BRUSSELS — From Reykjavík to The Hague, European governments are starting to prepare for a literal sea change that would end life as we know it on the continent.
In the depths of the North Atlantic, a vast system of swirling currents known as the Atlantic Meridional Overturning Circulation, or AMOC, carries warm tropical waters north, preventing Europe from freezing. But as humans continue pumping planet-warming gases into the atmosphere, this oceanic heat pump will weaken. It might even fizzle out.
A colder-than-usual patch of water just south of Greenland, nicknamed the “cold blob,” has some scientists worried this slowdown is already well underway. Other researchers have examined climate models, surveyed sea temperature records and ran simulations to conclude that the ocean could turn on us sooner than previously thought.
While this process would unfold over many decades, a severe slowdown or collapse of the AMOC would disrupt Europe’s agriculture, infrastructure, welfare and economy on a scale that would make this past summer’s heat and fires look like mild memories of calmer times. The continent could face glacial winters and dry summers, surging sea levels and ferocious windstorms.
Until recently, this prospect was considered remote: A nightmare scenario trotted out to warn of the catastrophic dangers of unchecked climate change. But as research on the likelihood of a major slowdown or — less likely — a total collapse mounts, governments are beginning to take it seriously and trying to work out how to minimize the damage.
Iceland has declared an AMOC collapse a national security risk. The Netherlands is investigating what a slowdown might mean for its sea defenses. Finland is examining the potential consequences. The United Kingdom is spending millions on an early-warning system. And Nordic ministers have begun discussing the threat.
For policymakers, the AMOC’s instability poses an unusual challenge: How do you prepare for a far-off disaster that may never happen — but that, if it does, would disrupt life in Europe on an unthinkable scale? But governments are increasingly concluding uncertainty itself is no excuse for waiting.
“It is irresponsible to wait for absolute certainty before preparing,” Jóhann Páll Jóhannsson, Iceland’s climate minister, told POLITICO. “Because, by the time the consequences become undeniable, it may already be too late to prevent them from happening.”
“This is not about panic or alarmism,” he added. “It’s just responsible governance.”
The sense of alarm has also reached Brussels, where last year the European Union’s green transition chief Teresa Ribera suggested adding the AMOC “to the list of national security acronyms in Europe.”
That sinking feeling
The AMOC’s engine lies in the North Atlantic, where cold, salty water sinks deep into the ocean. That sinking helps pull more warm water north — driving a circulation that has shaped Europe’s climate for millennia.
It helps explain why Paris doesn’t have Ottawa’s cold winters, even though the French capital lies slightly to the north of the Canadian city. It’s also part of why Iceland and Europe’s northern countries don’t suffer a Siberian climate.
But climate change is now threatening to disrupt this long-stable motor. As Greenland’s ice sheet melts and heavier rainfall adds more freshwater to the North Atlantic, the sea becomes warmer and less salty — and therefore less dense. It sinks less readily, weakening the circulation.
This can set off a feedback loop: Weaker currents carry less salt north, further freshening the water and slowing the AMOC even more. The fear is that, with enough warming, the churn could slow significantly or even stop.
If that sounds familiar, chances are it’s because of the 2004 disaster movie “The Day After Tomorrow,” which imagines the shutdown of Atlantic ocean currents triggering a flash freeze that plunges the world into a new ice age overnight. There is no evidence that such an extreme and rapid scenario is possible.
And yet, the danger isn’t confined to some distant future. Even if a full AMOC collapse would unfold over many decades, likely beyond the end of this century, parts of the system could start failing much sooner — with consequences felt well before the currents grind to a halt.
“Bits of the AMOC could begin collapsing on the journey to the full collapse,” said Laurie Laybourn, a fellow at Chatham House and director of the Strategic Climate Risks Initiative. “It’s a process that would have disruption along the way.”
Scientists are particularly worried about the subpolar gyre, a circular current south of Greenland that helps power the AMOC. Some studies suggest its water-mixing function could begin shutting down as early as the 2040s, triggering major changes within as little as a decade.
A collapse of the gyre wouldn’t plunge all of Northern Europe into the deep freeze associated with a full AMOC shutdown. But it could bring significantly colder winters and increase the risk of drought.
“When exactly is hard to say, but I do think there’s a substantial risk that it can happen within the coming 20 years,” said Swinda Falkena, a researcher studying the subpolar gyre at Utrecht University. “It basically would mean you need to start planning now.”
For the AMOC as a whole, scientists still don’t know at what point the currents could cross their so-called tipping point, after which a collapse into a very weak state becomes inevitable. Nor do they know how close they are to crossing it. Estimates range from global warming of 1.4 degrees Celsius above pre-industrial temperatures — a level the world has just reached — to 8 C.
