A “collapse” of key Atlantic ocean currents would cause winter temperatures to plunge across northern Europe, overriding the warming driven by human activity.

That is according to new research, published in Geophysical Research Letters, which looks at the combined impact of the shutdown of the Atlantic Meridional Overturning Circulation (AMOC) and global warming on temperatures in northern Europe.

Scientists have warned that human-caused climate change is likely causing AMOC to weaken and that continued warming could push it towards a “tipping point”.

The study suggests that, in an intermediate emissions scenario, greenhouse gas-driven warming would not be able to outweigh the cooling impact of an AMOC collapse.

In this modelled world, one-in-10 winters in London could see cold extremes approaching -20C.

Winter extremes in Oslo in Norway, meanwhile, could plummet to around -48C.

The cold temperatures are projected to be driven by the loss of heat transfer from the tropics via ocean currents, as well as the spread of sea ice to northern Europe in the winter months.

The research does not look at when AMOC might tip – instead, it focuses on scenarios in the far future when this has already happened, so as to explore what impact it would have.

Lead author Dr René van Westen, a researcher in oceanography at Utrecht University, says Europe might stand alone as the one region set to get “cooler in a warmer world”. He tells Carbon Brief:

“If the AMOC collapses, we need to prepare for substantially cooler winters. Winter extremes will be very substantial for some regions. Temperatures could go down to -50C in Scandinavia. At -40C and lower in Scandinavia – everything breaks down over there.”

The research is being published alongside an interactive map, featured below, which highlights how a collapsed AMOC under different warming scenarios could impact temperature averages, extremes and sea ice across Europe.

‘Will warming or cooling win?’

AMOC is a system of ocean currents which plays a crucial role in keeping Europe warm. It transports warm water northwards from the tropics to Europe and cold, deep waters back southwards.

The potential collapse of these ocean currents – caused by the influx of freshwater from melting ice as well as rising air temperatures – is seen by some scientists as a “tipping point” that, once triggered, would be irreversible on human timescales.

However, there is significant scientific debate around whether human-caused climate change is causing the AMOC to slow down – and whether and when it might “tip”.

(The “tipping” of AMOC is often referred to as a “collapse”, “breakdown” or “shutdown”.)

Some scientists have argued that ocean currents have been slowing down since the mid-20th century, whereas others say there has been no weakening since the 1960s.

On the risks of an approaching tipping point, some researchers have estimated a collapse could occur this century, but others have questioned the robustness of the early warning signals being interpreted as evidence of a forthcoming shutdown.

(Regular direct measurements of AMOC’s strength started in 2004. To estimate the ocean currents’ health prior to this, scientists turn to a number of methods, including looking at palaeoclimate records, running climate model “hindcasts” and analysing historical patterns in sea surface temperature.)

A paper published last year by van Westen and colleagues, which ranked second in Carbon Brief’s round-up of the most talked-about climate papers of 2024, found that the present-day AMOC is on a trajectory towards tipping.

That paper set out some of the climate impacts of such an event, including a 10-30C drop in average monthly winter temperatures in northern Europe within a century and a “drastic change” in rainfall patterns in the Amazon.

The scientist’s latest offering provides a more detailed look at how an AMOC tipping event might impact Europe, using simulations produced by the Community Earth System Model (CESM).

The research models the impact of an AMOC collapse in combination with the impacts of human-caused climate change, instead of looking at the collapse of the ocean currents in isolation.

Van Westen says the research was designed to answer the question of how warming from greenhouse gas emissions could offset cooling from an AMOC shutdown. He tells Carbon Brief:

“[A question we wanted to address was] what would happen in a scenario where we have climate change and an AMOC collapse. Will it get cooler over Europe, or will it get warmer? Will regional warming win or will the cooling win?”

Simulating AMOC ‘collapse’

To answer this question, the scientists run a raft of climate simulations, exploring different combinations of global temperature rise and AMOC collapse.

Specifically, the scientists explore the collapse of AMOC under three scenarios:

An “intermediate” climate scenario (RCP4.5), which is in line with current global climate policies.

A very high-emissions scenario (RCP8.5) where warming hits 4C above the pre-industrial average by 2100.

A “pre-industrial” scenario, without any human-caused global warming.

Across all three scenarios, the researchers run multiple simulations 500 years into the future, stabilising global temperature rise at 2C and above 4C from 2100 onwards. The researchers explore scenarios where AMOC is stable and when it has tipped.

The paper does not discuss the level of warming at which AMOC might tip – instead, it focuses on a point in the future after it has occurred, when the ocean currents and the climate have “equilibrated to a new background state”.

To simulate an AMOC collapse in the climate model under the two warming pathways, the researchers apply high levels of freshwater forcing to the north Atlantic.

Van Westen acknowledges the level of freshwater forcing applied to the model to create an AMOC shutdown is “unrealistic”, but says the adjustment is necessary to override a “bias” in climate models. He explains:

“[Climate models] have an overly stable AMOC. So, we need to add this kind of freshwater flux to get the AMOC in a more unstable regime which corresponds to actual observations.”

The paper focuses largely on impacts under the intermediate scenario with AMOC collapse. Under this combination, AMOC shutdown causes some global cooling, resulting in a world that is around 2C warmer than pre-industrial levels.

Prof Stefan Rahmstorf, a professor of physics of the oceans at Potsdam University who was not involved in the research, tells Carbon Brief the new study is “highly welcome”. He explains that “not many” studies have investigated the combined impact of global warming with AMOC collapse since a paper he co-authored in 1999, and adds:

“[The new study] uses a sophisticated climate model with good regional resolution – far better than what was possible 26 years ago. The model confirms the long-standing concern that an AMOC collapse would have massive impacts on European climate, in this case focusing on temperature extremes.”

Dr Alejandra Sanchez-Franks, senior research scientist in the marine physics and ocean climate group at National Oceanography Centre, who was also not involved in the research, says the study’s conclusions should not be used to explain how the European climate will respond in the near-term to changes in the strength of AMOC. She tells Carbon Brief:

“The study uses an idealised experiment with unrealistic freshwater changes to force an AMOC collapse. Very importantly, the author’s conclusions refer to the European climate 200 years after an AMOC change and do not describe what will happen to European temperatures and sea ice in the years and decades following an AMOC collapse.

“Therefore, the study does not serve to tell us how an AMOC tipping point or collapse will affect us immediately.”

‘Out of the freezer and into the frying pan’

The most “striking” finding of the paper, according to van Westen, is that an AMOC collapse in a world that is 2C warmer will result in a Europe that is cooler than it is today.

The research notes that – under this scenario – north-west Europe is set to face “profound cooling”, characterised by more intense winter extremes.

