It can be hard to picture the implications of climate change but walk along the promenade in Swansea and there are visible reminders that coastal flooding and sea level rise are a threat. Contractors are renewing and increasing the height of the sea wall in Mumbles in a £26m project designed with projected 2070 sea levels in mind while a low-lying beach underpass near the Civic Centre was permanently blocked off a couple of years ago.
Further west in Carmarthenshire an eye-opening council report this year said Bynea, near Llanelli, was likely to flood more often and more significantly within the next 30 years. The report said there was “little or no evidence both nationally and locally of forward-planning for the impacts of climate change and sea level rise” and warned: “As such the communication of these risks and engagement with our coastal communities at greatest risk from climate change and sea level rise is almost non-existent.”
Sea levels have been rising – by 20cm between 1901 and 2018, according to the Met Office – and the rate of increase is accelerating. Projections of future sea level rise vary but it’s something that coastal communities everywhere must adapt to.
What happens though if the link between rising greenhouse gas emissions, temperatures, and sea levels – caused by melting ice and thermal expansion of seawater – gets abruptly out of kilter? If a relatively small change had a huge and unexpected consequence? In a report for the UK Government about the economics of climate change 17 years ago economist Nicholas Stern – now Lord Stern – warned of “non-linear” changes in the system. He wrote: “Warming will increase the chance of triggering abrupt and large-scale changes.”
He went on: “The chaotic nature of the climate system means that relatively small amounts of warming can become amplified, leading to major shifts as the system adjusts to the new conditions.” There was a risk of crossing a threshold, he wrote, beyond which melting or even collapse of major ice sheets would be irreversible, committing the world to several metres of sea level rise long term. Crop yields, he said citing a study, could reduce by up to 70% by 2100 without adaptation. He added that abrupt changes such as these were hard to predict.
A section of the new sea wall in Mumbles
(Image: Richard Youle)
The blocked-off beach underpass west of the Civic Centre, Swansea
(Image: Richard Youle)
Climate tipping points have been explored more recently by the Global Systems Institute, based at Exeter University, which has backed calls for a special report on the subject by the United Nations Intergovernmental Panel on Climate Change (IPCC). The institute’s report published in December 2023 also showed how positive tipping points – such as the world’s rapidly-accelerating deployment of solar and wind power along with behavioural change – could help meet the urgency of the challenge.
The report, called Global Tipping Points, identified five major systems that were already at risk of crossing tipping points at the present level of global warming of around 1.2C. These were the Greenland and West Antarctic ice sheets, warm-water coral reefs, parts of permafrost regions facing abrupt warming, and a circulating North Atlantic current south of Greenland called the subpolar gyre, which among other things transports large amounts of atmospheric carbon into the deep ocean.
The report identified more than 20 other systems that have tipping points such as Amazon forest dieback and the collapse of some fisheries, which get closer with every fraction of a degree of warming. “In many cases the consequences of passing one tipping point make other connected tipping systems more or less likely to tip as a result,” it said. “If passing one tipping point makes another tipping point more likely then tipping points could cascade with a chain of tipping points triggering each other.”
It said tipping points showed that the overall threat posed by the climate and ecological problem was far more severe than was commonly understood and added: “The world is largely flying blind into this vast threat.” The report, which ran to 478 pages and had contributions from 200 researchers, acknowledged the complexity of the subject. “The associated uncertainty may sometimes seem huge and we must deal openly with it,” it said. Tipping point cascades, it added, were currently highly uncertain. But the report said it would be wrong to state that all tipping points were “inherently unpredictable”.
The authors urged a rapid cut in greenhouse gas emissions and recommended that countries assessed their own exposure to tipping points, put in place measures to help prevent them occurring, and planned for managing potential impacts. They also recommended strategies and interventions – technological innovation, financial investment, and political and social action – to encourage positive tipping points. Clearly humans possess remarkable ingenuity and many people want to do the right thing and not leave the environment worse for their children and grandchildren.
“Positive tipping points don’t just happen, they need to be actively enabled,” said the report. In the early 2000s the UK Government provided grants for offshore wind energy demonstration projects and then gave investors confidence by offering a guaranteed price for the electricity produced by offshore wind farms. The industry has expanded massively. There could be losers as well as winners though, said the report, and “the required scale and speed of change will only be possible with sufficient public consent”. Fairness, said the report, was crucial. Given that the richest 10% of the world’s population accounted for nearly half of all greenhouse gas emissions, it said, “luxury-focused” carbon taxes were necessary.