Just how much the currents will be disrupted remains a matter of debate; scientists are also still arguing over whether the slowing has already started. But they all agree that as the climate continues to warm, the AMOC will diminish.
In 2023, the Intergovernmental Panel on Climate Change — which releases reports that represent the current scientific consensus — concluded that the AMOC “is very likely to weaken over the 21st century,” with its strength falling 24% to 39% below pre-industrial levels.
The IPCC also expressed “medium confidence” that “an abrupt collapse is not expected before 2100” — but research published since the report’s release has raised the possibility that the system could reach a tipping point much earlier.
Two recent studies placed that threshold around the middle of this century. A separate paper found that even if planet-warming emissions are reduced, a collapse is more likely than not to begin before the end of the century. Yet another suggested that even with mild warming, the risk of an AMOC shutdown is around 25 percent. And a study this year concluded the currents would lose half their strength until 2100. (In contrast, one recent paper found complete collapse unlikely this century.)
“The risks,” said Jóhannsson, the Icelandic climate minister, “are appearing more serious than previously understood.”
Freezing future
Scientists are starting to sketch out what Europe could look like after an AMOC collapse, drawing on climate models and research into the currents’ effect on temperatures, rainfall, sea levels and ecosystems. The picture they paint, in published studies and interviews with POLITICO, is dramatic.
In winter, storms could lash the continent, fueled by the stark temperature difference between a newly frigid north and the warm-as-ever south.
Arctic sea ice could push south toward Scotland and the Nordic fjords. Icebreakers might be needed in the Baltic Sea. Amsterdam’s canals could freeze solid, as cold snaps send temperatures plunging to minus 20 C in the Netherlands and minus 40 C in Scandinavia.
Drought in West Africa could drive migrants northward as the tropical rainbelt gets pushed south. Meanwhile, Iceland could face economic devastation as fish stocks collapse, according to a scenario researchers drew up for the Nordic Council of Ministers.
Along Europe’s North Atlantic coast, higher sea levels could worsen flooding and push saltwater into low-lying farmland. Summers would still bring extreme heat, but a decline in rainfall could compound water shortages. One paper found that in the U.K., land suitable for crop farming would fall from 32% today to 7% after an AMOC collapse.
Concern over these possible impacts are starting to shape government planning. Iceland, which has declared an AMOC collapse a national security risk, brought the threat to the Nordic Council of Ministers this spring. “We discussed preparing a joint risk assessment for the Nordics,” said Jóhannsson.
In Finland, Climate Minister Sari Multala launched an assessment this summer of what an AMOC slowdown could mean for the country, including its consequences for the climate, the Baltic Sea and key sectors such as agriculture, energy and transport.
“It would be quite obvious that if the temperature were to drop so drastically as the worst-case scenarios are, the living conditions in Finland would deteriorate very much,” she told POLITICO. “Because I think we are on the front line when it comes to this tipping point, we want to be the ones that are having the best knowledge around it.”
The Netherlands is conducting a similar assessment, with a particular focus on the threat to its sea defenses. The Dutch Delta programme commissioner — a government appointee charged with protecting the country from water-related threats — is working to include the weakening of the AMOC as a “what-if scenario” in the country’s preparedness plans. Studies suggest an AMOC shutdown could add roughly half a meter to sea-level rise along parts of the North Atlantic, on top of the increase already caused by global warming.
“The speed is uncertain, the moment is uncertain, and the impact is uncertain,” said Saskia van Vuren, who advises the Delta commissioner on the AMOC. But it is already affecting planning on the ground. “We should acknowledge that ice sheets may be present [on rivers] in the future,” she added, pointing to ongoing river-restoration projects.
Still, major uncertainties remain. There’s a chance global warming cancels out any AMOC-related winter cooling, for example.
Yet “uncertainty is not a reason for inaction,” said Walid Oueslati, head of the Organisation for Economic Co-operation and Development’s climate division, who oversaw a report on how policymakers can approach such risks. “It’s a reason for better risk management.”
“Governments deal with uncertain risk every day,” he added, citing “the financial crisis, for example, or the pandemic, or earthquakes and other natural hazards.”
Ocean watch
One of the first lines of defense against an AMOC collapse is noticing when it starts. Governments and scientists are investing in early-warning systems to detect when critical parts of the circulation begin to approach a tipping point.
The British government has poured £81 million (€94 million) into a research program to create an early-warning mechanism for two key AMOC-linked systems that may themselves be approaching a point of no return: The Greenland ice sheet and the subpolar gyre.
“We’re trying to bring together teams to better observe, model and forecast tipping points, so that we might be able to respond better to them,” said Gemma Bale, one of the two scientists leading the program.
