Potential far-reaching economic consequences are growing more likely as the collapse of the Atlantic meridional overturning circulation ocean current (Amoc), which underpins Europe’s climate stability, is no longer considered a low-probability scenario, according to new research.
Amoc, which drives warm water northward from the tropics and contributes to the Gulf Stream weather system, is already at its weakest in 1,600 years.
The tipping point to make a shutdown inevitable could be reached within the next 10-20 years, according to a study published in the Environmental Research Letters journal, with a full collapse occurring later this century.
For businesses and governments, the risks are clear, as a collapse is likely to plunge northern Europe into prolonged cold winters and summer droughts, as rainfall belts that underpin global agriculture are shifted.
This could add as much as 50cm to sea levels already threatening coastal infrastructure.
Insurance costs, supply chains, energy demand and food security would all be exposed.
Under a forecasting model used by the scientists, a continued rise in carbon emissions would lead to a collapse of the current under 70% of the simulations run of the model.
Even if this does not lead to a northern Amoc shutdown the societal impacts "would likely be serious", the researchers said.
The findings come as corporates and investors grapple with climate-related risks.
If emissions growth is slowed to an intermediate level (known as scenario SSP245), this results in Amoc collapse in 37% of the models and even in the case of low future emissions, a drastic weakening of Amoc – short of full collapse – could materially disrupt European economies, energy markets and food production, with knock-on effects on trade and investment flows.
Researchers at the Potsdam Institute told the Guardian that the chance of collapse, even under low-emissions scenarios, is now closer to 25%:
"Even a 10% chance of Amoc collapse would be far too high … we have to act really fast in cutting down emissions."
Last year, scientists warned of consequences for UK and European agriculture, energy demand and other sectors in the event of a "tipping point" for the Atlantic ocean current.
Winters in Europe would between 5ºC and 10ºC colder, with more volatile levels of rainfall, while temperatures nearer the Equator would become even warmer.
While the Intergovernmental Panel on Climate Change (IPCC) had previously put the probability of a tipping point this century at less than 10%, more recent studies have warned the danger is rising.
The latest IPCC report concluded that there is "medium confidence that there will not be an abrupt collapse before 2100", which researchers noting that the lack of confidence is based on climate models having a tendency toward "unrealistic stability".