Study Finds AMOC Collapses Near 2°C Under Fast CO2 Rises, Stays Stable to 5.5°C if Slow
Updated
Updated · Nature.com · Aug 13
Study Finds AMOC Collapses Near 2°C Under Fast CO2 Rises, Stays Stable to 5.5°C if Slow
3 articles · Updated · Nature.com · Aug 13
Summary
Fast CO2 ramps of 2.5 and 5.0 ppm a year collapsed the AMOC at about 2.0°C warming in model runs, while a slow 0.5 ppm annual rise kept it stable through 5.5°C.
The study says collapse risk is set by the rate of radiative forcing change, not a fixed temperature threshold, because rapid warming prevents the Atlantic from adjusting surface and deep-ocean properties coherently.
Under slower warming, stronger evaporation, reduced sea ice and later Labrador Sea deep convection helped maintain dense-water formation and even increased AMOC stability over time.
At projected warming rates, the authors say a collapse onset around 2.5°C could arrive near 2060, below the often-cited 4°C threshold, making emissions cuts that slow warming central to lowering risk.
Could the sheer speed of global warming trigger a catastrophic and irreversible ocean current collapse as early as 2060?
If this vital ocean current permanently shuts down, could Europe suddenly face centuries of devastating freezes and extreme coastal flooding?
Are our climate goals fundamentally flawed by focusing on temperature limits instead of the dangerous speed of planetary heating?
AMOC at the Brink: Scientific Warnings, Global Cascades, and the Urgent Need for Action (2024–2026)
Overview
Human-driven global heating is rapidly warming the Arctic, causing northern ocean waters to cool more slowly and become less dense. At the same time, the accelerating melt of the Greenland Ice Sheet is pouring large amounts of freshwater into the North Atlantic, lowering salinity and further reducing water density. These changes are weakening the Atlantic Meridional Overturning Circulation (AMOC), with projections showing a 42% to 58% slowdown by 2100. If the AMOC collapses, it could trigger extreme regional temperature shifts, disrupt global weather and food production, cause mass migration, and push financial and insurance systems to a breaking point. As risks mount, scientists and governments are calling for urgent action and preparedness.