The program — and any effort to track the AMOC — depends on reliable, long-term observations of the ocean, she added.
Researchers have strung moorings across the Atlantic to measure the currents; one such array, known as RAPID, is the longest-running observational program with 20 years of consistent data.
“It’s the only thing that directly tells us how the AMOC is changing day to day, month to month, year to year,” said Penny Holliday, chief scientific officer at the U.K.’s National Oceanography Centre, which co-leads the project. So far, the array has recorded a slight decline in the AMOC, though scientists aren’t yet sure whether climate change is responsible.
But the monitoring network remains precarious. Many of the arrays are financed through short-term research grants, some of which run out by 2028, leaving decades-long observation programs vulnerable to shifting government priorities.
In the United States, for example, President Donald Trump’s administration decided to cut ocean observation funding and dismantle the buoys earlier this year, then backtracked after an outcry.
For scientists, the episode underscored the problem with treating long-term ocean monitoring as a string of short-term research projects. What they want instead is a permanent, internationally funded observing system — infrastructure on the scale governments already support for weather forecasting or space research.
“If we could get together collectively … then we would have an early-warning system,” said Holliday. “We’d be able to tell every nation whether that model-predicted AMOC decline has already started.”
The European Commission made a start this summer, announcing €92 million in funding for ocean observation; a pledging event in September raised the amount to €220 million. AMOC scientists welcomed the money but said a reliable Atlantic-wide system would require far more.
“You need about €500 million or €1 billion per year, and then you can measure the shit out of the oceans,” said Sjoerd Groeskamp, a researcher at the Royal Netherlands Institute for Sea Research. “Which sounds like a lot, but it’s not. The particle accelerator [at CERN] has a budget of €1 billion per year, right? The James Webb telescope was €10 billion.”
Groeskamp has teamed up with a handful of European Parliament lawmakers to lobby the Commission for an additional €25 million per year to monitor the AMOC.
Mohammed Chahim, a center-left Dutch MEP who led the campaign for extra funding, said Brussels should “create a structured financial program for ocean monitoring, like we’re doing for space.”
“AMOC is one of the biggest concerns I have,” he added. “If you look at the economic damages that we could see through AMOC, spending a couple of million or a couple of hundred million for a long-term observatory program plays an essential role.”
Win-win preparedness
Even if observational data only tells governments that an AMOC collapse has become inevitable — providing a late rather than early warning — that information would still matter, given the decades over which its impact would unfold.
“Once we know that the tipping point has been crossed, that the AMOC won’t suddenly recover but will continue to decline over the coming decades, that has a major impact on what adaptation measures are taken,” said Stefan Rahmstorf, an oceanographer at the Potsdam Institute for Climate Impact Research.
In the meantime, experts say there’s a range of “no-regret measures” policymakers can take that will protect their citizens if the currents collapse, and benefit countries even if the AMOC remains stable.
“There are win-win situations, such as improving home insulation, that help both against global warming and in the event of a significant cooling,” said Rahmstorf.
Many of the impacts of an AMOC shutdown would compound problems Europe already faces as the planet warms, including drought, extreme weather and rising seas. That means much of the necessary preparations are familiar: strengthening infrastructure against weather extremes, investing in coastal flood protection and building less brittle supply chains.
“We can identify some things that are no regrets,” said Laybourn, the Chatham House fellow. He pointed to retrofitting buildings, restoring nature to make agriculture more resilient and supporting countries in Africa where monsoons could be disrupted. “There are some things that work no matter what’s going to happen.”
The most important no-regret measure is also the only one scientists say can reduce the risk of the AMOC collapsing in the first place: cutting planet-warming emissions.
“The main response must be to stop dithering and delaying when it comes to reducing emissions and phasing out fossil fuels,” said Rahmstorf.
That is true even for parts of the system that could destabilize sooner, such as the subpolar gyre. “To reduce the risk of this happening, the only real thing you can do is just slow down global warming,” said Falkena, the Utrecht University researcher. “Reduce emissions as fast as you can.”
That message is increasingly being echoed by governments most exposed to the threat.
“The most important thing we can do to limit temperature increase is to reduce emissions rapidly,” said Norwegian Climate Minister Andreas Bjelland Eriksen when asked how his country is approaching the risk of an AMOC shutdown.
Iceland’s Jóhannsson compared his country’s reaction to the AMOC threat to the way rising seas have pushed Pacific island states to demand stronger global climate action.
“For us, the possibility of AMOC collapse is not an abstract scientific question,” he said. “It’s basically an existential one, because we know the destabilization of AMOC would bring profound disruption to our infrastructure, our ecosystems and our way of life.”
A climate nightmare lurks in the Atlantic. Europe is starting to pay attention.
Source: Viral Showbiz Pinay
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