A consortium of 81 scientists has warned that a decade-long surge of the potent greenhouse gas methane threatens to make the fight against global warming even harder.
Additional attention is urgently needed to quantify and reduce methane emissions, the scientists wrote in the Environmental Research Letters journal in a summary of the the consortium’s findings.
After rising slowly from 2000 to 2006, the concentration of methane in the air climbed 10 times more quickly the following decade, according to that study, which was published in the peer-reviewed Earth System Science Data.
“Keeping global warming below two degrees Celsius (3.6 degrees Fahrenheit) is already a challenging target,” they said, referring to the goal set in the 196-nation Paris climate pact, which entered into force last month.
“Such a target will become increasingly difficult if reductions in methane emissions are not also addressed strongly and rapidly.”
With only 1 C (1.8 F) of warming above pre-industrial era levels so far, the world has seen an uptick in extreme weather, including droughts, superstorms, heat waves and coastal flooding boosted by rising seas.
On current trends, average global temperatures are on track to rise by more than 3 C by 2100, even if national carbon-cutting pledges annexed to the Paris Agreement are honoured.
Without those pledges, the increase would be much higher.
To date, efforts to keep the planet from overheating have focused mostly on the main greenhouse gas carbon dioxide, a by-product of burning fossil fuels that accounts for at least 70 percent of warming.
But while scientists agree that total emissions of methane are rising sharply, they remain uncertain as to why.
Today, some 60 percent of methane originates from human activity, the rest coming from wetlands and other natural sources.
About a third of human-generated methane is a byproduct of the fossil fuel industry.
Researchers point to a surge in coal-generated power in China, along with leakage from the natural gas fracking boom in the United States.
“Both these regions are thought to play a role” in the sudden hike, said Marielle Saunois, lead author of the editorial as well as the review, and an assistant professor at the University of Versailles Saint Quentin.
But coal-fired plants and leaks from gas production are not sufficient and do not gel with the dramatic increase in the last two years, she told AFP.
A more likely culprit, the study concluded, is livestock production and agriculture (especially rice farming), which together account for nearly two-thirds of manmade methane emissions. Cows expel large quantities of methane and the flooded soils of rice paddies are homes for microbes that produce the gas.
A third possibility is a slow-down in the natural chemical reaction in the atmosphere that breaks down CH4.
Methane is much more short-lived in the atmosphere than CO2. This means that actions taken to reduce emissions will show rapid results, the researchers said.
This post is based on a report (here) in England’s Daily Telegraph.