When it comes to climate change, carbon dioxide usually dominates the conversation — but it might be time to start paying particular attention to another greenhouse gas. Methane is 86 times more effective at trapping heat over a 20-year period than carbon dioxide, and scientists just announced it is increasing at an alarming rate.
According to new analysis published concurrently in the journals Environmental Research Letters and Earth System Science Data, methane concentrations are now growing at a higher rate than at any other time over the last two decades. And if these recent spikes in methane levels aren’t reined in, the papers’ authors warn that global temperatures could climb by as much as 4°C (7.2°F), blowing past the 2°C benchmark set by the Paris climate agreement.
The researchers aren’t sure exactly what is responsible for the spike in methane emissions, but they point to two major, human-driven sources: the oil and gas industry, and agriculture. According to the Environmental Protection Agency, methane emissions from the oil and gas industry are the United States’ largest source of domestic methane emissions. But while the researchers acknowledge that the natural gas boom in the United States has certainly sent methane levels climbing — methane leaks from natural gas production effectively offset any climate benefits of natural gas — they suggest that, globally, agriculture might actually be the primary factor behind the increase in methane emissions.
“The fossil fuel industry has received most of the attention in recent years,” Rob Jackson, chair of Stanford’s Earth System Science Department, head of the Global Carbon Project, and co-author of the papers, said in a press release. “Agricultural emissions need similar scrutiny.”
The two primary sources of agricultural methane are ruminants, such as cows, and rice farming. Ruminants produce methane as they digest their food, through a process known as enteric fermentation — and then release methane in their burps. Animal manure also emits methane as it decomposes in closed-air containers known as lagoons, used by industrial animal farms to contain the huge amounts of waste produced by animals raised in closed quarters. Rice farms emit methane due to the cultivation technique used to grow the crop — when farmers flood rice paddies, it creates an oxygen-devoid environment in which bacteria feed on carbohydrates secreted by the rice plant’s root system during photosynthesis. And as the bacteria breaks down the carbohydrates, they emit methane as a byproduct.
Standford’s Jackson notes that while methane is more potent over the short-term than carbon dioxide, that also means that curbing methane emissions can have a more immediate benefit for the climate.
“Methane presents the best opportunity to slow climate change quickly,” Jackson said. “Carbon dioxide has a longer reach, but methane strikes faster.”
Some mitigation techniques for methane emissions suggested in the papers include better detection and removal of natural gas leaks, and covering landfills (which emit methane as trash decomposes). Earlier this year, the Obama administration released new regulations meant to decrease flaring — burning off methane at the site of extraction — by half at oil and gas operations on public lands, in an effort to cut down on methane emissions.
But that rule faces an uncertain future under the incoming Trump administration, which has filled several top cabinet positions with people tied to the fossil fuels industry. Jack Girard, head of the American Petroleum Institute, which lobbies on behalf of the oil and natural gas industries, has promised to “aggressively” pursue the rollback of the Obama administration’s methane regulations.
In agriculture, a considerable amount of research has been directed at trying to find a way to make both animal agriculture and rice production produce less methane. Some research has suggested that feeding cows more seaweed could reduce their methane production by as much as 70 percent. Other research suggests adding a particular kind of methane-inhibiting supplement to a cow’s diet to make them less flatulent. And some campaigns have simply tried to convince people to eat less meat, which would, in turn, drive down global methane emissions (and also lead to a decline in things like deforestation, species extinction, and fertilizer-driven dead zones in places like the Gulf of Mexico). But when the Dietary Guidelines Advisory Committee suggested in 2008 that the U.S. nutritional guidelines explicitly tell eaters to back off on meat, they were met with staunch opposition from the meat industry. In the end, those guidelines were not included.
As for rice — which provides 3.5 billion people with least 20 percent of their daily caloric intake — scientists have had some success engineering a strain that can cut methane emissions by up to 90 percent. (The strain has yet to be tested in large-scale experiments). In the United States, the Environmental Defense Fund (EDF), in conjunction with the USDA, has been working on a program to actually pay rice farmers for decreasing their greenhouse gas emissions using California’s carbon market. The program is fairly small, however — just under one percent of rice farmers in the United States currently participate.
The authors of the two papers acknowledge that carbon is still the primary focus for climate mitigation — but argue that without focusing on methane reductions as well, the world will have little-to-no chance of meeting the commitments made a year ago in Paris.
“We still need to cut carbon dioxide emissions, but cutting methane provides complementary benefits for climate, economies, and human health,” Stanford’s Jackson said.