For several years, climate scientists have shown that the Atlantic Meridional Overturning Circulation (AMOC) could come to a halt if the world warms too much. New research by researchers from Utrecht University shows that this picture is incomplete: the pace of warming also determines whether the AMOC stays stable. The study was published in the scientific journal Nature Climate Change.
The Atlantic Meridional Overturning Circulation, or AMOC, is the system of ocean currents that transports warm water from the tropics northward. It plays a major role in redistributing heat across the planet, and helps keep the climate in Western Europe relatively mild.
Scientists have long suspected that this ‘heat engine’ of the Atlantic Ocean could reach a tipping point. This means that the system would shift from its present-day strong state to a much weaker state within decades. Such a tipping event could be triggered by external influences, such as an increasing amount of meltwater from the polar regions, or global warming itself.
Temperature threshold
Until now, the AMOC was thought to tip and collapse around +4°C of warming. Researchers at the Institute for Marine and Atmospheric research Utrecht now show that there's more to the story. “Our results show there is not necessarily a fixed temperature beyond which the AMOC inevitably collapses," says lead author René van Westen . "The stability of the circulation depends on how fast the climate is changing."
Slow versus fast warming
To investigate how the rate of climate change affects the strength of the AMOC, Van Westen and his colleagues ran a climate model twice. In their simulations, they used a gradually increasing amount of atmospheric CO 2 , but at different speeds. In one simulation, CO 2 concentrations rose slowly (0.5 ppm per year); in the other, much faster (2.5 ppm per year), comparable to today's rate.
Under slow warming, the AMOC remained stable well beyond +4°C, and it did not collapse even at +5°C of warming. Under fast warming, the AMOC collapsed already at around +2°C. “We deliberately looked at a scenario that is much slower than what we're experiencing today,” explains co-author Reyk Börner . “That allowed us to isolate the effect of the warming rate alone, independent of how warm it eventually gets.”
Resilience
The explanation lies in how the ocean is able to adjust to change. “Under slow warming, the entire ocean, from the surface down to its deepest layers, has time to gradually reorganize and adapt to the changing conditions,” says co-author Henk Dijkstra , professor of Dynamical Oceanography. “Under faster warming, the ocean simply can't keep up.”
Flying off the road
According to the researchers, the critical warming rate lies around 0.3°C per decade, a pace the world is already approaching. Van Westen compares it to driving a car: “If you're driving toward a wall, it makes sense to steer around it. To do that, you need to brake, otherwise you fly off the road. When it comes to global warming, the world is still pressing extra hard on the accelerator right now.”
In perspective
The same research group has published on AMOC stability several times in recent years, each time from a slightly different angle.
Climate policy
The slower the warming, the more time the Atlantic Ocean has to adapt, and the lower the near-term risk of an AMOC collapse. That has implications for how we think about climate policy: much current policy, including the Paris Agreement, is aimed at limiting the eventual peak temperature. This is sometimes based on so-called overshoot pathways: temporary global warming past that limit, on the assumption that future technology could later bring the temperature back down.
Nature Climate Change
Computational simulation/modeling
Not applicable
Failure to track a stable AMOC state under rapid climate change
13-Aug-2026