At current rates, 5 key climate tipping points are already possible, new study warns
2 of the tipping points at highest risk are in Canada
Current rates of global warming have already moved the world perilously close to several tipping points that could send key global weather systems into irreversible collapse, a significant study from Europe has found.
The study builds upon the growing body of scientific research on non-linear changes in the climate — major, irreversible change that goes beyond the linear and gradual increase of average temperatures.
It found that five tipping points, including the abrupt thaw of the permafrost in the boreal forest, and the end of an ocean current system in the Labrador Sea are "possible" under current levels of global warming.
Those two tipping points are in Canada.
More alarmingly, the study published Friday in Science magazine suggests four tipping points will escalate from "possible" to "likely" at 1.5 C of global warming. These include the abrupt thaw of the boreal permafrost, the collapse of the ice sheets in Greenland and West Antarctica and a rapid die-off of coral reefs.
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"What we're looking at is various negative impacts like more sea level rise, coral reef die-off and things like that becoming locked in and having to be dealt with for future generations," said the paper's co-author David Armstrong McKay, a climate and biosphere scientist and visiting fellow at the University of Exeter in the U.K.
The findings raise questions about whether the goal of the international Paris Agreement, which aims to limit global warming to well below 2 C and ideally below 1.5 C, is enough to stave off climate catastrophe. The study effectively warns that the planet already left a safe climate state when it passed 1 C of global warming.
These tipping points would have devastating consequences for global weather patterns, sea-level rise and biodiversity, the study highlights. Some of these, like the thawing of the permafrost, would release even more greenhouse gases, accelerating climate change even further.
But the study authors say that while understanding of tipping points has improved over the past decade, there remains uncertainty over several factors. Some tipping points could be avoided if global warming overshoots 1.5 C in the coming years but then comes back down due to rapid emissions cuts.
The tipping points also have varying timescales. Some will happen more quickly: the coral reef die-off could happen over 10 years when triggered, and the abrupt thaw of the boreal permafrost could happen over 200 years. Others, such as the Greenland Ice Sheet collapse, would happen over 10,000 years once triggered, spreading its effect on the global weather system and sea-level rise over a long period.
"Every extra fraction of a degree that we avoid above 1.5 C reduces the likelihood of further tipping points being triggered or made possible," McKay said.
"So I'd say that this is not a 'game over' situation, it just shows what the stakes are in that 1.5- to two-degree range."
Permafrost in trouble
About half of Canada is covered in permafrost, where the ground remains at a temperature of 0 C or below. McKay says the gradual thawing of this permafrost has been a concern for a while, but there is now greater awareness of a possible abrupt thaw that could leave its mark on the local landscape — and have major consequences for the global climate.
That's because the permafrost contains carbon from the remains of dead plants and animals dating back millions of years. Right now, that carbon is locked safely in the ground, but if the permafrost thaws, it could be released into the atmosphere and speed up global warming.
"Our understanding of that is only starting to evolve and we reckon that could potentially increase emissions by something like 50 to 100 per cent on top of gradual thaw emissions," McKay said.
Jennifer Baltzer has seen the changes in the northern landscape up close and stresses the importance of these soils remaining the way they are.
"There's about twice as much carbon locked into permafrost soils as we have floating around in the atmosphere," said Baltzer, the Canada research chair in forests and global change at Wilfrid Laurier University.
"As those soils warm up and thaw, that carbon becomes available to the microbes in the soil and becomes available for decomposition and then the release of carbon dioxide and methane into the atmosphere."
It becomes a destructive cycle.
As the permafrost thaws and carbon is released, the planet continues to warm — speeding up the thawing of permafrost, which sends more carbon into the atmosphere.
Baltzer notes that the Arctic is warming at several times the average rate of the rest of the world, and so a 1.5 C increase in global temperatures would mean a four- to five-degree increase in the Arctic. At those temperatures, it would become difficult for the permafrost to maintain itself and hold all that carbon in, she said.
"The challenge is, with these additional Arctic contributions, it makes the whole process of trying to reach that net-zero goal even more challenging. And so the 1.5-degree mark is really, really essential for us to stay below."
Non-linear changes not easy to understand
Co-author Sina Loriani, a post-doctoral researcher at the Potsdam Institute for Climate Impact Research in Germany, said the idea of non-linear changes like tipping points, which can be uncontrollable and unpredictable, can be hard to understand.
And that can make it a difficult topic in climate negotiations.
"The essence of tipping points is there's a danger … that you trigger something that runs on itself," Loriani said. "I would say it's not accordingly represented in climate action today."
The study indicates there are varying levels of uncertainty over each tipping point, suggesting some climate systems need more research to understand exactly how they are changing.
Some areas of the global permafrost are better studied than others, Baltzer said, such as Siberia, which is a difficult environment to work in but contains the largest area of permafrost on the planet. With the political situation due to the war in Ukraine, research in that region has been further curtailed.
The world has already reached 1.1 C of global warming and is set to hit 1.5 C by the 2030s. The net-zero pledges and climate plans of countries, if implemented, could limit global warming to just under 2 C, according to research published in Nature in April.
But current policies are actually set to result in about 2.6 C of warming. The study published Friday warns that at those levels of warming, tipping points such as abrupt permafrost thaw and collapse of the Greenland and West Antarctic ice sheets will become "very" likely.
"Current policies leading to [about] 2 to 3 C warming are unsafe, because they would likely trigger multiple climate tipping points," the tipping point study concludes.
"Our updated assessment of climate tipping points provides strong scientific support for the Paris Agreement and associated efforts to limit global warming to 1.5 C."