Ellen Phiddian
Cosmos science journalist
Global methane emissions are rising at record levels, according to a new report.
Methane emissions have risen 20% in the past 20 years.
The findings come from the Global Methane Budget 2024, which is run by the Global Carbon Project, an international partnership between a variety of science bodies.
Methane holds much more heat in the atmosphere than carbon dioxide, making it an extremely potent greenhouse gas. But it doesn’t stay in the atmosphere for as long – turning into carbon dioxide after an average of 12 years.
Methane from anthropogenic sources has caused about 0.5°C of global warming to date.
The project team also compiles the annual Global Carbon Budget, which tracks CO2 emissions specifically, the Global Nitrous Oxide Budget, and an upcoming budget on hydrogen.
The latest Global Methane Budget, which updates on 2020 and 2016 publications, is published in Earth System Science Data, with a summary in Environmental Research Letters.
Some methane enters the atmosphere through natural sources, but at least two-thirds of methane emissions are caused by people, according to Dr Pep Canadell, executive director for the Global Carbon Project at the CSIRO.
The Budget found that 40% of human-caused methane emissions come from the agricultural sector, while 34% came from fossil fuels, 19% from waste, and 7% from biofuel and biomass.
Canadell tells Cosmos that some of these industries can reduce their methane emissions to zero, but others cannot.
“It will be very difficult, if not impossible, to completely get rid of emissions from agriculture,” he says.
“But you can do things to reduce emissions.”
Livestock, like cows and sheep, and rice paddies are major sources of methane in agriculture. But practices such as drying rice paddies periodically, and feeding cattle certain foods, can lower their methane production significantly. Changing consumption patterns around meat would also lower methane emissions.
Researchers around the world are working on livestock feeds that prevent methanogenesis in the stomachs of cattle and sheep. The CSIRO has seen some success with an Asparagopsis seaweed-based additive.
“With all these food additives, the real-world experiments are showing that you might be able to reduce emissions up to 30%,” says Canadell.
More research in the industry is needed to find other ways to drop emissions.
In the fossil fuel industry, conversely, the technology already exists to bring methane emissions to zero.
Canadell cites research done by the International Energy Agency that suggests methane emissions from fossil fuel mining could plummet very cheaply, by taking steps to capture methane leaks and sell the gas as a power source instead.
“It might have a cost, but it’s nothing that’s not possible with current technology.”
Methane emitted from landfill can be mitigated in 2 different ways.
“The easiest one is programs by which organic residues don’t make it to landfill,” says Canadell.
If all organic waste was composted or degraded in other ways, landfill wouldn’t generate methane.
“The other one is something that has been well established, and Australia has done it in some parts, particularly in some of the major landfills in cities: the landfills get covered, and the methane needs to be released for securing stability of the piles,” says Canadell.
This methane can then be used as a source of biogas.
Methane’s short, intense atmospheric life makes it a good target for quickly mitigating warming, according to Canadell.
At the UN’s COP26 Climate Conference, more than 100 countries signed the Global Methane Pledge, which aims to cut methane emissions by 30% by 2030. Australia did not join the pledge at the time, but signed on in 2022 following a change of federal government.
“Right now, the goals of the Global Methane Pledge seem as distant as a desert oasis,” says Professor Rob Jackson, chair of the Global Carbon Project and a researcher at Stanford University, USA.
“Only the European Union and possibly Australia appear to have decreased methane emissions from human activities over the past two decades,” says co-author Professor Marielle Saunois, a researcher at the Université Paris-Saclay in France.
“The largest regional increases have come from China and southeast Asia.”
Canadell says that Australia’s methane emissions have come down “very slowly”.
“For Australia, over the last 30 years, we had massive emission reductions due to the reduction of livestock in general,” he says.
The large reduction in sheep and cattle populations has driven the reduction in methane emissions.
Canadell adds that changes in climate may cause unpredictable fluctuations in natural methane sources.
“What we see is that the tropical wetlands are emitting the most natural methane emissions, and they’re the most sensitive to changes in the climate,” he says.
“Over the last three years of La Niña from 2020-2022, on top of the anthropogenic growth, we saw a massive release of methane from wetlands, particularly from the tropical regions.
“That’s because if it’s wet and you increase the temperature, microbes will do much better at producing processing organic matter and therefore producing more methane.”
But some of these regions may be drying out as the climate warms.
“Whether we end up having much more methane in the future because of the high temperatures, or less methane because parts of the tropics dry a little more than now, isn’t clear,” says Canadell.
“But the system is incredibly sensitive.”
