Critical ocean circulation is showing signs of instability. Its stop would have serious impacts on our weather. – .

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Critical ocean circulation is showing signs of instability. Its stop would have serious impacts on our weather. – .


(CNN) — A crucial system of currents in the Atlantic Ocean that helps control temperatures in the northern hemisphere and has implications for weather systems across the planet is showing signs of instability due to man-made climate change, have scientists said.
Its collapse would have disastrous consequences for our climate and our life on Earth.

The Atlantic Reversing Meridional Circulation (AMOC) – of which the Gulf Stream is an important part – helps maintain energy balance in the Atlantic Ocean. It is often described as a “conveyor belt” that takes warm surface water from the tropics and distributes it to the North Atlantic. The colder and more salty water then flows and flows towards the south.

A study, published Thursday in Nature and Climate Change, warned of “an almost complete loss of stability in AMOC over the past century. The researchers said it could be close to a collapse from strong to weak traffic, although the threshold for such a collapse is still uncertain.

Scientists have warned for years that traffic is weakening. Heavy rains and melting ice caps make the water in the North Atlantic Ocean less salty, making it lighter and less likely to sink. If the water in this area becomes too clear, all traffic could be disrupted.

Global weather conditions are closely linked to the circulation and transport of heat and nutrients around the planet. A collapse of this system would cause large and abrupt changes, including rapid sea level rise, more extreme winters in Western Europe, and disruption of monsoon systems in the tropics.

It could also have a cascading effect and destabilize other components of Earth’s climate system, including the Antarctic ice cap and the Amazon rainforest.

This scenario was the premise of the 2004 climate science fiction film “The Day After”, in which a series of extreme weather disasters struck after climate change caused the collapse of AMOC.

The circulation is weaker than it has been for about 1,000 years, scientists had said, but they were unsure whether it had really been destabilized or undergoing natural changes. This week’s study used eight datasets of surface temperatures and salinity in the North Atlantic over a 150-year period, and found that global warming was behind the destabilization.

“The difference is critical,” study author Niklas Boers of the Potsdam Institute for Climate Impact Research told CNN in an email.

“Imagine a chair, which can either be moved (with the four legs remaining on the floor) or tilted. Both change the position of the chair (corresponding to the change in the mean force of the AMOC), but in the former case the stability of the chair will not be affected, while in the latter case there is a critical point. If we tilt the chair a little further, it will fall. My results suggest that what happens to AMOC is more likely to be a tilt than just a change, so AMOC has moved towards the critical threshold at which it can collapse, ”he said. he declares.

Boers added that he himself was surprised by his findings that the AMOC had been destabilized and was “heading towards its critical threshold, at which it could collapse abruptly.”

A traffic collapse would mean significant cooling in Europe, Beors said, “but perhaps of more concern is the effect of an AMOC collapse on the tropical monsoon systems of South America, Africa. from the West and India; especially in West Africa, a collapse of AMOC could lead to permanent drought conditions.

Boers admits in his study that he and other scientists are still unsure if and when the current might collapse, but he called on the world to cut greenhouse gas emissions “as much and as quickly as possible.” .

“Each gram of additional greenhouse gases in the atmosphere will increase the likelihood of an AMOC collapse in the future, thus emitting as little as possible, both at the individual level but of course also at the collective level and international, is the key. “

The study precedes a major report by the United Nations International Panel on Climate Change on Monday, which took years of preparation and is expected to provide the most conclusive examination to date on the extent of climate change of human origin. It will also likely paint a picture of what the future might look like, based on the steps the world is taking to reduce its greenhouse gas emissions.

This story first appeared on CNN.com Critical ocean circulation is showing signs of instability. Stopping it would have serious repercussions on our weather.Sean Gallup / Getty Images



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