"If we've crossed this tipping point in London, it's -20°C in three frozen months of the year, and in Edinburgh it's -30°C in five and a half frozen months of the year."
Professor Tim Lenton OBE
Key points from the briefing
Tipping points are thresholds beyond which change becomes unstoppable. Once crossed, the climate can shift abruptly into a new stable state that is extremely hard to reverse.
The risk rises with every fraction of a degree. As global warming moves beyond 1.5°C, the likelihood of triggering multiple, interacting tipping points increases sharply - with cascading effects.
Some tipping points are already being crossed. Coral reef systems have effectively tipped, threatening the livelihoods of about 500 million people and removing vital coastal protection worldwide from storm surges made worse by rising sea levels.
The biggest risk for the UK is the failure of the Atlantic Meridional Overturning Circulation (AMOC). This great ocean current keeps the UK’s climate mild. It is already weakening and could tip at around 2°C of warming.
An AMOC tipping point would transform the UK into an unrecognisable place. There would be winters of -20°C in London and –30°C in Edinburgh, with Arctic sea ice likely to reach down as far as East Anglia. But there would also be hotter summers, combined with severe water shortages due to significantly lower rainfall. This would end large-scale agriculture in the UK.
Near 2°C, the odds of crossing this tipping point are worse than Russian roulette. By around 3°C, it becomes more likely than not.
There is only one credible way to reduce this risk: accelerate to zero emissions fast. The longer we linger above 1.5°C, the higher the danger.
The good news is that positive tipping points exist. Clean technologies and social change can also become self-reinforcing, driving rapid transformation - as the UK already proved by tipping coal out of power generation.
Strong policy triggers tipping points. We need clear ambitious phase-out dates for fossil fuels in cars, boilers, power and freight. We also need to activate market feedbacks that make clean options cheaper, faster and inevitable.
This is a race between two futures. Either we trigger positive societal tipping points toward a clean, prosperous system, or we gamble on dangerous climate tipping points we cannot control.
