Bottom-up evaluation of the regional methane budget of northern lands from 1980 to 2015

This study created a regional budget for methane (CH4) for Northern Europe, Siberia, and northern North America, based on a mission inventories, biogeochemical models, and land-surface satellite data. Natural sink and sources (wetlands, termites, wildfires, soil oxidation, and geological sources) and anthropogenic sources (fossil fuel extraction, industry and transportation, waste, agriculture, and livestock) were included. During 2000-2015, the region was estimated to be a net source of 57.2 Tg CH4 yr(-1), 40.8% of which was contributed by anthropogenic sources. Wetland emissions (33.9 Tg CH4 yr(-1)) were the largest sources in the region, followed by fossil fuel extraction, waste, and geological emissions. Comparisons with other estimates indicated an uncertainty of +/- 16.9 Tg CH4 yr(-1) for wetland emissions and +/- 6.9 Tg CH4 yr(-1) for anthropogenic emissions. Regional emissions reached a peak in 1988, troughs in 1996 and 2000, and then gradually increased to a maximum in 2015. The temporal patterns was attributable to variations of both anthropogenic and natural emissions. Spatial maps of CH4 sources, sinks, and net emissions were constructed to identify "hot spots" of emissions and their variations. Theanalyses revealed a need for further clarification of emissions from freshwater, permafrost thawing, biomass burning, and fossil fuel exploitation.