Rahmstorf warns AMOC may hit tipping point
- A Climate Emergency Forum video published April 26 put renewed attention on Stefan Rahmstorf’s warning that Atlantic overturning currents may be nearing a tipping point. - Recent papers discussed around that warning do not settle the timing: one review says collapse could begin this century, while another projects 18–43% weakening by 2100. - The dispute is no longer whether AMOC matters, but how close it is to abrupt change. (nature.com)
The Atlantic Meridional Overturning Circulation is the ocean’s heat conveyor, carrying warm surface water north and returning colder deep water south. A new video published April 26 revived Stefan Rahmstorf’s warning that this system may be approaching a tipping point. (climateemergencyforum.org) (youtube.com) The video was recorded on April 22 and features Herb Simmens, Peter Carter, and Paul Beckwith discussing recent AMOC research and Rahmstorf’s concerns. Its central claim is that several recent studies now put the risk of a severe AMOC shutdown this century near a coin flip. (climateemergencyforum.org) (youtube.com) AMOC is not a single current like a river. It is a basin-scale overturning loop that helps keep northwestern Europe milder, shifts tropical rainfall belts, and affects heat storage across the Atlantic. (tos.org) (pubmed.ncbi.nlm.nih.gov) Rahmstorf laid out that risk in an April 2024 overview article, writing that paleoclimate records show AMOC has flipped abruptly before. He argued that warming and freshwater input can push the system toward self-reinforcing change. (tos.org) (pik-potsdam.de) One major study behind the current alarm came from René van Westen, Michael Kliphuis, and Henk Dijkstra in *Science Advances* in February 2024. They reported a physics-based warning signal and said reanalysis products indicate the present-day AMOC is “on route to tipping.” (science.org) A separate 2024 preprint by van Westen and Dijkstra estimated a mean collapse year around 2050, with a 10–90% interval of 2037 to 2064, and put the chance of collapse before 2050 at 59% plus or minus 17 percentage points. That result has circulated widely, but it is not the same as a settled consensus estimate. (arxiv.org) Other recent research points in a less extreme direction. A *Nature Geoscience* paper published May 29, 2025 concluded that observational constraints imply AMOC weakening of about 3 to 6 Sverdrups, or roughly 18% to 43%, by 2100 regardless of emissions scenario. (nature.com) That paper does not say collapse is impossible. It says a large share of the spread in future AMOC projections comes from model biases in present-day ocean stratification, and that observations narrow the likely weakening range. (nature.com) Another strand of work published in 2025 pushed the concern back toward abrupt change, but mainly after 2100. A Potsdam Institute summary of an *Environmental Research Letters* study said high-emissions simulations showed deep overturning shutting down after 2100, with the triggering tipping point in key North Atlantic seas often appearing in the next few decades. (pik-potsdam.de) A 2026 review by Henk Dijkstra and René van Westen framed the policy question directly: the AMOC may transition to a climate-disrupting state within a century, and estimating the probability of onset before 2100 is now crucial for policymakers. (pubmed.ncbi.nlm.nih.gov) The live dispute, then, is not over whether AMOC is weakening under climate change. It is over whether the system is heading for a limited but serious slowdown this century, or whether the threshold for an abrupt transition is already close enough that planners should treat collapse risk as live. (nature.com) (pubmed.ncbi.nlm.nih.gov) (science.org) That is why Rahmstorf’s warning keeps resurfacing. The newest attention came from a video, but the underlying story is a widening stack of papers that disagree on timing while converging on one point: AMOC stability can no longer be treated as a fringe concern. (youtube.com) (pubmed.ncbi.nlm.nih.gov)
