Methane gas emissions are growing faster now than at any time in the last two decades, threatening efforts to limit global warming to two degrees celsius.
Scientists have warned that the proliferation of the powerful greenhouse gas could undermine progress made to curb other emissions like carbon dioxide.
A team of international scientists found that methane emissions began to surge in 2007 and shot up in 2014 and 2015 by 10 parts per billion each year.
While the cause of the spike is unclear, scientists suspect it comes from agricultural sources around the tropics, like rice paddies and cattle pastures.
There’s significantly less methane in the atmosphere than carbon dioxide, but it’s much more potent, trapping 28 times more heat.
“The levelling off we’ve seen in the last three years for carbon dioxide emissions is strikingly different from the recent rapid increase in methane,” said Robert Jackson, a co-author of the paper and a Professor in Earth System Science at Stanford University.
The results are “worrisome but provide an immediate opportunity for mitigation that complements efforts for carbon dioxide”, Jackson added.
Researchers looked at a range of information to make the calculations, including inventories of methane emissions, computer models and air measurements.
Methane growth was stagnant from 2000 to 2006, but surged after 2007, according to the analysis.
“Why this change happened is still not well understood,” said Marielle Saunois, lead author of the study and an assistant professor of Université de Versailles Saint Quentin and researcher at Laboratoire des Sciences du Climat et de l’Environnement in France.
“For the last two years especially, the growth rate has been faster than for the years before. It’s really intriguing.”
Despite the surge in emissions, the researchers are hopeful.
The tide of emissions from agriculture could be stemmed by feeding cows linseed oil, the researchers said.
“When it comes to methane, there has been a lot of focus on the fossil fuel industry, but we need to look just as hard if not harder at agriculture,” Jackson said. “The situation certainly isn’t hopeless. It’s a real opportunity.”