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
René van Westen, Utrecht University; Henk A. Dijkstra, Utrecht University, and Michael Kliphuis, Utrecht University
Fri, February 9, 2024
Too much fresh water from Greenland's ice sheet can slow the Atlantic Ocean's circulation. Paul Souders/Stone via Getty Images
Superstorms, abrupt climate shifts and New York City frozen in ice. That’s how the blockbuster Hollywood movie “The Day After Tomorrow” depicted an abrupt shutdown of the Atlantic Ocean’s circulation and the catastrophic consequences.
While Hollywood’s vision was over the top, the 2004 movie raised a serious question: If global warming shuts down the Atlantic Meridional Overturning Circulation, which is crucial for carrying heat from the tropics to the northern latitudes, how abrupt and severe would the climate changes be?
Twenty years after the movie’s release, we know a lot more about the Atlantic Ocean’s circulation. Instruments deployed in the ocean starting in 2004 show that the Atlantic Ocean circulation has observably slowed over the past two decades, possibly to its weakest state in almost a millennium. Studies also suggest that the circulation has reached a dangerous tipping point in the past that sent it into a precipitous, unstoppable decline, and that it could hit that tipping point again as the planet warms and glaciers and ice sheets melt.
In a new study using the latest generation of Earth’s climate models, we simulated the flow of fresh water until the ocean circulation reached that tipping point.
The results showed that the circulation could fully shut down within a century of hitting the tipping point, and that it’s headed in that direction. If that happened, average temperatures would drop by several degrees in North America, parts of Asia and Europe, and people would see severe and cascading consequences around the world.
We also discovered a physics-based early warning signal that can alert the world when the Atlantic Ocean circulation is nearing its tipping point.
The ocean’s conveyor belt
Ocean currents are driven by winds, tides and water density differences.
In the Atlantic Ocean circulation, the relatively warm and salty surface water near the equator flows toward Greenland. During its journey it crosses the Caribbean Sea, loops up into the Gulf of Mexico, and then flows along the U.S. East Coast before crossing the Atlantic.
How the Atlantic Ocean circulation changes as it slows. IPCC 6th Assessment Report
This current, also known as the Gulf Stream, brings heat to Europe. As it flows northward and cools, the water mass becomes heavier. By the time it reaches Greenland, it starts to sink and flow southward. The sinking of water near Greenland pulls water from elsewhere in the Atlantic Ocean and the cycle repeats, like a conveyor belt.
Too much fresh water from melting glaciers and the Greenland ice sheet can dilute the saltiness of the water, preventing it from sinking, and weaken this ocean conveyor belt. A weaker conveyor belt transports less heat northward and also enables less heavy water to reach Greenland, which further weakens the conveyor belt’s strength. Once it reaches the tipping point, it shuts down quickly.
What happens to the climate at the tipping point?
The existence of a tipping point was first noticed in an overly simplified model of the Atlantic Ocean circulation in the early 1960s. Today’s more detailed climate models indicate a continued slowing of the conveyor belt’s strength under climate change. However, an abrupt shutdown of the Atlantic Ocean circulation appeared to be absent in these climate models.
This is where our study comes in. We performed an experiment with a detailed climate model to find the tipping point for an abrupt shutdown by slowly increasing the input of fresh water.
We found that once it reaches the tipping point, the conveyor belt shuts down within 100 years. The heat transport toward the north is strongly reduced, leading to abrupt climate shifts.
The result: Dangerous cold in the North
Regions that are influenced by the Gulf Stream receive substantially less heat when the circulation stops. This cools the North American and European continents by a few degrees.
The European climate is much more influenced by the Gulf Stream than other regions. In our experiment, that meant parts of the continent warmed at more than 5 degrees Fahrenheit (3 degrees Celsius) per decade – far faster than today’s global warming of about 0.36 F (0.2 C) per decade. We found that parts of Norway would experience temperature drops of more than 36 F (20 C). On the other hand, regions in the Southern Hemisphere would warm by a few degrees.
The annual mean temperature changes after the conveyor belt stops reflect an extreme temperature drop in northern Europe in particular. René M. van Westen
These temperature changes develop over about 100 years. That might seem like a long time, but on typical climate time scales, it is abrupt.
