Crop yields in Britain will PLUMMET if climate change causes vital ocean currents to collapse

Crop yields in Britain will plummet if climate change causes vital ocean currents from the tropics to collapse — lowering temperatures by 6°F — a study has found.

The so-called Atlantic Meridional Overturning Circulation (AMOC) brings heat from the tropics, making Britain warmer and wetter than it would otherwise be.

Experts from the University of Exeter found that while a warming Britain would see boosted food production, the collapse of the AMOC would cripple arable farming. 

In this scenario, which would see reduced rainfall, the land area suitable for crops would shrink by a quarter, reducing yield values by around £346 million per year.

Such a collapse — which experts refer to as passing a climate change ‘tipping point’ — would leave Britain cooler, drier and unsuitable for many crops, researchers found.

Reduced rainfall would be the largest problem — and although irrigation could be used to compensate, the experts said that the costs of such would be prohibitive.

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‘If the AMOC collapsed, we would expect to see much more dramatic change than is currently expected due to climate change,’ said University of Exeter mathematician Paul Ritchie.

‘Such a collapse would reverse the effects of warming in Britain, creating an average temperature drop of 3.4°C [6.1°F] and leading to a substantial reduction in rainfall of 123 mm [4.8 inches] during the growing season,’ he added.

‘These changes, especially the drying, could make most land unsuitable for arable farming.’

According to experts, the AMOC — of which the Gulf Stream is a part — is one of the reasons why the average temperatures in Britain are typically warmer than many places at similar latitudes.

For example, chilly south Alaska and Moscow are located at higher latitudes than Edinburgh in the UK.

In their study, the researchers examined a ‘fast and early’ collapse of the AMOC. 

Although this scenario is currently considered to be of a ‘low-probability’, the AMOC has weakened by an estimated 15 per cent over the last 50 years.

Worst-case scenarios must be considered when calculating risks, said University of Exeter earth system scientist Tim Lenton.

‘Any risk assessment needs to get a handle on the large impacts if such a tipping point is reached, even if it is a low-probability event,’ he added.

‘The point of this detailed study was to discover how stark the impacts of AMOC collapse could be.’

Previous work by the team had warned of a possible ‘cascade’ of inter-related climate tipping points.

Professor Lenton said that the new study reinforces the notion that ‘we would be wise to act now to minimise the risk of passing climate tipping points.’

Growing crops is generally more profitable than using land as pasture for livestock rearing, but much of northern and western Britain is unsuitable for arable farming.

‘With the land area suitable for arable farming expected to drop from 32 per cent to 7 per cent under AMOC collapse, we could see a major reduction in the value of agricultural output,’ said paper author and environmental economist Ian Bateman.

‘In this scenario, we estimate a decrease of £346 million per year — a reduction of over 10 per cent in the net value of British farming.’

Professor Bateman noted that there is a common expectation that moderate warming will boost Britain’s agricultural production.

‘It’s important to note that the wider effects for the UK and beyond will be very negative as import costs rise steeply and the costs of most goods climb,’ he said.

Although the team focused their present study on agriculture, the collapse of the AMOC and the resulting temperature drop could also lead to a host of other economic drawbacks for the UK, the team warned.

The full findings of the study were published in the journal Nature Food.