Wednesday, December 06, 2023

Earth on verge of five catastrophic climate tipping points, scientists warn


Ajit Niranjan European environment correspondent
THE GUARDIAN
Tue, 5 December 2023 

Photograph: Michael Shortt/AP

Many of the gravest threats to humanity are drawing closer, as carbon pollution heats the planet to ever more dangerous levels, scientists have warned.

Five important natural thresholds already risk being crossed, according to the Global Tipping Points report, and three more may be reached in the 2030s if the world heats 1.5C (2.7F) above pre-industrial temperatures.

Triggering these planetary shifts will not cause temperatures to spiral out of control in the coming centuries but will unleash dangerous and sweeping damage to people and nature that cannot be undone.


“Tipping points in the Earth system pose threats of a magnitude never faced by humanity,” said Tim Lenton, from the University of Exeter’s Global Systems Institute. “They can trigger devastating domino effects, including the loss of whole ecosystems and capacity to grow staple crops, with societal impacts including mass displacement, political instability and financial collapse.”

The tipping points at risk include the collapse of big ice sheets in Greenland and the West Antarctic, the widespread thawing of permafrost, the death of coral reefs in warm waters, and the collapse of atmospheric circulation in the North Atlantic.

Unlike other changes to the climate such as hotter heatwaves and heavier rainfall, these systems do not slowly shift in line with greenhouse gas emissions but can instead flip from one state to an entirely different one. When a climatic system tips – sometimes with a sudden shock – it may permanently alter the way the planet works.

Scientists warn that there are large uncertainties around when such systems will shift but the report found that three more may soon join the list. These include mangroves and seagrass meadows, which are expected to die off in some regions if the temperatures rise between 1.5C and 2C, and boreal forests, which may tip as early as 1.4C of heating or as late as 5C.

The warning comes as world leaders meet for the Cop28 climate summit in Dubai. On Tuesday, Climate Action Tracker estimated that their emissions targets for 2030 put the planet on track to heat 2.5C by the end of the century, despite promises from countries at a previous summit to try to limit it to 1.5C.

The tipping point report, produced by an international team of 200 researchers and funded by Bezos Earth Fund, is the latest in a series of warnings about the most extreme effects of climate change.

Scientists have warned that some of the shifts can create feedback loops that heat the planet further or alter weather patterns in a way that triggers other tipping points.

The researchers said the systems were so tightly linked they could not rule out “tipping cascades”. If the Greenland ice sheet disintegrates, for instance, it could lead to an abrupt shift in the Atlantic Meridional Overturning Circulation, an important current that delivers most of the heat to the gulf stream. That, in turn, can intensify the El NiƱo southern oscillation, one of the most powerful weather patterns on the planet.

The co-author Sina Loriani, from the Potsdam Institute for Climate Impact Research, said tipping-point risks could be disastrous and should be taken very seriously, despite the remaining uncertainties.

“Crossing these thresholds may trigger fundamental and sometimes abrupt changes that could irreversibly determine the fate of essential parts of our Earth system for the coming hundreds or thousands of years,” he said.

In its latest review of climate change science, the Intergovernmental Panel on Climate Change found that tipping thresholds were unclear but the dangers would grow more likely as the planet heats up.

It said: “Risks associated with large-scale singular events or tipping points, such as ice-sheet instability or ecosystem loss from tropical forests, transition to high risk between 1.5C to 2.5C and to very high risk between 2.5C to 4C.”

The tipping point report also looked at what it called “positive tipping points”, such as the plummeting price of renewable energy and the growth in sales of electric vehicles. It found that such shifts do not happen by themselves but need to be enabled by stimulating innovation, shaping markets, regulating business, and educating and mobilising the public.

A study from the report’s co-author Manjana Milkoreit last year warned against overusing the label of social tipping points by promising solutions that did not exist at scale or could not be controlled.

“While scholarship benefits from hope, we need to exercise caution when offering social tipping points as potential solutions to the temporal squeeze of climate change,” she wrote.

Planet tipping points pose 'unprecedented' threat to humanity: report

Daniel Lawler
Tue, 5 December 2023 

Over the edge? The melting Greenland and West Antarctic icesheets are of Earth's two tipping points teetering on the point of no return, the report warned (Olivier MORIN)

Humanity faces an "unprecedented" risk from tipping points that could unleash a domino effect of irreversible catastrophes across the planet, researchers warned Wednesday.

The most comprehensive assessment ever conducted of Earth's invisible tripwires was released as leaders meet for UN climate talks in Dubai with 2023 set to smash all heat records.

