Climate 'tipping points' need not be the end of the world

Once triggered, tipping points may lead to abrupt changes such as the dieback of the Amazon rainforest or melting of major ice sheets.

Until now, crossing these thresholds has been assumed to be a point of no return, but the new study -- published in the journal Nature -- concludes that thresholds could be "temporarily exceeded" without prompting permanent shifts.

The research team, from the University of Exeter and the UK Centre for Ecology and Hydrology (UKCEH), say the time available to act would depend on the level of global warming and the timescale involved in each tipping point.

"The more extreme the warming, the less time we would have to prevent tipping points," said lead author Dr Paul Ritchie, of Exeter's Global Systems Institute and the Department of Mathematics.

"This is especially true for fast-onset tipping points like Amazon forest dieback and disruption to monsoons, where irreversible change could take place in a matter of decades.

"Slow-onset tipping points take place over a timescale of many centuries and -- depending on the level of warming -- this would give us more time to act."

Joe Clarke, also of the University of Exeter, said: "Fortunately, the tipping points that are believed to be closest are slow-onset tipping points. This may give us a lifeline to avoid dangerous climate change."

Concerns about tipping points like Greenland ice sheet melt are one of the reasons for the Paris Agreement targets to keep global warming below 1.5°C.

"However, current rates of warming make it almost inevitable that we will exceed that level," said Professor Peter Cox.

Dr Ritchie added: "It is widely assumed that this means we are now committed to suffering these tipping events.

"We show that this conventional wisdom may be flawed, especially for slow-onset tipping elements such as a collapse of the Atlantic Meridional Overturning Circulation or the melting of ice sheets."

The "time to act" was calculated as the time taken to reverse warming and stabilise at 1.5°C above pre-industrial levels.

"Ideally, we will not cross tipping point thresholds, but this gives hope we may be able to pull back from danger if needed," said Dr Chris Huntingford of UKCEH.