Modeling regional to global CH4 emissions of boreal and arctic wetlands

[1] Methane (CH4) emission from boreal, arctic and subarctic wetlands constitutes a potentially positive feedback to global climate warming. Many process‐based models have been developed, but high uncertainties remain in estimating the amount of CH4 released from wetlands at the global scale. This study tries to improve estimates of CH4 emissions by up‐scaling a wetland CH4 emission model, PEATLAND‐VU, to the global scale with a spatial resolution of 0.5 ° for the period 2001–2006. This up‐scaling was based on the global circum‐arctic distribution of wetlands with hydrological conditions being specified by a global hydrological model, PCR‐GLOBWB. In addition to the daily hydrological output from PCR‐GLOBWB, comprising water table depths and snow thickness, the parameterization included air temperature as obtained from the ECMWF Operational Archive. To establish the uncertainty in the representations of the circum‐arctic distribution of wetlands on the CH4 emission, several existing products were used to aggregate the emissions. Using the description of potential peatlands from the FAO Digital Soil Map of the World and the representation of floodplains by PCR‐GLOBWB, the average annual flux over the period 2001–2006 was estimated to be 78 Tg yr−1. I