New Warning on Climate Tipping Points

Running out of runway.

New Scientist (paywall):

The climate has warmed so much that we are already at risk of triggering five global “tipping points” that would have catastrophic effects worldwide and couldn’t be reversed easily if at all, according to a major report. As the world goes past 1.5°C of warming, it will be increasingly likely that we will cross these tipping points, and there will be a growing risk of this resulting in others as well.

“Triggering one tipping point could trigger another in a kind of dangerous domino effect,” says Tim Lenton at the University of Exeter in the UK, the report’s lead author. “But also these tipping points in the Earth system could, in turn, trigger damaging tipping points in societies, things like food security crises, mass displacement and conflicts. Stopping these threats is possible, but it’s going to require urgent global action.”

A tipping point is where a small alteration in a system can cause abrupt changes that are hard to reverse or are irreversible, because of amplifying feedback processes. Lenton says this is like leaning back on a chair: when it is near the balance point, just a small nudge can make the chair fall over.

According to the report, the five major tipping points we are near to crossing are: the loss of the Greenland ice sheet, the demise of the West Antarctic ice sheet, the die-off of tropical coral reefs, the abrupt thaw of large areas of Arctic permafrost and the slowing of an ocean current known as the North Atlantic subpolar gyre.

The subpolar gyre is a circular current south of Greenland where salty water cools and sinks. It is linked to the Atlantic meridional overturning circulation (AMOC), but there is growing evidence that the current could slow or stop separately from and sooner than the AMOC, says David Armstrong McKay, also at the University of Exeter.

“[The slowing of the subpolar gyre] could happen within about 10 years,” says McKay. “It would have pretty major impacts across both sides of the Atlantic. It would cause regional cooling and affect agriculture in Europe and North America, and change the patterns of extreme weather events.”

“For some tipping points, we have a very short window for preventive action open right now which might close as soon as the 2030s,” says Manjana Milkoreit at the University of Oslo in Norway, who also worked on the report.

“We think that the prevention of Earth system tipping points should be the core objective of governance efforts because of the scale and severity of the threats that they represent, their cascading potential and the irreversibility of many tipping processes on relevant human timescales,” she says.

Other tipping points include the die-off of seagrass meadows and mangrove forests, and the collapse of fisheries.

Associated Press:

In the Himalayas for example, glaciers are melting at such a rate that landslides, floods and other erratic weather has become common, said Izabella Koziell, from the International Centre for Integrated Mountain Development. Coral bleaching — which happens when the water is too hot — is blighting oceans from Australia to Florida. And some ice sheets near Earth’s poles are disappearing at an alarming rate. 

Tipping points “can trigger devastating domino effects, including the loss of whole ecosystems,” Lenton said. 

C. R. Babu of the Centre for Environmental Management of Degraded Ecosystems at University of Delhi, agreed that Earth warming past 1.5 degrees Celsius (2.7 degrees Fahrenheit) above preindustrial times may mean “the extinction of natural systems.”

Abhilash S from Cochin University of Science and Technology said it was almost certain that “some natural systems will be permanently damaged.” 

“Protecting them is beyond our control,” he warned. “We have already lost that chance.”

But the report’s bleak outlook is tempered with a message of hope, as researchers say there are positive tipping points that can be reached too, particularly in the transition from planet-warming fossil fuels to renewable energy, people changing to plant-based diets and social movements.

“Human history is full of examples of abrupt social and technological change,” said University of Exeter’s Steve Smith. “Many areas of society have the potential to be ‘tipped’ in this way.”