The world experienced its warmest January on record in 2025, raising fresh concerns about the pace of climate change. Scientists had expected temperatures to cool slightly compared to January 2024 due to a weakening El Niño pattern in the Pacific.
However, data from the European Copernicus Climate Service showed that last month exceeded the previous record by nearly 0.1°C. While greenhouse gas emissions from human activities remain the primary driver of global warming, researchers are struggling to explain why temperatures continue to rise so sharply.
The latest data continues a trend of unexpectedly high global temperatures since mid-2023, with figures about 0.2°C above projections. According to NASA’s Gavin Schmidt, the long-term warming trend is well understood, but the extreme warmth seen in 2023, 2024, and early 2025 involves additional, still-uncertain factors. January 2025 was 1.75°C warmer than the late 19th century, a stark reminder of the rapid changes underway.
Typically, the transition from El Niño to La Niña should bring cooler global temperatures, as La Niña is known for its cooling effects on the atmosphere. However, the expected cooling has not materialized. The UK Met Office’s Adam Scaife admitted that predictions had pointed to a cooler January, making the persistent warmth even more puzzling. This has led scientists to explore alternative explanations for the unexpected temperature records.
One theory suggests that the 2023-24 El Niño might have released stored ocean heat into the atmosphere, amplifying global temperatures. Since this El Niño followed an unusually long La Niña from 2020 to 2023, it may have triggered a delayed warming effect.
However, some scientists believe this explanation is losing credibility, as historical data indicates that the warming impact of El Niño should have faded by now.
Another potential factor is the continued rise in sea surface temperatures worldwide. Samantha Burgess of Copernicus highlighted how ocean temperatures play a critical role in influencing air temperatures. If the ocean’s behavior is changing, it could signal a more persistent and concerning trend in global warming.
The reduction of atmospheric aerosols—tiny particles that previously helped cool the planet by reflecting sunlight—could also be playing a role. Efforts to reduce air pollution, particularly from shipping and Chinese industry, have led to fewer aerosols in the atmosphere.
While this benefits air quality, it may also mean that less sunlight is being reflected, allowing more heat to accumulate in the atmosphere. Some scientists, such as James Hansen, argue that the cooling effect of aerosols has been underestimated, potentially accelerating climate change faster than expected.
Despite these uncertainties, one thing remains clear: record-breaking heat is becoming more frequent, and without a significant reduction in greenhouse gas emissions, the trend will continue. While some experts still expect 2025 to be slightly cooler than 2023 and 2024, the recent surge in temperatures has made predictions more difficult. Dr. Burgess warns that in the coming years, 2025 may be remembered as one of the cooler years in an increasingly warming world.
