C. Prigent18, F. Papa19, and J. O. Kaplan2
1Institut des Sciences de l'Evolution (UMR5554, CNRS), Université Montpellier 2, Place Eugène Bataillon, 34090 Montpellier, France
2ARVE Group, École Polytechnique Fédérale de Lausanne, Switzerland
3Swiss Federal Research Institute WSL, Switzerland
4Laboratoire des Sciences du Climat et de L'Environment, CNRS–CEA, UVSQ, Gif-sur Yvette, France
5BRIDGE, School of Geographical Sciences, Univerity of Bristol, UK
6Department of Earth Sciences, VU University, Amsterdam, The Netherlands
7Climate and Environmental Physics, Physics Institute & Oeschger Centre for Climate Change Research, University of Bern, Switzerland
8Dept. of Civil and Environmental Engineering, University of Washington, USA
9School of Earth and Ocean Sciences, University of Victoria, Canada
10International Center for Climate and Global Change Research and School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL 36849, USA
11A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Russia
12Kazan (Volga region) Federal University, Russia
13Earth Sciences Division (ESD), Lawrence Berkeley National Lab, USA
14Max Planck Institute für Meteorologie, Hamburg, Germany
15Department of Ecological Sciences, VU University, Amsterdam, The Netherlands
16Department of Earth and Environmental Sciences, Lehigh University, USA
17Dept. of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
18CNRS/LERMA, Observatoire de Paris, 61 Ave. de l'Observatoire, 75014 Paris, France
19LEGOS, 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

Abstract. The Wetland and Wetland CH4 Intercomparison of Models Project (WETCHIMP) was created to evaluate our present ability to simulate large-scale wetland characteristics and corresponding methane (CH4) 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 (CO2) forcing datasets. We reported the main conclusions from the intercomparison effort in a companion paper (Melton et al., 2012). 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 CO2 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 extents and CH4 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 CH4 fluxes from wetland systems. Even though modelling of wetland extents and CH4 emissions has progressed significantly over recent decades, large uncertainties still exist when estimating CH4 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.

Citation: Wania, R., Melton, J. R., Hodson, E. L., Poulter, B., Ringeval, B., Spahni, R., Bohn, T., Avis, C. A., Chen, G., Eliseev, A. V., Hopcroft, P. O., Riley, W. J., Subin, Z. M., Tian, H., Brovkin, V., van Bodegom, P. M., Kleinen, T., Yu, Z. C., Singarayer, J. S., Zürcher, S., Lettenmaier, D. P., Beerling, D. J., Denisov, S. N., Prigent, C., Papa, F., and Kaplan, J. O.: Present state of global wetland extent and wetland methane modelling: methodology of a model intercomparison project (WETCHIMP), Geosci. Model Dev. Discuss., 5, 4071-4136, doi:10.5194/gmdd-5-4071-2012, 2012.
 
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