The study builds on the growing body of scientific research on non-linear climate change – significant, irreversible change that goes beyond the linear and gradual increase in average temperatures. It found that five tipping points, including the precipitous thawing of permafrost in the boreal forest and the end of an ocean current system in the Labrador Sea are “likely” under current levels of global warming. These two tipping points are in Canada. More worryingly, the study published on Friday in the journal Science suggests that four tipping points will be scaled from “probable” to “probable” at 1.5C of global warming. These include the rapid thawing of the northern permafrost, the collapse of ice sheets in Greenland and West Antarctica, and the rapid elimination of coral reefs. This graph from the study maps the main climate tipping points around the world and the global warming temperature thresholds at which they are likely to occur. (McKay et al, 2022.) “What we’re looking at are various negative impacts, like more sea-level rise, coral reef removal, and things like that that get trapped and need to be addressed for future generations,” said paper co-author David Armstrong McKay. climate and biosphere scientist and visiting fellow at the University of Exeter in the UK The findings raise questions about whether the goal of the international Paris agreement, which aims to limit global warming to well below 2C and ideally below 1.5C, is enough to prevent climate catastrophe. The study essentially warns that the planet has already left a safe climate state when it exceeded 1 C of global warming. These tipping points will have devastating consequences for global weather patterns, sea level rise and biodiversity, the study highlights. Some of these, such as thawing permafrost, would release even more greenhouse gases, accelerating climate change even further. However, the study’s authors say that while understanding of endpoints has improved over the past decade, there is still uncertainty about many factors. Some tipping points could be avoided if global warming exceeds 1.5 degrees Celsius in the coming years, but then recedes due to rapid emissions cuts. The massive Greenland ice sheet could reach a tipping point at 1.5C of global warming, causing collapse but over a long period of time. (Brennan Linsley/The Associated Press) Tipping points also have different timelines. Some will happen faster: the shedding of coral reefs could happen within 10 years when triggered, and the precipitous thawing of the northern permafrost could happen within 200 years. Others, such as the collapse of the Greenland ice sheet, would occur within 10,000 years of triggering, spreading its effect on the global weather system and sea level rise over a long period of time. “Every additional fraction of a degree that we avoid above 1.5 C reduces the likelihood that further tipping points will be triggered or become strong,” McKay said. “So I would say 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 0 C or below. McKay says the gradual thawing of this permafrost has been a concern for a while, but now there’s greater awareness of a possible precipitous thaw that could leave its mark on the local landscape—and have major consequences for the global climate. This is because permafrost contains carbon from the remains of dead plants and animals dating back millions of years. Right now, this carbon is safely locked away in the ground, but if the permafrost thaws, it could be released into the atmosphere and accelerate global warming. “Our understanding of this is just beginning to develop, and we estimate that it could potentially increase emissions by about 50 to 100 percent above step-thaw emissions,” McKay said. Baltzer is the Canada Research Chair in Forests and Global Change at the University of Waterloo. Her research has given her a front-row seat to changes to the northern landscape, which is at risk of releasing even more carbon into the atmosphere from melting permafrost. (Angela Gzowski/University of Waterloo) Jennifer Baltzer has seen the changes to the northern landscape firsthand and emphasizes the importance of these lands remaining as they are. “There’s about twice as much carbon locked up in permafrost than we have floating around in the atmosphere,” said Baltzer, the Canada Research Chair in Forests and Global Change at the University of Waterloo. “As these soils warm and thaw, that carbon becomes available to soil microbes and becomes available to decompose and then release carbon dioxide and methane into the atmosphere.” Thawing in permafrost causes trees to lean, as seen in Baltzer’s field research. Her team studies changes in the north and how it will affect the larger climate system. (Contributed by Jennifer Baltzer) It becomes a vicious circle. As the permafrost thaws and the carbon is released, the planet continues to warm – accelerating the thawing of the permafrost, which sends more carbon into the atmosphere. Baltzer notes that the Arctic is warming at many times the average rate of the rest of the world, so a 1.5C increase in global temperatures would mean a four to five degree increase in the Arctic. At those temperatures, it would be difficult for permafrost to maintain and hold all that carbon in, he said. “The challenge is that, with these additional contributions in the Arctic, it makes the whole process of trying to reach that net zero goal even more difficult. And so the 1.5 degree mark is really, really important to stay under.” As permafrost destabilizes, it causes trees to lean. Trees try to compensate for this by creating thicker rings on one side and thinner rings on the other. (Angela Gzowski/University of Waterloo)
Nonlinear changes are not easy to understand
Co-author Sina Loriani, a postdoctoral researcher at the Potsdam Institute for Climate Impact Research in Germany, said the idea of non-linear changes such as tipping points, which can be uncontrollable and unpredictable, can be difficult to grasp. And that can make it a tricky issue in climate negotiations. “The essence of tipping points is that there is a risk … that you trigger something that runs itself,” Loriani said. “I would say it’s underrepresented in climate action today.” The study shows that there are different levels of uncertainty for each tipping point, suggesting that some climate systems need more research to understand exactly how they change. Some regions of 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. Due to the political situation due to the war in Ukraine, research in this area was further restricted. The world has already reached 1.1 C of global warming and is on track to reach 1.5 C by the 2030s. Zero pledges and countries’ climate plans, if implemented, could limit warming of the planet just below 2 C, according to research published in Nature in April. But current policies are actually set to lead to about 2.6 C of warming. The study published on Friday warns that at these levels of warming, tipping points such as the precipitous thawing of permafrost and the collapse of the Greenland ice sheets and of West Antarctica will become “very” likely. “Current policies lead to [about] Warming of 2 to 3 degrees Celsius is dangerous because it would likely trigger multiple climate tipping points,” the 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 1.5C.”
