Human-driven planetary warming threatens to collapse a system of currents in the Atlantic Ocean that regulate and impact weather across the globe, a new scientific study has found.
The Atlantic Meridional Overturning Circulation, or AMOC, a section of the Gulf Stream, transports warm water from the tropics northward and cold water from the North Atlantic to the south.
This natural redistribution of heat has long worked to stabilise regional climate and weather conditions; however, scientists have been warning that the system is slowing down. A 2019 United Nations report concluded that while the current is “very likely” to weaken this century, a total breakdown was unlikely.
But the new study, published on Thursday in the journal Nature Climate Change, indicates the situation could be far direr than previously thought. The current changes may be tied to “an almost complete loss of stability of the AMOC over the course of the last century,” the analysis states.
“The findings support the assessment that the AMOC decline is not just a fluctuation or a linear response to increasing temperatures but likely means the approaching of a critical threshold beyond which the circulation system could collapse,” Niklas Boers, a researcher at the Potsdam Institute for Climate Impact Research in Germany and the study’s author, said in a statement.
A crippled Atlantic current system could trigger catastrophic, potentially irreversible changes, from rising seas in North America to major disruptions to seasonal monsoon rains in Asia and South America.
“The mere possibility that the AMOC tipping point is close should be motivation enough for us to take countermeasures,” Levke Caesar, a climate physicist at Ireland’s Maynooth University, told The Washington Post. “The consequences of a collapse would likely be far-reaching.”
But Andreas Schmittner, a climate scientist at Oregon State University, is skeptical of the study’s conclusion.
“The method used in the paper has been developed and tested in very simple models of dynamical systems, but then it is applied to observations of sea surface temperatures and salinities,” he told HuffPost in an email. “I think their method is brand new and needs to be tested by different investigators and explored more in complex climate models to see if it works with the data they used. I think it is premature to conclude that the AMOC is on the brink of collapse.”
The study comes ahead of a major report from the United Nations’ Intergovernmental Panel on Climate Change, or IPCC, the leading consortium of researchers studying human-caused temperature rise. The assessment, due out Aug. 9 and authored by more than 200 scientists, will provide an up-to-date understanding of the crisis and its current and future effects around the globe.
There’s no way to pinpoint the level of greenhouse gas emissions that would lock in a total collapse of the AMOC, Boers told The Guardian. “The only thing to do,” he said, “is keep emissions as low as possible. The likelihood of this extremely high-impact event happening increases with every gram of CO2 that we put into the atmosphere.”