The planet logged its third hottest year on record in 2025, extending a run of unprecedented heat, with no relief expected in 2026, global climate monitors said on Wednesday.

The last 11 years have now been the warmest ever recorded, with 2024 topping the podium and 2023 in second place, according to the EU's Copernicus Climate Change Service and Berkeley Earth, a California-based non-profit research organisation.

"The warming spike observed from 2023-2025 has been extreme, and suggests an acceleration in the rate of the Earth's warming," Berkeley Earth said in a separate report.

Despite the cooling La Nina weather phenomenon, 2025 "was still one of the warmest years on record globally because of the accumulation of heat-trapping greenhouse gases in our atmosphere", World Meteorological Organization Secretary-General Celeste Saulo said in a statement.

Berkeley and Copernicus both warned that 2026 would not break the trend.

If the warming El Nino weather phenomenon appears this year, "this could make 2026 another record-breaking year", Carlo Buontempo, director of the Copernicus Climate Change Service, said.

"Temperatures are going up. So we are bound to see new records. Whether it will be 2026, 2027, 2028 doesn't matter too much. The direction of travel is very, very clear," Buontempo said.

Berkeley Earth said it expects this year to be similar to 2025, "with the most likely outcome being approximately the fourth-warmest year since 1850". (AFP)