“We are on a dangerous trajectory:” Global policy settings to trigger multiple climate tipping points

Current global climate policy is likely to trigger multiple climate “tipping points,” with major consequences for the Earth as a whole.

That’s the key message of a new study, from researchers at the University of Exeter, the Max Planck Institute and Universität Hamburg, which assessed the risk of different degrees of temperature rise triggering irreversible change in 16 systems – from ice sheet collapse to coral reef dieback – that have an impact on the Earth as a whole, or on regional ecosystems and communities.

It found that if the world sticks with current climate policies, there is a 62 per cent risk on average of triggering these 16 tipping points. But if global climate policy is strengthened, that risk could shrink to about 26 per cent. 

“Climate tipping points could have devastating consequences for humanity,” said Professor Tim Lenton, from the University of Exeter’s Global Systems Institute.

“It is clear that we are currently on a dangerous trajectory – with tipping points likely to be triggered unless we change course rapidly.”

What is a tipping point?

In climate systems research, a tipping point is a threshold beyond which a small change can seriously – and often irreversibly – alter the state of the system. 

“If you are tipping a chair, until a certain point it will always come back, and you can sit in it,” says study lead author Jakob Deutloff. “But beyond a certain point, it will fall.”

In its sixth assessment report (AR6), the IPCC lists fifteen systems susceptible to tipping points, including the global monsoon system, Arctic sea ice, Antarctic ice sheets, and ocean currents. 

The systems included in the IPCC report are by-and-large more general than the 16 systems – or ‘tipping elements’ – identified in this latest study.

They include the loss of Boreal permafrost, coral reef die-off, and Amazon rainforest dieback, and are based on a major literature synthesis from 2022.

The systems are divided based on the severity of impacts if they collapse.

The most important are the ‘global core’ tipping elements: “If one of them goes, then things would change all over the world,” says Deutloff.

The Atlantic Meridional Overturning Circulation (AMOC) is an example of a global core tipping element. 

The AMOC is the ocean current that transports heat and nutrients from the tropics to the northern hemisphere, keeping Europe’s winters relatively warm and wet. 

If the AMOC collapsed, Europe would experience significant local cooling, while parts of the Southern hemisphere – particularly the region around the Gulf of Mexico – would experience faster warming.

The AMOC has already been shown to be weakening. The collapse of the AMOC is estimated to occur if global temperatures rise by around 4°C, but statistical uncertainty around the triggering of tipping points is high, and the minimum threshold for its collapse is just 1.4°C of warming (the maximum is 8°C).

There are also ‘regional impact’ tipping elements. These are systems which, if their tipping points were triggered, would not affect the overall Earth system but could have devastating consequences at the local and regional level. They include the dieback of coral reefs in the tropics, and the abrupt loss of mountain glaciers.

The risky role of politics

The warming scenarios against which the 16 tipping elements were assessed were based on the five ‘Shared Socioeconomic Pathway’ (SSP) scenarios detailed in the IPCC’s latest report.

The SSPs predict how different global socioeconomic changes could affect warming to 2100. 

The SSP1 Sustainability pathway, also known as ‘Taking the Green Road’, describes a world that shifts towards sustainable, climate-friendly policy. 

The SSP3 Regional Rivalry pathway, by contrast, outlines a scenario in which resurgent nationalism and economic competition drive governments to prioritise economic prosperity and national security – including energy security – at the expense of climate policy (sound familiar?). 

“We found that under a scenario comparable to current policies, we have a high likelihood of triggering tipping points,” said Deutloff. 

“But the good news is if we move to a more sustainable scenario, which would lead to around two degrees warming by 2100, we can reduce the probability of triggering these tipping elements significantly. It’s not out of our hands.”

Deutloff said ambitious government policy was the only way to keep temperature rise manageable.

Was there any good news? 

Hearteningly, the study found that the tipping of any of the globally significant systems into an irreversible state of change was unlikely to produce enough warming to trigger changes in the other systems.

“They increase temperatures globally, but not enough to trigger those tipping cascades,” explains Deutloff.

But the positivity of that result is somewhat dampened by the reality of its parameters.

Under low emissions scenarios, the tipping points are unlikely to be triggered, and under high emissions scenarios, Deutloff explains, there will already be so much anthropogenic global warming that the impact of the additional carbon released by any one of the tipping elements will be dwarfed by the sheer boatload of carbon humanity has produced.