Summer temperatures, on the other hand, would be expected to remain just slightly cooler than they would in a pre-industral climate – meaning that Europeans would experience dramatic swings in temperatures throughout the year.

Increased winter storms and greater day-to-day temperature fluctuations are also expected in this scenario. This is due to a greater temperature contrast between northern Europe and southern Europe, which would be less impacted by a weakened AMOC.

The research notes that cooling from the reduced heat transfer from ocean currents would be amplified by “extensive” sea ice expansion to the coasts of north-west Europe. (Sea ice reflects incoming solar sunlight, resulting in less heat uptake and cooler temperatures overall.)

The map below shows the extent of sea ice in February under the scenario where AMOC collapses and the world is 2C warmer. It shows how Arctic sea ice – when at its yearly maximum – would cover the coasts of Scandinavia and much of the island of Great Britain.

February sea ice extent under an intermediate emissions scenario (RCP4.5) and AMOC collapse, where the blue line indicates the extent of sea ice. Credit: Amended from van Westen et al (2025).

Prof Tim Lenton, chair of climate change and Earth system science at the University of Exeter, who was not involved in the study, tells Carbon Brief it is “hard to over-stress how different” the climate simulated by the model is from present-day conditions. He says:

“The extreme winters would be like living in an ice age. But at the same time summer temperature extremes are barely impacted – they are slightly cooler than they would be due to global warming, but still with hotter extremes than the preindustrial climate.

“This means the seasonality of the climate is radically increased. In extreme years it would be like coming out of the freezer into a frying pan of summer heatwaves.”

The research also looks at the impacts of a shutdown of AMOC in a world that is 4C warmer.

It suggests that, under this scenario, cooling related to the shutdown of ocean currents would not outweigh global warming. Northern Europe would not experience extensive sea-ice expansion or the strong cooling projected under the 2C scenario.

Instead, temperatures would be expected to increase throughout the year and particularly in the summer months. However, northern Europe would be expected to see warming below the global average.

Frigid cities

While the paper itself uses the Dutch town of De Bilt as a case study, the researchers have published projections for a range of European cities under the scenarios explored in the study.

For example, the data shows that, under AMOC collapse in a 2C-warmer world, London could experience an average winter temperature of 1.9C, roughly 17.6 freezing days each year and one-in-10-year cold extremes of -19.3C.

In the Norwegian capital of Oslo, average winter temperatures are projected to plunge to -16.5C, with maximum daily temperatures not surpassing 0C for almost half the year, or 169 days. The research suggests the Norwegian city could experience cold extremes of -47.9C.

The map below shows projected cold extremes under 2C of warming and AMOC collapse in cities in Belgium, France, Ireland, the Netherlands, Switzerland and the UK. It shows how temperatures could drop to -29.7 in Edinburgh, -19.3C in London and -18C in Paris.

Cold extremes – defined as temperatures that could occur once every 10 years – under AMOC collapse and around 2C of warming (“RCP4.5”). Credit: Amended from van Westen et al (2025).

Van Westen says the findings are “highly relevant for society and policymakers” because they “shift the narrative” about the direction of Europe’s future climate. He explains:

“Parts of the Netherlands and parts of the UK will experience spectacular cold extremes down to -20C or even lower. Our societal structure and our infrastructure is not built for these cold extremes.”

The paper is being published alongside an interactive map, shown below, that shows ice cover, temperature averages and extremes across the world under five of the scenarios explored in the study. These are: a pre-industrial world with a stable AMOC, a pre-industrial world with a collapsed AMOC, a 2C world with a stable AMOC, a 2C world with a collapsed AMOC and a 4C world with a collapsed AMOC.

Future research

Scientists not involved in the study said the work would need to be followed up with further exploration of the interplay between global warming and potential AMOC collapse.

Dr Bablu Sinha, leader of climate and uncertainty, marine systems modelling at the National Oceanography Centre, told Carbon Brief:

“Given that observational data is limited, theoretical climate modelling approaches need to be taken to properly investigate this topic. Van Westen and Baatsen motivate the need for more detailed investigation into the combined impacts of global warming and AMOC decline on European extreme temperatures.”

Dr Yechul Chin, researcher at Seoul National University’s climate system lab, tells Carbon Brief:

“Although [this research] demonstrates the potential for more extreme weather under combined global warming and AMOC collapse scenarios, significant uncertainties remain that must be resolved before we can quantify risks or devise robust mitigation strategies.

“Projections about AMOC have a large spread and it means that alternative AMOC trajectories and different levels of warming could substantially widen the range of possible outcomes.”

His comments are echoed by Rahmstorf from Potsdam University, who points out that the “exact outcome” for Europe hinges on the development of “two opposing trends” – global warming due to greenhouse gases and regional cooling due to AMOC weakening. He says:

“The balance between those two will depend on the speed and extent of these trends and will, therefore, depend on the emission and AMOC weakening scenarios.

“Therefore, the more scenarios will be explored with different models in future, we will see a range of different outcomes for Europe as well as other parts of the world. A large uncertainty in this respect will remain.”

Chart of the Gulf Stream by Benjamin Franklin and Timothy Folge, 1769

A failure of the AMOC would adversely affect the climate of the UK and Europe and parts of North America (with a knock-on effect elsewhere), disrupting agriculture and causing mass migration and food shortages, affecting national security. Sea level rise will also be involved. We don’t know when it will happen, but it has been slowing down for years.

Background

The global thermohaline circulation is a ‘conveyor belt’ of water continuously circulating around the oceans of the world, mixing the waters. The portion of the current in the Atlantic Ocean is called the Atlantic Meridional Overturning Circulation (AMOC). The portion of the AMOC which flows from the Gulf of Mexico, through the Straits of Florida and up the U.S. East Coast is called the Gulf Stream. It then veers east near North Carolina and moves toward Northwest Europe, where it is called the North Atlantic Current, though in Britain I think we tend to still call it the Gulf Stream as it passes us, keeping us relatively warm, even though London is north of Calgary, Canada.

Thermohaline Circulation by NASA

Water from the warmer south heads northward near the surface, bringing warmth with it. It is also saltier than average, as it comes from an area where there is more evaporation. Being saltier, it is denser, and when it cools in the north it sinks and begins the return journey south. However, as a result of global warming the ocean remains warmer, plus melting ice sheets are adding more and more less-dense fresh water to the mix. Studies show that the AMOC has been weaker than before the Industrial Revolution for years. However, it is not known how much of that is due to natural variability – it has varied in the past, for example during the during the Late Pleistocene, as can be seen in Greenland which has been greener in the past. It is predicted to carry on weakening, however.

Climate models have been playing catch-up when it comes to factoring in the slowing down of the AMOC, which interacts with other causes and symptoms of global warming.

