By Seth Borenstein -
The Associated Press
A sharp disruption in Atlantic currents that could freeze large parts of Europe appears more likely than before after a complex new computer simulation found a “cliff-like” tipping point looms in the future.
It is
a long-feared nightmare,
triggered by the melting of the Greenland ice sheet due to global warming, and although it is still decades away it is not centuries away as it once seemed, according to a new study published on Friday in Science Advances.
The research, the first to use complex simulations and include multiple factors, uses a key measure to determine the strength of ocean circulation, which is declining.
[The main ocean current is at risk of imminent collapse: the consequences could freeze Europe or submerge New York]
A collapse of the current – called the Atlantic Meridional Overturning Circulation or AMOC – would change the global climate because it means the end of one of the planet's key climate and ocean forces.
According to the study, temperatures in northwestern Europe would drop by 9 to 27 degrees Fahrenheit (5 to 15 Celsius) over several decades, Arctic ice would extend much further south, heat would increase even further in the Southern Hemisphere, changes would global precipitation regimes and would alter the Amazon.
Other scientists pointed out that
it would be a catastrophe that could cause food and water shortages around the world
.
Greenland.Thomas Traasdahl / AFP via Getty Images
“We are getting closer (to collapse), but we are not sure to what extent
,” said René van Westen, a climate scientist and oceanographer at Utrecht University in the Netherlands and lead author of the study.
“We are heading towards an inflection point.”
When this global weather calamity – crudely depicted in the film
The Day After Tomorrow
– may occur is “the million-dollar question, which unfortunately we cannot answer at the moment,” van Westen said.
According to him, it is probably a century away from happening, but it could happen in his lifetime.
He just turned 30 years old.
“Warming is not hypothetical, but is already happening and is now having an impact on society”
Joel Hirschi HEAD OF DIVISION, UK NATIONAL OCEANOGRAPHY CENTER
“It also depends on the pace of climate change we cause as humanity,” van Westen said.
Studies have shown that the AMOC is slowing down, but the problem is its collapse or complete closure.
The United Nations Intergovernmental Panel on Climate Change, a group of hundreds of scientists that provides regular authoritative updates on warming, said it is moderately confident that a collapse will not occur before 2100 and, In general, he downplayed catastrophic scenarios.
But van Westen, several outside scientists and a study last year believe that may not be true.
Stefan Rahmstorf, head of Earth Systems Analysis at the Potsdam Climate Research Institute in Germany, was not involved in the research, but considered it “a major advance in the science of AMOC stability.”
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“The new study significantly increases the growing concern about a collapse of the AMOC in the not-too-distant future,” Rahmstorf said in an email.
“We will ignore it at our own risk.”
Tim Lenton, a climate scientist at the University of Exeter, who was also not involved in the research, said that after the study, he is even more concerned about the possibility of a collapse that would cause so many repercussions on the global climate "so
abrupt and severe that it would be almost impossible to adapt to them in some places
,” Lenton said.
There are signs that the AMOC has collapsed before, but it is not yet known when or how it will change in the future, explained oceanographer Wei Cheng of the US National Oceanic and Atmospheric Administration, who was not involved in the research.
The AMOC is part of an intricate global conveyor belt of ocean currents that move different levels of warm, salty water around the planet at different depths, following patterns that help regulate Earth's temperature, absorb carbon dioxide and fuel the cycle. of water, according to NASA.
When the AMOC stops, there is less heat exchange across the planet and “it severely affects Europe,” van Westen said.
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For thousands of years, Earth's oceans have relied on a circulation system that works like a conveyor belt.
It still works, but more and more slowly.
Its engine is located off the coast of Greenland, where, as more ice melts due to climate change, more fresh water flows into the North Atlantic and everything slows down, van Westen explained.
In the current system, colder and deeper fresh water heads south through the two Americas, and then east through Africa.
Meanwhile, saltier, warmer ocean water from the Pacific and Indian oceans pushes past the southern tip of Africa, diverts toward and around Florida, and continues up the east coast of the United States to Greenland.
The Netherlands team simulated its flow for 2,200 years, adding the effects of human-caused climate change.
At 1,750 years, they observed “an abrupt collapse of the AMOC,” but so far they have not been able to translate that simulated chronology into Earth's real future.
The key to monitoring what happens is a complicated flow measurement around the tip of Africa.
The more negative that measurement is, the slower the AMOC will go.
“This value becomes more negative with climate change,” van Westen said.
When you get to a certain point, it's not a gradual stop, but something "like a cliff," he added.
The world should pay attention to the possible collapse of the AMOC, said Joel Hirschi, division head of the United Kingdom's National Oceanography Centre.
But there is a bigger global priority, he said.
“In my opinion, the rapid increase in temperatures in recent years and the associated extreme temperatures are more worrying than the collapse of the AMOC,” he said.
“Warming is not hypothetical, but is already happening and is now having an impact on society.”