Study: Four major climate tipping points close to triggering

Even if the world somehow manages to limit future warming to the strictest international temperature goal, four Earth-changing climate “tipping points” are still likely to be triggered with a lot more looming as the planet heats more after that, a new study said.

An international team of scientists looked at 16 climate tipping points — when a warming side effect is irreversible, self-perpetuating and major — and calculated rough temperature thresholds at which they are triggered. None of them are considered likely at current temperatures, though a few are possible. But with only a few more tenths of a degree of warming from now, at 1.5 degrees Celsius (2.7 degrees Fahrenheit) warming since pre-industrial times, four move into the likely range, according to a study in Thursday’s journal Science.

The study said slow but irreversible collapse of the Greenland and West Antarctic ice sheets, more immediate loss of tropical coral reefs around the globe and thawing of high northern permafrost that releases massive amounts of greenhouse gases trapped in now frozen land are four significant tipping 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 now. Current policies and actions put Earth on a trajectory for 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 United Kingdom. “There’s a distinct chance some of these tipping points are going to be unavoidable. And therefore it’s really important we do some more thinking about how we’re going to adapt to the consequences.”

Timing is a key issue for...