A weakening AMOC would affect average air temperatures over Scandinavia, Great Britain and Ireland, which it currently warms.

It would also affect North America by accelerating sea level rise.

If it collapsed completely Europe would become considerably cooler on average with more rain and snow. This would be a major tipping point which it would be hard to recover from.

How we know

While seafarers no doubt knew about the Gulf stream earlier, Juan Ponce de León is the first European known to have mentioned it, in 1513. In 1751 Henry Ellis discovered that there was cold water at depth in the Atlantic, but did not realise the significance. In 1769 Benjamin Franklin had a chart of the Gulf stream printed based on the observations of his whaling captain cousin, Timothy Folger (see picture above).

Henry Stommel wrote a paper about how there can be “free convection between two interconnected reservoirs, due to density differences maintained by heat and salt transfer to the reservoirs” back in 1961 and thought it might be at play in oceanic circulation.

Wallace S. Broecker published the idea of a global conveyor belt back in 1997 (he popularized the term global warming back in 1975). He first conceived of the idea in 1984. He said in 1997 that “Were the ongoing increase in atmospheric CO2 levels to trigger another such reorganization, it would be bad news for a world striving to feed 11 to 16 billion people.”

I first heard about the AMOC years ago when I read that it was slowing down and that that would send Britain (where I live), North East America and parts of Europe into a big freeze, so naturally I have been paying attention. William H. Calvin warned of a “drastic cooling—a catastrophe that could threaten the survival of civilization” in 1998. The possibility that intense regional cooling could be triggered by global warming was included in the 2001 IPCC report. In 2003 Peter Schwartz and Doug Randall wrote a report for the Pentagon, “Imagining the Unthinkable”, which discussed the implications for United States National Security. They ‘created a climate change scenario that although not the most likely, is plausible, and would challenge United States national security in ways that should be considered immediately’. The 2004 American science fiction disaster film The Day After Tomorrow implicated the AMOC.

This is one way how, counterintuitively, global warming can cause colder weather in places.

In the decades since then, predictions as to how fast it was slowing and which parts of the world – if any – would freeze have varied, as more aspects were studied, and the warnings are getting stronger.

How much of that variability was due to developments in the science, and how much to journalistic license, I don’t know. Some ‘journalists’ tend to cherry pick and exaggerate those parts of studies which will get them the most clickbait (though it may only be those who write the headlines, and the actual articles are OK). And scientists tend to vary in their degree of optimism or pessimism like everyone else – glass half full or glass half empty. But more data keeps coming in and the warnings are not going away.

In 2004, the UK’s Rapid Climate Change (RAPID) project began providing hourly temperature and salinity data from instruments moored in the Atlantic ocean rather than 5-yearly ones from survey ships. 20 years on they have built up a much better picture of the variability of the current.

In November 2007 a program called Argo which had been proposed in 1999 achieved its planned array of 3,000 profiling floats used to observe temperature, salinity and currents (map).

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More recent news

A 2015 paper described how the AMOC has been weakening since 1975 (though it is variable), saying “Further melting of Greenland in the coming decades could contribute to further weakening of the AMOC”. The melting of the Greenland ice sheets affects the AMOC and vice versa. A 2019 paper said that this melting was not being incorporated into the climate model used by policy makers.

In 2020 news, “University of Exeter scientists show that, while warming Britain is expected to boost food production, if the AMOC collapses it would not just wipe out these gains but cause the “widespread cessation of arable (crop-growing) farming” across Britain.” It could have profound consequences for global food security. The science shows that “economic and land-use impacts of such a tipping point are likely to include widespread cessation of arable farming with losses of agricultural output that are an order of magnitude larger than the impacts of climate change without an AMOC collapse”. It was considered unlikely to collapse this century, but scientists have underestimated the speed of climate change before, so I am not betting on it. And the collapse of the AMOC is only one of the tipping points that we risk. They can cascade.

A series of studies around 2018 reinforced the conclusion that the AMOC is weakening, and Prof. Stefan Rahmstorf explained how the North Atlantic can be cooler yet Europe still have warm summers – “the heat transport in the Atlantic has not yet decreased strongly enough to cause cooling also over the adjacent land areas – but the cold of the sea surface is sufficient to influence the air pressure distribution. It does that in such a way that an influx of warm air from the south into Europe is encouraged”.

In 2021 a paper was published entitled “Current Atlantic Meridional Overturning Circulation weakest in last millenium”. Co-author Prof. Stefan Rahmstorf gives an overview with diagrams here.

In 2022 a new paper described how the effects of a collapsed AMOC would not be confined to the Atlantic, as Prof. Matt England explained. Another study gave details of the effects of previous collapses, for example “a torrential increase in rainfall in Northeast Brazil and a sharp drop in rainfall in Venezuela and the far north of Amazonia”.

In mid 2023 a study warned the AMOC could collapse by the middle of the century, possibly by 2025, but other researchers had their doubts. Prof Eleanor Frajka-Williams explains what is known from direct observation – the AMOC is very variable and can even briefly reverse due to wind.

In February this year a study looked at spotting early warning signals and showed that when the tipping point is reached – and it may be close – it could happen in as little as 100 years. In March global climate models still did not include a realistic amount of Greenland ice sheet meltwater. In June a study estimated that the AMOC would collapse between 2037 and 2067, with a probability of it happening before the year 2050 of 59 +/- 17%, and still scientists wrote in October that the UK is ‘flying blind’.

Also in October, a group of climate scientists wrote an open letter to the Nordic Council of Ministers which was meeting, warning that the “risk has so far been greatly underestimated”.

Only in November 2024 was a paper published which fully accounted for meltwater input, which improved the match between modelling and observation. Modelling has been underestimating the slowdown up to now.

Why the news can seem confusing

Some studies quoted by climate deniers cite papers with narrow focuses, for example studying a relatively short period when the AMOC was not demonstrably slowing (see postscript here).

The AMOC is a very large current near the surface of the ocean on its way north and in the depths of the ocean on its way south, and is weakening. The surface currents or eddies, however, have been growing stronger and could be worth including in future models.

As mentioned earlier, it is counterintuitive that global warming can cause more freezing in places.

The IPCC reports which policy-makers use tend to be small ‘c’ conservative, being agreed by committees, with less strong warnings.

One of the pieces of evidence of global warming which affects the AMOC is the appearance of a cold blob in the Atlantic.

The Gulf Stream is not the AMOC, only part of it.

Many articles have similar headlines.

So here we are

So now you are up to date. You should be planning for short term warming, or longer term freezing; more rain or less. But which? Definitely expect the food supply to be affected. Keep an eye on it – as more data comes in and models are improved, we should have a better idea of what to expect.

