The climate crisis has brought the world to the brink of multiple “disastrous” tipping points, according to a major study.
It shows five dangerous tipping points that may already be past due to the 1.1C global warming caused by humanity to date.
These include the collapse of the Greenland ice sheet, which will eventually lead to massive sea level rise, the collapse of a key current in the North Atlantic, disrupting the rain that billions of people depend on for food, and abrupt melting of carbon-rich permafrost.
At 1.5°C of warming, the smallest increase now expected, four of the five tipping points go from possible to likely, according to the analysis. Also at 1.5°C, five additional tipping points are possible, including changes in the vast northern forests and the loss of almost all mountain glaciers.
In all, the researchers found evidence of 16 tipping points, with the last six requiring global warming of at least 2°C to kick in, according to the scientists’ estimates. Tipping points would take effect on time scales ranging from a few years to centuries.
“Earth may have left a ‘safe’ climate state beyond 1C global warming,” the researchers concluded, with all of human civilization having developed in temperatures below this level. Passing one tipping point is likely to help trigger others, producing cascades. But this is still being studied and was not included, which means the analysis may present the least danger.
Professor Johan Rockström, director of the Potsdam Institute for Climate Impact Research, who was part of the study team, said: “The world is heading towards 2-3C of global warming.
“This puts Earth on a path to cross multiple dangerous tipping points that will be disastrous for people around the world. To maintain habitable conditions on Earth and enable stable societies, we must do everything we can to avoid crossing tipping points.”
Dr David Armstrong McKay of the University of Exeter, lead author of the study, said: “It’s really worrying. There are reasons for sorrow, but there are also reasons for hope.
“The study really supports why the Paris agreement target of 1.5°C is so important and should be fought for.
“We’re not saying that, because we’re probably going to hit some tipping points, all is lost and it’s game over. Every fraction of a degree we stop beyond 1.5C reduces the probability of reaching more tipping points.”
Recent research has shown signs of destabilization in the Amazon rainforest, the loss of which would have “profound” implications for global climate and biodiversity, as well as for the Greenland ice sheet and the currents of the Gulf Stream that scientists call circulation of southern overturning of the Atlantic (amoc).
A recent report by the Intergovernmental Panel on Climate Change said the risk of triggering climate tipping points becomes high at 2C of global warming.
the analysis published in the journal Science, evaluated more than 200 previous tipping point studies, climate observations, and modeling studies. A tipping point is when a temperature threshold is crossed, leading to unstoppable change in a climate system, even if global warming ends.
The nine identified global tipping points are: the collapse of Greenland, West Antarctica and two parts of the East Antarctic ice sheets, the partial and total collapse of the Amoc, the Amazon dieback, the collapse of permafrost and the loss of winter sea ice in the Arctic.
The Amazon tipping point assessment did not include the effects of deforestation. “The combination of warming and deforestation could bring that much sooner,” said Armstrong McKay.
Another seven tipping points would have serious regional effects, including the extinction of tropical coral reefs and changes in the West African monsoon. Other potential tipping points still being studied include ocean oxygen loss and major changes in the Indian summer monsoon.
Scientists define crossing a tipping point as “possible” when its minimum temperature threshold is passed and “likely” beyond the central threshold estimate.
Professor Niklas Boers, from the Technical University of Munich, said: “The review is a timely update on potential Earth tipping elements, and the threat of tipping events under further warming is real.”
He added that much more research was needed to lower critical temperature thresholds, and current estimates remain highly uncertain.
Professor Thomas Stocker, from the University of Bern, said: “The science on tipping points is far from over, it has barely begun, and much better models are needed to tackle the question. [of] what level of warming is critical for what tipping point.”
A special IPCC report on climate tipping points it was proposed in May by the Swiss government.
Professor Tim Lenton from the University of Exeter, co-author of the analysis, said: “Since I first assessed tipping points in 2008, the list has grown and our assessment of the risk they represent has increased dramatically.
“Our new work provides compelling evidence that the world must radically accelerate the decarbonisation of the economy. To achieve that, we need to trigger positive social tipping points.”