Rapid increase in methane emissions

Methane emissions from human activities have increased by 20% over the past two decades.

This is the finding of the recently released Global Methane Budget 2024, which is produced by CSIRO alongside international research partners as part of the Global Carbon Project.

Methane is one of three core greenhouse gases that contribute to climate change, alongside carbon dioxide and nitrous oxide. While methane only lasts in the atmosphere for a few decades — a shorter time than its counterparts — it has the highest short-term global warming potential as it holds more heat in the atmosphere.

Since reliable measurement began in 1986, methane concentrations have risen faster than ever in recent years, according to Pep Canadell, CSIRO’s Executive Director for the Global Carbon Project.

“We have seen higher growth rates for methane over the past three years, from 2020–2022, with a record high in 2021. This increase means methane concentrations in the atmosphere are 2.6 times higher than its pre-industrial (1750) levels,” Canadell said.

“Human activities are responsible for at least two-thirds of global methane emissions, adding about 0.5°C to global warming that has occurred to date.”

Of the industries contributing most to global methane emissions, the report found agriculture contributes 40%, followed by the fossil fuel sector (34%), solid waste and wastewater (19%), and biomass and biofuel burning (7%).

The top five country emitters of anthropogenic methane in 2020 were China (16%), India (9%), USA (7%), Brazil (6%) and Russia (5%).

Australasia and the European Union have been successful in reducing anthropogenic methane emissions over the past two decades. However, if the trend of anthropogenic methane emissions continues to increase globally, this would jeopardise the success of the Global Methane Pledge — an international commitment to reduce methane emissions by 30% by 2030.

“Methane is a short-lived greenhouse gas compared to carbon dioxide. 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.

“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% by 2050, relative to 2019 levels.”

Methods for reducing the agriculture sector’s methane emissions include improved land management practices, such as improving the efficiency of animal production; provision of feed additives that reduce enteric methane; and breeding animals that produce less methane.

Dr Michael Battaglia, CSIRO’s Towards Net Zero Lead, said CSIRO is working on a range of research projects to reduce methane emissions.

“Mitigation efforts include developing FutureFeed with partners Meat & Livestock Australia and James Cook University, an Asparagopsis seaweed-based feed additive to significantly reduce enteric methane emissions in livestock. This is one of an array of feed supplements in a suite of technologies to address ruminant methane,” Battaglia said.

“We’re also researching how legumes may be used to reduce methane in grazing livestock.”

The Global Methane Budget 2024 is the fourth such budget published in the journal Earth System Science Data. The summary paper is available through Environmental Research Letters.

Image credit: iStock.com/Clara Bastian