Hottest January on record mystifies climate scientists | Climate crisis | The Guardianhttps://www.theguardian.com/environment/2025/feb/06/hottest-january-on-record-climate-scientists-global-temperatures-highJanuary marked the 18th month of the past 19 to record global-average surface temperatures above the 1.5C preindustrial level.
Climate scientists had expected this exceptional spell to subside after a warming El Niño event peaked in January 2024 and conditions shifted to an opposing, cooling La Niña phase.
But the heat has lingered at record or near-record levels, prompting debate about what other factors could be driving it to the top end of expectations.
Julien Nicolas, a climate scientist at Copernicus, told Agence France-Presse: “This is what makes it a bit of a surprise: you’re not seeing this cooling effect, or temporary brake at least, on the global temperature that we were expecting to see.”
One theory is that a global shift to cleaner shipping fuels in 2020 accelerated warming by reducing sulphur emissions that make clouds more mirror-like and reflective of sunlight.
In December, another peer-reviewed paper looked at whether a reduction in low-lying clouds had let more heat reach the Earth’s surface. “It’s really still a matter of debate,” Nicolas said.