2025 to be among top three warmest years on record, UN says

An alarming streak of exceptional temperatures is continuing, with 2025 set to be among the hottest years ever recorded, the United Nations said Thursday, insisting though that the trend could still be reversed.

While this year will not surpass 2024 as the hottest ever recorded, it will rank second or third, the UN's weather and climate agency said, capping more than a decade of unprecedented heat.

Meanwhile concentrations of greenhouse gases grew to new record highs, locking in more heat for the future, the World Meteorological Organization warned in a report released ahead of next week's COP30 UN climate summit in Brazil.

Together, the developments make "it clear that it will be virtually impossible to limit global warming to 1.5C in the next few years without temporarily overshooting this target," WMO chief Celeste Saulo said in a statement.

The 2015 Paris climate accords aimed to limit global warming to well below two degrees Celsius above pre-industrial levels -- and to 1.5C if possible.

Saulo insisted that while the situation was dire, "the science is equally clear that it's still entirely possible and essential to bring temperatures back down to 1.5C by the end of the century".

UN chief Antonio Guterres emphasised what was at stake.

"Each year above 1.5 degrees will hammer economies, deepen inequalities and inflict irreversible damage," he said in the report.

"We must act now, at great speed and scale, to make the overshoot as small, as short, and as safe as possible -- and bring temperatures back below 1.5C before the end of the century."

But the world remains far off track.

Already, the years between 2015 and 2025 will individually have been the warmest since observations began 176 years ago, WMO said.

And 2023, 2024 and 2025 figure at the very top of that ranking.

In Thursday's report, the WMO said that the mean near-surface temperature -- about two metres (six feet) above the ground -- during the first eight months of this year stood at 1.42C above the pre-industrial average.

At the same time, concentrations of heat-trapping greenhouse gases in the atmosphere and ocean heat content continued to rise this year, up from 2024's already record levels, it found.