Some reference articles

Article: ‘Thermohaline circulation’ by Wikipedia.

Article: ‘Atlantic meridional overturning circulation’ by Wikipedia.

Article: ‘What is the Atlantic Meridional Overturning Circulation?’ by Met Office.

Article: ‘Tipping points in the climate system’ by Wikipedia.

Article: ‘What is the Atlantic Meridional Overturning Circulation (AMOC)?’ by NOAA.

Article: ‘Methodology’ by RAPID.

Article: ‘Argo (oceanography)’ by Wikipedia.

Article: ‘Gulf Stream’ by Wikipedia.

Article: ‘Cold blob’ by Wikipedia.

Further reading (ascending date order)

Article: ‘Juan Ponce de León’ by Wikipedia.

Article: ‘1785: Observations on the Gulf Stream’ by Benjamin Franklin.

Article: ‘Thermohaline Convection with Two Stable Regimes of Flow’ by Henry Stommel.

Article: ‘Climatic Change: Are We on the Brink of a Pronounced Global Warming?’ by Wallace S. Broecker.

Article: ‘Will Our Ride into the Greenhouse Future be a Smooth One?’ by Wallace S. Broecker.

Article: ‘Thermohaline Circulation, the Achilles Heel of Our Climate System: Will Man-Made CO2 Upset the Current Balance?’ by Wallace S. Broecker.

Article: ‘What If the Conveyor Were to Shut Down? Reflections on a Possible Outcome of the Great Global Experiment’ by W. S. Broecker.

Article: ‘The Great Climate Flip-Flop’ by William H. Calvin.

Article: ‘Climate Change 2001: The Scientific Basis’ by IPCC.

Movie: “The Day After Tomorrow”.

Article: ‘A sea change’ by Quirin Schiermeier.

Book: The Great Ocean Conveyor: Discovering the Trigger for Abrupt Climate Change by Wallace Broecker.

Article: ‘Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation’ by Stefan Rahmstorf, Jason E. Box, Georg Feulner, Michael E. Mann, Alexander Robinson, Scott Rutherford & Erik J. Schaffernicht.

Article: ‘Observing the Atlantic Meridional Overturning Circulation yields a decade of inevitable surprises’ by M. A. Srokosz and H. L. Bryden.

2018

Article: ‘Atlantic ‘conveyor belt’ has slowed by 15% since mid-20th century by Robert McSweeney.

Article: ‘The oceans’ circulation hasn’t been this sluggish in 1,000 years. That’s bad news. by Chris Mooney.

Article: ‘Ocean circulation is changing, and we need to know why by Nature.

Article: ‘Climate change is slowing Atlantic currents that help keep Europe warm by Peter T. Spooner .

Article: ‘The fast-melting Arctic is already messing with the ocean’s circulation, scientists say (about the Oltmanns paper) by Chris Mooney.

Article: ‘Greenland ice mass loss during the Younger Dryas driven by Atlantic Meridional Overturning Circulation feedbacks’ by Eleanor Rainsley, Laurie Menviel, Christopher J. Fogwill, Chris S. M. Turney, Anna L. C. Hughes & Dylan H. Rood.

2019

Article: ‘Global environmental consequences of twenty-first-century ice-sheet melt’ by Nicholas R. Golledge, Elizabeth D. Keller, Natalya Gomez, Kaitlin A. Naughten, Jorge Bernales, Luke D. Trusel & Tamsin L. Edwards .

Article: ‘Climate tipping points — too risky to bet against’ by Timothy M. Lenton, Johan Rockström, Owen Gaffney, Stefan Rahmstorf, Katherine Richardson, Will Steffen & Hans Joachim Schellnhuber.

Article: ‘Deep oceans can help us understand our climate’ by .

2020

Article: ‘Atlantic circulation collapse could cut British crop farming’ by Tim Lenton.

Article: ‘Map of the week – Argo floats’ by European Marine Observation and Data Network (EMODnet).

Article: ‘Running AMOC in the farming economy’ by Tim G. Benton.

Article: ‘Shifts in national land use and food production in Great Britain after a climate tipping point’ by Paul D. L. Ritchie, Greg S. Smith, Katrina J. Davis, Carlo Fezzi, Solmaria Halleck-Vega, Anna B. Harper, Chris A. Boulton, Amy R. Binner, Brett H. Day, Angela V. Gallego-Sala, Jennifer V. Mecking, Stephen A. Sitch, Timothy M. Lenton & Ian J. Bateman.

Article: ‘Could the Atlantic Overturning Circulation ‘shut down’?’ by Richard Wood, Laura Jackson.

Article: ‘Likely weakening of the Florida Current during the past century revealed by sea-level observations’ by Christopher G. Piecuch.

2021

Article: ”Just out: our new paper affirming the unprecedented slowdown of the Gulf Stream System (aka Atlantic meridional overturning circulation, 𝗔𝗠𝗢𝗖) in Nature Geoscience! @NatureGeosci A thread. 1/11” by Stefan Rahmstorf.

Article: ‘Scientists see stronger evidence of slowing Atlantic Ocean circulation, an ‘Achilles’ heel’ of the climate’ by Chris Mooney, Andrew Freedman.

Article: ‘Current Atlantic Meridional Overturning Circulation weakest in last millenium’ by L. Caesar, G. D. McCarthy, D. J. R. Thornalley, N. Cahill & S. Rahmstorf.

Article: ‘Atlantic Ocean circulation is the weakest in at least 1,600 years, study finds – here’s what that means for the climate’ by Jeff Berardelli.

Article: ‘In the Atlantic Ocean, Subtle Shifts Hint at Dramatic Dangers’ by Moises Velasquez-Manoff, Jeremy White.

Article: ‘Satellites reveal ocean currents are getting stronger, with potentially significant implications for climate change’ by Navid Constantinou, Adele Morrison, Andrew Kiss, Andy Hogg, Josué Martínez Moreno, Matthew England.

Article: ‘A critical ocean system may be heading for collapse due to climate change, study finds’ by Sarah Kaplan.

Article: ‘Climate crisis: Scientists spot warning signs of Gulf Stream collapse’ by Damian Carrington.

Article: ‘Observation-based early-warning signals for a collapse of the Atlantic Meridional Overturning Circulation’ by Niklas Boers.

Article: ‘A Crucial System of Ocean Currents Is Faltering, Research Suggests’ by Heather Murphy.

Article: ‘Gulf Stream could be veering toward irreversible collapse, a new analysis warns’ by Ben Turner.

Article: ‘A crucial ocean circulation is showing signs of instability. Its shutdown would have serious impacts on our weather.’ by Angela Dewan.

