At COP26 in Glasgow, more than 100 nations signed the Global Methane Pledge, promising to cut methane emissions 30% by 2030.
Methane recently reached 1,900 parts per billion (ppb) of Earth’s atmosphere according to measurements taken by NOAA. This compares to about 700 ppb before the industrial revolution.
Methane is a powerful greenhouse gas which lasts around nine year in the air. Its global warming impact since 1750 is roughly half that of CO2.
About 600 million tonnes of methane are released into the atmosphere every year. Estimates suggest two-fifths of these emissions come from natural sources, mostly rotting vegetation in swamps. The remaining three-fifths of emissions come from sources related to human activity.
Emissions from the fossil fuel industry are well over 100 million tonnes a year. Agriculture, which produces about 150 million tonnes a year, is the largest overall source. As well as urban landfills and sewage systems, contributing about 70 million tonnes annually.
From tropical swamps in the Amazon, Congo and Nile basins to tundra in Russia and bogs in Canada, wetlands emit roughly 200 million tonnes of methane a year. With increasing global temperatures, the rate at which wetlands generate and decompose biomass grows and these environments release more methane.
The microbes in the stomachs of ruminant animals like cattle, goars, sheep and camels are similar to wetland microbes. Ruminants produce nearly as much methane as fossil fuel emissions, roughly 115 million tonnes annually. About two-thirds of farmland globally is animal pasture.