The conveyor belt shutting down would also affect sea level and precipitation patterns, which can push other ecosystems closer to their tipping points. For example, the Amazon rainforest is vulnerable to declining precipitation. If its forest ecosystem turned to grassland, the transition would release carbon to the atmosphere and result in the loss of a valuable carbon sink, further accelerating climate change.
The Atlantic circulation has slowed significantly in the distant past. During glacial periods when ice sheets that covered large parts of the planet were melting, the influx of fresh water slowed the Atlantic circulation, triggering huge climate fluctuations.
So, when will we see this tipping point?
The big question – when will the Atlantic circulation reach a tipping point – remains unanswered. Observations don’t go back far enough to provide a clear result. While a recent study suggested that the conveyor belt is rapidly approaching its tipping point, possibly within a few years, these statistical analyses made several assumptions that give rise to uncertainty.
Instead, we were able to develop a physics-based and observable early warning signal involving the salinity transport at the southern boundary of the Atlantic Ocean. Once a threshold is reached, the tipping point is likely to follow in one to four decades.
A climate model experiment shows how quickly the AMOC slows once it reaches a tipping point with a threshold of fresh water entering the ocean. How soon that will happen remains an open question. René M. van Westen
The climate impacts from our study underline the severity of such an abrupt conveyor belt collapse. The temperature, sea level and precipitation changes will severely affect society, and the climate shifts are unstoppable on human time scales.
It might seem counterintuitive to worry about extreme cold as the planet warms, but if the main Atlantic Ocean circulation shuts down from too much meltwater pouring in, that’s the risk ahead.
This article is republished from The Conversation, a nonprofit, independent news organization bringing you facts and trustworthy analysis to help you make sense of our complex world. It was written by: René van Westen, Utrecht University; Henk A. Dijkstra, Utrecht University, and Michael Kliphuis, Utrecht University
Read more:
Ocean heat is off the charts – here’s what that means for humans and ecosystems around the world
The heroic effort to save Florida’s coral reef from extreme ocean heat as corals bleach across the Caribbean
Scientists envision an ‘internet of the ocean,’ with sensors and autonomous vehicles that can explore the deep sea and monitor its vital signs
René van Westen receives funding from the European Research Council (ERC-AdG project 101055096, TAOC).
Henk A. Dijkstra receives funding from the European Research Council (ERC-AdG project 101055096, TAOC, PI: Dijkstra).
Michael Kliphuis does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
Critical Atlantic Ocean current system is showing early signs of collapse, prompting warning from scientists
Laura Paddison, CNN
Fri, February 9, 2024
A crucial system of ocean currents may already be on course to collapse, according to a new report, with alarming implications for sea level rise and global weather — leading temperatures to plunge dramatically in some regions and rise in others.
Using exceptionally complex and expensive computing systems, scientists found a new way to detect an early warning signal for the collapse of these currents, according to the study published Friday in the journal Science Advances. And as the planet warms, there are already indications it is heading in this direction.
The Atlantic Meridional Overturning Circulation (the AMOC) — of which the Gulf Stream is part — works like a giant global conveyor belt, taking warm water from the tropics toward the far North Atlantic, where the water cools, becomes saltier and sinks deep into the ocean, before spreading southward.
The currents carry heat and nutrients to different areas of the globe and play a vital role in keeping the climate of large parts of the Northern Hemisphere relatively mild.
For decades, scientists have been sounding the alarm on the circulation’s stability as climate change warms the ocean and melts ice, disrupting the balance of heat and salt that determines the currents’ strength.
While many scientists believe the AMOC will slow under climate change, and could even grind to a halt, there remains huge uncertainty over when and how fast this could happen. The AMOC has only been monitored continuously since 2004.
Scientists do know — from building a picture of the past using things like ice cores and ocean sediments — the AMOC shut down more than 12,000 years ago following rapid glacier melt.
Now they are scrambling to work out if it could happen again.
This new study provides an “important breakthrough,” said René van Westen, a marine and atmospheric researcher at the University of Utrecht in the Netherlands and study co-author.
The scientists used a supercomputer to run complex climate models over a period of three months, simulating a gradual increase of freshwater to the AMOC — representing ice melt as well as rainfall and river runoff, which can dilute the ocean’s salinity and weaken the currents.
As they slowly increased the freshwater in the model, they saw the AMOC gradually weaken until it abruptly collapsed. It’s the first time a collapse has been detectable using these complex models, representing “bad news for the climate system and humanity,” the report says.
