National Emergency Briefing: Tipping Points
It was this speaker, Professor Tim Lenton OBE, who woke me up to the climate crisis and, specifically, it was him teaching about this topic, tipping points, that really hit home. Once you really grasp tipping points in the context of climate change you understand the precipice we are all teetering on the edge of.
Professor Lenton defines tipping points as ‘thresholds beyond which change becomes unstoppable. Once crossed, the climate can shift abruptly into a new stable state that is extremely hard to reverse.’ A familiar analogy that is often given is to think of rocking on the back two legs of a chair. To begin with you are completely in charge and can tip back onto all four legs any time you wish, but tip back one jot too far and you will cross the tipping point, you have crossed a point of no return, and crashing to the floor becomes inevitable, there is nothing you can do about it. A tipping point is this type of self-propelling change. Tipping points can happen in all sorts of complex systems, including the climate, the economy and societies. We have already crossed a tipping point for the world’s coral reefs ecosystems.
Climate change models identify many different tipping points, many of them can interact with each other, with one breach of a tipping point creating a cascade of others doing likewise. In a worst-case scenario, we risk a bad tipping point cascade leading to us losing control of the climate problem with damaging changes propelling one another.
The tipping point that creates the biggest risk for us in the UK is the failure of AMOC, the Atlantic Meridional Overturning Circulation part of which, the Gulf Stream, keeps our climate mild. Without it we would have seriously hotter summers and winters that could see temperatures such as -20°C in London for three months a year, and significantly lower rainfall, with insufficient rain falling in the winters to see us through the summers. Professor Lenton warns that ‘This would end large-scale agriculture in the UK’. On a global scale food production could be reduced by something like a half. At 3°C of warming the failure of AMOC becomes probable, at 2°C of warming the models show something like a 1 in 6 chance of it doing so.
The current rate of Arctic warming, leading to the melting of arctic and Greenland ice, pouring cold freshwater into the ocean, is one thing that contributes to the currently measured slow down in AMOC. We know that, without human intervention, AMOC turned on and off 5 times during the last ice age, so we know this is something that CAN happen. Many climate models predict this happening with climate change. Professor Lenton gave an example of one model that predicts it happening at around 2°C of warming.
Limiting the overshoot of 1.5°C of global climate warming, both with respect to duration and degree of overshoot, is the only way to avoid the catastrophic risks from climate tipping points.
Professor Lenton advocates accelerating to zero emissions by setting ‘clear ambition phase-out dates for fossil fuels in cars, boilers, power and freight’, as well as activating ‘market feedbacks that make clean options cheaper, faster and inevitable’, in effect, activating positive tipping points to achieve this.
This idea of positive tipping points was the good news in this presentation. We were told that positive tipping points can be self-reinforcing and drive rapid transformation, such as social change and the adoption of clean technologies. The unexpected speed at which coal has been removed from UK power generation being an example of this.
The most effective way to precipitate the transition to clean technologies, to create these climate positive tipping points, be that in power, or transport or other climate relevant areas, is to mandate to phase out the fossil fuel technologies and phase in the clean technologies. Examples would be the existing UK ban on new petrol and diesel cars from 2030, banning diesel trucks from 2040, and the proposed ban on gas boilers for residential heating. Helpfully, the more we adopt the clean technologies the better and the cheaper they become.
The presentation was summarised as follows: ‘The window for preventing damaging, irreversible climate tipping points is rapidly closing. Activating positive tipping points is the only way to rapidly accelerate decarbonisation and limit overshoot of 1.5 degrees.’ ‘Either we trigger positive societal tipping points toward a clean, prosperous system, or we gamble on dangerous climate tipping points we cannot control’. He emphasised that a radical acceleration of actions is called for. We need civil society and policy working together.
So, how can each and every one of us play our part in making sure that happens?
Watch Professor Lenton’s presentation here https://www.nebriefing.org/expert-briefings/tipping-points and for in depth reading in this area see https://global-tipping-points.org/ which includes the Climate Tipping Points Report 2025, with Professor Lenton being one of the editors of that publication.
Professor Tim Lenton is the founding Director of the Global Systems Institute at the University of Exeter and Chair in Climate Change and Earth System Science. He has more than 25 years research experience, focused on modelling of the biosphere, climate, biogeochemical cycles, and associated tipping points. He is a pioneer in identifying climate tipping points – the thresholds that can trigger irreversible shifts in the Earth's systems. He is also an expert in positive tipping dynamics, and his award-winning research has shaped understanding of the 1.5 °C target and pathways to sustainability.