Brussels: Last month was the hottest January on record, Europe’s climate monitor reported, despite expectations that cooler La Nina conditions might halt a streak of record-breaking global temperatures.
According to Bangladesh Sangbad Sangstha, the Copernicus Climate Change Service revealed that January was 1.75°C hotter than pre-industrial times, continuing a persistent trend of historic highs over 2023 and 2024, as human-caused greenhouse gas emissions heat the planet.
Climate scientists had anticipated this exceptional period to diminish following a warming El Nino event that peaked in January 2024, with conditions gradually transitioning to a cooling La Nina phase. However, the heat has persisted at record or near-record levels, prompting debate among scientists about what additional factors could be contributing to warming at the higher end of expectations.
Julien Nicolas, a climate scientist from Copernicus, explained, “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.” La Nina is predicted to be weak, with Copernicus noting that prevailing temperatures in parts of the equatorial Pacific Ocean suggested “a slowing or stalling of the move towards” the cooling phenomenon. Nicolas mentioned it could disappear entirely by March.
Scientists caution that every fraction of a degree of warming amplifies the intensity and frequency of extreme weather events such as heatwaves, heavy rainfall, and droughts. Last month, Copernicus indicated that global temperatures averaged across 2023 and 2024 had surpassed 1.5 degrees Celsius for the first time. This did not constitute a permanent breach of the long-term 1.5°C warming target under the Paris climate accord but was a clear indicator that the limit was being tested.
Copernicus reported that Arctic sea ice in January reached a monthly record low, virtually tied with 2018. Analysis from the United States this week ranked it as the second-lowest in that dataset. 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 stated it would closely monitor ocean temperatures throughout 2025 for insights into future climate behavior.
Oceans serve as vital climate regulators and carbon sinks, with cooler waters capable of absorbing greater amounts of heat from the atmosphere, thereby helping to reduce air temperatures. They also store 90 percent of the excess heat trapped by humanity’s release of greenhouse gases. Nicolas noted, “This heat is bound to resurface periodically… I think that’s also one of the questions — is this what has been happening over the past couple of years?”
Sea surface temperatures have been exceptionally warm over 2023 and 2024, with Copernicus reporting January readings as the second highest on record. Nicolas remarked, “That is the thing that is a little puzzling — why they remain so warm.”
Bill McGuire, a climate scientist from University College London, described it as “astonishing and frankly terrifying” that January remained at record highs despite La Nina’s emergence. Joel Hirschi, from the UK’s National Oceanography Centre, noted that record warmth persisting into La Nina was not unprecedented, citing similar patterns after recent El Nino phases. He advised caution in interpreting a single month’s data, stating, “Global sea surface temperatures are a bit lower than in 2024 and will likely remain lower as we move further into 2025.”
Scientists agree that burning fossil fuels has significantly contributed to long-term global warming, and natural climate variability can also influence temperatures from year to year. However, natural warming cycles like El Nino could not alone explain the atmospheric and oceanic changes, prompting investigations into other factors.
One theory suggests that a global shift to cleaner shipping fuels in 2020 accelerated warming by reducing sulphur emissions, which make clouds more reflective of sunlight. In December, a peer-reviewed paper examined whether a reduction in low-lying clouds allowed more heat to reach Earth’s surface. Nicolas stated, “It’s really still a matter of debate.”
The EU monitor employs billions of measurements from satellites, ships, aircraft, and weather stations to support its climate calculations. Its records date back to 1940, but other sources of climate data — such as ice cores, tree rings, and coral skeletons — enable scientists to extend their conclusions using evidence from much further in the past. Scientists assert that the current period is likely the warmest the Earth has been for the last 125,000 years.