User:Adiering3/Atmospheric methane

Natural sources of atmospheric methane
Any process that results in the production of methane and its release into the atmosphere can be considered a "source". Several main processes that are responsible for methane production include microorganisms anaerobically converting organic compounds into methane (methanogenesis), which are widespread in aquatic ecosystems and ruminant animals. Other natural sources include melting permafrost and methane clathrates.

Aquatic ecosystems
Natural and anthropogenic methane emissions from aquatic ecosystems are estimated to contribute about half of total global emissions. Urbanization and eutrophication are expected to lead to increased methane emissions from aquatic ecosystems.

Permafrost
Permafrost contains almost twice as much carbon as the atmosphere, with ~20 Gt of permafrost-associated methane trapped in methane clathrates. Permafrost thaw results in the formation of thermokarst lakes in ice-rich yedoma deposits. Methane frozen in permafrost is slowly released as permafrost melts. Radiocarbon dating of trace methane in lake bubbles and soil organic carbon concluded that 0.2 to 2.5 Pg of permafrost carbon has been released as methane and carbon dioxide over the last 60 years. The 2020 heat wave may have released significant methane from carbonate deposits in Siberian permafrost.

Methane emissions by the 'permafrost carbon feedback' -- amplification of surface warming due to enhanced radiative forcing by carbon release from permafrost -- could contribute an estimated 205 Gt of carbon emissions, leading up to 0.5°C (0.9°F) of additional warming by the end of the 21st century. However, recent research based on the carbon isotopic composition of atmospheric methane trapped in bubbles in Antarctic ice suggests that methane emissions from permafrost and methane hydrates were minor during the last deglaciation, suggesting that future permafrost methane emissions may be lower than previously estimated.