'Point of no return' collapse of Atlantic current could see UK temperatures plummet
Renowned climate scientist Professor James Hansen has warned that current warming targets are ‘dead’ - and that Britain could see temperatures drop.
The UK could face dramatically colder temperatures as climate change wreaks havoc on ocean currents in the Atlantic that contribute to Britain's weather, a renowned climate scientist has warned.
Professor James Hansen has warned that climate change could affect the Atlantic meridional overturning circulation (AMOC), a system of ocean currents in the Atlantic.
Hansen, who first sounded the alarm to the wider public on climate change in a speech in 1988, said current targets to keep international cooling under 2C are "dead".
He warned if temperatures were to rise above that level it would lead to AMOC shutting down within 20-30 years.
Hansen said if this were to happen it would have a dramatic effect on the British weather and would be disastrous for the rest of the world.
What is the AMOC?
The AMOC is a system of ocean currents in the North Atlantic that move heat northward through to higher latitudes. The AMOC is one of the reasons Britain and Europe are relatively warm compared to parts of the USA and Canada despite being similarly close to the Arctic.
The current moves warm water northward, which gets colder and denser as it travels. As it cools, it sinks lower and lower before eventually travelling southward again.
Why could it collapse?
The melting of ice sheets dilutes ocean water, making it less likely to sink, which then disrupts the AMOC's circulation.
Melting ice from the Greenland ice sheets could weaken AMOC or even cause it to stop abruptly.
It is already at its weakest in 1,600 years, and researchers spotted warning signs of a tipping point in research published in 2021.
What could happen if AMOC shuts down?
If the AMOC stopped working, Europe, including the UK, would rapidly become cooler.
Temperatures could drop by up to 10 degrees, the coast of Scotland would be frozen in sea ice, and the continent would see more storms.
Change could occur very quickly, in climate terms, over the space of a couple of decades.
Experts have warned that an AMOC collapse could have a devastating effect on life in the UK, affecting everything from weather patterns to the crops we grow.
Laura Jackson, a Met Office scientist who has studied North Atlantic ocean currents for decades, warned that in a rapid collapse. She said: "The cooling from AMOC weakening would be stronger than the background warming, and we would experience colder temperatures.
"It could have devastating impacts, causing cooling in the North Atlantic, large changes in precipitation, shifts in regional weather patterns and large impacts on ecosystems and human activities."
Research published in 2020 in the Nature Food Journal suggested that an abrupt shift could leave Britain 3.5C cooler and unable to grow many crops. Land suitable for arable farming could plunge by a quarter, reducing crop value by £346bn a year.
The main problem would be reduced rainfall and, although irrigation could be used to compensate, the researchers said the amount of water and the costs would be too high.
Dr Paul Ritchie, of Exeter University, said: "If the AMOC collapsed, we would expect to see much more dramatic change than is currently expected due to climate change.
"Such a collapse would reverse the effects of warming in Britain, creating an average temperature drop of 3.4C and leading to a substantial reduction in rainfall of 123mm during the growing season.
"These changes, especially the drying, could make most land unsuitable for arable farming."
An AMOC collapse would also disrupt rains, which would affect food supplies in Africa, India and South America.
Sea levels would rise on the east coast of North America, and the collapse would also further endanger the Amazon rainforest.
What has Professor Hansen warned?
In a study published in the journal Environment Hansen warned that the pace of global warming has been underestimated and that this means a greater risk of the collapse of ocean currents like AMOC.
Professor Hansen warned that measurements show accelerated global warming will increase ice melting in the Arctic.
He said: “As a result, the shutdown of the Atlantic Meridional Overturning Circulation (AMOC) is likely within the next 20-30 years unless actions are taken to reduce global warming – in contradiction to conclusions of IPCC.
"If AMOC is allowed to shut down, it will lock in major problems including sea level rise of several metres – thus, we describe AMOC shutdown as the point of no return."
When could it happen?
Some studies have suggested it could happen as early as this year, and another recent study suggested it could happen by 2050.
But a 2021 report by the International Panel on Climate Change (IPCC) said, with medium confidence, that it would not collapse abruptly before 2100.
Has anything similar happened before?
Scientists also believe a collapse is possible because it has happened before.
There is evidence of something similar happening in Europe 12,000 years ago, Professor Jon Robson, of the University of Reading, told Yahoo News last year.
Professor Robson said: "One thing that worries scientists is that there’s paleo evidence - evidence of the climate from the past - in stuff like ice cores, that there have been very rapid and abrupt changes in the North Atlantic region in the past, large cooling events over the space of a few decades.
"These have been linked to changes in the AMOC. The last time this happened was about 12,000 years ago. As we were coming out of the last ice age, there’s a rapid cooling of the North Atlantic region in particular."
Robson said that scientists fear that a "similar thing" might occur due to climate change, with a rapid weakening event triggered by warming water.