Methane concentrations in the atmosphere continue to increase, at a rate that has even accelerated in recent years, threatening the planet’s climate trajectory despite the promise of many countries to drastically reduce emissions of this powerful greenhouse gas, researchers warned Tuesday.
“Methane is increasing faster in relative terms than any other major greenhouse gas and is now at levels 2.6 times higher than in pre-industrial times,” writes an international team of scientists under the auspices of the Global Carbon Project, in a study published in the journal Environmental Research Letters.
Methane (CH4) is the second greenhouse gas linked to human activity after carbon dioxide (CO2).
About 40% of methane comes from natural sources, particularly in wetlands, but the majority (around 60%) is linked to human activities such as agriculture (ruminant breeding and rice cultivation), fossil fuels and waste.
Its warming potential is more than 80 times greater over 20 years than that of CO2but its lifespan is shorter, which makes it an important lever for trying to limit global warming in the short term.
But the inventory carried out by scientists shows that the trajectory followed is not the right one and that the concentrations of methane in the atmosphere – the methane emitted minus a part absorbed by the soil and by chemical reactions in the atmosphere – have continued to increase.
“Almost all countries”
The increase in the atmosphere averaged 6.1 million tonnes per year in the 2000s, then 20.9 million tonnes in the 2010s. Growth has accelerated further in recent years, at rates not seen since continuous measurements began in the 1980s, and for example reached 41.8 million tonnes in 2020, double the average for the years of the previous decade.
“Anthropogenic emissions have continued to increase in almost every country in the world, with the exception of Europe and Australia, which show a trajectory of slow decline,” Pep Canadell, executive director of the Global Carbon Project and co-author of the study, based in Canberra (Australia), told AFP.
The increases were driven mainly by emissions from coal mining, oil and gas production and use, cattle and sheep farming, and the decomposition of food and organic matter in landfills.
Natural causes also play a role. “The increase in 2020, and particularly the following two years, was caused by a rather exceptional period of the La Niña phenomenon, which brings wetter than average conditions in many parts of the world, particularly the tropics,” explains Pep Canadell.
These conditions favor the natural production of methane in humid areas, especially tropical ones, which represent the first natural source of emissions of the gas. And it is also expected that the La Niña phenomenon will return during this year.
The year 2020 also saw a paradoxical effect of the fight against COVID-19, already highlighted in a study: the drop in pollutants linked to transport (NOx) indirectly slowed the removal of methane from the atmosphere.
“Mirage”
In any case, the trajectory of methane appears to be out of step with what climate experts mandated by the UN (IPCC) are recommending to keep warming below 2°C, but also with the promises made by States.
A “global commitment” was launched in 2021 by the European Union and the United States to reduce global methane emissions by 30% by 2030 compared to 2020.
Today it includes more than 150 countries but not China, India or Russia.
These goals “seem as distant as an oasis in the desert,” said Rob Jackson of Stanford University, the study’s lead author. “We all hope they’re not a mirage.”
China, US jointly prepare summit on non-CO pollutant gases2including methane, perhaps opening the way to new commitments.