What the study doesn’t do, however, is give timeframes for a potential collapse. More research is needed, van Westen told CNN, including models which also mimic climate change impacts, such as increasing levels of planet-heating pollution, which this study did not.
“But we can at least say that we are heading in the direction of the tipping point under climate change,” van Westen said.
The impacts of the AMOC’s collapse could be catastrophic. Some parts of Europe might see temperatures plunge by up to 30 degrees Celsius over a century, the study finds, leading to a completely different climate over the course of just a decade or two.
“No realistic adaptation measures can deal with such rapid temperature changes,” the study authors write.
Countries in the Southern Hemisphere, on the other hand, could see increased warming, while the Amazon’s wet and dry seasons could flip, causing serious disruption to the ecosystem.
The AMOC’s collapse could also cause sea levels to surge by around 1 meter (3.3 feet), van Westen said.
Stefan Rahmstorf, a physical oceanographer at Potsdam University in Germany, who was not involved with the study, said it was “a major advance in AMOC stability science.”
“It confirms that the AMOC has a tipping point beyond which it breaks down if the Northern Atlantic Ocean is diluted with freshwater,” he told CNN.
Previous studies finding the AMOC’s tipping point used much simpler models, he said, giving hope to some scientists that it might not be found under more complex models.
This study crushes those hopes, Rahmstorf said.
Joel Hirschi, associate head of marine systems modeling at the National Oceanography Centre in the UK, said the study was the first to use complex climate models to show the AMOC can flip from “on” to “off” in response to relatively small amounts of freshwater entering the ocean.
But there are reasons to be cautious, he added. Even though the study used a complex model, it still has a low resolution, he said, meaning there could be limitations in representing some parts of the currents.
This study adds to the growing body of evidence that the AMOC may be approaching a tipping point — and that it could even be close.
A 2021 study found that the AMOC was weaker than any other time in the past 1,000 years. And a particularly alarming — and somewhat controversial — report published in July last year, concluded that the AMOC could be on course to collapse potentially as early as 2025.
Yet huge uncertainties remain. Jeffrey Kargel, senior scientist at the Planetary Science Institute in Arizona, said he suspected the theory of a potentially imminent shutdown of the AMOC “will remain somewhat controversial until, one year, we know that it is happening.”
He likened its potential collapse to the “wild gyrations of a stock market that precede a major crash” — it’s nearly impossible to unpick which changes are reversible, and which are a precursor to a disaster.
Modern data shows the AMOC’s strength fluctuates, but there is no observed evidence yet of a decline, Hirschi said. “Whether abrupt changes in the AMOC similar to those seen in the past will occur as our climate continues to warm is an important open question.”
This study is a piece of that puzzle, Rahmstorf said. “(It) adds significantly to the rising concern about an AMOC collapse in the not too distant future,” he said. “We will ignore this risk at our peril.”
Vital ocean currents regulating Earth’s climate ‘on course to a tipping point’
Nilima Marshall, PA Science Reporter
Fri, February 9, 2024
A large and vital system of ocean currents that helps maintain the world’s climate may already be on course to a tipping point, according to scientists.
Known as the Atlantic Meridional Overturning Circulation (Amoc), this network of deep and surface currents help keep temperatures milder in the UK and Western Europe compared to other regions at similar latitudes – such as parts of eastern Canada as well as Siberia.
Scientists say a breakdown of this system could potentially plunge the UK and large parts of the Northern Hemisphere into a new ice age – an outcome that was dramatised in the 2004 Hollywood blockbuster The Day After Tomorrow.
It would also disrupt rainfall that billions rely on for agriculture, cause sea levels to rise in many parts of the world and lead to changes in weather patterns with significant impacts on ecosystems and human societies.
Dr Rene van Westen, a postdoctoral researcher in climate physics at Utrecht University in the Netherlands, said: “Cooler temperatures over Europe may seem positive, but the repercussions are far-reaching, with other regions experiencing accelerated warming and altered precipitation patterns.
“Additionally, a 100cm rise in European sea levels is projected due to the abrupt ocean circulation collapse.”
The Amoc plays a key role in regulating Earth’s climate by transporting heat from the Equator towards the Poles.
But as global temperatures rise due to warming, freshwater is pouring into the system from the melting ice from Antarctica, Greenland and other sources, risking disruption to the circulation patterns that drive the Amoc.
