Methane levels in the atmosphere surged during 2020, marking the biggest increase since records began in 1983, in what scientists called a worrying development for the planet.
New data showed that both methane and carbon dioxide reached record amounts in the atmosphere last year, despite the coronavirus pandemic bringing much of the world’s economy to a halt.
Lori Bruhwiler, physical scientist at the US National Oceanic and Atmospheric Administration, said the jump in methane levels was “fairly surprising — and disturbing”.
“We don’t usually expect them to jump abruptly in a year,” said Bruhwiler. The exact reasons for the increase are not yet known, she added.
Methane, which is 28 times more potent than carbon dioxide as a factor in global warning, comes from using fossil fuels such as coal and gas and from microbial sources in wetlands, cows and landfill.
Around 60 per cent of methane emissions are linked to human activity, while the rest arise naturally from environments such as swamps or melting permafrost.
The NOAA data show that methane concentrations rose by 14.7 parts per billion in 2020.
Levels of carbon dioxide rose to 412.5 parts per million during 2020, according to NOAA, about 12 per cent higher than the levels in 2000.
Carbon dioxide emissions fell about 6 per cent last year because of the pandemic but, despite the reprieve, the concentration of CO2 in the atmosphere still rose as emissions continued.
The record CO2 levels of were expected because the gas stays in the atmosphere for up to 100 years, but the sudden increase in methane concentrations came as a surprise.
“It is very scary indeed,” said Euan Nisbet, professor of earth sciences at Royal Holloway University of London.
One hypothesis for the increase in methane is a rise in emissions from biological sources such as wetlands, according to Nisbet.
“Parts of the tropics have grown warmer and wetter” because of global warming, triggering the release of more methane, he explains.
Another hypothesis is that the atmosphere’s ability to “clean up” methane by breaking it down over time has declined.
“A warming planet could be causing more natural emissions of methane,” said Durwood Zaelke, president of the Institute for Governance and Sustainable Development, an environmental charity based in Washington DC that focuses on shortlived climate pollutants such as methane.
Cutting methane emissions can slow down global warming more quickly than reducing those of carbon dioxide, he adds, because methane does not stay in the atmosphere for as long.
Methane is also given off by oil and gas extraction, for example from leaks in gas pipelines.
Methane emissions from oil and gas have been an area of growing concern in the US; President Donald Trump loosened regulations governing them and President Joe Biden is preparing to tighten the rules.
While the NOAA data on methane levels are preliminary and may be updated later this year, they indicate that methane is rising at a faster rate than expected.
Nisbet said the current levels are far away from what would be needed to reasonably meet the Paris agreement target of limiting warming to 1.5C.
“I knew it was bad, but I didn’t know it was this bad,” Nisbet added, referring to the methane data. “This breaks my heart.”