While many of the 26 tipping points laid out in the report -- such as melting ice sheets -- are linked to global warming, other human activities like razing swathes of the Amazon rainforest could also push


 Earth's ecosystems to the brink.

Five of these are showing signs of tipping -- from melting ice sheets threatening catastrophic sea level rise, to mass die-off of tropical coral reefs -- the report warned.

Some may have already begun to irrecoverably transform.

Once the world crosses the threshold for just one tipping point, dealing with the immediate humanitarian disaster could distract attention away from stopping the others, creating a "vicious cycle" of mass hunger, displacement and conflict, the report warned.

Tim Lenton, an Earth system scientist at the University of Exeter and lead author of the report, told AFP that these tipping points pose a "threat of a magnitude that is unprecedented for humanity".

But it was not all bad news.

The report also highlighted a range of positive tipping points -- such as electric vehicles, renewable energy and changing to plant-based diets -- that have the potential to swiftly build momentum and tip things back the other way.

"Imagine leaning back on a chair to that balance point where a small nudge can make a big difference," Lenton said.

"You could end up sprawled on your back on the floor -- or if you're lucky, back upright."

- On the brink -

A key concern is if the melting West Antarctic and Greenland ice sheets collapse.

That could raise sea levels two metres by 2100, exposing nearly half a billion people to frequent coastal flooding, the report said.

The Greenland ice sheet has been shrinking at such a rate that it might already be too late.

"Is it past the tipping point or could it stop shrinking? No one's quite sure," Lenton said.

The other three tipping points most at risk are dying tropical coral reefs, melting permafrost and an ocean current called the North Atlantic subpolar gyre circulation.

Another ocean tipping point is the Atlantic Meridional Overturning Circulation (AMOC), a vast system that regulates the global transfer of heat from the tropics into the northern hemisphere.

The new report said it was plausible -- though unlikely -- that the AMOC would collapse this century.

This destabilising change could lead to vast regions getting far less rain, potentially halving the area worldwide where wheat and corn can be grown, it said.

"If that goes, suddenly there will be a global food security crisis and comparable water crisis as major monsoon systems in the tropics basically fail in India and West Africa. That will be a humanitarian catastrophe," Lenton said.

- 'Dire' -


Recent massive fires in the Amazon rainforest and Canada's boreal forests suggest they are also more immediately at risk of tipping than previously thought, he added.

Lenton compared the job of the more than 200 researchers who created the over-400 page Global Tipping Points Report to risk assessors analysing a new aeroplane.

AMOC collapsing was like spotting something that could cause that plane to "fall out of the sky", he said.

But there's no way to redesign the Earth to make it safer.

Co-author Manjana Milkoreit from the University of Oslo said that "our global governance system is inadequate to deal with the coming threats and implement the solutions urgently required."

The authors called for tipping points to be included in the global stocktake being debated at the COP28 talks, as well as in national targets to combat climate change.

They also urged more effort to push tipping points in the right direction, such as changing policies on energy, transport, food and green ammonia used for fertiliser.

Sarah Das, a scientist at the US Woods Hole Oceanographic Institution, who was not involved in the report, said the science was now "crystal clear".

"The risks for humanity in crossing tipping points into these unexplored states is dire, and the impact to human lives potentially horrific," she said.

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Climate tipping points are nearer than you think – our new report warns of catastrophic risk

James Dyke, Associate Professor in Earth System Science, University of Exeter
 David Armstrong McKay, Researcher in Earth System Resilience, Stockholm University
Wed, 6 December 2023 
The Conversation

lugazzotti / shutterstock

It’s now almost inevitable that 2023 will be the warmest year ever recorded by humans, probably the warmest for at least 125,000 years.

Multiple temperature records were smashed with global average temperatures for some periods well above 1.5°C. Antarctic sea ice loss is accelerating at frightening rates along with many other indicators of rapid climate change. Does this mean 2023 is the year parts of the climate tip into a much more dangerous state?

Most people expect that if a system, like someone’s body, an ecosystem, or part of the climate system, becomes stressed, it’ll respond fairly predictably – double the pressure, double the impact, and so on. This holds in many cases, but is not always true. Sometimes a system under stress changes steadily (or “linearly”) up to a point, but beyond that far bigger or abrupt changes can be locked in.

An example of such “nonlinear” changes are “tipping points”, which happen when a system is pushed past a threshold beyond which change becomes self-sustaining. This means that even if the original pressure eased off the change would keep on going until the system reaches a sometimes completely different state.

