It’s a cold, cold world out there due to global warming — and it could get even worse, according to new alarms being raised by British scientists.
A new study in the journal Nature Geoscience says that the Atlantic Ocean current that powers the Gulf Stream is weaker than it has been in a thousand years and is likely to get weaker due to global warming. The study calls the current by its formal name, the Atlantic Meridional Overturning Circulation, or more often by its acronym, AMOC.
“There is evidence that the AMOC is slowing down in response to anthropogenic global warming — as predicted by climate models — and that the AMOC is presently in its weakest state for more than 1,000 years,” the study said.
There is an issue with data, though.
“As continuous direct measurements of the AMOC started only in 2004, longer-term reconstruction must be based on proxy data,” the study said.
But using such data as it could find or construct, the study said that “the AMOC decline in the twentieth century is unprecedented and … over the past decades, the AMOC is in its weakest state in over a millennium.”
The ocean current is the driver of the Gulf Stream, which brings warmth from the Gulf of Mexico to places such as Britain and Western Europe. Because of it, winters are milder there than in North American places with similar latitudes.
If the current doesn’t move as fast as it has been, the Gulf Stream gets weaker and Europe is likely to shiver.
The study from the Potsdam Institute, Ireland’s Maynooth University and University College London says that the current is about 15 percent weaker now than in the 1950s, based on the study’s data.
“In 20 to 30 years it is likely to weaken further, and that will inevitably influence our weather, so we would see an increase in storms and heatwaves in Europe, and sea level rises on the East Coast of the U.S.,” Stefan Rahmstorf from the Potsdam Institute and an author of the study told the U.K. Daily Mail.
The British publication illustrated its report on the study with images from the film “The Day After Tomorrow,” which links the cessation of the current with massive, deadly storms.
“The Gulf Stream System works like a giant conveyor belt, carrying warm surface water from the equator up north, and sending cold, low-salinity deep water back down south. It moves nearly 20 million cubic meters of water per second, almost a hundred times the Amazon flow,” Rahmstorf said
“If we continue to drive global warming, the Gulf Stream System will weaken further — by 34 to 45 percent by 2100 according to the latest generation of climate models,” he said.
“This could bring us dangerously close to the tipping point at which the flow becomes unstable.”
Researcher Levke Caesar explained that the U.S. will not get off scot-free if this takes place.
“The northward surface flow of the AMOC leads to a deflection of water masses to the right, away from the U.S. East Coast,” she said. “This is due to Earth’s rotation that diverts moving objects such as currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
“As the current slows down, this effect weakens and more water can pile up at the U.S. East Coast, leading to an enhanced sea level rise.”
Andrew Meijers, Deputy Science Leader of Polar Oceans at British Antarctic Survey, said the study shows how climate change can impact the global community.
“This work provides new long-term context and reveals that prior to the era of human-induced climate change the Atlantic overturning circulation was relatively stable and stronger than it is now. This indicates that the slowdown is likely not a natural change, but the result of human influence,” he said.
“The AMOC has a profound influence on global climate, and particularly in North America and Europe, so this evidence of an ongoing weakening of the circulation is critical new evidence for the interpretation of future projections of regional and global climate.”
Because models developed by scientists say the AMOC might have “a tipping point below some circulation strength, a point at which the relatively stable overturning circulation becomes unstable or even collapses,” the slowing current is a warning, he said.
“The ongoing weakening of the overturning means we risk finding that point, which would have profound and likely irreversible impacts on climate,” he said.
Some researchers think this might not really happen.
“A few times a year the British media of all stripes goes into a tizzy of panic when one climate scientist or another states that there is a possibility that the North Atlantic ocean circulation, of which the Gulf Stream is a major part, will slow down in coming years or even stop,” Richard Seager of Columbia University wrote in comments posted on the school’s website.
“Whether the scientists statements are measured or inflammatory the media invariably warns that this will plunge Britain and Europe into a new ice age, pictures of the icy shores of Labrador are shown, created film of English Channel ferries making their way through sea ice are broadcast… And so the circus continues year after year.”
Seager disagrees with the concerns.
“A slowdown of the Gulf Stream and ocean circulation in the future, induced by freshening of the waters caused by anthropogenic climate change (via melting glaciers and increased water vapor transport into high latitudes) or simply by warming, would thus introduce a modest cooling tendency. This would leave the temperature contrast across the Atlantic unchanged and not plunge Europe back into the ice age or anything like it. In fact the cooling tendency would probably be overwhelmed by the direct radiatively-driven warming by rising greenhouse gases,” he wrote.
“It is long time that the Gulf Stream-European climate myth was resigned to the graveyard of defunct misconceptions along with the Earth being flat and the sun going around the Earth. In its place we need serious assessments of how changes in ocean circulation will impact climate change and a new look at the problem of abrupt climate change that gives the tropical climate system and the atmosphere their due as the primary drivers of regional climates around the world.”
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