Four important climatic critical points close to triggering

Four important climatic critical points close to triggering

Four important climatic critical points close to triggering

Even if the world somehow manages to limit future warming to the stricter international temperature target, four Earth-changing climate “tipping points” are likely to come into action with much more looming as the planet warms more afterwards. said a new study.

An international team of scientists examined 16 climate pain points – when a side effect of warming is irreversible, self-perpetuating and important – and calculated approximate temperature thresholds at which they are triggered. None of them are considered likely at current temperatures, although some are possible. But with only a few tenths of a degree more warming by now, at 1.5 degrees Celsius (2.7 degrees Fahrenheit) from the pre-industrial period, four are moving into the likely range, according to a study in the journal Science on Thursday.

The study said the slow but irreversible collapse of the Greenland and West Antarctic ice sheets, the most immediate loss of tropical coral reefs worldwide, and the thawing of northern high permafrost which releases enormous amounts of greenhouse gases trapped in the now frozen earth have four significant turning points that could be triggered at 1.5 degrees Celsius of warming, which is three-tenths of a degree (half a degree Fahrenheit) warmer than it is now. Current policies and actions put the Earth on a trajectory of about 2.7 degrees Celsius (4.9 degrees Fahrenheit) of warming since pre-industrial times, according to some projections.

“Let’s hope we’re not right,” said study co-author Tim Lenton, an earth systems scientist at the University of Exeter in the UK. “There is a clear possibility that some of these turning points are inevitable. And so it is really important to reflect a little more on how we will adapt to the consequences. “

Timing is a key issue for points of no return in two ways: when they are triggered and when they cause damage. And in many cases, such as the collapse of the ice sheet, they could be triggered early, but their impacts, although inevitable, take centuries to manifest, scientists said. Some, like the loss of coral reefs, cause more damage in just a decade or two.

“It’s a next-generation problem,” said study lead author David Armstrong McKay, a terrestrial systems scientist at the University of Exeter. “The collapse of the ice caps is kind of that thousand-year time scale, but it’s still bequeathing a completely different planet to our descendants.”

The concept of tipping points has been around for more than a decade, but this study goes further, looking at temperature thresholds for when they might be triggered and what impacts they would have on people and the Earth and over the past 15 years or so. ” risk continues to rise, “Lenton said.

Lenton likes to think of turning points as someone leaning back in a folding chair.

“When you start rolling backwards, then you have a very simple type of feedback about the forces of gravity working to push you back to SPLAT,” Lenton said.

Study co-author Johan Rockstrom, director of the Potsdam Institute for Climate Impact Research in Germany, compared it to someone lighting a fuse on a bomb “and then the fuse will burn until the big bang and big bang may be more. down the line. “

While ice sheets with several meters or yards of potential sea rise can reshape the coast over the centuries, Rockstrom told him that the loss of coral reefs is his greatest concern due to “immediate impacts on human livelihoods.” “. Hundreds of millions of people, especially residents of the poorest tropical areas, depend on coral reef fishing, McKay said.

With only a few tenths of a degree more new points of no return become more possible and even probable which include a slowdown in the circulation of the northern polar ocean which can ripple into dramatic weather changes especially in Europe, loss of some areas of Arctic sea ice, collapse of global glaciers and total failure of the Amazon rainforest.

Some of these tipping points, like permafrost thawing, add to and accelerate existing warming, but don’t think it’s “over” if temperatures reach 1.5 degrees of warming, which is quite likely, McKay said.

“Even if we were to hit some of these tipping points, it would still block really substantial impacts that we want to avoid, but it won’t trigger some sort of uncontrolled climate change process,” McKay said. “It’s not like that at 1.5 degrees. And that means that the further warming that occurs beyond 1.5 is still mostly within our power of effect. “

This is a crucial point that these are turning points for individual regional disasters, not for the planet as a whole, so it’s ugly, but it doesn’t have a world end, said climate scientist Zeke Hausfather of tech firm Stripe and Berkeley. Earth, who wasn’t part of the study, but said it was important nuanced research that quantified turning points better than before.

“Have we really contemplated what happens when we mess with our global and ecological systems so much?” Said Katharine Mach, a climate risk scientist at the University of Miami, who was not part of the study. She said that it shows ripples and waterfalls that are annoying “This is a profound cause for concern in a changing climate.”

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Follow Seth Borenstein on Twitter at @borenbears

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