Scientists have said they have spotted warning signs of the collapse of the Gulf Stream, a major “tipping point” in the fight against climate change.
Researchers found that there has been “an almost complete loss of stability over the last century” of natural ocean currents known as the Atlantic meridional overturning circulation (AMOC).
The currents were already thought to have been at their slowest point in over 1,500 years, but new studies suggest the AMOC may be nearing a complete shutdown.
“The signs of destabilisation being visible already is something that I wouldn’t have expected and that I find scary,” Niklas Boers, from the Potsdam Institute for Climate Impact Research in Germany, who did the research, told The Guardian. “It’s something you just can’t [allow to] happen.”
If that were to happen, it could spell catastrophe for billions of people around the world.
Here is everything you need to know about it.
What is the Gulf Stream?
The Gulf Stream is a warm and swift Atlantic ocean current that originates in the Gulf of Mexico and stretches past the tip of Florida and along the eastern coastline of North America, before it crosses the Atlantic Ocean as the North Atlantic Current.
The Gulf Stream influences the climate of the east coast of North America from Florida to Newfoundland and the west coast of Europe.
It transports heat from the warm waters of the tropics and Southern Hemisphere northwards, and is responsible for contributing to the relative warmth of Western and Northern Europe, which often experience higher temperatures than similar latitudes because of the North Atlantic Current.
What would happen if it collapsed?
A scientist at the Potsdam Institute for Climate Impact Research scientist said, Rahmstorf said: “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 US.”
But it’s not just Europe and the UK that would suffer – a collapse of the Gulf Stream would have dire consequences around the world.
It would disrupt monsoon seasons and rains in places like India, South America and West Africa, affecting crop production and creating food shortages for billions of people.
The decline of the Amazonian rainforest and the Antarctic ice sheets would also be put into fast forward.
When might a full collapse occur?
It’s hard to say exactly when such a collapse might happen.
These systems are complex, and the Gulf Stream is affected by other ocean and air currents just as much as it holds influence over them.
That means a forecast is extremely difficult to pin down; it could happen within one or two decades, or one of two centuries. But there is one thing scientists are in agreement about - it must not be allowed to happen.
“We risk triggering [a tipping point] in this century,” said Rahmstorf, “and the circulation would spin down within the next century. If we do not stop global warming, it is increasingly likely that we will trigger it.”
Rahmstorf was one of a group of researchers behind a study that found human-caused global warming had weakened the system behind the Gulf Stream to its lowest strength in more than a millennium; he told the paper the consequences of a breakdown of the AMOC were “massive”.
The study looked at Greenland ice cores, sediments and other data to learn weather patterns of the Atlantic Meridional Overturning Circulation (AMOC) since 400 AD.
“A fairly consistent picture of the AMOC emerges," said the study published in the journal Nature Geoscience. “After a long and relatively stable period, there was an initial weakening starting in the nineteenth century, followed by a second, more rapid, decline in the mid-twentieth century, leading to the weakest state of the AMOC occurring in recent decades.”
It’s believed a more definitive collapse would be triggered by an increase of CO2 emissions, although the exact level is again hard to pinpoint.
So experts say the best course of action is to limit pollution and carbon footprints as much as is possible in all areas.
"The only thing to do is keep emissions as low as possible,” Boers told The Guardian. “The likelihood of this extremely high-impact event happening increases with every gram of CO2 that we put into the atmosphere.”
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