Climate puzzle persists with unexpectedly warm January

The fact that sea temperatures in other regions of the world remain particularly warm could suggest “that the behaviour of the ocean is changing”, according to Samantha Burgess, deputy director of Copernicus.

“We’re really looking to see how the ocean temperatures evolve because they have a direct influence on air temperatures.”

Another prominent theory is a reduction in the number of small particles in the atmosphere, known as aerosols.

These tiny particles have historically masked some of the long-term warming from greenhouse gases like carbon dioxide and methane by helping to form bright clouds and reflecting some of the Sun’s energy back into space.

Aerosol numbers have been falling recently, thanks to reductions in tiny particles from shipping and Chinese industry, for example, aimed at cleaning the air that people breathe.

But it means they haven’t had as large a cooling effect to offset the continued warming caused by greenhouse gases.

And this cooling effect of aerosols has been underestimated by the UN, argues James Hansen, the scientist who made one of the first high-profile warnings on climate change to the US Senate in 1988.

Most scientists aren’t yet convinced that this is the case. But, if true, it could mean there is greater climate change in store than previously assumed.

The “nightmare scenario”, says Prof Scaife, would be an extra cloud feedback, where a warming ocean could cause low-level reflective clouds to dissipate, in turn warming the planet further.

This theory is also very uncertain. But the months ahead should help to shed some light on whether the “extra” warmth over the past couple of years is a blip, or marks an acceleration in warming beyond what scientists had anticipated.

Currently, most researchers still expect 2025 will end up slightly cooler than 2023 and 2024 – but the recent warmth means they can’t be sure.

What they do know, however, is that further records will follow sooner or later as humanity continues to heat up the planet.

“In time, 2025 is likely to be one of the cooler years that we experience,” Dr Burgess said.

“Unless we turn off that tap to [greenhouse gas] emissions, then global temperatures will continue to rise.”