Current rates of global warming have already brought the world perilously close to several tipping points that could plunge major global weather systems into irreversible collapse, a major study out of Europe has found.
The study builds on the growing body of scientific research on nonlinear climate change – large, irreversible changes that go beyond linear and gradual increases in average temperatures.
Five turning points, including the abrupt thaw of permafrost in the boreal forest and the end of an ocean current system in the Labrador Sea, turned out to be “possible” under current levels of global warming.
Both of these turning points are in Canada.
Even more alarmingly, the study, published in Science magazine on Friday, suggests four turning points will escalate from possible to likely at 1.5C of global warming. These include the abrupt thawing of the boreal permafrost, the collapse of the ice sheets in Greenland and West Antarctica, and a rapid die-off of coral reefs.
“What we’re seeing are various negative impacts like further sea level rise, coral reef deaths and things like that that need to be contained and 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 UK
The results raise questions as to 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 sufficient to avert the climate catastrophe. The study effectively warns that the planet has already left a safe climate state by the time it has exceeded 1°C of global warming.
The study points out that these tipping points would have devastating consequences for global weather patterns, sea-level rise and biodiversity. Some of these, like the thawing of the permafrost, would release even more greenhouse gases and further accelerate climate change.
However, the study’s authors say that while understanding of turning points has improved over the past decade, there is uncertainty about several factors. Some tipping points could be avoided if global warming spikes above 1.5°C in the coming years, but then declines on the back of rapid emissions cuts.
The tipping points also have different time scales. Some will happen faster: Coral reef diebacks could take over 10 years if triggered, and abrupt thawing of boreal permafrost could take over 200 years. Others, like the collapse of the Greenland ice sheet, would last over 10,000 years after triggering, spreading their effects on the global weather system and sea level rise over a long period of time.
“Each additional fraction of a degree that we avoid above 1.5C reduces the likelihood of triggering or enabling more tipping points,” McKay said.
“So I would say this isn’t a ‘game over’ situation, it just shows what’s at stake in that 1.5 to two degree range.”
permafrost in trouble
About half of Canada is covered with permafrost, where the ground temperature is 0 C or below. McKay says the gradual thawing of this permafrost has been a concern for some time, but now there is greater awareness of a possible abrupt thaw that could leave its mark on the local landscape — and have serious consequences for global climate .
That’s because the permafrost contains carbon from the remains of dead plants and animals that are millions of years old. For now, that carbon is safely locked in the ground, but as the permafrost thaws, it could be released into the atmosphere and accelerate global warming.
“Our understanding of this is only beginning to develop, and we believe emissions could potentially increase by about 50 to 100 percent, on top of gradual thaw emissions,” McKay said.
Jennifer Baltzer has witnessed the changes in the northern landscape first hand and emphasizes the importance of keeping these soils as they are.
“About twice as much carbon is trapped in permafrost as we have floating around in the atmosphere,” said Baltzer, the Canadian Research Chair in Forests and Global Change at Wilfrid Laurier University.
“As these soils warm and thaw, that carbon becomes available to the microbes in the soil and is available for decomposition and then 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 — accelerating the thawing of the permafrost, which releases more carbon into the atmosphere.
Baltzer notes that the Arctic is warming many times faster than the rest of the world, and therefore a 1.5°C rise in global temperatures would mean a four to five degree rise in the Arctic. At those temperatures, it would become difficult for the permafrost to sustain itself and hold all the carbon, she said.
“The challenge is that with these additional Arctic contributions, the whole process of trying to reach that net zero goal becomes even more difficult. And so the 1.5 degree mark is really, really important to keep us below that.”
Nonlinear changes not easy to understand
Co-author Sina Loriani, a postdoctoral fellow at the Potsdam Institute for Climate Impact Research in Germany, said the notion of nonlinear changes like tipping points, which can be uncontrollable and unpredictable, can be difficult to understand.
And that can make it a difficult issue in the climate negotiations.
“The essence of tipping points is that you run the risk of triggering something that runs on itself,” Loriani said. “I would say that it is not adequately represented in climate protection today.”
The study shows that there are different uncertainties at each turning point, suggesting that some climate systems need more research to understand exactly how they’re changing.
Some areas of global permafrost are better studied than others, Baltzer said, such as Siberia, which presents a difficult working environment but contains the largest area of permafrost on the planet. With the political situation due to the war in Ukraine, research in this region was further restricted.
Global warming has already reached 1.1°C and is projected to reach 1.5°C by 2030. According to a study published in Nature in April, countries’ net-zero pledges and climate plans, if implemented, could limit global warming to just under 2°C.
But current policies are actually set to result in about 2.6°C of warming. The study, released on Friday, warns that at these levels of warming, turning points such as the abrupt thawing of permafrost and the collapse of the Greenland and West Antarctic ice sheets become “very” likely.
“The current policy leads to [about] Warming of 2 to 3°C is uncertain as it 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 related efforts to limit global warming to 1.5°C.”