Dr Van Westen, along with a team of researchers at Utrecht University, designed a simulation where they gradually introduced surface freshwater over the course of 2,200 model years.
The findings, published in the journal Science Advances, showed a gradual decline of the Amoc over 1700 model years, followed by an abrupt tipping event beginning around the year 1758 and lasting for about a century.
Simulations showed that during this time, the European climate cooled by about 1C per decade, with regions experiencing over 3C cooling per decade.
The researchers said that comparing these figures to the current global warming rate of 0.2C per decade underscores the devastating impact an Amoc tipping event could have on the planet.
Dr Van Westen said: “Once the Atlantic Ocean circulation collapses, the resulting climate impacts are nearly irreversible on human timescales, as our earlier research has shown.
“Staying clear of this tipping point is imperative for avoiding devastating consequences on climate, society, and the environment.”
Scientists says large parts of the Northern Hemisphere could be plunged into a new ice age (Alamy/PA)
The researchers said that while current observational records are too short to make a reliable estimation, there are early warning indicators suggesting “we are moving in the direction of the tipping point”.
The team also said it also found a new way to detect an early warning signal for the collapse of the Amoc – a minimum of freshwater transport occurring at 34 degrees south of the Equator in the Atlantic.
Commenting on the study, Professor Tim Lenton, director of the Global Systems Institute at University of Exeter, said: “The research makes a convincing case that the Amoc is approaching a tipping point based on a robust, physically-based early warning indicator.
“What it cannot – and does not – say is how close the tipping point, because as it shows that there is insufficient data to make a statistically reliable estimate of that.
“We have to plan for the worst.
“We should invest in collecting relevant data and improving estimation of how close a tipping point is, improving assessment of what its impacts would be, and getting pre-prepared for how we could best manage and adapt to those impacts if they start to unfold.”
Professor Jon Robson, research fellow at the University of Reading’s National Centre for Atmospheric Science, said that although climate models can simulate such abrupt Amoc weakening events, it is important to keep in mind that the current study is based on only one imperfect climate model.
He said: “We need to see if this freshwater diagnostic is really a robust early warning indicator of abrupt Amoc changes.”
Ocean system that moves heat gets closer to collapse, which could cause weather chaos, study says
SETH BORENSTEIN
Updated Fri, February 9, 2024
People swim in the Atlantic Ocean in Biarritz, southwestern France, Oct. 27, 2021. An abrupt shutdown of Atlantic Ocean currents that could put large parts of Europe in a deep freeze is looking a bit more likely and closer than before, according to a new story.
(AP Photo/Bob Edme, File)
An abrupt shutdown of Atlantic Ocean currents that could put large parts of Europe in a deep freeze is looking a bit more likely and closer than before as a new complex computer simulation finds a “cliff-like” tipping point looming in the future.
A long-worried nightmare scenario, triggered by Greenland's ice sheet melting from global warming, still is at least decades away if not longer, but maybe not the centuries that it once seemed, a new study in Friday's Science Advances finds. The study, the first to use complex simulations and include multiple factors, uses a key measurement to track the strength of vital overall ocean circulation, which is slowing.
A collapse of the current — called the Atlantic Meridional Overturning Circulation or AMOC — would change weather worldwide because it means a shutdown of one of key the climate and ocean forces of the planet. It would plunge northwestern European temperatures by 9 to 27 degrees (5 to 15 degrees Celsius) over the decades, extend Arctic ice much farther south, turn up the heat even more in the Southern Hemisphere, change global rainfall patterns and disrupt the Amazon, the study said. Other scientists said it would be a catastrophe that could cause worldwide food and water shortages.
“We are moving closer (to the collapse), but we we're not sure how much closer,” said study lead author Rene van Westen, a climate scientist and oceanographer at Utrecht University in the Netherlands. “We are heading towards a tipping point.”
When this global weather calamity — grossly fictionalized in the movie “The Day After Tomorrow” — may happen is “the million-dollar question, which we unfortunately can't answer at the moment,” van Westen said. He said it's likely a century away but still could happen in his lifetime. He just turned 30.
“It also depends on the rate of climate change we are inducing as humanity,” van Westen said.
Studies have shown the AMOC to be slowing, but the issue is about a complete collapse or shutdown. The United Nations' Intergovernmental Panel on Climate Change, which is a group of hundreds of scientists that gives regular authoritative updates on warming, said it has medium confidence that there will not be a collapse before 2100 and generally downplayed disaster scenarios. But van Westen, several outside scientists and a study last year say that may not be right.
