Of all the possible climate futures, there’s a scenario where the United Kingdom and north-west Europe buck the trend of global warming and instead face plunging temperatures and freezing winters. It’s not the most likely outcome, but a number of scientists fear that the chance of it happening is growing, and that the consequences would be so great that it deserves proper consideration.
They are concerned that the ocean currents that bring warm water from the tropics to the North Atlantic could weaken – or even collapse – in response to climate change. Huge uncertainties remain about when – or even whether – a collapse could happen. So, how likely is it, and what would it mean?
The system of Atlantic currents, called the Atlantic Meridional Overturning Circulation (Amoc), is a key reason why the UK is warmer than Moscow, despite being a similar distance from the Equator. Forming a vital part of our climate system, this conveyor belt distributes energy around the planet, bringing warm, salty water from the tropical Atlantic to cooler regions south of Greenland and Iceland, and also the Nordic Seas.
But Amoc appears to be getting weaker. We don’t know for sure, because direct and continuous measurements of Amoc strength have only been taken since 2004. That’s not long enough to be able to identify a definite change. But indirect evidence suggests it could have already slowed by around 15% over the last couple of centuries, although not all scientists agree.
In the UK, it could “become horribly, horribly cold … like living in northern Norway,” Prof Thornalley warns. “Our infrastructure is not set up for that.” There could be global consequences too, such as shifts to the tropical rain belts. “That’s a big story,” warns Prof Lenton. “If you lost the monsoon or seriously disrupted it, you’d have humanitarian catastrophes, in simple terms, in west Africa [and] probably in India.”
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