Back in 2004, Hollywood conjured up a disaster thriller, "The Day After Tomorrow," which was based upon an ingeniously disturbing premise: Global warming caused the melting of the Arctic ice sheet, which in turn altered the salinity of the oceans and altered their circulation. In a cruel paradox, that effect of global warming shut down the Gulf Stream and its warming effects, instantly triggering a new Ice Age.
While the wild scenario in that flick got a thumbs down on accuracy and plausibility from actual climate researchers, it did contain at least one grain of truth.
As the United Nations' Intergovernmental Panel on Climate Change noted in 2013, scientists do indeed think that the melting of Arctic ice is slowing a pattern called the Atlantic Meridional Overturning Circulation, which transports warm water from the tropics to the North Atlantic and helps keep Europe's climate relatively mild for its latitude. The catch has been that they haven't been sure exactly how much the circulation has been slowing.
NEWS: Best Map of Ocean Currents from Space
But now, a recently-published study in the journal Nature Climate Change concludes that the North Atlantic circulation is about 15 to 20 percent weaker than normal. That may not seem like a lot, but the rate of the decrease is unprecedented over the past 1,100 years.
That's nowhere near dramatic of a shift to cause a sudden global disaster, and it's not going to cause Europe to freeze over, since the reduced cooling effect from a weakened Gulf Stream is likely to be offset by the overall warming trend, as this article by Washington Post science writer Chris Mooney notes.
NEWS: Gulf Stream Moved 125 Miles North in a Year
But the ocean circulation slowdown could cause other worrisome effects, including a faster rise in sea levels along the U.S. East Coast, disruption of the fishing industry upon humans depend for much of their food, and harsher storms for Europe.
Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research, lead author of the new study, notes in a blog post for Real Climate that while the effects seen in "The Day After Tomorrow" isn't going to happen, "they would not be harmless either."
Hat tip: EarthSky