Stefan Rahmstorf, head of Earth Systems Analysis at the Potsdam Institute for Climate Research in Germany, was not part of the research, but called it “a major advance in AMOC stability science.”
“The new study adds significantly to the rising concern about an AMOC collapse in the not too distant future,” Rahmstorf said in an email. “We will ignore this at our peril.”
University of Exeter climate scientist Tim Lenton, also not part of the research, said the new study makes him more concerned about a collapse.
An AMOC collapse would cause so many ripples throughout the world's climate that are “so abrupt and severe that they would be near impossible to adapt to in some locations,” Lenton said.
There are signs showing that the AMOC has collapsed in the past, but when and how it will change in the future is still uncertain, said U.S. National Oceanic and Atmospheric Administration oceanographer Wei Cheng, who wasn't part of the research.
The AMOC is part of an intricate global conveyor belt of ocean currents that move different levels of salt and warm water around the globe at different depths in patterns that helps regulate Earth's temperature, absorbs carbon dioxide and fuels the water cycle, according to NASA.
When the AMOC shuts down, there's less heat exchanged across the globe and “it really impacts Europe quite severely,” van Westen said.
For thousands of years, Earth's oceans have relied on a circulation system that runs like a conveyor belt. It's still going but slowing.
The engine of this conveyor belt is off the coast of Greenland, where, as more ice melts from climate change, more freshwater flows into the North Atlantic and slows everything down, van Westen said. In the current system, cold deeper fresher water heads south past both Americas and then east past Africa. Meanwhile saltier warmer ocean water, coming from the Pacific and Indian oceans, pushes past the southern tip of Africa, veers to and around Florida and continues up the U.S. East Coast on up to Greenland.
The Dutch team simulated 2,200 years of its flow, adding in what human-caused climate change does to it. They found after 1,750 years “an abrupt AMOC collapse,” but so far are unable to translate that simulated timeline to Earth's real future. Key to monitoring what happens is a complicated measurement of flow around the tip of Africa. The more negative that measurement, the slower AMOC runs.
"This value is getting more negative under climate change,” van Westen said. When it reaches a certain point it's not a gradual stop but something that is “cliff-like,” he said.
The world should pay attention to potential AMOC collapse, said Joel Hirschi, division leader at the United Kingdom's National Oceanography Centre. But there's a bigger global priority, he said.
“To me, the rapidly increasing temperatures we have been witnessing in recent years and associated temperature extremes are of more immediate concern than the AMOC shutting down,” Hirschi said. “The warming is not hypothetical but is already happening and impacting society now.” ___
Read more of AP’s climate coverage at http://www.apnews.com/climate-and-environment
___
Follow Seth Borenstein on X at @borenbears
___
The Associated Press’ climate and environmental coverage receives financial support from multiple private foundations. AP is solely responsible for all content. Find AP’s standards for working with philanthropies, a list of supporters and funded coverage areas at AP.org.
Oops, Scientists May Have Miscalculated Our Global Warming Timeline
An abrupt shutdown of Atlantic Ocean currents that could put large parts of Europe in a deep freeze is looking a bit more likely and closer than before as a new complex computer simulation finds a “cliff-like” tipping point looming in the future.
A long-worried nightmare scenario, triggered by Greenland's ice sheet melting from global warming, still is at least decades away if not longer, but maybe not the centuries that it once seemed, a new study in Friday's Science Advances finds. The study, the first to use complex simulations and include multiple factors, uses a key measurement to track the strength of vital overall ocean circulation, which is slowing.
A collapse of the current — called the Atlantic Meridional Overturning Circulation or AMOC — would change weather worldwide because it means a shutdown of one of key the climate and ocean forces of the planet. It would plunge northwestern European temperatures by 9 to 27 degrees (5 to 15 degrees Celsius) over the decades, extend Arctic ice much farther south, turn up the heat even more in the Southern Hemisphere, change global rainfall patterns and disrupt the Amazon, the study said. Other scientists said it would be a catastrophe that could cause worldwide food and water shortages.
“We are moving closer (to the collapse), but we we're not sure how much closer,” said study lead author Rene van Westen, a climate scientist and oceanographer at Utrecht University in the Netherlands. “We are heading towards a tipping point.”
