Rising methane emissions in response to climate change in Northern Eurasia during the 21st century

We used a biogeochemistry model, the Terrestrial Ecosystem Model (TEM), to examine the methane (CH4) exchanges between terrestrial ecosystems and the atmosphere in Northern Eurasia from 1971 to 2100. Multiple model simulations using various wetland extent datasets and climate change scenarios were conducted to assess the uncertainty of CH4 fluxes, including emissions and consumption. On the basis of these simulations we estimate the current net emissions in the region to be 20-24 Tg CH4 yr(-1) (1 Tg = 10(12) g), two-thirds of which are emitted during the summer. In response to climate change over the 21st century, the annual CH4 emissions in the region are projected to increase at a rate of 0.06 Tg CH4 yr(-1), which is an order of magnitude greater than that of annual CH4 consumption. Further, the annual net CH4 emissions are projected to increase by 6-51% under various wetland extent datasets and climate scenarios by the end of the 21st century, relative to present conditions. Spatial patterns of net CH4 emissions were determined by wetland extent. Net CH4 emissions were dominated by wetlands within boreal forests, grasslands and wet tundra areas in the region. Correlation analyses indicated that water table depth and soil temperature were the two most important environmental controls on both CH4 emissions and consumption in the region. Our uncertainty analyses indicated that the uncertainty in wetland extent had a larger effect on future CH4 emissions than the uncertainty in future climate. This study suggests that better characterization of the spatial distribution and the natural diversity of wetlands should be a research priority for quantifying CH4 fluxes in this region.