More than 100 countries representing more than 70% of the global economy agreed to cut their emissions of climate-busting methane 30% by 2030, in a much-anticipated announcement on the second day of the United Nations climate change conference, COP 26, in Glasgow Scotland.

The agreement was greeted as a potential breakthrough, though it falls short of the target laid out in a United Nations-supported assessment in May.

“The Global Methane Pledge, which was first announced in September, now includes half of the top 30 methane emitters,” Reuters reports, citing U.S. government officials. It includes Brazil, one of the world’s top five methane emitters, but has still not won the support of China, Russia, or India.

In the days leading up to the COP, Australia Prime Minister Scott Morrison let it be known his climate denying, coal- and liquefied natural gas-friendly government would not be signing on.

Methane is a shorter-lived greenhouse gas than carbon dioxide, but it is 80 to 85 times more potent a global warming agent over a 20-year span—the crucial period in which humanity will be scrambling to get the climate emergency under control. When the Intergovernmental Panel on Climate Change issued its most recent, alarming science assessment in August, methane controls emerged as the single most important step governments could take to reduce emissions over the shorter term.

So “while it is not part of the formal UN negotiations, the methane pledge could rank among the most significant outcomes from the COP 26 conference, given its potential impact in holding off disastrous climate change,” Reuters writes. The news agency says the announcement covers all the major methane-emitting sectors, including “leaky oil and gas infrastructure, old coal mines, agriculture, and landfill sites.”

A report released last May by the Climate and Clean Air Coalition and the UN Environment Programme concluded that a 45% methane reduction this decade could shave almost 0.3°C off future global warming by the 2040s. That’s a considerably more ambitious target than countries adopted this week, but on track with a trilateral agreement that then-U.S. president Barack Obama, Canadian Prime Minister Justin Trudeau, and then-Mexican president Enrique Peña-Nieto reached in June, 2016, before the U.S. withdrew all support from international climate initiatives for four deeply dysfunctional years.

Alongside the Global Pledge announcement, President Joe Biden unveiled new methane control rules from the U.S. Environmental Protection Agency, including more frequent and stringent leak monitoring, control on natural gas flaring at fossil fuel plants, and methane standards for about 300,000 existing oil and gas wells across the country. The announcement marked “the first time the [U.S.] federal government has moved to comprehensively tackle the seepage of methane from U.S. oil and gas infrastructure,” the Washington Post reports.

The U.S. plan also addresses methane releases from food waste, manure management on farms, and landfills, the Post says.

The announcement drew a mostly positive reaction from climate watchers attending the COP.

“Never before have countries come together to tackle this key part of the climate puzzle,” World Resources Institute CEO and President Ani Dasgupta said in a prepared statement. “The next step is for countries to put the pledge in motion with serious policies across agriculture, energy, and waste. Solutions to tackle methane are readily available, cost-effective, and bring wins for climate and development.”

“Methane is a greenhouse gas strongly associated with the fossil fuel industry, with what are known as ‘fugitive emissions’ evaporating from coal mines, from oil and gas extraction, and from pipelines. Methane is but another reason why the fossil fuel industry has to end—and soon,” said Christian Aid climate policy lead Dr. Kat Kramer.

“For the poorest and most vulnerable people who are already being hit by catastrophic climate impacts, the climate co-benefits of shutting down the fossil fuel industry and gaining the double whammy of reduced methane and carbon dioxide emissions will help to reduce their future suffering, but these polluters also need to pay for the damage they have already wrought,” Kramer added.

Dave Jones of climate think tank Ember called the announcement “a game changing moment,” showing “that the world is waking up to methane’s staggering climate impact.” 

But “for countries to cut as much methane as possible, they must target all sources,” he added. “Coal mine methane is fairly quick and cheap to do something about and a massive contributor to global heating,” yet four of the world’s top coal mine methane emitters—China, Russia, India, and Australia—opted out of signing the pledge.

In an analysis published yesterday, Ember calls coal mine methane “the climate crisis multiplier that few are talking about,” responsible for more short-term climate impact than the aviation and shipping industries combined.