What’s happening? There is a significant likelihood that multiple climate tipping points could be passed if global temperatures rise 1.5C above pre-industrial levels, according to new research published in Science. (Carbon Brief)

Why does this matter? The concept of tipping points was introduced in 2008 when researchers first identified elements of the Earth system whose destabilisation could have severe and far-reaching impacts across continents. Since then, this area of research has made significant progress and has been at the centre of a debate about the remaining time window for climate action.

Defining tipping points – To provide an overview of the current state of knowledge, scientists have reviewed the evidence for tipping points from more than 200 papers published in the last 14 years. The research team defined tipping points as major biophysical elements in the Earth’s climate regulating system that would – once a certain temperature threshold is crossed – be subject to self-perpetuating change and shift to a new state even without further warming.

Overall, the authors identified 16 tipping points, nine of which affect the entire Earth system, including the collapse of the Antarctic ice sheets and the dieback of the Amazon rainforest. A further seven, for example the loss of extra-polar mountain glaciers and tropical coral reefs, would have profound regional impacts.

Where are we now? The study warns that five tipping points could already be triggered at the current level of warming (1.1C above pre-industrial times). There is evidence that two of them – the Greenland and West Antarctic ice sheets – may have already been crossed. Complete melting of the Greenland Ice Sheet would raise global sea levels by 7.4 metres, while the West Antarctic Ice Sheet holds enough water to add 3.3 metres.

Future projections – At 1.5C, four of these tipping points would move from “possible” to likely”, the study states, while five additional ones would come within reach. These include important systems such as mountain glaciers in Asia, the Americas, and Europe, which supply fresh water to 1.9 billion people.

Lastly, the scientists analysed the impacts of 2.6C of global warming, which could be reached even if all current climate pledges and targets are met. In this scenario, 13 out of 16 tipping points would be either likely or possible, posing a substantial threat to all life on Earth. This presents a significant divergence from previous estimates and stresses the importance of strengthening national climate targets before the next UN climate summit.

But what if we could change? On a more positive note, researchers have recently discussed the concept of positive tipping points in human societies. The idea is that once a certain threshold is reached, transport, energy or other social systems could tip to a new (more sustainable) state due to self-enforcing feedback loops. The uptake of electric vehicles and renewable energy have been named as examples.

However, some have pointed out that many societies also contain self-regulating negative feedback mechanisms to prevent rapid change, which differentiates them from the Earth’s climate system. Nevertheless, there is a consensus that enabling positive social tipping points requires multiple factors, such as policy interventions and a shift in cultural norms, highlighting the importance of government action.