2022

Article: ‘A major Atlantic current is at a critical transition point’ by Kara Norton.

Article: ‘The Gulf Stream continues to slow down, new data shows, with freshwater creating an imbalance in the current, pushing it closer to a Collapse point’ by Andrej Flis.

Article: ‘Has The Atlantic Ocean Circulation Been In Long-term Decline?’ by Jon Robson.

Article: ‘Our new paper exploring the global climate response to a shutdown in the Atlantic Meridional Overturning Circulation. … (thread)’ by Prof. Matt England.

Article: ‘Interbasin and interhemispheric impacts of a collapsed Atlantic Overturning Circulation’ by Bryam Orihuela-Pinto, Matthew H. England & Andréa S. Taschetto.

Article: ‘Early warning signal for a tipping point suggested by a millennial Atlantic Multidecadal Variability reconstruction’ by Simon L. L. Michel, Didier Swingedouw, Pablo Ortega, Guillaume Gastineau, Juliette Mignot, Gerard McCarthy & Myriam Khodri.

Article: ‘Scientists discover mechanism that can cause collapse of great Atlantic circulation system’ by José Tadeu Arantes.

2023

Article: ‘Ocean, Cryosphere and Sea Level Change’ by ipcc.

Article: ‘Vital Atlantic Ocean current could collapse as soon as 2025’ by Madeleine Cuff.

Article: ‘Will the #AMOC collapse by 2025? Here’s what we know from direct observations (since 2004). Image from Srokosz & Bryden (2015) https://shorturl.at/ryB34 A thread’ by Prof Eleanor Frajka-Williams.

Article: ‘expert reaction to paper warning of a collapse of the Atlantic meridional overturning circulation’ by science media centre.

Article: ”Uhmm – not the Gulf Stream but the AMOC. The AMOC contributes about 15 million m3/s to the Gulf Stream, the latter totals 90. But the AMOC delivers the bulk of the heat so it matters to climate. What I think about the new study:” by Prof. Stefan Rahmstorf.

Article: ‘Warning of a forthcoming collapse of the Atlantic meridional overturning circulation’ by Peter Ditlevsen, Susanne Ditlevsen..

Article: ‘Will the #AMOC collapse by 2025? Here’s what we know from direct observations (since 2004). Image from Srokosz & Bryden (2015) https://shorturl.at/ryB34 A thread’ by Prof Eleanor Frajka-Williams.

Article: ‘The tipping point of the Atlantic overturning circulation in under 10 Minutes: watch my keynote at the Exeter conference on Climate Tipping Points’ by Prof. Stefan Rahmstorf.

Article: ”Here’s a thread in pictures about the Atlantic overturning circulation # AMOC which is making headlines this week. I’ve studied this topic since 1991 and will show key data and models & some video. Let’s go: observed…” by Prof. Stefan Rahmstorf.

Article: ‘Evolution of Atlantic Meridional Overturning Circulation since the last glaciation: model simulations and relevance to present and future’ by Zhengyu Liu.

Video: ‘Tipping of the Atlantic Ocean Circulation’ by Henk Dijkstra.

Article: ‘Abrupt global ocean circulation collapse. Time to start prepping?’ by David Ullrich.

2024

Article: ‘Atlantic Ocean circulation nearing ‘devastating’ tipping point, study finds’ by Jonathan Watts.

Article: ‘New study suggests the Atlantic overturning circulation AMOC “is on tipping course”’ by Stefan.

Article: ‘Critical Atlantic Ocean current system is showing early signs of collapse, prompting warning from scientists’ by Laura Paddison.

Article: ‘Atlantic Ocean is headed for a tipping point − once melting glaciers shut down the Gulf Stream, we would see extreme climate change within decades, study shows’ by René van Westen, Henk A. Dijkstra, Michael Kliphuis.

Article: ‘Physics-based early warning signal shows that AMOC is on tipping course’ by René M. van Westen, Michael Kliphuis, Henk A. Dijkstra.

Article: ‘A clear explainer by the authors of last week’s AMOC shutdown paper. They propose a way that *may* let us spot when shutdown is imminent. NB they’re *NOT* saying it is imminent or unavoidable (yet). It would be devastating though – we must not risk it’ by Prof Richard Betts.

Article: ‘Ocean response to a century of observation-based freshwater forcing around Greenland in EC-Earth3’ by Marion Devilliers, Shuting Yang, Annika Drews, Torben Schmith & Steffen M. Olsen.

Article: ‘Tipping risk of the Atlantic Ocean’s overturning circulation, AMOC. Keynote by Prof. Rahmstorf Earth System Analysis – Potsdam Institute’ by Prof. Rahmstorf.

Article: ‘Emma J.V. Smolders, René M. van Westen, Henk A. Dijkstra’ by Emma J.V. Smolders, René M. van Westen, Henk A. Dijkstra.

Article: ‘Atlantic Ocean Conveyor Likely to Collapse Before 2050, Say Climate Scientists’ by The Physics arXiv Blog.

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Article: ‘When the Arctic Melts’ by Elizabeth Kolbert.

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Article: ‘Open Letter by Climate Scientists to the Nordic Council of Ministers’ by various.

Article: ‘Key Atlantic current could collapse soon, ‘impacting the entire world for centuries to come,’ leading climate scientists warn’ by Sascha Pare.

Article: ‘‘We don’t know where the tipping point is’: climate expert on potential collapse of Atlantic circulation’ by Jonathan Watts.

Article: ‘AMOC Collapse Risks Hugely Underestimated according to Open Letter by Prominent Climate Scientists’ by Paul Beckwith.

Video: ‘Is the AMOC Shutting Down? – Atlantic Meridional Overturning Circulation’ by Arctic Circle.

Tweet: ‘The risk of AMOC collapse leaves the UK and Western Europe in an impossible situation. How to we plan and prepare for a near future which could be much hotter, or much, much colder? How do we prepare for both? How?’ by Dr Charlie Gardner.

Article: ‘Is the Gulf Stream in Danger of Collapse?’ by Thomas Neuburger.

Article: ”We don’t really consider it low probability anymore’: Collapse of key Atlantic current could have catastrophic impacts, says oceanographer Stefan Rahmstorf’ by Ben Turner.

Video: ‘Is the AMOC Shutting Down?’ by Earth System Analysis – Potsdam Institute.

Article: ‘Is the Gulf Stream in Danger of Collapse?’ by Thomas Neuburger.

Article: ‘Antarctica’s Fate Will Impact the World. Is It Time to Give The Region a Voice at Climate Talks?’ by Katie Surma.

Article: ‘Scientists Warn Of Possible Collapse Of Atlantic Currents’ by AFP.

