Scientists say the Atlantic Meridional Overturning Circulation, or AMOC, is weakening, and a new study suggests the ocean system could reach a tipping point by the middle of the century. Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research said the shutdown “is not a low-probability event anymore.”
Rahmstorf said he spent a 30-year career treating the tipping risk as fairly low, but “It starts to look likely, maybe even very likely.” He said impacts could be felt in the next few decades unless carbon emissions are reduced very fast, with cooling starting in the late 2030s or 2040s.
Atlantic Ocean warning signs
The latest research points to a sharp contrast in the North Atlantic: a patch of ocean south of Greenland and Iceland has cooled over the last century while much of the world’s oceans have warmed. Scientists often call that area the Atlantic “cold blob” or “warming hole.”
The study says that cooling is not simply the result of sea surface heat loss, changing winds, or cloud patterns. It ties the pattern to a declining AMOC, with climate change described as the main driver of the weakening through warming seas, melting ice, and increased rainfall that have disrupted the temperature and salt balance of the North Atlantic.
Stefan Rahmstorf and the new forecast
The new finding sharpens an argument that has been building for years: scientists say the AMOC has been weakening, but the latest research says the slowdown may arrive earlier and more sharply than many climate models had projected. In April, another study indicated a sharp AMOC decline of roughly 50 percent by the end of the century, a separate estimate that points in the same direction even if it does not use the same endpoint as the latest work.
Rahmstorf’s warning matters because the system helps move warm, salty tropical water northward before it cools, sinks, and returns south at deeper depths. A weaker circulation would not stop that process overnight, but it could change how quickly heat is distributed across the Atlantic and push climate effects into the next few decades, before any full collapse by 2100.
New England and Europe
People in New England and across the Atlantic and Europe are among those most likely to feel the first changes in weather patterns if the AMOC keeps weakening. Rahmstorf said the impacts could start before any shutdown, and the study says the timing and severity depend on future emissions.
Gerard McCarthy of Maynooth said, “That cold isn’t a kind of a get-out-of-jail-free card in terms of global warming.” He added that “Some of the hot extremes can actually be exacerbated by this cold blob in the Atlantic,” a reminder that the cooling patch is not a sign the climate danger has gone away.
The open question now is how fast climate and weather impacts intensify if emissions are not cut very fast, with the latest research putting the most visible changes in the late 2030s or 2040s rather than waiting for a full shutdown. That gives the forecast a narrower window than many earlier projections, and it is the window that matters for people in New England and across the Atlantic now.
