January 2025 has been confirmed as the warmest January on record, surpassing the previous record set in January 2024 by nearly 0.1 degrees Celsius. The unexpected rise in global temperatures has left climate scientists searching for answers, as it defies earlier predictions that this year would be cooler due to the waning influence of El Niño.
The European Copernicus Climate Service reported that global temperatures last month were 1.75 degrees Celsius warmer than those of the late 19th century, before human-induced climate change significantly accelerated. Scientists widely acknowledge that greenhouse gas emissions from burning fossil fuels are the primary driver of global warming. However, they are struggling to explain why January 2025 was particularly warm, especially given the transition away from the warming effects of El Niño to the typically cooling influence of La Niña.
The unexpected warmth continues a trend of large temperature records since mid-2023, with global temperatures running around 0.2 degrees Celsius above what had been anticipated. Gavin Schmidt, director of the National Aeronautics and Space Administration’s Goddard Institute for Space Studies, stated that while the long-term warming trend is well understood, the extreme warmth of recent years suggests additional factors at play.
Early last year, global temperatures were influenced by El Niño, a natural climate pattern that results in unusually warm surface waters across the eastern tropical Pacific, releasing extra heat into the atmosphere. Now, La Niña conditions are developing, according to the United States National Oceanic and Atmospheric Administration, and should be exerting a cooling effect. However, the cooling expected from La Niña has not yet materialized, leaving scientists puzzled.
Adam Scaife, head of monthly to decadal predictions at the United Kingdom Met Office, admitted that previous forecasts suggested January 2025 would be cooler than January 2024. “We now know it isn’t, and we don’t really know why that is,” Adam Scaife said.
Several theories have been proposed to explain the persistent warmth. One hypothesis suggests that the 2023-2024 El Niño may have triggered a delayed ocean response, releasing stored heat accumulated during the preceding La Niña period from 2020 to 2023. However, scientists remain uncertain whether this effect could still be influencing global temperatures nearly a year after El Niño ended.
Another theory suggests that changes in ocean temperatures beyond the Pacific region could indicate a shift in oceanic behavior. Samantha Burgess, deputy director of the European Copernicus Climate Service, noted that “the behavior of the ocean is changing,” with persistently high sea surface temperatures contributing to warmer air temperatures.
A separate factor under consideration is the reduction in atmospheric aerosols—tiny particles that historically helped cool the planet by reflecting sunlight back into space. These aerosols, produced by industrial activity, have decreased in recent years due to stricter air quality regulations, particularly in the shipping industry and China. This reduction may have weakened their cooling effect, allowing greenhouse gas-induced warming to become more pronounced.
James Hansen, the climate scientist who first warned the United States Senate about global warming in 1988, has argued that the cooling effect of aerosols has been underestimated. If true, this could indicate that the planet is undergoing greater climate change than previously expected.
Some researchers have also raised concerns about a “nightmare scenario” in which warming oceans reduce the presence of low-level reflective clouds, leading to further warming. While this theory remains uncertain, scientists are closely monitoring developments in the coming months to determine whether the recent surge in temperatures is a temporary anomaly or marks an acceleration of climate change.
Despite the uncertainty, most scientists still expect 2025 to be slightly cooler than 2023 and 2024. However, the unexpected warmth of recent months has made future predictions less certain. What remains clear is that unless greenhouse gas emissions are significantly reduced, global temperatures will continue to rise.
“In time, 2025 is likely to be one of the cooler years that we experience,” Samantha Burgess stated. “Unless we turn off that tap to greenhouse gas emissions, then global temperatures will continue to rise.”
