Rising emissions and temperatures: The cost of Trump's climate retreat is now clear

For over a decade, scientists have warned the world must limit global warming to 1.5 degrees Celsius (2.7 Fahrenheit) to avoid the most severe consequences of climate change.

Decades of "insufficient" action on cutting the fossil fuel emissions heating the planet means overshooting 1.5-degree temperature threshold is now "imminent and unavoidable," according to the United Nations Environment Program's (UNEP) annual Emissions Gap Report.

If current climate policies continue, temperatures will rise by an average of 2.8 degrees Celsius above pre-industrial levels within this century. But even if countries meet their new climate pledges, global warming is still projected to reach 2.6 degrees Celsius. Both scenarios would tip the world into a period of catastrophic weather extremes.

The projections reflect a gap between what governments promise to do and the action they are taking to curb emissions. Some 167 countries have submitted climate action plans to the UN, covering 83% of global greenhouse gas emissions. But those pledges to cut emissions fall far short of what is needed to limit warming.

Among the world's largest emitters, Indonesia, China and the United States saw emissions rise in 2025, according to preliminary estimates. The increase in the US "far exceeded that of all other countries," driven by a resurgence of coal — the dirtiest fossil fuel source — and rising electricity demand, partly linked to massive AI data center expansion.

The outlook has worsened in part because of US President Donald Trump's withdrawal of the United States from the historic Paris climate accord in which the world came together in 2015 to agree to halt climate change. The US is the second-largest annual emitter of climate-warping greenhouse gases.

Since Trump entered the Oval Office for a second time, his administration has taken a sledgehammer to climate policy, gutting environmental regulations and expanding oil and gas production.

"The main takeaway is simple — governments need to get on with enacting policies that cut fossil fuel use as soon as possible," said Bill Hare, CEO of the global science and policy institute Climate Analytics, of the report.

Exceeding 1.5 degrees Celsius even temporarily sets humanity on a dangerous course, as it increases the risk of triggering potentially irreversible or difficult-to-undo "tipping points," like the loss of coral reefs, long-term retreat of ice sheets, and the Amazon Rainforest turning into a grassland.

As ecosystems disappear and sea levels rise, these changes could trigger a deadly chain reaction, releasing more greenhouse gases and accelerating warming, dramatically increasing the likelihood of deadly extreme weather.

This summer alone, Europe recorded more than 32,000 excess deaths related to heat and nearly 1,500 people died in a flash floods in Nepal and Tibet, after climate change laid the groundwork for a glacier to collapse.

But scientists maintain 1.5 degrees Celsius is not a magic number, and that every fraction of a degree of warming brings escalating risks. To reduce the risk of future damage, countries should still focus on rapidly transitioning away from fossil fuels, the largest contributor to global climate change, and toward renewable energy like solar and wind.

Now the best-case scenario is overshooting 1.5 degrees Celsius for a short time before bringing temperatures back down quickly.

"Overshoot is not surrender," UN Secretary-General Antonio Guterres said in a press statement. "We can still keep it as small and as short as possible — and bring temperatures back below 1.5 degrees before the end of the century."

UNEP lays out a scenario in which the world sees warming peak at 1.7 to 1.8 degrees Celsius around mid-century, before falling back to 1.5 Celsius by 2100. Getting there would require steep emissions cuts of 69% by 2040, relative to 2025 levels.

It would also require removing 330 billion metric tons of carbon dioxide from the atmosphere and storing it in the ground. But recent studies have cast doubt on the feasibility and costs of the technology, as well as the nascent carbon removal industry's ability to scale as quickly as required to meet climate goals.

The UN warns any delays will make the challenge harder, saying that every five years that emissions remain at current levels adds about 0.1 Celsius to projected peak warming.

"We must pull out all the stops to minimize peak warming and return to 1.5 Celsius by the end of the century," Inger Andersen, Executive Director of UNEP, said in a press release. "This is possible."

Still, climate policies have proven effective in reducing emissions. The UNEP report draws on more than 200 studies that analyze how measures like carbon taxes, government climate targets, building codes and subsidies for low-carbon technologies are working.

Carbon-pricing schemes have been the most widely studied so far. China's pilot schemes reduced emissions by about 11%, while the European Union's emissions trading system saw an 8% cut, compared with projected levels without these policies.

"There are more opportunities than ever to accelerate action," according to the report, pointing to the boom in renewable energy since the adoption of the Paris Agreement a decade ago.

Global renewable electricity capacity has grown three times faster than anticipated, and solar build-out grew seven times faster. In 2024, more than 90% of renewable projects were cheaper than fossil fuel alternatives.

While total energy supply from coal, oil and gas has continued to rise, that's happened at a slower rate than was projected in 2015. And coal use is likely to peak and decline by the end of the decade.

"We have a wealth of success stories showing that emissions can be cut quickly," Andersen said. "It is now up to nations to urgently put in place policies that spark fast, deep and sustained emissions reductions, and put the world on track for a more stable climate and more stable economies and societies."