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BELEM, Brazil — For each of the past several years, scientists, analysts and officials have been hoping that it would be the year when emissions from the burning of coal, oil and natural gas would stop going up.
They'll have to wait another year.
For the second straight year, emissions from fossil fuels rose 1.1% in 2025, scientists reported Wednesday at United Nations climate negotiations. It's not a big jump. It's one of the smallest in recent non-pandemic years. But negotiators gathering for the COP30 conference on the edge of the Amazon are trying to curb warming global temperatures by getting fossil fuel emissions to stop rising and then plunge.
"It's disappointing that we haven't brought down carbon dioxide emissions," said University of Exeter scientist Stephen Sitch, a member of the Global Carbon Project, which uses data from around the world to calculate the yearly emissions figure and publishes it in two scientific journals. His colleague, Glen Peters of CICERO Center for International Climate Research in Norway, called carbon emissions increase "relentless."
A second report from a different scientific group examined how much warming the world is on track for, given this year's carbon emissions and governmental policies. The report by Climate Action Tracker shows the last four years of climate fighting efforts haven't much changed projections for a hotter future. In fact, the scientists found that actions by President Donald Trump's administration this year have added a bit more warmth to their projections.
"Unless there's a change in political momentum, we're going to cook. There's no doubt about it," said Climate Analytics CEO Bill Hare, one of the report's authors.
Climate Action Tracker said the world is now on target for 4.7 degrees Fahrenheit of warming above mid-1800s levels, a slight drop from last year's projections of 4.9 degrees Fahrenheit, but most of that drop was from changes in the way scientists looked at China's numbers, not that much from new policies put in place.
The 2015 Paris Agreement set an international goal of limiting warming to 2.7 degrees Fahrenheit since the mid-1800s.
Climate Action Tracker also looked at projections based on each country's climate-fighting plan submitted this year, leading up to the climate conference in Belem, Brazil. The future based on those pledges looks a tenth of a degree warmer than it did a year ago, according to their report. Much of that is the result of Trump's dismantling of American pollution-fighting efforts, said Ana Missirliu of the NewClimate Institute, an author of the report.
If countries do what they promise, the world is heading to 2.2 degrees Celsius (4 degrees Fahrenheit) of warming above 1800s levels, the report said.
Experts at the climate conference said they see hope and progress, but the emission numbers from this year still hurt.
"When I hear that emissions are still going up, I'm truly troubled," said former German top climate negotiator Jennifer Morgan.
The carbon project scientists projected that this year, the burning of fossil fuels and the making of cement will have put another 42 billion tons of carbon dioxide in the air. That's the equivalent of nearly 2.7 million pounds of heat-trapping gas going into the air every second.
It's more than double the emissions the world put up in 1983.
One bright point is that 35 countries cut their fossil fuel emissions from last year and were still thriving economically, Sitch said. But at the same time, the United States, which used to be cutting fossil fuel carbon dioxide emissions, spewed 2% more pollution in 2025 than in 2024.
China stayed the same as the year before, giving scientists and analysts hope that emissions from the No. 1 carbon polluting country may have peaked.
Aviation pollution went up 6.8% from 2024 to 2025, the report said.
And the slight rise in carbon pollution from fossil fuels was balanced out by a big drop in deforestation and other land use changes. Between land use and fossil fuels, Earth's overall emissions were about the same as in 2024, the report said.
Contributing: Melina Walling