Think of rolling a boulder up a hill. This takes a lot of energy. If that energy input is stopped then the ball will roll back down. But when the top of the hill is reached and the boulder is balanced right at the very top, a tiny push, perhaps even a gust of wind, can be enough to send it rolling down the other side.

The climate system has many potential tipping points, such as ice sheets disappearing or dense rainforests becoming significantly drier and more open. It would be very difficult, effectively impossible, to recover these systems once they go beyond a tipping point.

We along with 200 other scientists from around the world just published the new Global Tipping Points Report at the COP28 UN climate talks in Dubai. Our report sets out the science on the “negative” tipping points in the Earth system that could harm both nature and people, as well as the potential “positive” societal tipping points that could accelerate sustainability action. Here we look at the key messages from report sections on tipping points in the Earth system, their effects on people, and how to govern these changes.

Tipping points in air, land and sea


Having scoured scientific evidence of past and current changes, and factored in projections from computer models, we have identified over 25 tipping points in the Earth system.

Six of these are in the icebound parts of the planet (the “cryosphere”), including the collapse of massive ice sheets in Greenland and different parts of Antarctica, as well as localised tipping in glaciers and thawing permafrost. Sixteen are in the “biosphere” – the sum of all the world’s ecosystems – including trees dying on a massive scale in parts of the Amazon and northern boreal forests, degradation of savannas and drylands, nutrient overloading of lakes, coral reef mass mortality, and many mangroves and seagrass meadows dying off.

Finally, we identified four potential tipping points in the circulation of the oceans and atmosphere, including collapse of deep ocean mixing in the North Atlantic and in the Southern Ocean around Antarctica, and disruption of the West African monsoon.

Human activities are already pushing some of these close to tipping points. The exact thresholds are uncertain, but at today’s global warming of 1.2°C, the widespread loss of warm water coral reefs is already becoming likely, while tipping in another four vital climate systems is possible. These are Greenland and West Antarctic ice sheet collapse, North Atlantic circulation collapse, and widespread localised thaw of permafrost.

Beyond 1.5°C several of these become likely, and other systems like mangroves, seagrass meadows, and parts of the boreal forest start to become vulnerable. Some systems can also tip or have their warming thresholds reduced due to other drivers, such as deforestation in the Amazon.

It can be hard to comprehend the consequences of crossing these tipping points. For example, if parts of the Amazon rainforest die, countless species would be lost, and warming would be further amplified as billions of tons of carbon currently locked up in trees and soils makes its way into the atmosphere. Within the region, this could cause trillions of dollars of economic impacts, and expose millions of people to extreme heat.

Given the sheer scale of risks from tipping points, you may assume that economic assessments of climate change include them. Alas, most assessments effectively ignore tipping point risks. This is perhaps the most frightening conclusion of the new report.
Human societies could tip into something much worse

There is also the potential for negative tipping in human societies, causing further financial instability, displacement, conflict or polarisation. These would hamper our efforts to limit further Earth system tipping points, and could even bring about a shift to a social system characterised by greater authoritarianism, hostility and alienation that could entirely derail sustainability transitions.


White coral with fish

A further risk is that most of Earth’s tipping systems interact in ways that destabilise one another. In the worst case, tipping one system makes connected systems more likely to tip too. This could produce a “tipping cascade” like falling dominoes.

The Global Tipping Points Report makes clear that climate change is a key driver for most of these tipping points, and the risk of crossing them can be reduced by urgently cutting greenhouse gas emissions to zero (which “positive tipping points” could accelerate). To help prevent tipping points in the biosphere, we’ll also need to rapidly reduce habitat loss and pollution while supporting ecological restoration and sustainable livelihoods.

Ambitious new governance approaches are needed. Our report recommends international bodies like the UN’s climate talks urgently start taking tipping points into account. Their understanding of dangerous climate change needs a serious update.


This article is republished from The Conversation under a Creative Commons license. Read the original article.


James Dyke receives funding from the Open Society Foundations. He is an advisor to Faculty for a Future.

David Armstrong McKay is a Research Impact Fellow at the University of Exeter's Global Systems Institute and an Associated Researcher at Stockholm Resilience Centre. He is currently researching Earth system tipping points as part of the Global Tipping Points Report project (funded by the Bezos Earth Fund) and with the Earth Commission (hosted by non-profit research network Future Earth and is the science component of the Global Commons Alliance, a sponsored project of Rockefeller Philanthropy Advisors, with support from Oak Foundation, MAVA, Porticus, Gordon and Betty Moore Foundation, Herlin Foundation, the Global Environment Facility, and Generation Foundation). He is also a freelance research consultant and science communicator.

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