The amount of heat trapped by the Earth reached record levels in 2025, with the consequences of such warming feared to last for thousands of years, the United Nations warned on Monday.

The 11 hottest years ever recorded were all between 2015 and 2025, the UN's World Meteorological Organisation (WMO) confirmed in its flagship State of the Global Climate annual report.

Last year was the second or third hottest year on record, at about 1.43 Celsius above the 1850-1900 average, the WMO said.

"The global climate is in a state of emergency. Planet Earth is being pushed beyond its limits. Every key climate indicator is flashing red," said UN Secretary-General Antonio Guterres.

"Humanity has just endured the 11 hottest years on record. When history repeats itself 11 times, it is no longer a coincidence. It is a call to action."

For the first time, the WMO climate report includes the planet's energy imbalance: the rate at which energy enters and leaves the Earth system.

Under a stable climate, incoming energy from the sun is about the same as the amount of outgoing energy, the Geneva-based agency said.

However the increase in concentrations of heat-trapping greenhouse gases – carbon dioxide, methane and nitrous oxide – "to their highest level in at least 800,000 years" has "upset this equilibrium", the WMO said.

"The Earth's energy imbalance has increased since its observational record began in 1960, particularly in the past 20 years. It reached a new high in 2025."

"Human activities are increasingly disrupting the natural equilibrium and we will live with these consequences for hundreds and thousands of years," WMO chief Celeste Saulo said.

More than 91 percent of the excess heat is stored in the ocean.

"Ocean heat content reached a new record high in 2025 and its rate of warming more than doubled from 1960-2005 to 2005-2025," the WMO said.

Ocean warming has far-reaching consequences, such as degradation of marine ecosystems, biodiversity loss and reduction of the ocean carbon sink, the agency said.

"It fuels tropical and subtropical storms and exacerbates ongoing sea-ice loss in the polar regions."

The Antarctic and Greenland ice sheets have both lost considerable mass, and the annual average extent of Arctic sea ice in 2025 was the lowest or second-lowest ever recorded in the satellite era.

Last year, the global mean sea level was around 11 centimetres higher than when satellite altimetry records began in 1993.

Ocean warming and sea level rise are projected to continue for centuries. (AFP)


Edited by Tony Sabine