Methane Pollution Just Reached New Heights, And The Sources May Not Be What You Think
Methane recently reached 1,900 parts per billion (ppb) of Earth's atmosphere according to measurements taken by the National Oceanic and Atmospheric Administration (NOAA) in the US. This compares with about 700 ppb before the industrial revolution.
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After rising sharply in the 1980s and 1990s, atmospheric methane then stabilized. Growth resumed in 2007 and has accelerated in recent years – the sharpest rise on record happened in 2020.
This was not expected when world leaders signed the 2015 Paris Agreement. Methane is becoming the largest discrepancy from emissions trajectories necessary for meeting the agreement's target.
So what's behind the recent surge – and is there a way to reverse it?
Where methane comes from
About 600 million metric tons of methane are released into the atmosphere each year. Estimates suggest two-fifths of these emissions come from natural sources, mainly rotting vegetation in swamps. The remaining three-fifths of emissions come from sources tied to human activity.
Emissions from the fossil fuel industry are well over 100 million metric tons a year and grew rapidly in the 1980s. Natural gas, which in the UK heats homes and generates roughly half of electricity, is mainly methane.
Gas industry leaks are widespread at wells and pipelines and from distribution pipes under streets and home boilers. The coal industry was responsible for up to one-third of fossil fuel emissions between 2000 and 2017 via ventilation shafts in mines and during the transportation and crushing of coal for power stations.
Agriculture, producing about 150 million metric tons a year, is the largest overall source. As are urban landfills and sewage systems, contributing about 70 million metric tons annually.
Scientists can identify sources of methane by studying the proportion of carbon-12 to carbon-13 in the atmosphere. These different forms of carbon – chemically similar but with different masses – are known as isotopes.
Biogenic methane, made by microbes in rotting vegetation or in cow stomachs, is relatively rich in carbon-12, while methane from fossil fuels and fires has comparatively more carbon-13.
For two centuries, rapidly expanding gas, coal and oil industries steadily drove atmospheric methane richer in carbon-13. Since 2007, that trend has reversed, and the proportion of carbon-13 in atmospheric methane has decreased. Although fossil fuel emissions may still be growing,
soaring methane emissions are now primarily the result of faster-growing biogenic sources....
From tropical swamps in the Amazon, Nile and Congo basins to tundra in Russia and muskeg bogs in Canada, wetlands emit roughly 200 million metric tons of methane a year. As global temperatures increase, the rate at which wetlands generate and decompose biomass grows and these environments release more methane.
Methane emissions accelerate climate change and climate change causes the release of more methane – a positive feedback of warming feeding more warming.
The microbes in the stomachs of ruminant animals like cattle, sheep, goats and camels are similar to wetland microbes. In effect, cows are walking wetlands. Ruminants produce nearly as much methane as fossil fuel emissions, roughly 115 million metric tons of annually. Globally, about two-thirds of farmland is animal pasture.
...and more including tackling all our emissions we can stop or reduce.
https://www.sciencealert.com/atmospheric-methane-has-reached-new-records-here-s-what-that-means