Environmental (Commonwealth Union)_ The Atlantic Meridional Overturning Circulation (AMOC), the enormous ocean conveyor belt that determines the global climate, teeters on the brink of collapse, claims startling new science that radically rearranges previous estimates of danger. What had been deemed a far-off worst-case scenario by scientists now appears increasingly probable in decades to come, with profound implications for global weather patterns, food security, and sea-level rise. The study, published in Environmental Research Letters, determines that even when taking extremely optimistic emission scenarios in line with the Paris Agreement, there remains a 25% chance of collapse of the AMOC, a risk scientists describe as playing Russian roulette with humankind’s future.
AMOC is Earth’s climate stabiliser, transporting warm tropical water towards the north, where it cools, sinks, and makes its way back southward in deep ocean streams. This system makes Europe’s winters quite mild and governs rain patterns in the tropics. But freshwater from melting ice and increased rainfall is freshening up the North Atlantic, reducing salinity and water density and inhibiting sinking that drives the whole circulation. Climate projections to 2300-2500 paint a ghastly feedback loop: the decelerating current itself creates conditions that further decelerate, eventually reaching a tipping point past which there is no recovery.
The numbers are dire:
- 70% possibility of collapse under high-emission scenarios.
- There is a 37% possibility of collapse even with intermediate reductions in emissions.
- 25% possibility under Paris Agreement levels
- Tipping point most likely within 10-20 years
- Collapse complete, possibly 50-100 years past tipping point
Potsdam Institute Professor Stefan Rahmstorf, a once-near-term collapse sceptic, is now warning, “Even a 10% probability would be much too high. We’re talking about rebuilding the whole global climate system.” The consequences would be catastrophic: European winters dropping to Arctic levels, constant drought over agricultural centres of production, the tropical rain belt shifting south at the cost of food production for billions, and a further 50cm of sea-level rise above current coastal vulnerability.
The analysed IPCC climate models extended beyond their typical 2100 endpoint, and numerous models that seem stable this century in fact conceal inescapable collapse paths in the coming decades. Of most concern is new evidence confirming the projected slowdown; deep North Atlantic ocean water already shows diminishing circulation as predicted by models. Another research using different methodology independently arrived at the same conclusion, with the mid-century tipping point passage as a suggestion.
Even with the dire conclusions, scientists are quick to stress that the future is still in human control. Met Office Hadley Centre’s Dr Jonathan Baker says that while total collapse this century is still improbable, “a major weakening is expected” and with serious consequences no matter what. The gap between complete collapse and major weakening is the space where urgent emissions cuts could still prevent worst-case outcomes. The study is warning and motive: the fate of the AMOC is not yet sealed, but the time to act is running out quickly. In the words of Professor Sybren Drijfhout, “The shutdown risk is more serious than many people realise,” and learning to recognise this risk may be our best hope for preventing it.
