Climate Change: January 2025 heat record surpasses expectations despite US cold and La Niña influence

The planet recorded yet another monthly heat record in January, according to the Copernicus European climate service.
This happened despite unusually cold conditions in the United States, a cooling La Niña, and forecasts predicting a slightly cooler 2025. La Niña is a natural climate pattern that cools the central Pacific Ocean and usually helps lower global temperatures, but its influence wasn’t enough to prevent another record-breaking month.
Data shows January 2025 was 0.09°C warmer than January 2024, the previous hottest January, and 1.75°C above pre-industrial levels. Global temperatures have hit or passed the 1.5°C warming mark for 18 of the last 19 months. However, this limit is only officially broken if temperatures stay above it for 20 years.
Copernicus records start in 1940, but British and American data go back to 1850. Evidence from tree rings shows this is the warmest period in about 120,000 years.
Greenhouse gas emissions from fossil fuels remain the primary cause of record temperatures, although anticipated natural temperature influences have behaved unexpectedly, according to Samantha Burgess of the European weather agency.
Pacific Ocean temperature cycles typically influence global climate significantly. El Nino periods, characterised by warm central Pacific waters, typically lead to temperature spikes. Despite 2024’s substantial El Nino ending in June, temperatures exceeded expectations, setting new records.
La Nina typically moderates global warming effects. Following months of development, La Nina emerged in January, leading scientists to forecast lower temperatures for 2025 compared to 2024 and 2023.
Burgess notes that despite unfavourable Pacific conditions, record temperatures persist, largely due to unprecedented warmth in other oceanic regions.
The typical post-El Nino temperature decline hasn’t materialised, said Burgess’s as reported by the Associated Press.
Whilst Americans experienced a notably cold January, this represents only a small portion of Earth’s surface. Burgess explains that significantly larger areas experienced above-average temperatures.
The Arctic saw unusually mild conditions, with parts of the Canadian Arctic experiencing temperatures 30 C above average, causing sea ice to melt. Copernicus reported January Arctic sea ice matched the record low.
According to Burgess, February has begun cooler than last year.
The unexpected January heat record aligns with recent research by former Nasa scientist James Hansen and colleagues, suggesting an acceleration in global warming.
Hansen maintains 2025 could still become the warmest year. His research in Environment: Science and Policy for Sustainable Development indicates warming rates have doubled in the past 15 years compared to the previous 40.
Hansen expressed confidence in continued elevated warming rates. He noted recent shipping regulation changes reducing sunlight-reflecting sulfur pollution have contributed to warming.
Jonathan Overpeck from the University of Michigan describes the persistent record warmth as concerning. However, Princeton’s Gabe Vecchi and Pennsylvania’s Michael Mann dispute the acceleration theory, suggesting current temperatures align with existing climate models.