A vital Atlantic Ocean current system that affects weather around the world could collapse by the late 2030s, scientists estimate in a new study – a planetary-scale catastrophe that will transform weather and climate.

Several studies in recent years have suggested that the critical system — the Atlantic Meridional Overturning Circulation, or AMOC — could be on the verge of collapse, weakened by warmer ocean temperatures and salinity disruption caused by climate change. from human.

But the new research, which has been peer-reviewed but not yet published in a journal, uses a state-of-the-art model to estimate when it could collapse, suggesting it could happen between 2037 and 2064.

This research shows that it is most likely to collapse by 2050.

“This is really worrying,” said René van Westen, a marine and atmospheric researcher at Utrecht University in the Netherlands and co-author of the study.

“All the negative side effects of human-caused climate change will continue, like more heat waves, more droughts, more floods,” he told CNN. “Then if there is also a collapse of the AMOC … the climate will become even more distorted.”

Like a conveyor belt, the AMOC pulls warm surface water from the Southern Hemisphere and tropics and distributes it into the cold North Atlantic. The colder, saltier water then sinks and flows south. The mechanism protects parts of the southern hemisphere from overheating and parts of the northern hemisphere from extreme cold, while distributing life-sustaining nutrients to marine ecosystems.

The effects of an AMOC collapse will leave parts of the world unrecognizable.

In the decades after a collapse, the Arctic ice would begin to creep south, and after 100 years it would extend as far as the south coast of England. Europe’s average temperature would drop, as would North America – including parts of the US. The Amazon rainforest would see a complete reversal in its seasons, in the current dry season the months would become rainy and vice versa.

An AMOC collapse “is a really big risk that we have to do everything we can to avoid,” said Stefan Rahmstorf, a physical oceanographer at the University of Potsdam in Germany, who was not involved in the latest research.

To reach their conclusions, scientists from Utrecht used state-of-the-art models and for the first time identified an area of ​​the South Atlantic Ocean as the optimal place to monitor for changes in circulation and using observational data. They looked at ocean temperatures and salinity to confirm earlier predictions about when the AMOC might reach its tipping point.

The emphasis in ocean research on the timing of the collapse is a relatively new development, Rahmstorf said. But it does speak to how far scientists’ understanding of the weakening of the AMOC has come.

“Until a few years ago, we were talking about whether it would happen at all, as a kind of low-probability, high-impact risk,” Rahmstorf told CNN. “And now it seems much more likely than it did a few years ago that this will happen. Now people are starting to finalize when it will happen.”

Rahmstorf said that about 5 years ago he would have agreed that an AMOC collapse this century was unlikely, although even a 10% risk is still quite high “for a catastrophic effect of this magnitude”.

“There are now 5 papers, basically, that indicate it could very well happen this century or even before mid-century,” Rahmstof said. “My overall assessment now is that the risk of us passing the tipping point this century is probably even greater than 50%.

While advances in AMOC research have been rapid, and models trying to predict its collapse have progressed at lightning speed, they have issues.

For example, the models do not take into account a critical factor in the collapse of the AMOC – the melting of the Greenland ice sheet. Huge amounts of fresh water are being washed away from the ice sheet and flowing into the North Atlantic, disrupting one of the circulation’s driving forces: salt.

“You’re already getting a huge influx of fresh water into the North Atlantic, which is going to completely disrupt the system,” Rahmstorf said.

That research gap means forecasts could underestimate how soon or quickly a collapse will occur, Rahmstof said.