Sea ice on the coast of Scotland with bitterly cold, stormy winters and temperatures in Europe dropping by 10 degrees. It doesn't sound like the average climate forecast.
But it's a realistic scenario, and it could happen in the space of a few decades, experts warn. The culprit is man-made CO2 emissions.
Although the world has warmed in recent decades, there are signs that the North Atlantic Ocean has failed to keep up - and that could be a warning sign of things to come, explains Professor Jon Robson from the University of Reading . The potential culprit is the AMOC (Atlantic Meridional Overturning Circulation), a system of ocean currents in the North Atlantic that moves heat northward to higher latitudes.
Professor Robson says: 'As that water moves north, it gets colder. It becomes denser, it sinks and then returns. It's part of the reason why the North Atlantic is relatively warmer, and so the European climate is relatively warmer than, for example, the North American climate.'
But scientists are increasingly concerned that the AMOC could quickly weaken as climate change warms Atlantic Ocean waters, lowering temperatures in Europe.
Some measurements indicate that the AMOC is already weakening, and research suggests that it could reach a 'tipping point' that would quickly change its potential.
One of the reasons scientists are concerned is that there is evidence that something similar happened in Europe 12,000 years ago, explains Professor Robson.
'One thing that worries scientists is that there is 'paleo' evidence - evidence of past climate - in things like ice cores, that there have been very rapid and abrupt changes in the North Atlantic region in the past. a span of several decades," explains Prof. Robson.
"These have been associated with changes in the AMOC. The last time this happened was about 12,000 years ago. As we emerged from the last ice age, rapid cooling occurred especially in the North Atlantic region."
Robson says scientists fear something similar could happen as a result of climate change, with rapid weakening caused by warming waters meaning the AMOC could decline rapidly over a few decades.
The AMOC is driven by the cooling and densification of the water in the North Atlantic Ocean, but climate change will make the water in the North Atlantic Ocean warmer and less dense.
Much of the warming caused by human-induced climate change is absorbed by the oceans, and over time this could cause changes in currents such as the AMOC.
Professor Robson says: 'This slows down the formation of this dense water which flows south and completes the circuit. That's the main reason why we think it's going to slow down.
"It will transport less heat to the North Atlantic, and so could potentially change the way temperatures in the North Atlantic change over the next hundred years."
But some scientists fear this change could happen quickly, Professor Robson warns - not overnight, but over the space of several decades.
"A tipping point can simply be seen as a kind of threshold where changes in the climate system - in this case the AMOC - change very quickly. There are indications that such an abrupt weakening of AMOC has occurred before during times of major climate change. , such as the last deglaciation, and climate models suggest that the AMOC could weaken abruptly under specific conditions.
"Tippling points are also associated with changes that are difficult to undo. So there is concern that as the climate continues to warm, we may exceed a critical threshold that leads to a rapid and abrupt decline in AMOC, even if we reach net zero. If the AMOC collapses, it could also remain 'off' for hundreds of years.
"Tipping points are thought to exist in the AMOC because it is thought to be self-perpetuating. This is because water that is both salty and warm moves into the North Atlantic Ocean. The salt helps provide the higher water density needed to So if the AMOC weakens, it may get to a point where it can no longer maintain its own strength and weakens.
"However, how close we are to such a critical threshold, and whether such a threshold even exists in the real world, is not well understood."
If the AMOC were to weaken rapidly, temperatures in Britain would change, dropping by as much as 10 degrees over the space of a few decades.
Professor Robson says: "Temperatures in western Europe could fall by 10 degrees. You would have sea ice along the coast of Scotland, along with a big rise in sea levels across western Europe - with windy, stormy winters. "
Research from 2020 suggested that crop production in Britain could plummet if the AMOC were to weaken quickly.
The amount of land suitable for arable farming could fall by a quarter, reducing crop values by £346 billion a year.
There are some signs that AMOC could be declining, but further research is needed, Robson says.
'The North Atlantic Ocean is warming less quickly than the rest of the world, especially if you look at the past hundred years. Some people point this out and say this is consistent with what we would expect if AMOC declines.
But Professor Robson says these signals are inconclusive.
"We have only been observing the AMOC for the past 20 years, and during that time there has been some weakening, but not much, and the variability is enormous. There may already be some long-term weakening of the AMOC." but it is difficult to recognize it in the observations we have so far."
Further research using better climate models can help us understand whether the AMOC will reach a 'tipping point' in the near future, says Professor Robson.
'Much of this work on abrupt climate changes is based on climate models, because we have no other laboratory. But they are not perfect - and we try to test these hypotheses using very advanced models compared to the ones that are cheaper to run."
There is no alternative way to stop the weakening of the AMOC bar limiting human climate emissions, says Professor Robson.
The more carbon we emit into the atmosphere, the more likely it is that the AMOC will decrease very abruptly. To stay protected, we must reduce emissions as quickly as possible; there is no other reasonable approach.
