CWR Talks to Prof. Stefan Rahmstorf on the Decades Away Breakdown of the Atlantic Current

By Stefan Rahmstorf 23 September, 2025

What is AMOC and why would its collapse catastrophically disrupt the global climate? Hear from the leading expert Prof. Rahmstorf about this looming climate threat you probably haven't heard of

AMOC, a key climate-regulating ocean current, is destabilising – tipping points could be passed in the next few decades, thereafter a full collapse becomes practically inevitable due to self-amplifying feedback
>40 experts warned Nordic governments as AMOC collapse would trigger severe global impacts e.g. dramatic cooling in Europe & >1m of sea level rise along Atlantic coasts
Urgent global action is needed to avert disaster through a complete fossil fuel phase-out, minimizing overshoot of the 1.5°C threshold & other tipping points
Author: Stefan Rahmstorf
Stefan Rahmstorf is Co-Head of Research Department on Earth System Analysis of the Potsdam Institute for Climate Impact Research (PIK) and Professor of Physics of the Oceans at the University of Potsdam. A physicist and physical oceanographer by training, Stefan Rahmstorf's research focusses on paleoclimate, ocean circulation, sea level, extreme weather events and Earth System modeling. After working at the New Zealand Oceanographic Institute and the Institute of Marine Science in Kiel, Stefan Rahmstorf joined PIK in 1996. He holds a professorship of Physics of the Oceans at the University of Potsdam since 2000. From 2004 to 2013 Stefan Rahmstorf advised the German government as a member of its Advisory Council on Global Change (WBGU). He is not only an outstanding and highly cited scientist but also a sought-after science communicator and speaker, winning e.g. the Climate Communication Prize of the American Geophysical Union in 2017. He co-founded the award-winning Realclimate and KlimaLounge blogs and is Europe’s climate scientist with the most Twitter followers (2020).
Read more from Stefan Rahmstorf →

The Atlantic Meridional Overturning Circulation (AMOC) – a critical system of ocean currents that regulates global climate – is showing alarming signs of instability. Recent studies suggest it could collapse within decades, with devastating consequences for weather patterns, ecosystems, and food security. But what exactly is AMOC, why is it at risk, and how urgent is the threat?

To unpack these questions, we spoke with Professor Stefan Rahmstorf, Co-Head of Research Department on Earth System Analysis of the Potsdam Institute for Climate Impact Research (PIK) and Professor of Physics of the Oceans at the University of Potsdam. He is also a signatory of an open letter to the Nordic Council of Ministers, urging immediate action to address this looming crisis.

CWR: To start off, can you explain what AMOC is, and why is it so critical to our climate system? Why is the Arctic region “ground zero” for planetary tipping point risks?

Prof. Stefan Rahmstorf (SR): AMOC stands for Atlantic Meridional Overturning Circulation, and it is the major ocean heat transport mechanism reaching from the Southern Ocean north across the equator, along the Gulf Stream and all the way up into the Greenland-Norwegian Sea. This is responsible for the mild climate in Europe, as well as many other features of the global climate system.

AMOC instabilities have driven the most abrupt climate shifts in recent Earth history…

Instabilities in the AMOC have played the main role in the most dramatic and rapid climate changes seen in recent Earth history, documented for example in Greenland ice cores as well as ocean sediments covering the last 100,000 years. This sensitivity of the AMOC has raised concerns since the 1970s about the danger of destabilising it again due to the current human-caused global warming.

CWR: The latest IPCC assessment notes with “medium confidence” that AMOC won’t collapse before 2100 but now there are prominent publications showing that it could collapse before 2100 which could be as early as the 2050s. What’s driving this drastic shift?

SR: I’d say there is a misunderstanding here. The IPCC says that the AMOC will probably not reach a collapsed state by 2100. Several recent studies suggest that the AMOC may well be destabilised – that means passing its tipping point – in the next few decades.

 AMOC is destablising & may pass its tipping point within decades…

That means the full collapse then becomes practically inevitable due to a self-amplifying feedback. But for the AMOC to fully wind down would still take roughly a hundred years. So by 2100 the AMOC would be well on the way to collapse, but not yet fully collapsed.

CWR: Clearly, scientists are so alarmed about the early collapse of AMOC that they got together to sign an open letter to Nordic governments to take urgent action. Why compelled you to take such action and what do you hope to achieve from it?

SR: Indeed more than 40 AMOC experts felt a responsibility to alert the public and policy makers of this major under-appreciated risk before it is too late to prevent it. We addressed it to the Nordic Council of Ministers because the Nordic countries are particularly directly and strongly affected by AMOC changes. We are hoping that they use their diplomatic soft power to push the world for rapid and ambitious emissions reductions – in fact just to take the 1.5 °C warming limit of the Paris Climate Accord very seriously.

As the 1.5°C goal is legally binding, fossil fuel expansion may constitute a “wrongful act”

I was happy to see that just recently, the International Court of Justice has supported this case by finding that the 1.5°C Paris threshold is legally binding and that failure to act to prevent significant harm can lead to sanctions. They say that “the granting of fossil fuel exploration licences and subsidies may constitute an internationally wrongful act.”

CWR: If AMOC were to collapse, what would be the immediate and long-term impacts? Would impact be contained within North America & Europe or will it have implications for the rest of the world?

SR: The main impacts would be cooling in Northwestern Europe, sea-level rise by up to a meter around the northern Atlantic coasts in addition to the global rise, major impacts on North Atlantic ocean ecosystems and fisheries, reduced CO2 uptake by the ocean, and around the tropics major rainfall changes due to the southward shift of tropical rainfall belts, leading to drought in some regions and flooding problems in others.

“I personally believe it should be top priority of policy makers around the world to minimise these risks”

This is such a major reorganisation of the workings of the global climate system that impacts are hard to predict in detail, but the experience of Earth history suggests they will be dramatic. So dramatic in fact that I personally believe it should be top priority of policy makers around the world to minimise these risks.

CWR: AMOC is increasingly at risk of passing a tipping point which can occur within the 1.5-2°C climate range. As our current climate policies are far above this range, what’s the message to policy makers at the upcoming COP30? What can policymakers do to reduce the risk of an AMOC collapse?

SR: In short: get out of fossil fuels as fast as we can. And minimise emissions (including leakage) of some non-CO2 greenhouse gases like methane. It is critical to limit the now inevitable overshoot over 1.5°C to short duration in order to reduce the risk of passing the AMOC tipping point, as well as other climate tipping points.

CWR: This is indeed a scary large-scale singular event yet many of us don’t even know it’s happening! Can we as individuals do anything about it? Can public pressure/action help?

SR: Indeed it is already starting, in that the northern Atlantic south of Greenland and west of Britain is the only part of the world that has cooled since the 19th century, while the rest of our planet Earth has warmed. That points to an AMOC slowing underway already. What the public can do is get well-informed from reliable scientific sources, don’t get fooled by fossil fuel propaganda of which there is a lot, and if you have the fortune of living in a democracy, use it to vote for stabilising the climate!

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