The collapse of one of Earth’s most important ocean currents could trigger a huge dip in global food production, scientists have warned.
The Atlantic Meridional Overturning Circulation (AMOC) is a vast network of ocean currents carrying warmth from the tropics to Europe, of which the Gulf Stream is one small part.
Recent data suggests that human–caused climate change could be driving the system to a tipping point, plunging northern Europe into a ‘new Ice Age’ and disrupting crucial monsoon rains in Africa and Asia.
Now, scientists have warned that a weakening current could cripple agriculture in key parts of the world – with the UK heavily affected.
As part of a new study, researchers found that some countries could see their wheat, maize and rice production drop by nearly a fifth.
And this could trigger a spike in food prices that could be felt across the globe.
‘The ultimate price impact of an AMOC collapse will depend heavily on the ability of global agricultural supply and demand to adapt to the altered yield environment,’ they said.
‘If the biophysical shock were to outpace adaptation, the economic impacts could be severe, driving a short–term global price spike of up to 40 per cent above baseline levels.’
The team discovered that by the 50–year mark, global yields for the most common varieties of wheat, maize and rice decreased by 5.3 per cent
For the study, which has not yet been peer reviewed, a team from the non–profit Alliance to Feed the Earth in Disasters (ALLFED) used a computer model to simulate the AMOC’s future decline.
They programmed the system to model the next 100 years, incorporating a 2°C warming above pre–industrial temperatures.
In one simulation they also included an AMOC slowdown over the first 50 years, to allow them to compare the world with and without an AMOC collapse.
Analysis revealed that an AMOC slowdown would trigger overall cooling in the Northern Hemisphere, along with a southern shift of the belt of clouds and rain near the equator.
The team discovered that by the 50–year mark, global yields for the most common varieties of wheat, maize and rice decreased by 5.3 per cent.
However, some areas were more affected than others.
Countries like Germany and Ukraine lost up to 19 per cent of their yields due to sudden, sharp cooling, while Canada showed a 12 per cent decline in production for the same reason.
‘Scandinavia, the United Kingdom and Canada are particularly exposed,’ Michael Hinge, senior economist at ALLFED, told Live Science.
Some areas would be more affected than others, the researchers warned – with countries like Ukraine and Germany losing up to 19 per cent of their yields
The findings build on earlier research led by Paul Ritchie, a climate scientist from the University of Exeter.
His study found that in an AMOC collapse scenario, average British temperatures would fall by about 3.4°C by 2080, relative to a scenario without an AMOC collapse.
Rainfall during the April to September season would fall by about 123mm, and the area of Great Britain suitable for arable farming would plunge from about 32 per cent to just 7 per cent.
As part of the new study, the researchers said countries will need to prepare for major changes in where food is produced, with crops potentially having to move into regions where the new climate is more suitable.
But relocating agriculture is far from simple, requiring land, water, infrastructure and investment –and the areas gaining suitable conditions may not have the capacity to take over production.
The scientists also warn that countries cannot simply look after their own food supplies.
Maintaining international trade would be crucial, because restricting exports when harvests fall could amplify shortages elsewhere, they said.
Countries would need to co–ordinate rather than retreat behind protectionist policies – otherwise a fall in production in one part of the world could rapidly become a global food crisis.
There is a 10 to 24 per cent chance that the collapse of one of Earth’s most important ocean currents may already be locked in, a separate study revealed
The team said they hope their work can help governments understand the need to take swift, effective action if a collapse were to occur.
Mr Hinge warned that currently, ‘if that warning light starts flashing, we’re not sure what to do with it’.
‘There are no easy answers here – an AMOC [collapse] would be deeply catastrophic,’ he added.
Studies have shown that AMOC has already slowed by about 15 per cent since the mid–20th century due to climate change, and could be driven into total collapse in the future.
Scientists say there is an almost one–in–four chance that this catastrophic collapse is already inevitable.
ATLANTIC OCEAN CIRCULATION PLAYS A KEY ROLE IN REGULATING THE GLOBAL CLIMATE
When it comes to regulating global climate, the circulation of the Atlantic Ocean plays a key role.
This is due to a constantly moving system of deep-water circulation often referred to as the Global Ocean Conveyor Belt which sends warm, salty Gulf Stream water to the North Atlantic where it releases heat to the atmosphere and warms Western Europe.
The cooler water then sinks to great depths and travels all the way to Antarctica and eventually circulates back up to the Gulf Stream.
When it comes to regulating global climate, the circulation of the Atlantic Ocean plays a key role
This motion is fuelled by thermohaline currents – a combination of temperature and salt.
It takes thousands of years for water to complete a continuous journey around the world.
Researchers believe that as the North Atlantic began to warm near the end of the Little Ice Age, freshwater disrupted the system, called the Atlantic Meridional Overturning Circulation (AMOC).
Arctic sea ice, and ice sheets and glaciers surrounding the Arctic began to melt, forming a huge natural tap of fresh water that gushed into the North Atlantic.
This huge influx of freshwater diluted the surface seawater, making it lighter and less able to sink deep, slowing down the AMOC system.
Researchers found the AMOC has been weakening more rapidly since 1950 in response to recent global warming.
