Thawing permafrost and methane emission in Siberia: Synthesis of observations, reanalysis, and predictive modeling.

Permafrost has been warming in the last decade at rates up to 0.39 °C 10 year-1, raising public concerns about the local and global impacts, such as methane emission. We used satellite data on atmospheric methane concentrations to retrieve information about methane emission in permafrost and non-permafrost environments in Siberia with different biogeochemical conditions in river valleys, thermokarst lakes, wetlands, and lowlands. We evaluated the statistical links with air temperature, precipitation, depth of seasonal thawing, and freezing and developed a statistical model. We demonstrated that by the mid-21st century methane emission in Siberian permafrost regions will increase by less than 20 Tg year-1, which is at the lower end of other estimates. Such changes will lead to less than 0.02 °C global temperature rise. These findings do not support the "methane bomb" concept. They demonstrate that the feedback between thawing Siberian wetlands and the global climate has been significantly overestimated.