Gulf Stream System Could Be on the Verge of Collapse

One of the climate change tipping points scientists are most worried about could arrive sooner than expected, with potentially disastrous consequences for billions of people, according to new research. In a study published in the journal Nature, Danish researcher Peter Ditlevsen, a climate scientist, and his sister Susanne Ditlevsen, a professor of statistics, said their analysis suggests that the Atlantic Meridional Overturning Circulation—AMOC—network of ocean currents, which includes the Gulf Stream, could collapse before the end of this century. They said AMOC could severely weaken or shut down as soon as 2025 or as late as 2095, though the most likely time is midcentury under the "current scenario of future emissions, the New York Times reports.

The AMOC moves warm water from the tropics to the North Atlantic, but melting ice is a major problem, the researchers say. "Greenhouse gas emissions cause global warming, which speeds up the melting of Greenland ice," the Ditlevsens explain to USA Today. "The melted freshwater entering the North Atlantic can then disrupt the AMOC, potentially causing major climate disruptions." The extra freshwater, they say, is "lighter than the salty seawater around it" and can "disrupt the normal sinking of the salty water, weakening or even shutting down the AMOC." If the AMOC is shut down disrupted, it could cool Europe and North America by a few degrees—but there would also be sea level rises and huge disruptions to rainfall in North America and beyond.

The change would disrupt agriculture in Asia, South America, and Africa, endangering the food supply for billions, the Guardian reports. "This would be a very, very large change," Peter Ditlevsen says. "The AMOC has not been shut off for 12,000 years." He says the research shows the urgent need to reduce emissions of greenhouse gases. While other scientists agree on the need to reduce emissions, some disagree with the Ditlevsens' analysis, saying there is still much uncertainty about the tipping point for the AMOC and any collapse. One problem with the statistical analysis other researchers pointed to was the use of potentially inaccurate records going back to 1870. (More ocean currents stories.)