GLOBAL WARMING – ” Bad news for the climate system and humanity “. This is how a team presents its latest study, published on February 9 in the journal Science Advances. The latter focuses on the system encompassing marine currents in the Atlantic Ocean (including the well-known Gulf Stream).
Called AMOC in English (for Atlantic southern overturning circulation), it is a sort of gigantic ocean treadmill regulating the temperature of the oceans. It redistributes heat, carbon and nutrients essential to life around the world. But since 1950, Amoc has decreased by 15%. Worse, it is in its weakest state in more than a millennium.
To put it simply, the melting of Greenland’s glaciers and the Arctic ice caps are the main culprits for this slowdown. It is happening much faster than expected, and is causing large quantities of fresh water to pour into the sea, preventing saltier water from flowing southward.
At the edge of the cliff
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 compiled a set of pre-existing data to carry out a simulation, the most precise to date. This is where they confirmed that this natural phenomenon was advancing towards the edge of the cliff.
This tipping point does not have a precise date. A previous study estimated that it could occur between 2025 and 2095. Conversely, the UK Met Office said significant and rapid changes in Amoc were “ very unlikely » during the 21st century. For now, 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 the transport of salinity to the southern border of the Atlantic Ocean. Once a certain threshold is reached, it is the signal 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 a change on the climate, it’s ridiculous. “ What surprised us is how quickly the switchover is happening said the paper’s lead author, René van Westen of Utrecht University, adding that it will simply be ” devastating ».
Today, global warming continues at a rate of 0.2°C per decade, and we are already seeing the effects. If Amoc collapses or stops, we will move at a rate of +3°C per decade. Regions of the southern hemisphere would thus quickly warm by several degrees. At the same time, this collapse of Atlantic marine currents will cause a gigantic cold wave localized on the Old Continent.
Added to this will be a one-meter rise in sea levels in the Atlantic, flooding many coastal cities. The dry and wet seasons would reverse in the Amazon, ending the forest for good. All these changes happening much, much faster than the current warming of the climate, would prevent humanity from adapting. A very bleak program.
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