When this global weather calamity — grossly fictionalized in the movie “The Day After Tomorrow” — may happen is “the million-dollar question, which we unfortunately can't answer at the moment,” van Westen said. He said it's likely a century away but still could happen in his lifetime. He just turned 30.
“It also depends on the rate of climate change we are inducing as humanity,” van Westen said.
Studies have shown the AMOC to be slowing, but the issue is about a complete collapse or shutdown. The United Nations' Intergovernmental Panel on Climate Change, which is a group of hundreds of scientists that gives regular authoritative updates on warming, said it has medium confidence that there will not be a collapse before 2100 and generally downplayed disaster scenarios. But van Westen, several outside scientists and a study last year say that may not be right.
Stefan Rahmstorf, head of Earth Systems Analysis at the Potsdam Institute for Climate Research in Germany, was not part of the research, but called it “a major advance in AMOC stability science.”
“The new study adds significantly to the rising concern about an AMOC collapse in the not too distant future,” Rahmstorf said in an email. “We will ignore this at our peril.”
University of Exeter climate scientist Tim Lenton, also not part of the research, said the new study makes him more concerned about a collapse.
An AMOC collapse would cause so many ripples throughout the world's climate that are “so abrupt and severe that they would be near impossible to adapt to in some locations,” Lenton said.
There are signs showing that the AMOC has collapsed in the past, but when and how it will change in the future is still uncertain, said U.S. National Oceanic and Atmospheric Administration oceanographer Wei Cheng, who wasn't part of the research.
The AMOC is part of an intricate global conveyor belt of ocean currents that move different levels of salt and warm water around the globe at different depths in patterns that helps regulate Earth's temperature, absorbs carbon dioxide and fuels the water cycle, according to NASA.
When the AMOC shuts down, there's less heat exchanged across the globe and “it really impacts Europe quite severely,” van Westen said.
For thousands of years, Earth's oceans have relied on a circulation system that runs like a conveyor belt. It's still going but slowing.
The engine of this conveyor belt is off the coast of Greenland, where, as more ice melts from climate change, more freshwater flows into the North Atlantic and slows everything down, van Westen said. In the current system, cold deeper fresher water heads south past both Americas and then east past Africa. Meanwhile saltier warmer ocean water, coming from the Pacific and Indian oceans, pushes past the southern tip of Africa, veers to and around Florida and continues up the U.S. East Coast on up to Greenland.
The Dutch team simulated 2,200 years of its flow, adding in what human-caused climate change does to it. They found after 1,750 years “an abrupt AMOC collapse,” but so far are unable to translate that simulated timeline to Earth's real future. Key to monitoring what happens is a complicated measurement of flow around the tip of Africa. The more negative that measurement, the slower AMOC runs.
"This value is getting more negative under climate change,” van Westen said. When it reaches a certain point it's not a gradual stop but something that is “cliff-like,” he said.
The world should pay attention to potential AMOC collapse, said Joel Hirschi, division leader at the United Kingdom's National Oceanography Centre. But there's a bigger global priority, he said.
“To me, the rapidly increasing temperatures we have been witnessing in recent years and associated temperature extremes are of more immediate concern than the AMOC shutting down,” Hirschi said. “The warming is not hypothetical but is already happening and impacting society now.” ___
Read more of AP’s climate coverage at http://www.apnews.com/climate-and-environment
___
Follow Seth Borenstein on X at @borenbears
___
The Associated Press’ climate and environmental coverage receives financial support from multiple private foundations. AP is solely responsible for all content. Find AP’s standards for working with philanthropies, a list of supporters and funded coverage areas at AP.org.
Oops, Scientists May Have Miscalculated Our Global Warming Timeline
Darren Orf
Fri, February 9, 2024
Surasak Suwanmake - Getty Images
The Paris Climate Accords in 2015 set an ambitious (and necessary) goal of keeping global temperatures at 1.5 degrees Celsius above pre-industrial temps. But a new study says we might’ve blown past that threshold several years ago.
A new study from University Western Australia Oceans Institute studied long-lived Caribbean sclerosponges and created an ocean temperature timeline dating back to the 1700s.
While the study claims that we surpassed 1.5 degrees Celsius in 2020, other scientists question if data from just one part of the world is enough to capture the immense thermal complexity of our oceans.
