Human Activity Responsible for Adding 0.5 Degrees to Global Warming: Researcher

Methane emissions from human activities have risen by 20 percent in the last two decades, according to a new report.

The Global Methane Budget 2024, produced by international research partners including Australia's national science agency, the CSIRO, found that methane had increased by 61 million metric tonnes per year.

Methane is a colorless odorless gas that is both produced naturally when plants decompose underwater, along with industrially. Scientists regard methane most prominent greenhouse gas after carbon dioxide.

The report found China was the top emitter of anthropogenic methane in 2020 at 16 percent, followed by India at 9 percent and United States at 7 percent.

Executive Director for the Global Carbon Project Pep Canadell from the CSIRO said methane concentrations have recently risen "faster than ever." Reliable measurements started in 1986, Canadell pointed out.

Canadell explained the study showed human activities were responsible for at least two-thirds of global methane emissions, adding about 0.5 degrees Celsius to global warming.

Methane stays in the atmosphere for just a few decades, shorter than carbon dioxide and nitrous oxide, and therefore, has what the CSIRO calls the "highest short-term global warming potential."

"Most emissions, and therefore their warming effect in the atmosphere, occur during the first 20 years after being released, so it's a good target for fast mitigation of global warming," Canadell said.

Meanwhile, the report said agriculture contributes 40 percent of global methane emissions from human activities.

This was followed by 34 percent in the fossil fuel sector, 19 percent in solid waste and wastewater, and 7 percent biomass and biofuel burning.

Researchers noted the European Union and Australasia had successfully reduced their methane emissions derived from human activity in the last 20 years.

However, they raised concerns that a continued global rise in methane emissions could jeopardise the success of the Global Methane Pledge. This is a global commitment to cut methane emissions by 30 percent by the year 2030.

"For net-zero emission pathways consistent with the Paris Agreement, which is stabilising temperatures below 2°C from pre-industrial levels, anthropogenic methane emissions need to decline by 45 percent by 2050, relative to 2019 levels," Canadell said.

The scientists suggested a range of strategies to lower methane emissions from the agriculture sector, including improving animal production efficiency, "feed additives" to reduce enteric methane, and breeding animals that produce lower methane levels.

CSIRO's Towards Net Zero Lead, Michael Battaglia, said they were working a range of research and innovation research to reduce methane emissions.

"Mitigation efforts include developing FutureFeed, with partners Meat and Livestock Australia and James Cook University, an Asparagopsis seaweed-based feed additive to significantly reduce enteric methane emissions in livestock," Battaglia said.

"This is one of an array of feed supplements in a suite of technologies to address ruminant methane. We're also researching how legumes may be used to reduce methane in grazing livestock."

The study, published in Communications Earth and Environment in April, found emissions from oil and gas exploitations had stabilised the atmospheric methane rate in the late 1990s and early 2000s.

However emissions from farmed animals, waste management, and coal mining had contributed to the rise since 2006.

Meanwhile, the National Aeronautics and Space Administration (NASA) says an estimated 60 percent of today's methane emissions come from human activities.

"The largest sources of methane are agriculture, fossil fuels, and decomposition of landfill waste. Natural processes account for 40 percent of methane emissions, with wetlands being the largest natural source," NASA states.