Paris (AFP)
According to new research, sudden disturbances in Earth’s climate thousands of years ago that caused massive sea level rise and mass ice melting could serve as an early warning system for the planet’s current tipping point.
The tipping point of climate – irreversible for centuries or more – is the threshold in the past at which large and rapid changes in nature could occur.
They include looming disasters such as the melting of ice sheets in Greenland and West Antarctica, which contain enough frozen water to lift the oceans more than ten meters (40 feet).
But it is difficult to predict, given the changes in relatively small or increasing variables such as atmospheric carbon concentration that they cause.
In a review of past climate events published in Nature Geoscience, an international team of scientists examined two major instabilities in the Earth’s system, caused by changes in ice and ocean patterns as well as rainfall.
They studied the conditions that caused global warming at Bowling Allerud nearly 15,000 years ago, which saw surface air temperatures rise as high as 14°C over Greenland.
The team also studied the end of the so-called African Wet Period some 6000-5000 years ago, which led to regional changes in ecosystems and human prehistoric societies.
They found that many past climate systems, such as ocean dynamics and rainfall patterns, tended to slow down when they reached a tipping point, after which they failed to recover from disturbances.
“Earth’s recent past shows us how sudden changes in Earth’s systems have a ripple effect on human ecosystems and societies, as they struggle to adapt,” said Tim Linton, co-author of the review and director of the University’s World Systems Institute. from Exeter.
“We are in danger of tipping over again – but this time we are making our own, and the effect will be global,” Linton said.
“In the face of this danger, we can tackle some early warning systems.”
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While current atmospheric carbon dioxide levels of around 412 parts per million have some precedent – at least 800,000 years ago – levels of carbon dioxide accumulation did not.
Scientists are divided over when or whether most of the tipping points will be triggered, but many believe that effects like melting of the ice sheet are already “limited” by carbon pollution.
The authors of the review, published online Thursday, said it showed evidence that the combined effects of sudden changes in the Earth’s system caused disruption across the planet.
Changes in sea ice levels and currents, for example, at the onset of the Pauling-Allerud warming cause cascading effects such as decreased ocean oxygen levels, vegetation, and atmospheric carbon dioxide and methane levels.
“It seems illogical, but to predict the future we may need to look to the past,” said lead author Viktor Brovkin of the Max Planck Meteorological Institute.
“The chances of detecting sudden changes and tipping points – where small changes lead to large effects – increase with the length of the observation, he said.
“This is why analysis of sudden changes and their sequences recorded in geological archives is so important.”
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