Analysis: Warming Could Push the Atlantic Past a ‘Tipping Point’ This Century

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The last time there was a major slowdown in the mighty network of ocean currents that shapes the climate around the North Atlantic, it seems to have plunged Europe into a deep cold for over a millennium.

That was roughly 12,800 years ago, when not many people were around to experience it. But in recent decades, human-driven warming could be causing the currents to slow once more, and scientists have been working to determine whether and when they might undergo another great weakening, which would have ripple effects for weather patterns across a swath of the globe.

A pair of researchers in Denmark this week put forth a bold answer: A sharp weakening of the currents, or even a shutdown, could be upon us by century’s end.

It was a surprise even to the researchers that their analysis showed a potential collapse coming so soon, one of them, Susanne Ditlevsen, a professor of statistics at the University of Copenhagen, said in an interview. Climate scientists generally agree that the Atlantic circulation will decline this century, but there’s no consensus on whether it will stall out before 2100.

Which is why it was also a surprise, Dr. Ditlevsen said, that she and her co-author were able to pin down the timing of a collapse at all. Scientists are bound to continue studying and debating the issue, but Dr. Ditlevsen said the new findings were reason enough not to regard a shutdown as an abstract, far-off concern. “It’s now,” she said.

The new research, published on Tuesday in the journal Nature Communications, adds to a growing body of scientific work that describes how humankind’s continued emissions of heat-trapping gases could set off climate “tipping points,” or rapid and hard-to-reverse changes in the environment.

Abrupt thawing of the Arctic permafrost. Loss of the Amazon rain forest. Collapse of the Greenland and West Antarctic ice sheets. Once the world warms past a certain point, these and other events could be set into swift motion, scientists warn, though the exact thresholds at which this would occur are still highly uncertain.

In the Atlantic, researchers have been searching for harbingers of tipping-point-like change in a tangle of ocean currents that goes by an unlovely name: the Atlantic Meridional Overturning Circulation, or AMOC (pronounced “AY-mock”).

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