PARIS: Last month was the hottest January on record, blitzing the previous high and stunning climate scientists who expected cooler La Nina conditions to finally start quelling a long-running heat streak.
The Copernicus Climate Change Service said January was 1.75C hotter than pre-industrial times, extending a persistent run of historic highs over 2023 and 2024, as human-caused greenhouse gas emissions heat the planet.
Climate scientists had expected this exceptional spell to subside after a warming El Nino event peaked in January 2024 and conditions gradually shifted to a cooling La Nina phase.
But the heat has lingered at record or near-record levels ever since, sparking debate among scientists about what other factors could be driving warming to the top end of expectations.
Scientists warn that every fraction of a degree of warming increases the intensity and frequency of extreme weather events like heatwaves, heavy rainfall and droughts.
January was 0.09C hotter than the previous high of January 2024 — a “sizeable margin” in global temperature terms, said Julien Nicolas, a climate scientist from Copernicus.
“This is what makes it a bit of a surprise… you´re not seeing this cooling effect, or temporary brake at least, on the global temperature that we were expecting to see,” he told AFP.
Stefan Rahmstorf, from the University of Potsdam, said it was the first time that temperatures recorded during a La Nina period were above those of a preceding El Nino.
“This is of serious concern — over the past sixty years, all twenty five La Nina January´s have been cooler than surrounding years,” he said.
This year La Nina is expected to be weak and Copernicus said prevailing temperatures in parts of the equatorial Pacific Ocean suggested “a slowing or stalling of the move towards” the cooling phenomenon.
Nicolas said it could disappear completely by March.
Last month, Copernicus said that global temperatures averaged across 2023 and 2024 had exceeded 1.5 degrees Celsius for the first time. This did not constitute a permanent breach of the long-term 1.5C warming target under the Paris climate accord — but was a clear sign that the limit was being tested.
Overall, 2025 is not expected to follow 2023 and 2024 into the history books: scientists predict it will rank as the third hottest year yet.
Copernicus said it would be closely monitoring ocean temperatures throughout 2025 for hints about how the climate might behave.
