SYDNEY • More than half of the tipping points that could lead to long-term irreversible changes on Earth and threaten civilisation have been activated, scientists warned.

The scientists, including Emeritus Professor Will Steffen from the Australian National University in Canberra, argued in an article published in the journal Nature that the nine tipping points could act like a row of dominoes.

"As soon as one or two climate dominoes are knocked over, they push Earth towards others," Prof Steffen said in a statement released by the university yesterday to accompany the Nature article.

"We fear it may become impossible to stop the whole row of dominoes from tumbling over, forming a cascade that could threaten the existence of human civilisations."

The active tipping points include the loss of Arctic sea ice and ice sheets in Greenland and Antarctica, the thawing of permafrost and the destruction of boreal forest and the Amazon rainforest.

"The biosphere tipping points could trigger the uncontrollable release into the atmosphere of carbon that had been previously stored in the Earth, accelerating the heating and further destabilising the ice sheets," Prof Steffen said.

The melting of the ice sheets would lead to an "irreversible sea-level rise" of around 10m, he added.

The scientists called for urgent action to prevent the cascade by stronger action to reduce emissions way beyond the 2015 Paris Agreement. "We are rapidly running out of time to respond," the scientists said.

Despite most countries having signed the agreement to keep global warming to well below 2 deg C, the world is on track for a rise of at least 3 deg C, they said.

DPA