The Atlantic Meridional Overturning Circulation (AMOC) is a major system of ocean currents that transports warm, salty surface water northward in the Atlantic and returns colder, denser water southward at depth.
It carries roughly 1.2–1.3 petawatts of heat northward—far more energy than all human energy use combined—and helps keep northwestern Europe and parts of the North Atlantic relatively mild.
A substantial weakening or full collapse (a transition to a much weaker or near-shutdown state) would produce large, often abrupt, regional and global climate impacts. These are drawn from climate model experiments (including “hosing” simulations that add freshwater to the North Atlantic), paleoclimate analogs (e.g., Heinrich and Dansgaard-Oeschger events), and assessments such as the IPCC and Global Tipping Points reports.
Note that projected impacts vary with the degree of weakening, the background global warming level, and the specific model; a full collapse is considered less likely this century by some assessments but remains a significant risk under rapid warming.
A recent modeling study finds that the Atlantic Meridional Overturning Circulation (AMOC) has no fixed global-temperature tipping threshold; its stability depends strongly on the rate of warming. Rapid CO₂-driven warming (near today’s pace) can trigger collapse near ~2°C above pre-industrial levels, while much slower warming can keep it stable well past 5°C.
The paper, “Failure to track a stable AMOC state under rapid climate change” (van Westen, Börner & Dijkstra, Nature Climate Change, August 2026), used the Community Earth System Model with controlled CO₂ ramps:
Slow ramp (+0.5 ppm/year): AMOC stayed intact even as global mean surface temperature reached ~+5.5°C.
Faster ramps (+2.5 ppm/year, comparable to the recent ~2.6 ppm/year Mauna Loa average, and +5.0 ppm/year): AMOC collapsed near ~+2°C.
Previous estimates often cited a rough ~4°C (range ~1.4–8°C) temperature threshold.
The new work shows that figure is not universal: under rapid forcing the system fails to track a stable “AMOC-on” equilibrium because surface and interior ocean properties cannot adjust coherently.
Slow forcing allows stabilizing processes—enhanced evaporation, reduced sea-ice extent, and better vertical adjustment—to counteract the destabilizing salt-advection and density feedbacks.
Researchers estimate a critical warming rate near ~0.3°C per decade (the world is already approaching this range). Under continued high rates, collapse indicators could appear around mid-century (e.g., ~2060 in some projections tied to ~2–2.5°C).
Slowing the rate of CO₂ increase can therefore be more important for AMOC resilience than the eventual total warming level alone.
Results come from one state-of-the-art model (and supporting conceptual analysis). Other models show varying AMOC sensitivity; some suggest greater resilience even under strong forcing. Real-world behavior also depends on freshwater input from ice melt, precipitation changes, and internal variability.
An AMOC collapse would still carry major regional impacts (stronger cooling/shifts in the North Atlantic and Europe, altered rainfall patterns, etc.), even if global mean temperature effects are more complex.
In short, the headline is accurate: the pace of warming can determine whether the AMOC tips near 2°C or remains functional at much higher levels. Rapid emissions cuts that slow the rate of change improve the odds of avoiding collapse.
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Failure to track a stable AMOC state under rapid climate change
“Failure to track a stable AMOC state under rapid climate change” is a peer-reviewed paper by René M. van Westen, Reyk Börner, and Henk A. Dijkstra (Institute for Marine and Atmospheric research Utrecht, Utrecht University), published in Nature Climate Change on 13 August 2026 (DOI: 10.1038/s41558-026-02730-w; arXiv:2602.09964).
The Atlantic Meridional Overturning Circulation (AMOC) does not have a universal global-mean surface temperature (GMST) tipping threshold.
Its stability depends primarily on the rate of radiative forcing (CO₂ increase), not on a fixed warming level. Rapid forcing can cause rate-induced tipping (failure to track a stable “AMOC-on” equilibrium), while slower forcing allows the system to remain stable at much higher temperatures.
Previous estimates often placed a collapse threshold near +4.0 °C (range ~1.4–8 °C). The new results show this is not meaningful in isolation.
Simulations started from a quasi-equilibrium pre-industrial state with a background freshwater “hosing” flux ( Sv over the North Atlantic) that places the AMOC in a more vulnerable regime (a bias-correction approach, as pure models often require unrealistically large freshwater input to tip).
Slow CO₂ ramp: +0.5 ppm yr⁻¹ → AMOC remains stable up to ~+5.5 °C GMST anomaly.
Faster CO₂ ramps: +2.5 ppm yr⁻¹ and +5.0 ppm yr⁻¹ (the former comparable to the recent Mauna Loa average of ~+2.6 ppm yr⁻¹) → AMOC collapses near ~+2 °C.
Comparable behavior appears in extended RCP scenarios (collapse under RCP4.5/RCP8.5 at lower warming levels under the same background hosing; recovery possible under RCP2.6).
Supporting analysis uses a conceptual 5-box AMOC model to illustrate the moving saddle-node bifurcation and rate-dependent tracking failure.
Slow warming permits coherent adjustment between surface and interior ocean properties.
Higher sea-surface temperatures drive enhanced net evaporation and reduced sea-ice extent over the Atlantic.
These effects salinify the ocean and counteract the destabilizing salt-advection feedback. This stabilizing process operates on timescales longer than present-day forcing rates, so rapid warming outpaces it and the AMOC fails to track the stable state.
There is no “magic” temperature level that guarantees collapse or survival.
The critical factor is the warming rate (researchers note a rough critical rate around ~0.3 °C per decade under current conditions; the world is already approaching this range).
Limiting the rate of greenhouse-gas emissions is therefore critical for reducing near-term AMOC collapse risk, even if total cumulative emissions (and eventual temperature) are not fully constrained.
Under continued rapid rates, collapse onset could occur around mid-century in some projections tied to ~2–2.5 °C.
Results are from one comprehensive climate model (plus conceptual analysis and some CMIP6 context).
Other models show varying AMOC sensitivity; some indicate greater resilience even under strong forcing. Real-world thresholds also depend on ice-melt freshwater, precipitation changes, aerosols, internal variability, and model biases.
An AMOC collapse would still produce large regional climate impacts (e.g., stronger cooling and shifts over the North Atlantic/Europe) regardless of the exact trigger mechanism.
Published: Nature Climate Change
DOI: 10.1038/s41558-026-02730-w
Provided: Utrecht University
Authors: René M. van Westen,
Reyk Börner &
Henk A. Dijkstra
Abstract
The Atlantic Meridional Overturning Circulation (AMOC), a tipping element of the climate system, currently has an estimated global warming threshold for collapse of +4.0 °C (uncertainty range 1.4–8 °C). However, such a threshold may not be meaningful because AMOC stability depends on the rate of radiative forcing change, not a set temperature. Here we identify an AMOC stabilizing mechanism that operates on timescales slower than present-day warming rates. Slow forcing permits coherent adjustment of surface and interior ocean properties, supported by enhanced evaporation and reduced sea-ice extent, counteracting destabilizing feedbacks. Using a slow CO2 ramp (+0.5 ppm yr−1) climate model simulation, we explicitly demonstrate the AMOC remains stable up to +5.5 °C of global warming. By contrast, under faster CO2 ramps, the AMOC collapses at substantially lower warming levels (+2 °C). Our findings demonstrate rate-induced AMOC tipping and imply that limiting the rate of emissions is critical for reducing the risk of an AMOC collapse.
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