Even as much of the US shivered under frigid conditions last month, the planet as a whole had its warmest January on record, scientists said on Thursday.

The warmth came as something of a surprise to climate researchers. It occurred during La Niña conditions in the Pacific Ocean, which tend to lower the globe’s average temperature, at least temporarily.

Earth’s surface has now been so warm for so much of the past two years that scientists are examining whether something else in the planet’s chemistry might have changed, something that is boosting temperatures beyond what carbon emissions alone can explain. Those emissions, the byproduct of burning coal, gas and oil, remain the main driver of global warming, which reached record levels in both 2023 and 2024.

It’s because of La Niña that scientists expected this year to be slightly cooler than the past two years, both of which experienced the opposite pattern, El Niño. The waters of the eastern tropical Pacific oscillate between El Niño and La Niña conditions, influencing weather worldwide by changing the balance between heat in the ocean and heat in the air.

But a host of other factors figure into global temperatures as well. At the moment, chances aren’t high that 2025 will end up being the hottest year on the books, Russell Vose, a climate scientist at the National Oceanic and Atmospheric Administration, told reporters recently. But this time last year, researchers were saying much the same thing about 2024, Dr Vose said. They were wrong. “So it’s a tough game, forecasting global temperature,” Dr Vose said.

New York Times News Service