LONDON — The United Nations warned Friday that based on the most recent action plans submitted by 191 countries to curb greenhouse gas emissions, the planet is on track to warm by more than 2.7 degrees Celsius by the end of the century — far above what world leaders have said is the acceptable upper limit of global warming.

Even a lower increase would mean millions of people losing their homes to rising seas, vast sections of permafrost lost and extinction for scores of animal species.

The report set the stakes as President Biden gathered the world’s biggest emitters to the White House on Friday to try reach an agreement among some of them to cut methane — a potent greenhouse gas — by 30 percent by 2030.

The U.N. report said that it had received 86 new plans — known as nationally determined contributions or NDCs — but that as of the end of July, nearly as many countries had still not stepped forward with new road maps. The plans submitted thus far would, if implemented, lead to a 12 percent reduction in their greenhouse gases by 2030 compared with 2010.

But the U.N. warned that if other nations — including China and India — did not submit new, more ambitious plans and continued on their current paths, greenhouse gas emissions would increase by 16 percent by the end of the decade. That would put the planet on a trajectory to warm by 2.7 degrees Celsius (4.9 degrees Fahrenheit) by the end of the century compared with the end of the 1800s.

Patricia Espinosa, executive secretary of U.N. Climate Change, called the numbers “sobering.” In a news conference Friday marking the release of the report, she said, “It is not enough, what we have on the table.”

“The 16 percent increase is a huge cause of concern,” she said. “It is in sharp contrast with the calls by science for rapid, sustained and large-scale emission reductions to prevent the most severe climate consequences and suffering, especially of the most vulnerable, throughout the world.”

In its most recent landmark report in August, the Intergovernmental Panel on Climate Change estimated that limiting global average temperature increases to 1.5C requires a 45 percent reduction in CO2 emissions by 2030, or a 25 percent reduction by 2030 to limit warming to 2C.

Many of the biggest emitters, such as China, India and Turkey, have yet to formally commit to a 2030 emissions reduction target. Equally worrying, Brazil and Mexico both put forward weaker emissions targets than the ones they submitted five years ago. Russia said it could emit more in 2030 than it does now.

The disappointing reality — captured in this snapshot of how plans fail to meet goals — comes ahead of the White House meeting Friday and the U.N. General Assembly gathering next week.

On Friday, Biden urged a group of foreign leaders to sign onto the pledge to cut global methane emissions by about a third by 2030.

“Without adequate commitments from every nation in this room, the goal of limiting warming to 1.5 degrees slips through our hands and that’s a disaster,” Biden said.

Methane is the world’s second-most prevalent greenhouse gas and, in the short term, is about 85 times more potent than carbon dioxide in warming the planet.

As atmospheric concentrations of methane have continued to soar in recent years, international climate negotiators and scientists have focused more than ever on finding ways to rein in the powerful gas.

Biden, who was joined by Secretary of State Antony Blinken and U.S. climate envoy John F. Kerry, said he called the meeting “to candidly assess our progress” ahead of the U.N. global climate summit in Glasgow, Scotland, in early November.

Biden has spent much of the last two weeks focused on climate change, traveling around the United States to visit areas devastated by extreme-weather events. He has underscored that the country faces a “code red” moment, as he pushes an expansive economic agenda that includes billions of dollars to combat the impacts of the warming planet.

In his remarks, Blinken highlighted findings from a report last month by the U.N. Intergovernmental Panel on Climate Change that he said provided “irrefutable evidence of the crisis now upon us.”

“No challenge will have a more significant impact on the world or require a greater level of international cooperation,” he said. “And no challenge ranks higher on the list of global priorities for this administration.”

Espinosa said she hoped to see more nations submit plans with more ambitious targets before the summit in Scotland. Japan and South Korea will submit new, more ambitious goals in the coming weeks.

She said that there is still time and that her U.N. group will issue another report synthesizing the commitments before the Glasgow negotiations begin.

U.N. Secretary General António Guterres in a statement said, “The world is on a catastrophic pathway to 2.7-degrees of heating.”

He warned that “there is high risk of failure” at the coming climate summit.

“It is clear that everyone must assume their responsibilities,” he said, stressing that the world’s wealthiest countries must fulfill long-standing pledges to provide $100 billion a year to support developing countries trying to reduce their own emissions and prepare for a warmer world with more droughts and flooding.

The planet has already warmed by over 1 degree Celsius since the dawn of the industrial revolution.

The U.N. synthesis released on Friday, based on the national plans, concluded that “unless actions are taken immediately,” the projected emissions “may lead to a temperature rise of about 2.7C by the end of the century.”

Alok Sharma, the British government minister who will serve as president of the meeting in Glasgow, said in a statement: “This report is clear: ambitious climate action can avoid the most devastating effects of climate change, but only if all nations act together. Those nations which have submitted new and ambitious climate plans are already bending the curve of emissions downwards. But without action from all countries, especially the biggest economies, these efforts risk being in vain.”

Pager reported from Washington. Brady Dennis and John Wagner contributed to this report.