Global warming is now set to breach the 1.5C target limit set out in the 2015 Paris Agreement, after decades of insufficient climate action, the United Nations Environment Programme has warned. Temperatures could still be reduced, but only with far larger emissions cuts and the removal of vast amounts of carbon dioxide from the atmosphere using methods the UN says are "costly and risky".
The chances of keeping average warming to 1.5C have effectively vanished – at least temporarily – the UN Environment Programme (UNEP) said in its annual Emissions Gap Report published on Wednesday.
The report comes ahead of Cop31, the UN climate conference to be held in Antalya, Turkey next month. UNEP had already raised the prospect of an overshoot – temporarily exceeding the 1.5C limit before bringing temperatures back down – in its Limiting Overshoot report in September.
Average global warming is already around 1.4C above pre-industrial times, when economic development in the West began warming the planet. The past nine years have been the hottest on record.
The year 2024 was the first individual year to average more than 1.5C above pre-industrial levels, however the Paris Agreement target refers to long-term warming, typically measured over around 20 years.
In 2025, global emissions stood at 58.4 gigatonnes of CO2 equivalent, a measure used to compare the warming effect of different gases.
That total was roughly unchanged from 2024, but CO2 from fossil fuels, nitrous oxide and fluorinated gases are still rising, so it is too early to say emissions have peaked, UNEP warned.
Smaller releases from forest fires, after an exceptional 2024, offset those increases.
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'Imminent and unavoidable'
After decades of falling short on emissions cuts, a larger overshoot of the 1.5C limit is now “imminent and unavoidable”, the report said.
Passing 1.5C does not trigger a single sudden shift. Instead, each additional fraction of a degree adds to the damage, shrinking sea ice, thawing permafrost, killing corals and worsening droughts and fires, with knock-on effects on health and on food and energy prices.
The challenge is to keep warming well below 2C while limiting how far and how long temperatures overshoot 1.5C, with a credible return by the end of the century, the report said. Some changes, including glacier melt, cannot be reversed.
“Overshoot is not surrender. We can still keep it as small and as short as possible,” UN secretary-general Antonio Guterres said in a video message released with the report.
In the best-case scenario, warming would peak at 1.7 or 1.8C around the middle of this century before falling. This scenario gives an approximately 50 percent chance of returning to 1.5C or below by 2100. Emissions would have to fall by 18 percent by 2030, 45 percent by 2035 and 69 percent by 2040 – so almost 6 percent a year.
“This 18 percent reduction in greenhouse gas emissions makes complete sense. If we act very quickly, with political will and courage, it is entirely possible,” UNEP executive director Inger Andersen said at a press conference.
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Pledges off track
Even if governments fully implemented their national climate plans, emissions would fall by only 5-8 percent by 2030 and 11-15 percent by 2035, the report found.
Warming would still reach about 2.6C by the end of the century on that basis, or 2.8C under current policies. Without urgent action, keeping peak warming below 1.7 or 1.8C will soon become impossible.
Returning to 1.5C would also require cutting coal’s share of the world’s energy supply by 55 percent by 2035, oil by 15 percent and gas by 5 percent. Coal-fired electricity would need to be effectively phased out worldwide by 2040, even as China and India continue building new plants.
Methane, a powerful greenhouse gas, would need to fall at least 25 percent below 2025 levels by 2035 and at least 40 percent by 2040. Such cuts are within technical reach if governments find the will to repair leaks that satellites can now track.
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Carbon removal gamble
Deep emissions cuts would not be enough on their own. Bringing temperatures back down would also require removing CO2 already in the atmosphere.
The best-case pathway would require removing and storing about 320 gigatonnes of CO2 over the century, equivalent to roughly eight years of emissions.
Carbon could be removed through nature-based measures such as planting forests and improving wetland management, as well as technologies that capture emissions during energy production or remove CO2 directly from the air, report author Keywan Riahi explained.
But both natural and technological approaches may fail to remove carbon on the scale required. Climate change is weakening nature’s ability to absorb CO2, while technological solutions remain uncertain.
“All of those technologies come with risks,” said Riahi, director of the Energy, Climate and Environment Program at the International Institute for Applied Systems Analysis, an Austria-based research centre.
The aim should therefore be to keep the overshoot as low as possible so the world does not have to depend heavily on carbon-removal technologies later, he said.
UNEP had already warned in its September report that large-scale carbon removal carried major risks. “Removal on such a scale is costly and risky,” UNEP science advisor Anne Olhoff said.
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Solar boom, fossil reliance
One area in which progress has been made is clean energy. Solar power has expanded seven times faster than expected since the Paris Agreement, the report found, while renewables are on track to meet the goal of tripling global capacity by 2030.
Andersen said this showed climate policies can work, although clean-energy growth alone would not be enough.
Fossil-fuel use has not fallen at the same pace.
Oil, gas and coal still provide 80-86 percent of the world’s energy supply, while demand is rising with growth in emerging economies, electric vehicle sales and data centres. Reducing energy demand, which science recognises as an effective way to cut emissions, is not mentioned in the report.
Countries in attendance at the Cop28 UN climate summit in Dubai in 2023 agreed to transition away from fossil fuels in energy systems.
“Developing renewable energy is of course critically important, but we increasingly need to focus on phasing out fossil fuels. We are not seeing progress anywhere near what is needed,” Olhoff said.
This article was adapted from the original version in French by Géraud Bosman-Delzons.