At current rates, 5 key climate tipping points are already possible, new study warns

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. 

"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."

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.