Climate tipping points possible at current heating levels: study

Destabilizing and dangerous climate tipping points are possible even at current levels of global heating, a new study has found.

Chances of the collapse of vital earth systems rises to 50 percent if temperatures rise above 4 degrees Celsius (6.4 Fahrenheit) — even if society successfully brings them to safe levels later, according to the study in Nature Climate Change.

Fully avoiding such a collapse is only possible at less than 1 degree Celsius of global heating (1.8 Fahrenheit) above pre-industrial levels, the authors at the Potsdam Institute for Climate Impact Research wrote in a statement.

The globe is now at 1.2 degrees Celsius above pre-industrial temperatures.

The Potsdam team was looking at the impacts of varying forms of “overshoot,” in which global heating passes agreed-upon red lines, even if it is later brought under control.

The relationship is straightforward, Potsdam’s Nico Wunderling explained. 

“We found that the risk for the emergence of at least one tipping event increases with rising peak temperatures,” he said in a statement.

Even with a brief time at 3 degrees Celsius of heating, one-third of all simulations evaluated by Potsdam led to a system collapse. 

At four degrees of warming — even when brought back down later — more than half the simulations showed a major collapse.

For comparison, current emissions-reducing policies would lead to between 2 and 3.6 Celsius (3.8 to 6.4 Fahrenheit) in average heating.

Those temperature rises would mean a substantial risk of collapse in one of the four vast systems that each contribute to the stability of our current climate.

These are the circulating Atlantic current, the West Antarctic and Greenland ice sheets and the Amazon rainforest.

While the vulnerable ice sheets are at particular risk, the Amazon and the Atlantic current — while more resistant to high temperatures — are more likely to fall apart with stunning speed once the collapse begins, the scientists noted.

And the collapse in any system risks triggering “cascading interactions between the four elements,” the authors wrote.

The paper demonstrates why current climate efforts are “not enough,” Potsdam’s Jonathan Donges said in a statement.

“Even though a temporary temperature overshoot would definitely be better than reaching a peak temperature and remaining there, some of the overshoot impacts may lead to irreversible damages in a high climate risk zone,” Donges said.

His colleague Ricarda Winkelmann offered a more pointed summary. “Every tenth of a degree counts. We must do what we can to limit global warming as quickly as possible.”