Global Warming – ” Bad news for the climate system and humanity This is how the team presents its latest study, published February 9 in the journal Advancement of science. The latter focuses on the system involving the ocean currents of the Atlantic Ocean (including the well-known currents Gulf Stream).
Called AMOC in English (for South Atlantic Overturning Circulation), it is a kind of giant ocean treadmill that regulates ocean temperature. It redistributes heat, carbon and nutrients essential for life around the world. But since 1950, the AMOC rate has declined by 15%. Worse still, it is at its weakest point in more than a thousand years.
Simply put, the melting of Greenland's glaciers and the Arctic ice caps is the main reason for this slowdown. It is happening much faster than expected, and is causing large amounts of fresh water to flow into the sea, preventing salt water from flowing south.
On the edge of the abyss
The researchers tried to find out what would happen in the event of an irreversible decline in AMOC. To do this, they used computer models and combined a set of pre-existing data to run their most accurate simulation yet. Here they confirmed that this natural phenomenon was progressing towards the brink of the abyss.
This turning point has no specific date. A previous study estimated that it could happen between 2025 and 2095. Conversely, the UK Met Office stated that the large and rapid changes in AMOC were “ Very unlikely » During the twenty-first century. At the moment, there is no specific date for when this moment will arrive.
However, researchers have developed a warning signal to indicate when this famous tipping point will occur. It is based on transporting salinity to the southern borders of the Atlantic Ocean. Once a certain threshold is reached, this is an indication that the shift is likely to occur within the next four decades.
Forty years may seem like a long time, but when you look at the consequences of such change on climate, it's ridiculous. ” What surprised us was how quickly the transformation occurred The study's lead author, René van Westen from Utrecht University, said, adding that it would simply be ” “Severe”.
Today, global warming continues at a rate of 0.2°C every decade, and we are already beginning to see the effects. If AMOC collapses or stops, we will move at a rate of +3°C per decade. Hence, regions of the Southern Hemisphere will rapidly rise in temperature by several degrees. At the same time, this collapse of the Atlantic ocean currents will cause a giant cold wave centered on the ancient continent.
In addition, sea levels will rise by one meter in the Atlantic Ocean, which will submerge many coastal cities. The dry and wet seasons will reverse in the Amazon, ending the forest forever. All of these changes, occurring much faster than the current climate is warming, would prevent humanity from adapting. A very depressing programme.
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