New research has found that an Atlantic current is at risk of collapse, which would plunge the UK into extreme cold. The Atlantic meridional overturning circulation (AMOC) is the main ocean current system in the Atlantic Ocean.

It is part of the Earth's ocean circulation system, bringing warm, more saline water north and taking cold, less salty, deep water south. It includes the Gulf Stream and plays an important role in the climate system, regulating regional and global climates by distributing heat and carbon around the planet.

But new research has found it is at its weakest in 1,600 years due to climate change. If carbon emissions rise, 70% of models ended in the current’s collapse by 2100. With intermediate emissions, the current failed 37% of the time. But even when run on low emissions, models found AMOC had a 25% chance of failure, showing it may already be too late. Scientists have said the collapse of AMOC must be avoided “at all costs.” It would raise sea levels by 50 cm, move the tropical rain belt that millions rely on for crops, and dramatically alter Europe’s climate.

The UK would become subject to freezing winters. The cold extreme could drop as low as -30C in Scotland, with the country experiencing almost half of the year below freezing.

London could experience cold extremes of -19C and be sub-zero for two months of the year, Belfast could get as low as -22C and Cardiff to -20C.

UK summers would likely become much shorter and cooler, with significant impacts on rainfall and agriculture. Less cloud cover, potential droughts and a decrease in overall rainfall would also be a result.

The study, published in Environmental Research Letters, found that the collapse will start around 2050 when heavy, cold, and salty surface water fails to sink and blend with deeper ocean water. This would weaken the AMOC, leading it to collapse within 50 to 100 years.

Dr Jonathan Baker of the Met Office Hadley Centre, who led the study, said: “This new study highlights that the risk rises after 2100,” he said. “[But] these percentages should be treated with caution – the sample size is small, so more simulations [beyond 2100] are needed to better quantify the risk.

“The ocean is already changing, and projected shifts in North Atlantic convection are a real concern. Even if a collapse is unlikely, a major weakening is expected, and that alone could have serious impacts on Europe’s climate in the decades to come. But the future of the Atlantic circulation is still in our hands.”