Scientists at Utrecht University have published findings indicating that the Atlantic Meridional Overturning Circulation (AMOC) may be more resilient to warming than previously thought, provided the rate of temperature increase remains gradual. The AMOC is a major ocean current system that transports warm water northward from tropical regions and significantly influences global climate patterns, particularly maintaining relatively mild conditions in Western Europe. Researchers have long identified this circulation as vulnerable to potential collapse if global temperatures rise sufficiently.
Traditional climate models estimated that the AMOC could reach a tipping point around 4°C of global warming. However, the new research published in Nature Climate Change challenges this fixed threshold concept. Lead researcher René van Westen stated that the circulation’s stability depends substantially on the pace at which climate change occurs rather than being determined by temperature alone. To demonstrate this relationship, researchers conducted climate simulations with identical eventual CO2 levels but different rates of increase. When atmospheric carbon dioxide rose slowly at 0.5 parts per million annually, the AMOC remained stable even beyond 5°C of warming. In contrast, when CO2 increased rapidly at 2.5 parts per million annually, the circulation collapsed around 2°C of warming.
The researchers attribute this difference to the ocean’s capacity to adapt to changing conditions. Slow warming allows the entire ocean, from surface to deepest layers, time to gradually reorganize and maintain stability. Rapid warming outpaces the ocean’s adjustment capabilities, leaving the circulation more vulnerable to instability. The study identifies a critical warming rate of approximately 0.3°C per decade as a key threshold.
These findings carry significant implications for climate policy. Current approaches, including the Paris Agreement, primarily focus on limiting final temperature levels. Some strategies involve overshoot pathways where temperatures temporarily exceed targets before future reductions occur. The research suggests that the pathway taken toward any given temperature target may be equally important to the endpoint itself, potentially affecting decisions about how quickly emissions reductions should be pursued.
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