Article: ‘Weakening of the Atlantic Meridional Overturning Circulation driven by subarctic freshening since the mid-twentieth century’ by Gabriel M. Pontes & Laurie Menviel.

Article: ‘Vital Atlantic Ocean current is already weakening due to melting ice’ by James Woodford.

Article: ‘Meltwater from Greenland and the Arctic is weakening ocean circulation, speeding up warming down south’ by Laurie Menviel, Gabriel Pontes .

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Article: ‘Artificial intelligence finds previously undetected historical climate extremes’ by David Appell.

As anyone who has seen ‘The Day After Tomorrow’ can attest, the world would look dramatically different if the Gulf Stream gave way.

In the 2004 blockbuster film starring Jake Gyllenhaal, an enormous ‘superstorm’ triggered by the collapse of the Gulf Stream sets off catastrophic natural disasters.

Around the world, people are frozen under layers of snow, drowned in massive tsunamis and dramatically crushed under vehicles thrown by tornados.

Now, scientists at the Met Office warn that Earth’s system of ocean currents is ‘weakening’, although it is unlikely to collapse this century.

The Gulf Stream is only a small part of a much wider system of currents, officially called the Atlantic Meridional Overturning Circulation or AMOC.

Described as ‘the conveyor belt of the ocean’, it transports warm water near the ocean’s surface northwards from the tropics up to the northern hemisphere, keeping Europe, the UK and the US east coast temperate.

Lead author Dr Jonathan Baker, a senior scientist at the Met Office, said: ‘The AMOC has a crucial role in regulating our climate; without it, northwest Europe’s temperatures would be much cooler.

‘Although our study shows that collapse over the next 75 years is unlikely, the AMOC is very likely to weaken, which will present climate challenges for Europe and beyond.’

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In the 2004 blockbuster film starring Jake Gyllenhaal , an enormous ‘superstorm’ triggered by the collapse of the Gulf Stream sets off catastrophic natural disasters

Characters are frozen under layers of snow, drowned in massive tsunamis and dramatically crushed under vehicles thrown by tornados

‘If the AMOC were to collapse, it could also lead to significant cooling in northwest Europe and chaotic weather patterns worldwide, affecting crops yields and ecosystems,’ Dr Baker said.

The academic stress that his study found the AMOC is unlikely to collapse this century, but a weakened AMOC poses ‘serious climate challenges’.

‘A weaker AMOC could alter global rainfall patterns, disrupt marine ecosystems, reduce the ocean’s ability to store carbon, and accelerate sea level rise along the US east coast,’ he said.

Professor David Thornalley, a climate scientist at University College London who was not involved with the study, said temperatures would plummet if the AMOC collapsed.

‘An AMOC collapse could cause more weather extremes, so as well as overall colder-than-average conditions, we also expect that there would be more winter storms caused by stronger westerly winds,’ he told MailOnline.

‘Unfortunately people would die due to stronger winter storms and flooding, and many old and young would be vulnerable to the very cold winter temperatures.’

However, in the UK, the effects would be ‘minor’ compared with elsewhere around the world, Professor Thornalley added.

‘A collapse in AMOC would cause a shift in the tropical rainfall belt which would massively disrupt agriculture and water supplies across huge swathes of the globe,’ he said.

The Gulf Stream is only a small part of a much wider system of currents, officially called the Atlantic Meridional Overturning Circulation (AMOC). This map indicates surface currents (solid curves) and deep currents (dashed curves) that form a portion of the AMOC. Colours of curves indicate approximate temperatures

In the Hollywood blockbuster The Day After Tomorrow (pictured), ocean currents around the world stop as a result of global warming, triggering a new ice age on Earth

What is the AMOC? The Gulf Stream is a small part of a much wider system of currents, officially called the Atlantic Meridional Overturning Circulation or AMOC. Described as ‘the conveyor belt of the ocean’, it transports warm water near the ocean’s surface northwards – from the tropics to the northern hemisphere. When the warm water reaches the North Atlantic (Europe and the UK, and the US east coast), it releases the heat and then freezes. As this ice forms, salt is left behind in the ocean water. Due to the large amount of salt in the water, it becomes denser, sinks, and is carried southwards – back towards the tropics – in the depths below. Eventually, the water gets pulled back up towards the surface and warms up in a process called upwelling, completing the cycle. Scientists think AMOC brings enough warmth to the northern hemisphere that without it, large parts of Europe could enter a deep freeze. Advertisement

‘Many millions would be affected and suffer from drought, famine and flooding, in countries that are already struggling to deal with these issues. There would be huge numbers of climate refugees, geopolitical tensions would rise.’

Jonathan Bamber, a professor of Earth observation at the University of Bristol, agreed that if the AMOC were to collapse, the climate of northwest Europe would be ‘unrecognisable compared to what it is today’.

‘It would be several degrees cooler so that winters would be more typical of Arctic Canada and precipitation would decrease also,’ he told MailOnline. ‘Very harsh, cold winters would certainly be a threat to life.’

In ‘The Day After Tomorrow’, a collapse of the AMOC takes place over a matter of days and the fictional weather immediately switches to extreme cold.

Thankfully, such a rapid transition will not happen in real life, said Penny Holliday, head of marine physics and ocean circulation at the National Oceanography Centre in Southampton.

‘If the AMOC does reach a tipping point it will happen over several decades at least,’ she told MailOnline.

‘However a slowdown of the AMOC, whether it is fast-acting or takes place over many decades, will lead to the generation of more extreme and violent weather systems that have the potential to cause deaths and major damage.’

Already, researchers have suggested that AMOC will weaken or collapse at some point in the 21st century as greenhouse gas emissions increase.

This illustration from the new Nature study depicts the AMOC’s upwelling pathways – where deep, cold water rises toward the surface – in the present day

Formally known as the Atlantic Meridional Overturning Circulation (AMOC), it powers the Gulf Stream that brings warm water from the Gulf of Mexico to the northeastern US coast

However, the extent of AMOC weakening is uncertain with wide variation across climate models, according to the researchers at the Met Office.

To find out more, the team, led by Dr Jonathan Baker, used 34 computer models to assess the AMOC’s response to extreme changes in greenhouse gas concentrations and rising sea levels.

Their findings, published in the journal Nature, reveal the AMOC would weaken, but is likely to withstand future global warming and won’t collapse this century.

This is because strong Southern Ocean winds act like a powerful pump, continuously pulling deep water to the surface, keeping the system running even under extreme climate change.

Met Office says that the effect of a weaker AMOC is included when making projections of future climate change for the UK.

Interestingly, a weaker AMOC will bring less warm water northwards, and this will partly offset the warming effect of the greenhouse gases over western Europe.