Whatever your stance is on climate change (it’s real, let’s move on), it’s impossible to have missed the near-ubiquitous call to action to “keep temperatures from exceeding 1.5 degrees Celsius compared to pre-industrial levels.” Over the past few years, the somewhat bureaucratic phrase has become a rallying cry for the climate conscious.
This ambitious target first surfaced following the Paris Climate Agreement, and describes a sort of climate threshold—if we pass a long-term average increase in temperature of 1.5 degrees Celsius, and hold at those levels for several years, we’re going to do some serious damage to ourselves and our environment.
Well, a new paper from the University Western Australia Oceans Institute has some bad news: the world might’ve blown past that threshold four years ago. Published in the journal Nature Climate Change, the paper reaches this conclusion via an unlikely route—analyzing six sclerosponges, a kind of sea sponge that clings to underwater caves in the ocean. These sponges are commonly studied by climate scientists and are referred to as “natural archives” because they grow so slowly. Like, a-fraction-of-a-millimeter-a-year slow. This essentially allows them to lock away climate data in their limestone skeletons, not entirely unlike tree rings or ice cores.
By analyzing strontium to calcium ratios in these sponges, the team could effectively calculate water temperatures dating back to 1700. The sponges watery home in the Caribbean is also a plus, as major ocean currents don’t muck up or distort temperature readings. This data could be particularly useful,as direct human measurement of sea temperature only dates back to roughly 1850, when sailors dipped buckets into the ocean. That”s why the Intergovernmental Panel on Climate Change (IPCC) uses 1850 and 1900 as its preindustrial baseline, according to the website Grist.
“The big picture is that the global warming clock for emissions reductions to minimize the risk of dangerous climate change has been brought forward by at least a decade,” Malcolm McCulloch, lead author of the study, told the Associated Press. “Basically, time’s running out.”
The study concludes that the world started warming roughly 80 years before the IPCC’s estimates, and that we already surpassed 1.7 degrees Celsius in 2020. That’s a big “woah, if true” moment, but some scientists are skeptical. One such scientist, speaking with LiveScience, said that “ it begs credulity to claim that the instrumental record is wrong based on paleosponges from one region of the world… It honestly doesn’t make any sense to me.” Other experts expressed wanting to see more data before completely upending the IPCC’s climate goalposts, which say the Earth is currently hovering at a long-term temperature change of around 1.2 degrees Celsius.
Unfortunately, even if the sponges are wrong, there’s mounting evidence that we are in the process of crossing that 1.5 degree threshold as we speak. This January was the hottest on record, clocking in at 1.7 degrees above pre-industrial temperatures. According to New Scientist, that means we’ve been above 1.5 degrees of change for at least a year. That doesn’t jump the long-term average over the 1.5-line, but it’s certainly a sign we’re getting close fast.
Regardless of the percentage, one thing is certain—climate change is an all-hands-on-deck crisis. In order to save the planet for future habitability, humans need to curtail emissions immediately—after all, the sea sponges are telling us so.
The Paris Climate Accords in 2015 set an ambitious (and necessary) goal of keeping global temperatures at 1.5 degrees Celsius above pre-industrial temps. But a new study says we might’ve blown past that threshold several years ago.
A new study from University Western Australia Oceans Institute studied long-lived Caribbean sclerosponges and created an ocean temperature timeline dating back to the 1700s.
While the study claims that we surpassed 1.5 degrees Celsius in 2020, other scientists question if data from just one part of the world is enough to capture the immense thermal complexity of our oceans.
Whatever your stance is on climate change (it’s real, let’s move on), it’s impossible to have missed the near-ubiquitous call to action to “keep temperatures from exceeding 1.5 degrees Celsius compared to pre-industrial levels.” Over the past few years, the somewhat bureaucratic phrase has become a rallying cry for the climate conscious.
This ambitious target first surfaced following the Paris Climate Agreement, and describes a sort of climate threshold—if we pass a long-term average increase in temperature of 1.5 degrees Celsius, and hold at those levels for several years, we’re going to do some serious damage to ourselves and our environment.
Well, a new paper from the University Western Australia Oceans Institute has some bad news: the world might’ve blown past that threshold four years ago. Published in the journal Nature Climate Change, the paper reaches this conclusion via an unlikely route—analyzing six sclerosponges, a kind of sea sponge that clings to underwater caves in the ocean. These sponges are commonly studied by climate scientists and are referred to as “natural archives” because they grow so slowly. Like, a-fraction-of-a-millimeter-a-year slow. This essentially allows them to lock away climate data in their limestone skeletons, not entirely unlike tree rings or ice cores.
