New simulations show a 10 to 23 percent chance that the Atlantic Meridional Overturning Circulation has already reached a point of no return.
Researchers ran 21 computer models with different emissions peaks and Greenland ice melt rates. The results indicate that even under conservative assumptions with emissions peaking in 2025, there is a 10 percent chance the circulation is committed to collapse.
Phil Holden at the Open University said there is a significant probability that collapse is already inevitable. Under higher melt rates adding 274 millimetres to sea level by 2100, that probability rises to 23 percent.
If emissions do not reach net zero until 2100, the chance of collapse reaches 80 percent. Any collapse would still be decades away, with an average delay of 84 years after commitment and the earliest possible shutdown around 2060.
Tim Lenton at the University of Exeter noted that rapid emissions cuts could keep the risk closer to the lower end of the estimates.