For the gradual weakening that is likely over the 21st century, but the overall effect is still a warming.

Professor Rowan Sutton, director of the Met Office Hadley Centre who was not involved with the study, said it brings ‘important new insights’ into AMOC’s future.

‘The Day After Tomorrow’ is based on the 1999 book The Coming Global Superstorm by Art Bell and Whitley Strieber

Professor Rowan Sutton, director of the Met Office Hadley Centre who was not involved with the study, said it brings ‘important new insights’ into AMOC’s future.

‘It shows that aspects of the AMOC may be more robust to a changing climate than some previous research has suggested,’ he said.

‘However, it doesn’t change our expectation that the AMOC will weaken over the twenty first century, and that this weakening will have important impacts on climate.’

But study author Geoff Vallis, climate scientist at the University of Exeter, said it does ‘not in any way mean that global warming is not a severe problem for society and our planet’.

‘I think it very unlikely that my house will burn down in the coming years; however, I still buy insurance to guard against that risk,’ Professor Vallis said.

The AMOC, often referred to as the “great ocean conveyor,” plays a crucial role in regulating global climate. This complex system of currents, which includes the Gulf Stream, transports warm, salty water from the tropics northward into the North Atlantic. As this water cools and becomes denser, it sinks and flows back southward at deeper levels, creating a continuous loop of circulation.

The significance of the AMOC cannot be overstated :

It transports vast amounts of heat, equivalent to boiling about a thousand billion kettles

Responsible for 25% of the total heat flowing into the northern hemisphere

Contributes to the relatively mild climate in Northwest Europe

Helps prevent Arctic sea ice from spreading beyond Norway

The AMOC’s influence extends beyond regional climates. A weakening of this system could shift all climate belts of the world, including the equatorial rainfall belt, further south. This shift would have profound consequences for global weather patterns, potentially leading to altered tropical rainfall, droughts, floods, and more extreme weather events in Europe.

Recent studies suggest that the AMOC may be approaching a critical tipping point. The collapse of this Atlantic current will trigger dangerous cooling in certain regions, while causing other areas to experience rapid warming and sea-level rise. The potential consequences of such a collapse are far-reaching and could reshape our planet’s climate in ways we are only beginning to understand.

Evidence of amoc weakening and future projections

Scientists have been closely monitoring the AMOC’s strength and behavior through various methods. While direct instrumental measurements only began in 2004 with the installation of the RAPID array across the Atlantic, indirect evidence suggests a concerning trend :

A 10% decrease in AMOC strength since 2004

Cooling trend in sea surface temperatures south of Greenland

Buildup of salty water in the South Atlantic

Palaeoclimatological data indicating unprecedented weakening in the last 1,600 years

Climate models project a potential 30-50% weakening of the AMOC by the end of the 21st century if greenhouse gas emissions continue at current rates. However, some researchers warn that even with minimal climate warming, the AMOC could switch from strong to very weak, or shut down entirely, within decades.

The “salt feedback” mechanism is a key factor in the potential collapse of the AMOC. As the system weakens, the surface of the Atlantic becomes fresher, leading to further weakening in a runaway process. This positive feedback loop could be triggered by ongoing events such as the melting of the Greenland ice sheet.

Global consequences of amoc collapse

The potential collapse of the AMOC would have far-reaching consequences for our planet. Some of the most significant impacts include :

Region Potential Impact Europe Icy winds, frozen rivers, crop failures US East Coast Rising sea levels, increased flooding Amazon Ecological chaos, altered wet and dry seasons Global Shifted climate belts, extreme weather events

These changes would have profound implications for agriculture, water resources, and human habitation patterns. The disruption of food supplies and water resources could lead to increased energy demands for heating and strain existing infrastructure.

Moreover, the collapse of the AMOC could exacerbate other climate-related issues. European glaciers in France, Italy, and Pyrenees face potential extinction within years, a process that could be accelerated by the disruption of Atlantic currents. Additionally, climate change is making our oceans dangerously noisy, further impacting marine ecosystems already stressed by changing currents and temperatures.

Mitigating risks and building resilience

The looming threat of AMOC collapse underscores the urgent need for action to address climate change. Key steps include :

Rapidly reducing greenhouse gas emissions Investing in renewable energy sources Implementing adaptive strategies for vulnerable regions Enhancing climate monitoring systems Fostering international cooperation on climate action

Building climate resilience is crucial to mitigate the potential impacts of AMOC collapse. This involves strengthening infrastructure, diversifying food and water sources, and developing early warning systems for extreme weather events.

As we face the possibility of a dramatically altered climate system, it is imperative that we act swiftly and decisively. The potential collapse of the Atlantic Ocean’s currents serves as a stark reminder of the interconnectedness of our planet’s systems and the far-reaching consequences of human-induced climate change. By taking bold action now, we can work to preserve the delicate balance that sustains life on Earth and secure a more stable future for generations to come.

Scientists warn that the Atlantic Meridional Overturning Circulation, a system of ocean currents crucial for global climate stability, is weakening faster than previously thought.

The weakening of the AMOC could trigger extreme weather, disrupt rainfall patterns and harm marine ecosystems.

Urgent global action to reduce emissions is needed to prevent catastrophic tipping points, writes the author of this commentary.

The views in the commentary are that of the author. See All Key Ideas

In October this year, a group of climate scientists wrote an open letter to the Nordic Council of Ministers, expressing their concerns about the serious risk of a major ocean circulation change in the Atlantic ocean. This letter published online and signed by eminent climate scientists, argues that the danger of a weakening ocean circulation in the Atlantic, greatly underestimated even by the Intergovernmental Panel on Climate Change (IPCC), warrants urgent action.

The Atlantic Meridional Overturning Circulation (AMOC), the dominant mechanism of northward heat transport in the North Atlantic, is critical to life conditions for all people in the Arctic region and beyond. The scientists worry that a shift in this circulation could cause major cooling in Nordic countries and affect the entire globe, disrupting tropical rainfall in the Indian Ocean and reducing the ocean’s ability to absorb carbon dioxide. This, they believe, calls for greater urgency in the global effort to reduce emissions as early as possible.

Climate scientists have known long that the Arctic region is the “ground zero” for many global changes. The U.S. government’s National Oceanic and Atmospheric Administration’s (NOAA) 2021 Arctic Report Card showcases the numerous ways climate change continues to alter the Arctic, which recalls the image of an ever-frozen landscape.

The report by NOAA mentions how the increasing heat and the ice loss are transforming this land into a warmer, less frozen one with an unpredictable future trajectory. Studies from another part of ground zero – Greenland – reveal a risky proposition that by 2100, this part of the Arctic will be shedding ice at its fastest rate in the past 12,000 years. To sum up, the Greenland Ice Sheet, the Barents Sea ice, drainage of lakes in the Arctic and boreal lowland permafrost regions, the sub polar deep-water formations and the AMOC, are all becoming increasingly vulnerable to major, interconnected, but non-linear changes.

