BBC reports that this year, after nearly a decade of stability, methane in the atmosphere has increased. Both wind and isotope analyses indicate that the source is probably the Arctic wetlands, melting permafrost. "Some stations around the Arctic showed rises of more than double" the global average, 0.5%.
Nearly 60% of atmospheric methane is man-made:
herds of cattle and other ungulates, rice production, and leaks of natural gas from pipelines, according to the IPCC. In addition, natural sources of methane include wetlands, termites, oceans, and gas hydrate nodules on the sea floor.
Methane contributes to tropospheric ozone, another greenhouse gas. Low atmosphere ozone is also a primary source of smog. Reducing methane in the atmosphere would thus have a double benefit.
We need more thinking about methane sequestration and the methane cycle.
Methane is a more effective greenhouse gas than CO2, although it's lifecycle in the atmosphere is less than a decade. CO2 takes about a century to pass through the troposphere and out of the stratosphere.
Methane is measured in parts per billion (ppb) rather than parts per million (ppm) as carbon is. According to 1998 figures, there are 1,745 ppb of methane in the atmosphere.
The Earth's methane concentration has increased by about 150% since 1750, and it accounts for 20% of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases.[11]
Sequestering 40 million tons of Methane would be the equivalent of sequestering 1 billion tons of carbon dioxide.
Previously
Towards Zero Emissions: The Methane Cycle