Tipping Points need to be on the agenda for COP30

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If you lean back on a chair, the balance becomes more and more precarious until you reach a point beyond which you will crash to the ground.

If you stretch a rubber band, it gets thinner and thinner, until you reach a point beyond which the elastic simply snaps.

If you run down your body – by sleeping too little, working too hard, protracted exposure to heat, insufficient hydration, inadequate nutrition – you will become sicker and sicker until you reach a point beyond which your organs will fail.

These are all examples of points of no return, or tipping points, when change within a system becomes self-propelling. They mark a switch from one state to another (balanced to collapsed, stretching to snapped, declining health to incurably sick) that is typically sudden and irreversible.

Tipping points are also found in climate and nature. Scientists have found evidence of rapid, catastrophic change in ice core records of the distant past, supercomputer projections of the near future, and local data collected in the here and now.

They can take many forms: the degradation of the Amazon rainforest into a dry savanna, the collapse of polar ice sheets, the slowdown of ocean circulation, the breakdown of coral reef systems, and many other apocalyptic scenarios that would make the Earth less habitable for the vast majority of its species, including humans. The risks are existential.

Determining where those tipping points lie ought be a scientific and political priority, but the subject has been repeatedly nudged into the background at the United Nations. The failure to fully engage at the UN Intergovernmental Panel on Climate Change (the IPCC, the world’s top scientific advisory body) is usually explained away by people who say tipping point studies are more complex and less certain than other aspects of climate science so they might confuse the public with doomsday scenarios that are less likely than other outcomes. It is no coincidence that the countries using this excuse for inaction are mostly oil producers.

But this is patronising, misleading and negligent. Even if the probability is low (which is no longer the case), the risks are too enormous to ignore. To draw a comparison with aviation, passengers on a plane want to know that every safety precaution has been taken even though the possibility of a crash is far lower than that of a smooth flight.

Many of the world’s leading scientists are now insisting that more attention be paid to catastrophic dangers. Hundreds of them met last week at a global tipping point conference in Exeter, the UK. They have updated their own report, identifying 16 major threats and localised areas where tipping points have already been passed. “If anything we have under-estimated the risks,” said the conference organiser Tim Lenton. “In the climate science community, we have tended to concentrate on assessing what’s the most likely thing to happen but the more important question is, what’s the worst thing that could happen?”

Among those in attendance was Brazilian climate scientist Carlos Nobre, who was one of the first to warn about the risks of a tipping point in the Amazon that would irreversibly transform the world’s biggest tropical rainforest into a drier savanna with sparse, shrubby plant cover and low biodiversity. This would be more vulnerable to fire, less effective at drawing down carbon from the atmosphere, and weaker at pumping moisture across the continent. Nobre told SUMAÚMA that a tipping point could be reached if deforestation reaches 20-25% or global heating rises to 2.0-2.5C. “It is very, very serious,’ he said. “Today 18% of the Amazon has been cleared and the world has warmed by 1.5C and is on course to reach 2.0-2.5C by 2050.”

“Forty-five years ago, the annual dry season in the southern Amazon used to last three to four months and even then there would be some rain. But today, it is four to five weeks longer and there is 20% less rain. If this trend continues, we will reach a point of no return in two or three decades. Once the dry season extends to six months, there is no way to avoid self-degradation. We are perilously close to a point of no return.”

If the Amazon hits a tipping point, Nobre’s calculations indicate the forest would lose more than half of its vegetation, releasing between 200 and 250bn tonnes of carbon dioxide between 2050 and 2100, making it completely impossible to limit global warming to 1.5C. After two years of record drought, he is more worried than ever.

Tipping points have already been reached at a local level. Along the arc of deforestation in Mato Grosso, southern Pará and elsewhere in southeastern Amazon, the land is already so degraded by cattle ranching and soy production that it now emits more carbon than it sequesters. Coral reef systems in the

Caribbean are so damaged that experts say they have largely passed the point of no return. Some glaciologists believe the loss of the West Antarctic ice sheet may now be inevitable because of the warming of the oceans.

Scientists often talk about these changes as “non-linear”, which means they happen abruptly – a jolt rather than a steady, predictable transition. This is particularly concerning when it happens as a cascade – one tipping point triggering another tipping point, like a row of falling dominoes.

The non-linear, self-propelling nature of tipping points is highlighted by Polar scientist Louise Sime, who describes how sea ice in Antarctica seemed relatively stable until 2023, when there was an enormous drop. About 2.5 million sq km of Antarctic sea ice went missing relative to the average – an anomaly that should theoretically happen only once in tens of thousands of years. This coincided with an equally improbable heatwave. This had a knock-on effect because the melting of so much ice exposed more of the ocean to the sun, which means more water evaporates. A freakishly enormous atmospheric river formed over East Antarctica, substantially changing weather patterns in the region.

Sime said a tipping point in East Antarctic could eventually add four metres to global sea levels, which would be catastrophic for billions of people. She does not know when this might happen, but she said the risks are growing:  “It’s unthinkable, but it’s not impossible, and it looks more likely with each day that we continue burning fossil fuels. It’s beyond worrying.”

Uncertainty about the timing should not be an excuse for inaction. Given the scale of the risks, it is essential for the world to have a better understanding of such tipping points. Without this, it is impossible for politicians and economists to justify the radical change of direction that is needed to avoid these dangers. Currently, for example, most economic models do not account for tipping points or other forms of catastrophic change, which means they can blithely suggest global heating will only have a tiny impact on the world.

This assumption is called out by Genevieve Guenther, the founder of End Climate Silence, which studies the representation of global heating in public discourse: “The idea that climate change will just take off only a small margin of economic growth is not founded on anything empirical. It’s just a kind of quasi religious faith in the power of capitalism to decouple itself from the planet on which it exists. That’s absurd and it’s unscientific,” she says.

This is vitally important because it shows that most national decisions are based on a complacent misunderstanding of the climate crisis. If you assume that it only means linear, incremental adjustments, then it feels manageable – a chronic medical condition like diabetes that can be handled with very few lifestyle changes. But if you seriously consider the risks of tipping points and collapse, then suddenly the challenge is life-threatening and demands a transformational response.

In this edition of SUMAÚMA, it is very clear that Brasil’s president Luis Inácio Lula da Silva, like many other world leaders, is either ill advised or too weak to grasp the scale of the change that is needed. Why else would he push ahead with sales of oil exploration lots, as detailed in two stories by reporter Claudia Antunes? Why wouldn’t he respond more forcefully to evidence that forest fires are rapidly driving up Amazon deforestation, as shown in a powerful article by Rafael Moro Martins? How could forest-and-river-threatening projects be pushed ahead as we read here in articles about Belo Monte hydroelectric dam by Rubens Valente and the destruction of the Pedral do Lourenção on the Tocantins River, investigated by Catarina Barbosa?

It will come as no surprise to readers of SUMAÚMA that it is left to forest people to respond to the scale of the threat. For inspiration, look no further than the triumph of the Kichwa people of Sarayaku in driving an oil company from the Ecuadorean Amazon, as detailed by one of their leaders Patricia Gualinga, or the interview with Juma Xipaia, whose fight for the forest is vividly portrayed in a new film Yanuni.

Or, further afield, consider the role of imagination and courage in facing up to the threats we face, as sketched out by Sidarta Ribeiro in his exhortation for people to avoid the deserts of the mind.

These are examples of potentially positive tipping points – changes in society, culture, technology or consciousness that can help us to overcome emergencies. First though, we need to fully recognise that threats are catastrophic as well as incremental. That should be one of the priorities of COP30 in Belém.