What is AMOC?

It was probably Wallace S. Broeker, in his now famous 1987 commentary in the journal Nature, Unpleasant Surprises in the Greenhouse?, first mentioned the “flip-flops” of the “Atlantic Conveyor Belt”. Now referred to as the AMOC, it is a system of ocean currents that circulates water within the Atlantic Ocean, from north to south and back, distributing heat, moisture, and nutrients throughout the world’s oceans. We must recognise the ocean as water on the move, controlling our climate, ecosystem, seafood, and ocean currents operating both on the ocean’s surface and in its depths. Winds, water density, and tides drive ocean currents. Earth’s rotation results in the Coriolis Effect, which influences ocean currents.

The AMOC brings warmth to various parts of the globe and plays a crucial role in ocean life. Surface currents are formed by wind and tides in the upper 100 metres of the sea. The slower currents arise from the surface and travel deeper to the ocean floor (average depth 4.6 km). These deep-ocean currents are driven by differences in the water’s density, controlled by temperature (thermos) and salinity (haline) – a process known as thermohaline circulation. It is initiated in the Earth’s Polar Regions where ocean water gets cold, forming sea ice.

Consequently, the surrounding seawater gets saltier because as the sea ice forms, salt from the water is left behind. As the seawater gets saltier, its density increases and starts to sink. Gradually, surface water begins to flow in to occupy the space left by the sinking water. This renewed water supply would eventually become cold, salty and dense enough to sink. As it begins to sink, the deep-ocean currents are initiated, akin to a global conveyor belt that starts in the Norwegian Sea. As warm water is transported to the north, the cooler water sinks and moves south to make room for the incoming warm water. The cold bottom current flows south of the equator down to Antarctica and eventually returns to the surface as warm and dense through mixing and wind-driven upwelling, continuing as a conveyor belt that encircles the globe.

Although the process sounds very dynamic, the entire circulation cycle of the AMOC and the movement of the conveyor belt is quite slow. It is estimated that a parcel of a cubic metre of water would take about 1,000 years to complete its journey along the belt. What makes the AMOC newsworthy is the likelihood of its slowing down further, which will have major global impacts on the climate system. Even though the processes leading to the ‘slowdown’ of AMOC take time because of compounding and interacting effects, like most Earth processes, its non-linear progression to dysfunctionality is less felt until it reaches the tipping point.

Th implications of a slower AMOC

The AMOC carries heat all around the globe and redistributes it from the tropics to the Arctic. Therefore, it has a large role in the evolution of the global climate system. The heat carried by the Gulf Stream to Iceland and Northern Europe results in a more temperate climate in these regions, which does not happen without the AMOC. Similarly, the deep southbound current brings cold water to the Antarctic, and as it wells up to the surface from the depths, it gets enriched in nutrients – a boon for marine life.

These processes are sustainable only if the wholeness of the AMOC is left unimpaired. The scientists suspect that the AMOC will not stay inviolable if any causative parameters change fundamentally. The problem emanates from the rapid melting of ice in the Polar Regions. As the melting of Greenland ice sheets releases large quantities of freshwater, this water is less dense than saltwater would join the North Atlantic Current. As the region gets flushed with water that cannot sink easily, the downward flow towards the ocean floor slows down, resulting in a slower conveyor belt motion that redistributes lesser heat in the “no melt” scenario. This would affect the ocean temperature and the air, and the consequent changes would upset the rainfall patterns.

In effect, a weakened AMOC could lead to colder temperatures in Europe and greater snowfall there in winter. Shifts in precipitation patterns could lead to drought in some areas and flooding in others, impacting agriculture. A weaker AMOC could result in depleted nutrients in seawater and disruption in their distribution- both in content and spatial patterns. This could affect sea life, from plankton and sea birds to fish and whales. Scientists predict far-reaching and unexpected fallouts from the weaker AMOC that might affect the Amazonia, in the far south. Although the impact on vegetation is not well constrained, models predict drier conditions in the north and wetter in the south.

Some researchers have used the silty particles (their deposition implies speed of movement of silt in sediment cores) to reconstruct the flow speed of the AMOC in the past 1,600 years and others have analysed temperature anomalies in the North Atlantic sub polar region, to infer changes in AMOC flow in the past century. These studies conclude that the AMOC has weakened by about 15% since the 1950s, although there is no clarity on when the decline would have started.

What about the future in the age of global warming? Climate models predict that if greenhouse gas emissions continue unabated and the global temperatures keep rising, AMOC could weaken by 30-50 percent at the end of the 21st century. This transformation can generate extreme weather conditions in Europe, alter tropical rainfall patterns, and regional changes in sea levels. A more catastrophic future may lie ahead, even with only a small amount of climate warming, the AMOC may switch from strong to very weak or shut down in decades. This is called a tipping point, and models suggest it could lead to the severe climate impacts outlined earlier. However, the 2021 IPCC consensus view is more optimistic, and their models indicate that a complete AMOC collapse before 2100 is unlikely.

How will a slower AMOC impact Asian weather and the Indian Monsoon, which are linked with the Intertropical Convergence Zone (ITCZ)? The position of the ITCZ location affects the distribution of tropical rainfall and is a fundamental component of the global monsoon. A strong AMOC, as it happens in normal conditions, transports more heat northward in the ocean and consequently controls atmospheric energy flow across the equator shifts southward, pushing the ITCZ north of the equator.

New research from IIT Bhubaneswar comments on the implications of a slowing AMOC on the ITCZ and the Indian Monsoon. The study concludes that as the climate warms and the AMOC is expected to slow down, it would reduce the northward movement of warm water and energy. This would push the ITCZ to shift southward, potentially weakening the Indian summer monsoon in the future.

Returning to Waly Broeker’s paper, he warns, “We play Russian roulette with climate, hoping that the future will hold no unpleasant surprises. No one knows what lies in the active chamber of the gun, but I am less optimistic about its contents than many.”

The restoration course is amply clear: reduce emissions as quickly as possible to stay close to the 1.5ºC target set by the Paris Agreement. Are the decision makers at COP29 listening?

The author is an adjunct professor at the National Institute of Advanced Studies, Bengaluru, and the director of the Consortium for Sustainable Development, Connecticut, U.S.A.

Banner image: Scientists place a portable climate observatory, across an open-water lead in the Arctic in December 2020. Image by Lianna Nixon-Alfred-Wegener Institut via Wikimedia Commons (CC BY 4.0).