US Faces Chill While La Nina Typically Cools; Yet Earth Breaks Heat Record Again

January marked another month of record heat globally, even amidst an unusually cold spell in the United States, ongoing La Niña conditions, and projections of a slightly cooler 2025. The European climate service Copernicus reported this trend, revealing that January 2025 was 0.09 degrees Celsius (0.16 degrees Fahrenheit) warmer than January 2024, which had been the hottest January recorded prior.

The January heat records sparked discussion among climate scientists. A study led by former NASA scientist James Hansen asserts that global warming is accelerating, a claim that has sparked debate among experts. Copernicus noted that global temperatures for January were 1.75 degrees Celsius (3.15 degrees Fahrenheit) above pre-industrial levels, exceeding the critical threshold of 1.5 degrees Celsius for 18 of the last 19 months.

Historical data from Copernicus, which dates back to 1940, suggests we are in an unprecedented warming period, with other records extending back to 1850. This timeframe is thought to be the warmest in approximately 120,000 years, significantly influencing weather patterns worldwide.

The primary contributor to this increase in temperature remains the accumulation of greenhouse gases from fossil fuel combustion. However, the effects of natural cycles, particularly changes in the Pacific Ocean, have unexpectedly muted the warming effects, according to Samantha Burgess from the European weather agency. Traditionally, the El Niño cycle leads to spikes in global temperatures, but last year’s substantial El Niño ended in June.

Compounding these complexities, the La Niña phenomenon has emerged. While typically it could suppress record temperatures, Burgess points out that record warm ocean temperatures globally are still driving up heat levels. For Americans experiencing an unusually cold January, Burgess emphasizes the broader context: much of the planet was significantly warmer during this period.

Arctic conditions were particularly remarkable, with parts of the Canadian Arctic experiencing temperature anomalies of up to 30 degrees Celsius (54 degrees Fahrenheit) above average, causing localized sea ice melting. The month tied with the record for lowest sea ice extent, as noted by both Copernicus and the National Snow and Ice Data Center.

Despite February beginning on a cooler note, Hansen warns against dismissing 2025 in the contest for the hottest year record. His study indicates that warming over the last 15 years has occurred at twice the rate of the previous four decades. He believes this trend will persist, creating a competitive situation between 2024 and 2025.

Experts are divided on the implications of recent temperature trends. Hansen maintains that observed increases are significant, irrespective of El Niño’s variability, while some researchers, including those from Princeton and the University of Pennsylvania, question whether recent changes indicate a true acceleration in warming, emphasizing the need for more data to draw definitive conclusions.