The climate crisis has brought the world to the brink of multiple “disastrous” tipping points, according to a major study.
It shows that five dangerous tipping points may have already been passed due to the 1.1°C global warming caused by humanity to date.
These include the collapse of the Greenland ice sheet, ultimately producing huge sea level rise, the collapse of a key current in the North Atlantic, disruptive rains on which billions of people depend for feed and a sudden melting of the carbon-rich permafrost.
At 1.5°C of heating, the minimum rise now expected, four of the five tipping points move from possible to probable, according to the analysis. Still at 1.5°C, five additional tipping points become possible, including changes to the vast northern forests and the loss of nearly all mountain glaciers.
In total, the researchers found evidence of 16 tipping points, with the latest six requiring a global warming of at least 2C to be triggered, according to scientists’ estimates. Tipping points would take effect on time scales ranging from years to centuries.
“Earth may have left a ‘safe’ climatic state beyond 1°C global warming,” the researchers concluded, with all of human civilization having developed at temperatures below that level. Exceeding one tipping point is often likely to help trigger others, producing cascades. But this is still under study and has not been included, which means that the analysis may present the minimum 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 track to pass several dangerous tipping points that will be disastrous for people around the world. To maintain livable conditions on Earth and enable stable societies, we must do all we can to avoid crossing tipping points.
Dr David Armstrong McKay from the University of Exeter, one of the study’s lead authors, said: “It’s really worrying. There are reasons for sorrow, but there are also still reasons for hope.
“The study really explains why the Paris Agreement target of 1.5°C is so important and must be defended.
“We’re not saying that because we’re probably going to hit tipping points, all is lost and it’s game over. Every fraction of a degree we stop above 1.5°C reduces the likelihood of hitting higher tipping points.
Recent research has shown signs of destabilization of the Amazon rainforest, the loss of which would have “profound” implications for global climate and biodiversity, as well as the Greenland Ice Sheet and Gulf Stream currents that scientists call the Atlantic overturning meridian circulation (Amoc).
A recent report by the Intergovernmental Panel on Climate Change said the risk of triggering climate tipping points becomes high with 2C of global warming.
The analysis, published in the journal Science, assessed more than 200 previous studies of past tipping points, climate observations and modeling studies. A tipping point occurs when a temperature threshold is exceeded, causing an irreversible change in a climate system, even if global warming ends.
The nine global tipping points identified are: the collapse of Greenland, West Antarctica and two parts of East Antarctica, the partial and total collapse of Amoc, the dieback of the Amazon, the collapse of permafrost and the loss of sea ice in winter in the Arctic.
The Amazon tipping point assessment did not include the effects of deforestation. “The combination of warming and deforestation could bring this much sooner,” Armstrong McKay said.
Seven other tipping points would have severe regional effects, including mass mortality of tropical coral reefs and changes to the West African monsoon. Other potential tipping points still under consideration include loss of oxygen in the oceans and major shifts in the Indian summer monsoon.
Scientists define the crossing of a tipping point as “possible” when its minimum temperature threshold is exceeded and “probable” beyond the central threshold estimate.
Professor Niklas Boers, of the Technical University of Munich, said: “The review is a timely update on potential Earth tilting elements, and the threat of tilting events under further warming is real. .”
He added that much more research was needed to lower critical temperature thresholds, with current estimates remaining highly uncertain.
Professor Thomas Stocker, from the University of Bern, said: “The science on tipping points is far from over – it has only just begun – and much better models are needed to answer the question. [of] which level of warming is critical for which tipping point.
A special IPCC report on climate tipping points was proposed in May by the Swiss government.
Professor Tim Lenton of 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 pose has increased dramatically.
“Our new work provides compelling evidence that the world needs to radically accelerate the decarbonization of the economy. To achieve this, we need to trigger positive social tipping points.
World on the brink of five ‘disastrous’ climate tipping points, study finds