Losing more ground in the fight against climate change, humanity is heading for a hotter world than experts projected last year - and the United States is a big reason for that, a new United Nations report says.
If all the countries do what they promise to reduce heat-trapping emissions, Earth will likely still warm another 2.2 degrees Fahrenheit (1.2 degrees Celsius) above current temperatures, according to Wednesday's update of climate calculations by the United Nations Environment Programme. That's about two-tenths of a degree Fahrenheit (0.1 degrees Celsius) more than last year's projections by the same science team.
"This is a worse outcome than expected last year, as a result of the formal withdrawal of the United States of America from the Paris Agreement and revised estimates of historical emissions," the report said. The report also blames the United States for increased emissions last year, saying all the other top 20 major economies reduced their carbon pollution or at least slowed the growth in how much carbon dioxide was spewed from the burning of coal, oil and gas.
"In terms of magnitude, the increase in the United States of America (133 megatons of CO2 equivalent) far exceeded that of all other countries and was driven by increased electricity demand and a rebound of coal power generation," the report said. The 124 countries that increased emissions - not counting the 63 that decreased like most European nations - added 400 million tons of carbon dioxide in 2025, and 33% of that increase came from the U.S., according to the report.
The United States is going "hell-for-leather trying to block renewables while actively promoting and subsidizing dirty coal - and its diplomacy is trying to make other countries also pull back on action. It is looking at the fire, denying there is a fire, and then pouring more petrol on it," said Australian climate scientist Bill Hare, CEO of Climate Analytics, which measures countries' climate fighting plans. He wasn't part of the U.N. report but, like several other outside scientists, said it was scientifically sound.
Shooting far past Paris climate goal
The new calculations say that if countries do all they promise in the climate fighting plans they submitted to the United Nations, by 2100 the globe will be 2.6 degrees Celsius (4.7 degrees Fahrenheit) hotter than pre-industrial times. If the world continues on its current path - without national promises - it will be 2.8 degrees Celsius (5 degrees Fahrenheit) warmer than the last half of the 19th century, the same as last year's projection.
Both of those temperatures blow far past the goal of less than 2 degrees Celsius (3.6 degrees Fahrenheit) and preferably 1.5 degrees Celsius (2.7 degrees Fahrenheit) adopted by the 2015 Paris climate pact. The world is now at about 1.4 degrees Celsius (2.5 degrees Fahrenheit) above pre-industrial times and earlier this year - and again in this report - United Nations officials conceded that there is no way of limiting warming to the 1.5-degree goal that they had embraced. Instead, officials are pinning their hopes of limiting warming to about 1.8 degrees Celsius (3.2 degrees Fahrenheit) and then somehow pulling enough carbon dioxide out of the air to lower temperatures back down to 1.5 degrees.
The world is falling "dangerously short" of even those goals, United Nations Secretary-General António Guterres said, "but we have the tools to change course and pull back from the brink."
Drastically cutting global carbon emissions - by 18% by 2030 and 69% by 2040 - "is the only way that we can get back to a semblance of a reality that is still largely manageable without major impacts and therefore that makes every sense," said UNEP Executive Director Inger Andersen.
"The report's message is clear," said climate scientist Adelle Thomas, vice chair of a United Nations scientific assessment on climate impacts. She wasn't part of this study. "We know what needs to be done. We have the tools to do it. And delay only makes the challenge more dangerous and more expensive for all."
An added tenth of a degree of danger
Report lead author Anne Olhoff, director of UNEP Copenhagen Climate Centre, said the U.S. policy change will likely add one-tenth of a degree Celsius (nearly two-tenths of a degree Fahrenheit) to global temperatures by the end of the century.
"This report shows that America's retreat isn't just a political embarrassment. It has real consequences for the planet and for millions of people around the world," said Mohamed Adow, director of Power Shift Africa, a climate organization. "An extra tenth of a degree might sound insignificant, but in climate terms it is enormous. It means more dangerous heat waves, more destructive floods, more failed harvests and more lives lost. For vulnerable communities in Africa, already living on the front lines of the climate crisis, every fraction of a degree matters. These are not abstract numbers. They are human lives."
Hare said that extra one-tenth of a degree pushes an additional 140 million people "into dangerously hot conditions" and increases the odds of the collapse of the Amazon rainforest or ice sheets in Greenland and Antarctica. It also would cost the world and shave about $1.2 trillion from the global economy, said University of Pennsylvania climate scientist Michael Mann.
And the U.S. effect is probably even bigger than what the United Nations calculates because if the world's largest historical climate polluter doesn't do much to fight global warming other nations ease off in their efforts too, said Johan Rockstrom, director of the Potsdam Institute for Climate Impacts Research in Germany.
"The rest of the world is exhausted when it comes to counting the damage that the U.S. is willingly doing to allies, multilateral structures, economic cooperation, disaster relief," Australian climate scientist Malte Meinshausen said. "The rest of the world should probably continue to focus even less on the U.S."
