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Past climate changes provided early clues to help predict big changes, scientists say

Researchers find ‘early warning signals’ in Earth’s past before sudden environmental shifts

Ian Johnston
Thursday 29 July 2021 19:09 BST
A phase-out of coal-fired power will be vital to meeting world’s climate goals, scientists say
A phase-out of coal-fired power will be vital to meeting world’s climate goals, scientists say (AFP via Getty Images)

Analysing abrupt changes to the climate in the past could help to inform the world’s response to the current climate crisis, an international team of natural and social scientists says.

Researchers from Germany’s Max Planck Institute for Meterology, the University of Exeter, Arizona State University and other institutions analysed sudden changes to the climate over the last 30,000 years.

The team found that there were “early warning signals” before these “tipping points”, critical thresholds when abrupt and cascading changes to the environment, society and ecology took place.

Identifying similar signals, by measuring how close environmental systems are to tipping points, could inform the world’s response to the climate emergency today, the researchers say.

Their paper, published in the journal Nature Geoscience, analysed several “tipping points” in the past, including the abrupt warming that took place about 14,700 years ago at the end of the last Ice Age, known as the Bolling-Allerod warming.

They also looked at how Africa’s climate changed 6,000 to 5,000 years ago when the humid period ended, before which most of northern Africa was covered by grass, trees and lakes and the Sahara was not a desert.

Lead author Professor Victor Brovkin, of the Max Planck Institute for Metereology, said: “For humans, it is crucial to anticipate the future – we need to know what surprises are ahead”.

“It sounds counter-intuitive, but to foresee the future we may need to look into the past.

“The chance to detect abrupt changes and tipping points – when small changes lead to big impacts – increases with the length of observations.

“This is why analysis of abrupt changes and their cascades recorded in geological archives is of enormous importance.”

Professor Tim Lenton, who directs the Global Systems Institute at the Univesrsity of Exeter, a trans-disciplinary group of academics whose research relates to the UN Sustainable Development Goals (SDGs), said: ““We face the risk of cascading tipping points again now – but this time it is of our own making, and the impacts will be global.

“Faced with that risk, we could do with some early warning signals.

“What examples from the past show is that different climate, ecological, or social systems all become slower at recovering from perturbations before they reach a tipping point – where they fail to recover at all.”

Examples of abrupt changes that could be caused by man-made climate change include the disintegration of ice sheets, permafrost thaw, dying of tropical forests, the slowing of ocean circulation and loss of oxygen in the ocean.

Commenting on the concept of early warning signals, Dr Sebastian Bathiany, from the Helmholtz Center Hereon, said: “There are useful statistical indicators that can be interpreted as precursors of abrupt changes.

“Those include so-called slowing down before abrupt changes in oceanic circulation, or increased spatial variance of vegetation cover before the end of African humid period.

“At the same time, one needs to be cautious as some abrupt changes, such as the Black Sea flooding about 9,500 years ago, cannot not be detected with such methods.”

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