Hottest January on the Books Stumps Scientists

The world warmed to yet another monthly heat record in January, despite an abnormally chilly US, a cooling La Nina, and predictions of a slightly less-hot 2025, per European climate service Copernicus. The surprising January heat record coincides with a new study by a climate science heavyweight, former top NASA scientist James Hansen, and others arguing that global warming is accelerating—a claim dividing the research community, per the AP.

• Last month globally was 0.09 degrees Celsius (or 0.16 degrees Fahrenheit) warmer than January 2024, the previous hottest January, and was 1.75 C (3.15 F) warmer than it was before industrial times, according to Copernicus. It was the 18th month of the last 19 that the world hit or passed the internationally agreed-upon warming limit of 1.5 C (2.7 F) above preindustrial times.

• Scientists won't regard the limit as breached until global temperatures stay above it for 20 years. Copernicus records date to 1940, but other US and British records go back to 1850, and scientists using proxies such as tree rings say this era is the warmest in about 120,000 years, or since the start of human civilization.
• By far the biggest driver of record heat is greenhouse gas buildup from the burning of fossil fuels, but natural contributions to temperature change haven't been acting quite as expected, said Copernicus rep Samantha Burgess.
• Last year was a substantial El Nino, though it ended last June, and the year was the hottest on record.
• El Nino's cooler flip side, La Nina, tends to dampen the effects of global warming, making record temperatures far less likely. Just last month, climate scientists were predicting that 2025 wouldn't be as hot as 2024 or 2023, with La Nina a major reason. Usually after an El Nino like last year, temperatures fall rapidly, but "we've not seen that," Burgess said.
• For Americans, news of a record warm January might seem odd given how cold it's been. But the US is just a tiny fraction of the planet's surface, and "a much larger area of the planet's surface was much, much warmer than average," Burgess noted. February, however, has already started off cooler than last year, she added.

More here. (More global warming stories.)