A landmark United Nations report is expected to declare that reducing emissions of methane, the main component of natural gas, will need to play a far more vital role in warding off the worst effects of climate change.

The global methane assessment, compiled by an international team of scientists, reflects a growing recognition that the world needs to start reining in planet-warming emissions more rapidly, and that abating methane, a particularly potent greenhouse gas, will be critical in the short term.

It follows new data that showed that both carbon dioxide and methane levels in the atmosphere reached record highs last year, even as the coronavirus pandemic brought much of the global economy to a halt. The report also comes as a growing body of scientific evidence has shown that releases of methane from oil and gas production, one of the biggest sources of methane linked to human activity, may be larger than earlier estimates.

The report, a detailed summary of which was reviewed by The New York Times, singles out the fossil fuel industry as holding the greatest potential to cut its methane emissions at little or no cost. It also says that — unless there is significant deployment of unproven technologies capable of pulling greenhouse gases out of the air — expanding the use of natural gas is incompatible with keeping global warming to 1.5 degrees Celsius, a goal of the international Paris Agreement.

The reason methane would be particularly valuable in the short-term fight against climate change: While methane is an extremely potent greenhouse gas, it is also relatively short-lived, lasting just a decade or so in the atmosphere before breaking down. That means cutting new methane emissions today, and starting to reduce methane concentrations in the atmosphere, could more quickly help the world meet its midcentury targets for fighting global warming.

By contrast, carbon dioxide, the main greenhouse gas, lasts for hundreds of years in the atmosphere. So while it remains critical to keep reducing carbon emissions, which make up the bulk of our greenhouse gas emissions, it would take until the second half of the century to see the climate effects.

Over all, a concerted effort to reduce methane from the fossil fuel, waste and agricultural sectors could slash methane emissions by as much as 45 percent by 2030, helping to avoid nearly 0.3 degrees Celsius of global warming as early as the 2040s, the report says.

While cutting back on carbon dioxide emissions will remain urgent, “it’s going to be next to impossible to remove enough carbon dioxide to get any real benefits for the climate in the first half of the century,” said Drew Shindell, the study’s lead author and a professor of earth science at Duke University. “But if we can make a big enough cut in methane in the next decade, we’ll see public health benefits within the decade, and climate benefits within two decades,” he said.

The U.N. report, which is expected to be published next month by the Climate and Clean Air Coalition and the United Nations Environment Programme, signals a shift in the global discussion of climate change, which has focused on reducing carbon dioxide, the largest long-term driver of climate change.

Most climate policies — including net-zero targets set by nations, states and cities as well as businesses — have tended to focus on longer-term targets for reducing carbon dioxide emissions. But methane has begun to gain prominence in the global conversation.

At a climate summit in Washington this week, President Vladimir Putin of Russia, on top of pledging to “significantly” reduce the country’s emissions in the next three decades, called for a global reduction of methane. “The fate of our entire planet, the development prospects of each country, the well-being and quality of life of people largely depend on the success of these efforts,” Mr. Putin said.

Separately, the United States Senate is expected to vote next week to reverse President Donald J. Trump’s effort to unravel restrictions on methane emissions that had been put in place during the Obama administration.

“Methane gets less attention than its big bad brother, carbon dioxide, but in truth methane is like carbon dioxide on steroids,” Senator Chuck Schumer, the majority leader, said on Thursday.

If the Senate does vote to reverse the policy, it could become the first official reinstatement of one of the many climate regulations that Mr. Trump weakened during his administration.

For scientists who have long focused on methane, its rising prominence in climate policy is a welcome development.

Greenhouse gases in the atmosphere warm the planet by acting like a blanket, trapping the sun’s heat. Carbon dioxide is the biggest driver of climate change, but methane is more potent in the shorter term, warming the atmosphere more than 80 times as much as the same amount of carbon dioxide does over a 20-year period.

That’s bad news, but it also means that cutting methane emissions may be one of the most effective ways to immediately slow rising global temperatures.

“You have a near immediate slowdown in the rate of warming,” said Ilissa B. Ocko, senior climate scientist at Environmental Defense Fund, whose own recent research found that going all-in on reducing methane emissions from the most polluting industries could slow the rate of global warming by 30 percent. “That’s really powerful.”

And while cutting down on carbon dioxide emissions will require sweeping changes to virtually every corner of the economy — replacing the world’s gasoline cars with electric ones, for example, and shuttering almost all of its coal-fired power plants — shrinking the world’s methane footprint might be an easier lift.

Unlike carbon dioxide or most other air pollution, methane isn’t released by burning fossil fuels, but comes from leaks and other releases from oil and gas infrastructure, among other sources. A growing body of research has shown that these oil and gas emissions are larger than previously thought, and a likely driver of the global increase of methane in the atmosphere.

“This means we need to place even more emphasis on the oil and gas sector,” said Robert Howarth, professor of ecology and environmental biology at Cornell University. He has argued that past assessments overestimated agricultural sources of methane, like cattle ranching, and underestimated emissions from fossil fuels, particularly oil and gas. “We need independent verification and monitoring of these emissions,” he said.

Fixing those leaks in theory should pay for themselves by saving money, because capturing the gas means companies capture more product. That potential makes plugging leaks from oil and gas infrastructure the most effective and cheapest way to slow emissions, the U.N. report says.

The world’s largest oil and gas companies pledged in 2018 to reduce the proportion of methane released from their operations by one fifth, to less than a quarter of a percentage of the gas they sell, by 2025 — a target the companies said they reached last year — with an ambition of achieving 0.2 percent.

Bjorn Otto Sverdrup, chairman of the executive committee of the Oil and Gas Climate Initiative, which represents 12 of the world’s biggest oil and gas producers, said the group “shares the determination to reduce methane emissions.”

He added, “We have made progress on the ambitions set only a few years back through new measurement and technologies, and we will continue to update our ambitions as we make progress.”

Minimizing methane from landfills also plays a role, as does lowering methane emissions from livestock. But emissions-reduction technologies are less certain in those fields. Releases from livestock, in particular, are expected to make up a growing share of future methane emissions unless there are technological breakthroughs, or the world’s top meat consumers change their diets.

Over all, more than half of global methane emissions stem from human activities in three sectors: fossil fuels, landfill and other waste, and livestock and other agriculture. Methane also seeps from wetlands and other natural sources.

The U.N. report also underscores how reducing methane emissions may bring significant public health benefits. Methane is an important contributor to the formation of ozone near the earth’s surface. Ozone is known to increase the risk of hospitalizations and early deaths. It also reduces crop yields and forest growth.

Rolling back methane emissions would prevent more than 250,000 premature deaths, and more than 750,000 asthma-related hospital visits, each year from 2030 onward, the report finds. The lower emissions would also prevent more than 70 billion hours of lost labor from extreme heat and more than 25 million tons of crop losses a year.

The flip side is that, with no action, methane emissions may help push the world to the brink of catastrophic climate change. If left unchecked, methane emissions are projected to continue rising through at least 2040, the U.N. report predicts.

“We’re still going wildly in the wrong direction, but we can turn that around very, very quickly,” Dr. Shindell said. “We could all use a climate success story.”

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