According to a major review study published in the journal Science, if global temperature rises beyond 1.5°C above pre-industrial levels, multiple dangerous climate tipping points would be triggered, with this risk increasing substantially with every tenth of a degree of future warming. These findings provide strong scientific support for the Paris Agreement and associated efforts to limit global warming to 1.5°C, by showing that the risk of tipping points escalates beyond this level.
By synthesizing evidence for tipping points, their temperature thresholds, timescales, and impact from a comprehensive review of more than 200 scientific articles published after 2008 – when the notion of “tipping points” was first introduced in the scientific vocabulary and rigorously defined – the researchers found that human emissions have already pushed our planet into the danger zone.
The analysis revealed that five of the sixteen tipping points currently identified may be triggered even at today’s temperatures: melting of the Greenland and West Antarctic ice sheets, widespread abrupt permafrost thaw, collapse of convection in the Labrador Sea, and large-scale die-offs of tropical coral reefs.
“We can see signs of destabilization already in parts of the West Antarctic and Greenland ice sheets, in permafrost regions, the Amazon rainforest, and potentially the Atlantic overturning circulation as well,” said study lead author David Armstrong McKay, a georesilience analyst at the Stockholm Resilience Center. “The world is already at risk of some tipping points. As global temperatures rise further, more tipping points become possible.”
According to Dr. McKay and his colleagues, the chance of crossing more tipping points could be reduced by rapidly and immediately cutting greenhouse gas emissions. However, while the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) argued that risks of triggering climate tipping points become high at 2°C above pre-industrial temperatures and very high at 2.5-4°C, this new analysis indicates that our planet may have already left a “safe” climate state when temperatures exceeded just 1°C. Thus, even if temperatures stop rising, once the ice sheets, oceans, or rainforests have passed a threshold, they will carry on degrading for decades, even if emissions are stopped.
“The world is heading towards 2-3°C of global warming. This sets Earth on course to cross multiple dangerous tipping points that will be disastrous for people across the world. To maintain livable conditions on Earth, protect people from rising extremes, and enable stable societies, we must do everything possible to prevent crossing tipping points. Every tenth of a degree counts,” concluded study co-author Johan Rockström, the director of the Potsdam Institute for Climate Impact Research.