Climate and environment researcher
Last month, January was the hottest January in the world, which recorded further questions about the pace of climate change, scientists say.
It was expected that January 2025 would be a little colder than January 2024. Due to deviations from the natural weather pattern in the Pacific known as El Niño.
But instead, last month he overthrew the record in January 2024.
World warming was due to the emissions of gases that heats the planet from human activities – mostly fossil fuel burning – but scientists say they cannot fully explain why it was particularly hot last month.
It continues a series of surprisingly large temperature records from mid -2023, with temperatures around 0.2 ° C above what was expected.
“The basic reason why we broke down the records and we had a long warning trend for decades, is that we increase the amount of greenhouse gases in the atmosphere,” Gavin Schmidt, Director of the NASA Institute for Space Studies, told BBC News.
“Specificities precisely why 2023 and 2024 and [the start of] 2025, they were so warm that other elements were included there. We try to score them. “
January 2025 ended 1.75C warmer than January of the end of the 19th century, before people began to significantly heat up the climate.
At the beginning of last year, global temperatures increased Natural Time Sample El Niñowhere unusually warm surface water spread across the eastern tropical Pacific Ocean. This releases extra warmth into the atmosphere, raising global temperatures.
This year, the conditions of La Niña develop instead, according to the American Science Group Noah, which should have the opposite effect.
Although La Niña is currently weak – and sometimes it takes several months to completely affect temperatures – it was expected to lead to colder January.
“If you had asked me a few months ago what it would look like in January 2025. Compared to January 2024, my best recording would be cooler,” said Adam Scaife, head of monthly predictions in decadal predictions in the UK office, he said.
“We know now that it’s not, and we don’t really know why it is.”
Numerous theories have been brought out why they have been warmer in recent years than predicted.
One idea includes the long-lasting response of the Ocean on El Niño 2023-24.
Although he was not particularly strong, he followed Unusually long-lasting phase La Niña from 2020-23.
The El Niño event may have “raised the lid” to warm up, allowing the oceanic warmth that accumulated to escape into the atmosphere.
But it is not clear how this would still directly affect global temperatures Almost a year after El Niño ended.
“Based on historical data, this effect will be reduced so far, so I think that if the current record continues, that explanation is becoming more likely,” says Prof. Scaife.
The fact that marine temperatures in other world regions remain a particularly warm one could suggest “to change the behavior of the ocean”, according to Samantha Burgess, deputy director of Copernicus.
“We really ask how to develop ocean temperatures because they have a direct effect on the air temperature.”
Another prominent theory is to reduce the number of small particles in the atmosphere, known as aerosols.
These small particles historically masked a part of long warming from greenhouse gases such as carbon dioxide and methane by helping the formation of bright clouds and reflecting some of the sun’s energy into space.
Aerosol numbers recently fall, thanks to reducing small particles from shipping and Chinese industry, for example, aimed at cleaning the air that people breathe.
But that means that they did not have such a large cooling effect to compensate for continuous heating caused by greenhouse gases.
And this Aerosol refrigerant was underestimated by the UN, according to James Hansen, a scientist who gave one of the first alerts of climate change in US Senate in 1988.
Most scientists are not yet convinced that this is the case. But if it is true, it could mean that there are major climate change in the trade than the previously assumed.
“The nightmare scenario,” says prof. Scaife, there would be additional feedback in the cloud, where heating ocean could cause a low -level reflective clouds to waste, in turn heating the planet further.
This theory is also very uncertain. But the months ahead should help illuminate whether “additional” heat in the last few years is a piston or indicates acceleration in heating outside what scientists have predicted.
Currently, most researchers are still expecting that 2025 will finish a little colder than 2023 and 2024 – but recent heat means I can’t be sure.
What they know, however, is that further records will follow sooner or later while humanity continues to heat the planet.
“Over time, 2025 will probably be one of the colder years we experience,” said Dr. Burgess.
“Unless we turn that touch on [greenhouse gas] Shows, then global temperatures will continue to grow. “
Graphics Erwan Rivault
