US and EU-led initiative aims to reduce emissions of potent greenhouse gas methane by a third from 2020 levels by 2030, which could immediately slow down climate change.
Dozens of countries have joined a United States and European Union pledge to cut emissions of methane, the most potent greenhouse gas, by 30 percent this decade, in the most significant climate commitment so far at COP26.
The initiative, which experts say could have a powerful short-term impact on global heating, was announced on Tuesday following an agreement to end deforestation by 2030.
"One of the most important things we can do between now and 2030, to keep 1.5C in reach, is reduce our methane emissions as soon as possible," said US President Joe Biden, referring to the central goal of the 2015 Paris agreement.
He called the pledge, which has so far been signed by more than 100 nations, a "game-changing commitment" that covered countries responsible for around half of global methane emissions.
European Commission head Ursula Von der Leyen said that the methane cut would "immediately slow down climate change".
"We cannot wait until 2050. We have to cut emissions fast and methane is one of the gases we can cut the fastest," she said.
Twin announcements on second day
Decades of climate pledges have been rooted in reducing carbon dioxide emissions. Yet methane (CH4) is more than 80 times more potent than CO2, and its sources, such as open pit coal mines and livestock, have received relatively little attention until now.
The United Nations last month said that global methane emissions could be slashed by 20 percent at little or no cost using existing practices or technologies.
A report from earlier this year showed that "available targeted methane measures" could see CH4 levels reduced by 45 percent by 2030.
This would shave 0.3C off projected warming, save a quarter of a million air pollution deaths and increase global crop yields by 26 million tonnes, the UN's Environment Programme said.
"Strong and rapid action to cut methane emissions offers a range of benefits, from limiting near-term warming and curbing air pollution to improved food security and better public health," said Helen Mountford from the World Resources Institute.
Heads of state and government are gathered in Glasgow for a two-day high-level summit that host Britain is hoping will kick start ambitious climate action during the two-week COP26.
While the summit's first day passed with much rhetoric but only lukewarm climate pledges, Tuesday's twin announcements regarding deforestation and methane emissions were broadly welcomed by campaigners.