The effects of global warming have brought our planet to the brink of a number of tipping points. Passing one tipping point is often likely to help trigger others.
“The Earth may have left a ‘safe’ climate state beyond 1C global warming,” the researchers concluded.
A major study shows five dangerous tipping points may already have been passed due to the 1.1C of global heating caused by humanity to date.
The analysis, published in the journal Science, assessed more than 200 previous studies on past tipping points, climate observations and modelling studies. A tipping point is when a temperature threshold is passed, leading to unstoppable change in a climate system, even if global heating ends.
These include the collapse of Greenland’s ice cap, eventually producing a huge sea level rise, the collapse of a key current in the north Atlantic, disrupting rain upon which billions of people depend for food, and an abrupt melting of carbon-rich permafrost.
At 1.5C of heating, the minimum rise now expected, four of the five tipping points move from being possible to likely, the analysis said. Also at 1.5C, an additional five tipping points become possible, including changes to vast northern forests and the loss of almost all mountain glaciers.
In total, the researchers found evidence for 16 tipping points, with the final six requiring global heating of at least 2C to be triggered, according to the scientists’ estimations. The tipping points would take effect on timescales varying from a few years to centuries.
Prof Johan Rockström, the 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 sets Earth on course to cross multiple dangerous tipping points that will be disastrous for people across the world. To maintain liveable conditions on Earth and enable stable societies, we must do everything possible to prevent crossing tipping points.”
The nine global tipping points identified are: the collapse of the Greenland, west Antarctic and two parts of the east Antarctic ice sheets, the partial and total collapse of Amoc, Amazon dieback, permafrost collapse and winter sea ice loss in the Arctic.
A further seven tipping points would have severe regional effects, including the die-off of tropical coral reefs and changes to the west African monsoon. Other potential tipping points still being studied include the loss of ocean oxygen and major shifts in the Indian summer monsoon.
The assessment of the Amazon tipping point did not include the effects of deforestation. “The combination of the warming and the deforestation could bring that a lot sooner,” Dr David Armstrong McKay at the University of Exeter, a lead author of the study, said.
The scientists define crossing a tipping point as “possible” when its minimum temperature threshold is passed and “likely” beyond the central threshold estimate.
Prof Niklas Boers, at the Technical University of Munich, said: “The review is a timely update on the Earth’s potential tipping elements, and the threat of tipping events under further warming is real.”
World on brink of five ‘disastrous’ climate tipping points, study finds | Climate crisis | The Guardian
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