Even if the world somehow succeeds in limiting future warming to the strictest international temperature target, the four “tipping points” that are changing Earth’s climate are still likely to have much larger impacts as the planet warms more afterward, according to a new study.
An international team of scientists studied 16 climate tipping points – when the side effect of warming is irreversible, self-perpetuating and severe – and calculated the approximate temperature thresholds at which they are triggered. None of these are considered likely at present temperatures, although some are possible. But with only a few tenths of a degree of warming since now, 1.5 degrees Celsius (2.7 degrees Fahrenheit) warming since pre-industrial times, four are approaching the likely range, according to a study published Thursday in the journal Science.
The slow but irreversible destruction of the Greenland and West Antarctic ice sheets, the more immediate loss of tropical coral reefs around the world, and the melting of northern permafrost, which releases massive amounts of greenhouse gases trapped in the now frozen ground, are four major tipping points, the study says. . could work at 1.5 degrees Celsius, which is three tenths of a degree (half a degree Fahrenheit) warmer than it is now. By some projections, current policies and actions put the Earth on a warming trajectory of about 2.7 degrees Celsius (4.9 degrees Fahrenheit) since pre-industrial times.
“Let’s hope we’re wrong,” said study co-author Tim Lenton, an Earth systems specialist at the University of Exeter in the United Kingdom. “There is a clear chance that some of these tipping points will become inevitable. And so it is very important that we think a little more about how we are going to adapt to the consequences.”
Timing is a key issue for tipping points in two respects: when they work and when they cause harm. And in many cases, like the collapse of an ice sheet, they can be triggered soon, but their effects, while inevitable, last for centuries, scientists say. Some, such as the loss of coral reefs, cause more damage in just one to two decades.
“This is a future generation problem,” said study lead author David Armstrong McKay, an earth systems specialist at the University of Exeter. “The collapse of the ice sheets is kind of a thousand-year timeline, but it still leaves a completely different planet as a legacy for our descendants.”
The concept of tipping points has been around for more than a decade, but this study is looking at temperature thresholds, when they can kick in and what impact they will have on humans and the Earth, and over the last 15 years or so, “risk levels just keep going up” – said Lenton.
Lenton likes to think of turning points like someone leaning back in a folding chair.
“When you start tipping back, in this case you have very simple feedback with the forces of gravity acting to push you back up to the point of SPLAT,” Lenton said.
Study co-author Johan Rockstrom, director of the Potsdam Institute for Climate Impact Research in Germany, compared it to someone lighting the fuse of a bomb, “and then the fuse will burn until the Big Bang happens, and the Big Bang can go further.” “. line.”
While ice sheets with potential sea level rise of several meters or yards could change coastlines over the centuries, Rockstrom told him that the loss of coral reefs is his biggest concern due to “the direct impact on people’s livelihoods.” Hundreds of millions of people, especially the poor in the tropics, depend on coral reef fisheries, McKay said.
A few more tenths of a degree are becoming more likely and even more likely, including a slowdown in the circulation of the northern polar ocean, which could lead to dramatic weather changes, especially in Europe, the loss of certain areas of Arctic sea ice, the destruction of glaciers. worldwide and the complete failure of the Amazon rainforest.
Some of these tipping points, such as melting permafrost, amplify and accelerate existing warming, but don’t think it’s “game over” if temperatures reach 1.5 degrees warming, which is likely, McKay said.
“Even if we reach some of these tipping points, it will still fix the really significant impacts that we want to avoid, but it will not trigger some kind of runaway climate change process,” McKay said. “It’s not like that at 1.5 degrees. And that means that further warming beyond 1.5 is still largely up to us.”
It’s critical that these are tipping points for individual regional disasters and not for the planet as a whole, so it’s bad, but not the end of the world, said climate scientist Zeke Hausfather of tech company Stripe and Berkeley Earth, who was not part of the study, but said that it was important to have a detailed study that would better than before identify the turning points.
“Have we really thought about what happens when you impact our global and ecological systems to this extent?” said Catherine Mach, a climate risk specialist at the University of Miami who was not involved in the study. She said it shows ripples and cascades that are uncomfortable. “This is a major cause for concern in a changing climate.”
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