WASHINGTON — Global greenhouse gas emissions have almost completely rebounded after slumping during the coronavirus pandemic, leaving the world with just 11 years of burning carbon at the current rate if humanity hopes to avoid catastrophic warming.

The latest Global Carbon Budget report comes in the middle of a high-stakes U.N. climate summit in Glasgow. Its findings, which draw upon atmospheric measurements, energy statistics and deforestation models, among other data, underscore just how far humanity must go to shift course on global warming.

The annual report is a joint project of researchers from 70 institutions on five continents. Since 2015, the project has tracked the dwindling amount of carbon dioxide humanity can afford to emit if it hopes to meet the Paris Agreement’s aim of limiting global temperature rise to 1.5 degrees Celsius (2.7 degrees Fahrenheit) above preindustrial levels.

Back then the quota was 903 gigatons — about 20 years’ worth of emissions. But annual production of greenhouse gases continued to increase, despite the global agreement to take action. In just six years, humanity burned through more than half of its remaining carbon allotment.

Corrine Le Quere, a climate scientist at the University of East Anglia and one of the report’s co-authors, said that only coordinated global action like the kind being negotiated at the COP26 summit in Glasgow can spur the change on the scale that is required.

“It’s really important what happens these next two weeks,” Le Quere said.

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Emissions from burning coal and natural gas reached even higher levels in 2021 than in 2019, scientists found. The leading cause of the surge was economic growth in China — the world’s top emitter, which gets the bulk of its energy from coal. India, another coal-dependent country, likewise saw a spike in emissions as its economy restarted.

Planet-warming pollution also grew 7.6% in the United States and the European Union, the second and third biggest sources of greenhouse gases. By the end of the year, total emissions from these regions are expected to be just a few percentage points below their pre-pandemic levels.

Despite some small signs of progress — renewable energy sources continued to grow, and the amount of carbon being taken up by restored forests and revitalized soils has increased — “all the emissions are back on their long-term trajectories,” Le Quere said.

“This is a reality check,” she added, for anyone who hoped that a year of historic social and economic upheaval would shake humanity out of its fossil fuel dependency.

The scattered corporate commitments and modest investments included in COVID-19 economic recovery packages were not sufficient to put the world on a more sustainable path. Nor do the voluntary pledges countries have submitted under the Paris accord add up to the reductions required.

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To have even a 50% chance of hitting that ambitious target, the world must immediately start cutting carbon dioxide emissions by about 1.4 gigatons per year, the equivalent of planting about 21 billion trees annually.

Emissions from coal and gas are now 1% and 2% higher, respectively, than before the pandemic began, the carbon budget report found. Oil-associated emissions remain slightly lower than they were pre-COVID because of the relatively slow rebound of the transportation sector. But this number could also rise as more people book air travel and hit the roads.

“We are still waiting to see the implementation of climate policies across the world that would actually bend the curve,” said University of Exeter climate scientist Pierre Friedlingstein, the lead author of the carbon budget.

The researchers did not expect 2020’s unprecedented 5.4% drop in emissions to last: COVID shutdowns are not the same thing as climate policy, they said.

But this year’s surge shows that the pandemic was not a turning point. In their haste to jump-start their economies, most countries turned right back to the cheapest and easiest fuels available, regardless of the climate toll.

A separate report from Energy Policy Tracker, a consortium of nonprofit and academic researchers, found that the world’s 20 biggest economies have directed at least $318 billion toward the fossil fuel industry as part of their pandemic response. By contrast, those same countries have dedicated about $279 billion in support of clean energy.

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The United States is among the worst offenders, according to the report: Since January 2020, more than 70% of public finance for the energy industry has gone to fossil fuels.

In China, Le Quere said, the flood of economic recovery funds seems to have accelerated emissions. The country was among the only places in the world where carbon pollution did not fall last year, and the reliance on coal to power industrial production means that emissions now are higher than they might have been had the pandemic not occurred.

Even as emissions spiked in 2021, this year has seen a flurry of new commitments to reduce greenhouse gases. G-20 governments agreed to stop public financing for overseas coal plants. As of Tuesday, more than 100 countries have pledged to curb emissions of methane, which is 80 times more potent than carbon dioxide over a 20-year span.

It is still technically possible for the world to limit warming to 1.5 degrees Celsius above preindustrial levels, Le Quere said. She pointed to one bright spot of the carbon budget report: Emissions declined over the past decade in 23 countries whose economies were growing before the pandemic. Most were wealthy European countries, but the list also included the United States, Mexico, Barbados and Tuvalu.

“These successes can be replicated,” Le Quere said. “There is no reason why this cannot be set in motion other than political will.”

But given the fraught COP26 negotiations over emissions reduction strategies and funding to help more vulnerable countries adapt, experts are increasingly pessimistic that the world will act in time to minimize climate impacts.

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Harjeet Singh, a New Delhi-based senior adviser for Climate Action Network International, said the disparity between the world’s emissions pledges and humanity’s remaining carbon budget shows a fundamental weakness in the structure of the Paris Agreement.

Allowing countries to determine their own contributions to global climate efforts, he said, means “we’re only talking about what we want to do, not about what needs to done.”

Meanwhile, the chances hitting the 1.5 degree target grow more and more slim — forcing governments, scientists and advocacy groups alike to consider a future that is far different from the world we live in now.

If warming reaches 2 degrees Celsius (3.6 degrees Fahrenheit), one in three people will experience regular severe heat waves, according to UN scientists. Coral reefs will be almost completely obliterated. The yields of important food crops will decline 7%.

But countries’ current climate commitments would push the planet past that point, reaching 2.7 degrees Celsius (4.9 degrees Fahrenheit) of warming by the end of the decade, the U.N. has found. At that point, humanity risks triggering permanent loss of species, inexorable ice sheet melt and catastrophic sea level rise. Deadly weather disasters, chronic food and water shortages and intolerable heat will become fixtures of life for much of the world.

“It isn’t, ‘1.5 or we are doomed,'” Friedlingstein said. Humanity can and probably will have to adapt to an even warmer planet. “But people shouldn’t think we can get to 2.7 degrees and be fine. It will not be fine.”