Removing CO2 from atmosphere vital to avoid catastrophic tipping points, leading scientist says | Cop30

Removing carbon from the atmosphere will be necessary to avoid catastrophic tipping points, one of the world’s leading scientists has warned, as even in the best-case scenario the world will heat by about 1.7C.

Johan Rockström of the Potsdam Institute for Climate Impact Research, who is one of the chief scientific advisers to the UN and the Cop30 presidency, said 10bn tonnes of carbon dioxide needed to be removed from the air every year even to limit global heating to 1.7C (3.1F) above preindustrial levels.

To achieve this through technological means, such as direct air capture, would require the construction of the world’s second biggest industry, after oil and gas, and require expenditures of about a trillion dollars a year, scientists said. It would need to be done alongside much more drastic emissions cuts and could also have unintended consequences.

Rockström was among several leading climate experts who spoke at a first public event for the Science Council, which was set up as an advisory body by the Belém Cop30 presidency.

In the next five to 10 years, they said the world would overshoot the 1.5C target of the Paris agreement.

This already happened temporarily in 2024, but UN scientists do not consider the goal breached until the trend is confirmed over an average of 10 years combined with forecasts of the following 10 years, said Thelma Krug, the coordinator of the council.

Another member, Chris Field of Stanford University, said that despite the overshoot, the world should retain the 1.5C target because the longer and higher the world remains beyond that, the greater the risk of more dangerous tipping points in the Antarctic, Greenland, ocean circulation and the Amazon rainforest. It is thought that many coral reef systems will already have passed that point of no return at 1.5C of heating.

Tim Lenton, a tipping point expert at the University of Exeter, outlined the range of risks that are already close. Still greater dangers lie ahead, he warned, particularly if there is a collapse of the Atlantic meridional overturning circulation system of ocean currents.

“This would trigger other tipping points,” Lenton said. “We must do everything we can to prevent this.”

Field said 200bn tonnes of carbon dioxide would have to be removed from the atmosphere to cope with every tenth of a degree rise.

At the most, he said this could cope with two-tenths of a degree, but even this would be slow, expensive and could bring a wide range of unintended consequences.

There are a number of options for capturing carbon. The most effective and cheapest is growing forest, which costs about $50 (£38) for every tonne of CO2, but means the land cannot be used for other purposes such as agriculture. The most expensive is direct air capture, an industrial process that has never been used at scale, which costs at least $200 per tonne. In between are riskier strategies such as ocean fertilisation, which could disrupt marine ecosystems.

Krug said the UN’s main climate science body, the Intergovernmental Panel on Climate Change (IPCC), had started a study on different mechanisms for carbon removal. Rockström told the Guardian he would like the Cop30 presidency to put carbon removal in its declarations to focus attention on the risks and costs ahead.

He said Potsdam Institute modelling had shown that, even with ambitious carbon removal and strong government actions to reduce emissions, it was still only possible to limit heating to between 1.6C and 1.8C. Even this would require far stronger policies to reduce fossil fuel emissions than those currently adopted by governments, which would allow the world to heat by at least 2.7C.

Despite the enormous costs involved, he said the alternative was more devastating droughts, fire storms and suffering.

“Every tenth of a degree matters,” he said. “We are seriously seeing that we are heading at high speed towards a dead end. Scientists continue publishing papers but we are getting nervous. We are seeing really worrying signs,” he said.

Scientists want the prevention of tipping points to be included in the global stocktake of the Cop process. Lenton said he welcomed the fact that the the IPCC had started studying these risks. He emphasised there were also positive tipping points, when social, economic or technological drivers could push change towards a more stable climate.

He said the Cop30 presidency’s willingness to engage was a good sign, though the political circumstances elsewhere in the world were making action difficult.

“I’d love to think this Cop could be its own tipping point,” he said. “It should be, in the sense that the tipping point risks are staring us in the face now, particularly, for example, with the coral reef collapse and the Amazon around us suffering extraordinary droughts and fires.

“There won’t be a new legally binding agreement, but the Cop presidency might put together some new alliances that take into account the tipping point risks and the potential for positive tipping point change. I think that could be the best outcome to hope for.”

One country that will not be part of any new alliance is the US, which under President Donald Trump has withdrawn from the Paris agreement again, and is one of four countries – along with Afghanistan, Myanmar and San Marino – not to register a single delegate at the summit.

Christiana Figueres, one of the architects of the Paris deal, expressed relief at the absence of the US, addressing Trump with the words “Ciao bambino!”

“I think it actually is a good thing,” she told reporters. “They won’t be able to do their direct bullying.

“Honestly, the decarbonisation of the global economy is irreversible,” she said. “Momentum is building into the point where it is simply unstoppable, with or without the US.”

Meanwhile, Ethiopia was named as the expected host of Cop32 in 2027, but the host of Cop31 next year remains uncertain, with neither of the two bidders, Australia and Turkey, showing any sign of backing down.