Scientists say the ocean current known as the Atlantic Meridional Overturning Circulation may be on the verge of collapsing, and the warning now reaches far beyond the North Atlantic. If the AMOC fails, Chicago could face weather changes for 1,000 years.
Stefan Rahmstorf says he has revised the chance of crossing the tipping point from a few percent to 50/50. The Potsdam Institute for Climate Impact Research expert said the shift reflects work over the last 5 years and that an eventual collapse is no longer a low-probability event.
Aidan Burdick And Chicago
In Chicago, that risk lands as a long-range climate warning, not a short-term forecast. Rahmstorf said the impacts would be so massive that it is very hard to imagine that we could sensibly adapt, and his projection points to a huge change in rainfall patterns around the world, with some areas getting much drier.
He also said climate changes could affect where people can grow food, which could lead to mass migration and even political instability. Temperatures in northwest Europe and parts of North America would cool down significantly, especially in the winter, while sea levels on the East Coast would rise a foot and a half, with more frequent coastal flooding in major cities.
Greenland Meltwater And AMOC
The mechanics run through Greenland. Fresh water from melting Greenland ice and pouring into the North Atlantic is disrupting a delicate balance and slowing the current down. The Atlantic Meridional Overturning Circulation acts as a massive conveyer belt of heat, carrying that heat from Florida to Europe.
That is where the laboratory work connects to the ocean warning. Aidan Burdick, a Northwestern University PhD student in Earth and Environmental Science, spends his days sifting through mud to look for fossilized flies. In his lab, he said, “By far the biggest control on where these different species live is the air temperature,” a reminder that climate shifts leave traces in the ground long before they register in daily life.
Erin Pettit In Greenland
Fieldwork in Greenland is helping scientists measure that change more directly. Erin Pettit spent six weeks there over the summer measuring glacier melt, and she said the team used underwater robots to drill little microphones onto the glacier face.
“We were pretty sure we were underestimating the rate at which ice is melting,” Pettit said. “The process of melting glacier ice is really noisy, and so we can actually use the sounds to get an idea of how fast the ice is melting.”
Rahmstorf’s warning sits alongside a more cautious line in the latest international climate change report, which finds moderate confidence that the current won't abruptly collapse this century. Even so, he said that even if the full shutdown isn't reached before 2100, the models show that it may well already be less than half as strong as it used to be.
That leaves the hardest question hanging over the research: when, if ever, will scientists be able to say whether the AMOC will actually cross its tipping point?