The Amazon rainforest is facing twin threats
(Image: Ricardo Lima/Getty Images)
The Greenland ice sheet is said to be already at risk of crossing a tipping point
(Image: Getty Images)
Dr Chris Boulton, a co-author of Global Tipping Points, specialises in the study of early warning signals. Asked if we’d actually know if we’d crossed a climate tipping point he said this would vary. The collapse of a monsoon system, he said, could happen extremely quickly whereas we might not observe a strong dieback of the Amazon rainforest for decades despite a line being crossed. Dr Boulton, of the Global Systems Institute at Exeter University, said it was possible that new climate tipping points might emerge although scientists had a reasonably strong understanding of the climate system by now.
He added: “Each tipping point system behaves in its own way and we often link them to changes in global mean temperature. We believe systems such as the Greenland or West Antarctic ice sheets are likely to tip with around 1.5C of warming but boreal forests (found across Russia, Canada, and Alaska) with much more warming. For other systems it’s clearly not just the global mean temperature that plays a role. The Amazon rainforest is highly affected by deforestation, which destabilises the atmospherics that cause rainfall much deeper into the forest.”
Dr Boulton said he believed political leaders were starting to be sufficiently briefed on climate tipping points and that the report he helped draw up was partly driven by a desire to fill that gap. Asked if he felt we were still largely “flying blind” into this threat, as the report warned, he said: “Not as blind as we were. I think people are starting to take notice.”
Was there a climate tipping point which gave him particular cause for concern? The Amazon rainforest, he said, given it was “vitally important” in combating climate change and that it has faced an additional human pressure – deforestation – as well as rising global temperatures. Asked what technological, economic, or social tipping points he was most encouraged by he said the uptake of electric vehicles (EVs). He said: “I know there are concerns regarding mining for materials for them but globally emissions from EVs are reduced compared to petrol vehicles.”
He added: “If it can be called one the want and need for people to take action on climate could also be called a social tipping point.” He said he felt all the climate rallies which have started happening wouldn’t have had the same traction a decade or so ago. Dr Boulton said as a scientist it was exciting when he identified a really strong result in a climate dataset but added: “Then you think: ‘What does that mean for the world?’ It’s quite conflicting sometimes.”
The report he helped write also warned of “pusle-like mirgration” and even “mass displacement” from severely affected countries if climate tipping points were crossed. What we considered to be “business as usual” would not exist. Social systems “likely characterised by greater authoritarianism, hostility, discord and alienation” could be ushered in. On the other hand, well-planned and funded interventions could bring about positive tipping point “cascades”.
In a separate report published in the magazine New Scientist this month, scientists said an area of sea ice nearly 6.5 times the size of the UK has disappeared from Antarctica in the past two years. It’s the equivalent of the ring of sea ice which forms every winter around the Antarctic continent shrinking by an by an average of 75 miles.
Swansea University professor Mary Gagen, who studies forests and the records of past global change contained in ancient trees, described climate tipping points as “fast, disruptive, and one-directional”. She said they were also extremely complex. A warming Atlantic, for example, might potentially drive more rainfall towards the Amazon, providing some benefit.
Prof Gagen was the lead author of a technical briefing for the World Wide Fund for Nature in 2022 which found that just over 34% of the entire Amazon had reached at least one of three theoretical tipping point thresholds: decreasing annual rainfall, increasing dry season length, and percentage of forest loss. Areas of the Amazon are now emitting more carbon, for example through the clearing and burning of trees, than they absorb. The briefing described a tipping point as a “critical threshold” above which a further change could alter an entire system which would be irreversible on human timescales. It added that it was possible to stress the Amazon to a state of permanent degradation.
Prof Gagen, who wasn’t a contributor to the Global Systems Institute report, said tipping points relied on modelling. Real-world evidence of crossing them, she said, would provide proof but was equally “the one thing we don’t want to happen”. She said: “We need to take a precautionary approach. Less warming means less tipping point risk. The impact of tipping points [being crossed] would be so serious that we need to act anyway. The single biggest risk is breaching 1.5C.”