Global methane emissions soar to record levels

Global methane emissions have reached the highest levels recorded. The increases are primarily due to growth in emissions from coal mining, oil and natural gas production, cattle and sheep farming, and landfills.

Between 2000 and 2017, levels of the potent greenhouse gases shot up the routes that climate models suggest will lead to a warming of 3-4 degrees Celsius before the end of this century. This is a dangerous temperature threshold at which scientists warn that natural disasters, including forest fires, droughts and floods, and social disruptions such as famines and mass migrations become almost common. The findings are summarized in two articles published on July 14 in Earth system scientific data and Environmental Research Letters by researchers at the Global Carbon Project, an initiative led by Stanford University scientist Rob Jackson.

In 2017, last year, when comprehensive global methane data is available, Earth’s atmosphere absorbed nearly 600 million tons of colorless, odorless gas that is 28 times more powerful than carbon dioxide to trap heat in a 100 years span. More than half of all methane emissions now come from human activities. Annual methane emissions increased 9 percent, or 50 million tons per year, from the early 2000s, when methane concentrations in the atmosphere were relatively stable.

In terms of warming potential, adding this additional amount of methane to the atmosphere since 2000 is similar to putting 350 million more cars on the world’s roads or doubling the total emissions of Germany or France. “We haven’t turned methane around yet,” said Jackson, a professor of earth system science at the Stanford Earth Science, Energy and Environment School.

Increasing sources of methane

Globally, fossil fuel sources and cows are twin engines that drive the upward climb of methane. “Emissions from livestock and other ruminants are almost as great as those from the fossil fuel industry for methane,” said Jackson. “People joke about burping cows without realizing how big the fountain really is.”

Throughout the study period, agriculture accounted for approximately two thirds of all methane emissions related to human activities; fossil fuels contributed most of the remaining third. However, those two sources have contributed roughly equal to the increases observed since the early 2000s.

Methane emissions from agriculture increased to 227 million tons of methane in 2017, almost 11 percent more than the 2000-2006 average. Methane from the production and use of fossil fuels reached 108 million tons in 2017, almost 15 percent more than in the previous period.

Amid the coronavirus pandemic, carbon emissions plummeted as manufacturing and transportation halted. “There is no chance of methane emissions falling as much as carbon dioxide emissions due to the virus,” said Jackson. “We are still heating our houses and buildings, and agriculture continues to grow.”

Emissions worldwide.

Methane emissions increased most strongly in Africa and the Middle East; China; and South Asia and Oceania, which includes Australia and many Pacific islands. Each of these three regions increased emissions by an estimated 10 to 15 million tons per year during the study period. The United States followed closely behind, increasing methane emissions by 4.5 million tons, mainly due to increased drilling, distribution and consumption of natural gas.

“The use of natural gas is increasing rapidly here in the United States and around the world,” said Jackson. “It is offsetting carbon in the power sector and reducing carbon dioxide emissions, but increasing methane emissions in that sector.” The United States and Canada are also producing more natural gas. “As a result, we are emitting more methane from oil and gas wells and leaking pipelines,” said Jackson, who is also a member of the Stanford Institute for Environment and Energy Resource.

Europe stands out as the only region where methane emissions have decreased in the past two decades, in part by reducing emissions from chemical manufacturing and food farming more efficiently. “Policies and better management have reduced emissions from landfills, manure and other sources here in Europe. People are also eating less beef and more poultry and fish,” said Marielle Saunois of the University of Versailles Saint-Quentin in France, lead author of the paper in Earth system scientific data.

Possible solutions

Tropical and temperate regions have seen the biggest jump in methane emissions. The boreal and polar systems have played a minor role. Despite fears that melting in the Arctic may release a methane explosion by thawing permafrost, the researchers found no evidence of increased methane emissions in the Arctic, at least until 2017.

Human-powered emissions are in many ways easier to pin down than from natural sources. “We have a surprisingly difficult time identifying where methane is emitted in the tropics and elsewhere due to daily and seasonal changes in the way waterlogged soils are found,” said Jackson, who also heads a group at Stanford that works to map wetlands and waterlogged soils worldwide using satellites, flow towers and other tools.

According to Jackson and colleagues, reducing methane emissions will require reducing fossil fuel use and controlling fugitive emissions, such as leaking pipes and wells, as well as changes in the way we feed livestock, grow rice, and eat. “We will need to eat less meat and reduce the emissions associated with growing cattle and rice,” Jackson said, “and replace the oil and natural gas in our cars and homes.”

Food supplements, such as algae, can help reduce cows’ methane burps, and rice cultivation can go from permanent ponding that maximizes methane production in low-oxygen environments. Planes, drones, and satellites hold promise for monitoring methane from oil and gas wells. Jackson said: “I am optimistic that, in the next five years, we will make real progress in that area.”

Provided by the Stanford School of Earth, Energy and Environmental Sciences