The Intergovernmental Panel on Climate Change (IPCC) defines tipping points as "critical thresholds in a system that, when exceeded, can lead to a significant change in the state of the system, often with an understanding that the change is irreversible."
Published in the journal Nature Climate Change, a new study focuses on the potential shutdown of the Atlantic Meridional Overturning Circulation (AMOC), the Amazon rainforest shifting to savannah, and the collapse of the Greenland and West Antarctic ice sheets.
"To effectively prevent all tipping risks, the global mean temperature increase would need to be limited to no more than 1°C—we are currently already at about 1.2°C," noted study co-author Jonathan Donges, co-lead of the FutureLab on Earth Resilience in the Anthropocene at the Potsdam Institute for Climate Impact Research (PIK). "The latest IPCC report is showing that we're most likely on a path to temporarily overshoot the 1.5°C temperature threshold."
"Even if we would manage to limit global warming to 1.5°C after an overshoot of more than 2°C, this would not be enough as the risk of triggering one or more global tipping points would still be more than 50%," lead author and PIK scientist Nico Wunderling explained. "With more warming in the long-term, the risks increase dramatically."
According to the study, "Our model analysis reveals that temporary overshoots can increase tipping risks by up to 72% compared with non-overshoot scenarios, even when the long-term equilibrium temperature stabilizes within the Paris range."
Study co-author Ricarda Winkelmann, co-lead of the FutureLab on Earth Resilience in the Anthropocene at PIK, pointed out that "especially the Greenland and the West Antarctic ice sheet are at risk of tipping even for small overshoots, underlining that they are among the most vulnerable tipping elements."
"While it would take a long time for the ice loss to fully unfold, the temperature levels at which such changes are triggered could already be reached soon," she said. "Our action in the coming years can thus decide the future trajectory of the ice sheets for centuries or even millennia to come."