If global temperatures rise beyond 1.5°C above pre-industrial levels, the planet will undergo more tipping points.
If global temperatures rise beyond 1.5°C above pre-industrial levels, the planet will begin to undergo as many as 16 tipping points. Worse: many of those tipping points are already a risk, whose likelihoods will increase with each tenth of a degree of further warming.
This is according to an international team of researchers who scrutinized evidence for a study on climate tipping points, including their temperature thresholds, timescales, and impacts by reviewing more than 200 papers published since 2008 when climate tipping points were first specifically defined.
Carbon emissions have already pushed the planet into the “tipping points danger zone,” the scientists warn, adding that five of the 16 could be triggered even at current temperatures.
The scientists, who examined paleoclimate data, current observations and climate models, say that 16 major biophysical systems involved in regulating Earth’s climate (so-called ‘tipping elements’) could cross tipping points where change becomes self-sustaining.
“That means that even if temperature stops rising, once the ice sheet, ocean or rainforest has passed a tipping point it will carry on changing to a new state,” the scientists explain.
“How long the transition takes varies from decades to thousands of years depending on the system. For example, ecosystems and atmospheric circulation patterns can change quickly, whilst ice sheet collapse is slower but leads to unavoidable sea level rise of several metres,” they add.
The researchers have categorised the tipping elements into nine planetary systems that affect the entire Earth such as Antarctica and the Amazon rainforest. They have also identified another seven systems that would have profound regional consequences if they tipped over a threshhold, including the West African monsoon and the mass death of most coral reefs around the equator.
The five most imminent tipping points include the melting of ice sheets in Greenland and West Antarctic; the widespread thaw of permafrost; and a massive die-off of tropical coral reefs. Four of the 16 tipping points identified would move from “possible events” to “likely events” at 1.5°C global warming and another five would become “possible” around this level of heating.
“We can see signs of destabilisation already in parts of the West Antarctic and Greenland ice sheets, in permafrost regions, the Amazon rainforest, and potentially the Atlantic overturning circulation as well,” says David Armstrong McKay, a scientist at the University of Exeter and the Earth Commission.
“The world is already at risk of some tipping points. As global temperatures rise further, more tipping points become possible.” he explains. “The chance of crossing tipping points can be reduced by rapidly cutting greenhouse gas emissions, starting immediately.”
According to the Intergovernmental Panel on Climate Change (IPCC), risks of tipping points in the climate become high by around 2°C above preindustrial temperatures and very high by between 2.5°C and 4°C. However, based on the new analysis Earth may already have left a “safe” climate state when global temperatures exceeded a warming of around 1°C.
“A conclusion of the research is that even the United Nations’ Paris Agreement goal to limit warming to well-below 2°C and preferably 1.5°C is not enough to fully avoid dangerous climate change. According to [our] assessment, tipping point likelihood increases markedly in the ‘Paris range’ of 1.5-2°C warming, with even higher risks beyond 2°C,” the scientists write in a statement.
In order to have a 50% chance of keeping warming below 1.5°C, global greenhouse gas emissions must be curtailed by half within a decade and must reach net-zero by 2050.
“The world is heading towards 2-3°C of global warming. This sets Earth on course to cross multiple dangerous tipping points that will be disastrous for people across the world,” says Johan Rockström, director of the Potsdam Institute for Climate Impact Research who was an author of the study,
“To maintain liveable conditions on Earth, protect people from rising extremes, and enable stable societies, we must do everything possible to prevent crossing tipping points. Every tenth of a degree counts,” Rockström stresses.
Tipping points in the climate are becoming better understood and this new research sheds new light on them, its authors say. “Since I first assessed climate tipping points in 2008 the list has grown and our assessment of the risk they pose has increased dramatically,” says Tim Lenton, director of the Global Systems Institute at the University of Exeter and a member of the Earth Commission.
“Our new work provides compelling evidence that the world must radically accelerate decarbonising the economy to limit the risk of crossing climate tipping points. To achieve that we now need to trigger positive social tipping points that accelerate the transformation to a clean energy future,” he says.
“We may also have to adapt to cope with climate tipping points that we fail to avoid, and support those who could suffer uninsurable losses and damages,” Lenton adds.