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A major study has shown that five dangerous climate tipping points may have already been passed because of the 1.1C of global heating that the world has experienced.
The tipping points include the collapse of Greenland’s ice cap, the collapse of a key current in the north Atlantic and the sudden melting of an Arctic permafrost.
The minimum rise now expected is 1.5C and, should that occur, four of the five tipping points become likely, rather than just possible. At this stage, five additional tipping points become possible which range from changes to a huge stretch of coniferous forest in the far northern latitudes and the loss of almost all mountain glaciers.
The research found a total of 16 tipping points with the final six needing a global rise of 2C to be triggered.
The tipping points have knock-on effects - for example the collapse of the current in the north Atlantic would disrupt rain which millions of people depend on for food and the collapse of the Greenland ice cap would eventually lead to a huge sea level rise.
The outlook was bleak from the director of the Potsdam Institute for Climate Impact Research, Professor Johan Rockström who was part of the study team. He 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.”
One of the lead authors of the study, the University of Exeter’s Dr David Armstrong McKay, said: “It’s really worrying. There are grounds for grief, but there are also still grounds for hope.
“The study really underpins why the Paris agreement goal of 1.5C is so important and must be fought for.
“We’re not saying that, because we’re probably going to hit some tipping points, everything is lost and it’s game over. Every fraction of a degree that we stop beyond 1.5C reduces the likelihood of hitting more tipping points.”
The Swiss government has proposed an Intergovernmental Panel on Climate Change report on climate tipping points.
The University of Bern’s Professor Thomas Stocker added: “The science on tipping points is far from done – it has barely begun – and much better models are needed to address the question [of] what warming level is critical for which tipping point.”