By analyzing strontium to calcium ratios in these sponges, the team could effectively calculate water temperatures dating back to 1700. The sponges watery home in the Caribbean is also a plus, as major ocean currents don’t muck up or distort temperature readings. This data could be particularly useful,as direct human measurement of sea temperature only dates back to roughly 1850, when sailors dipped buckets into the ocean. That”s why the Intergovernmental Panel on Climate Change (IPCC) uses 1850 and 1900 as its preindustrial baseline, according to the website Grist.
“The big picture is that the global warming clock for emissions reductions to minimize the risk of dangerous climate change has been brought forward by at least a decade,” Malcolm McCulloch, lead author of the study, told the Associated Press. “Basically, time’s running out.”
The study concludes that the world started warming roughly 80 years before the IPCC’s estimates, and that we already surpassed 1.7 degrees Celsius in 2020. That’s a big “woah, if true” moment, but some scientists are skeptical. One such scientist, speaking with LiveScience, said that “ it begs credulity to claim that the instrumental record is wrong based on paleosponges from one region of the world… It honestly doesn’t make any sense to me.” Other experts expressed wanting to see more data before completely upending the IPCC’s climate goalposts, which say the Earth is currently hovering at a long-term temperature change of around 1.2 degrees Celsius.
Unfortunately, even if the sponges are wrong, there’s mounting evidence that we are in the process of crossing that 1.5 degree threshold as we speak. This January was the hottest on record, clocking in at 1.7 degrees above pre-industrial temperatures. According to New Scientist, that means we’ve been above 1.5 degrees of change for at least a year. That doesn’t jump the long-term average over the 1.5-line, but it’s certainly a sign we’re getting close fast.
Regardless of the percentage, one thing is certain—climate change is an all-hands-on-deck crisis. In order to save the planet for future habitability, humans need to curtail emissions immediately—after all, the sea sponges are telling us so.
Climate change row as British scientists claim ‘Day After Tomorrow’ modelling is wrong
Sarah Knapton
THE TORY TELEGRAPH
Fri, February 9, 2024
In the film The Day After Tomorrow, the ocean system is disrupted by climate change, plunging the northern hemisphere into a permanent winter
Fri, February 9, 2024
In the film The Day After Tomorrow, the ocean system is disrupted by climate change, plunging the northern hemisphere into a permanent winter
- 20th CENTURY FOX/EPA
A climate model predicting a devastating ‘Day After Tomorrow’ collapse of ocean systems has been criticised for relying on ‘entirely unrealistic’ scenarios.
A Dutch team from Utrecht University published work in the journal of Science Advances this week suggesting that the Atlantic Meridional Overturning Circulation (AMOC) could reach a tipping point, triggering a new ice age.
The AMOC transports heat and salt throughout the world’s oceans and helps regulate the global climate, driving the Gulf Stream that keeps Britain warmer than it should be for its northerly latitude.
In the apocalyptic science fiction film The Day After Tomorrow, the ocean system is disrupted by climate change, plunging the northern hemisphere into a permanent winter.
Although ice-core data suggests the AMOC can switch off, recent sophisticated modelling has not been able to reproduce the effect, leading many scientists to think a collapse is unlikely to happen.
The new study claims to have shown that AMOC is “on route to tipping”, a prospect that the authors say is “bad news for the climate system and humanity”.
However British scientists warned that the outcome had been “forced” by using unlikely variables, such as assuming large influxes of freshwater into the Atlantic.
Prof Jonathan Bamber, director of the Bristol Glaciology Centre at Bristol University, said: “They did this by imposing a huge freshwater forcing to the North Atlantic that is entirely unrealistic for even the most extreme warming scenario over the next century.
“Their freshwater forcing applied to the North Atlantic is equivalent to six cm/year of sea level rise by the end of the experiment, which is more than seen during the collapse of the ice sheet that covered North America during the last glaciation.”
The UN’s Intergovernmental Panel on Climate Change has said that the AMOC is unlikely to collapse this century, and many scientists do not believe it will fail even if the climate continues to warm.
Observational data for the ocean system only goes back to 2004, making it difficult to predict, and because it spans the globe, most models cannot account for all the nuances and influences.
Commenting on the new research, Prof Andrew Watson, of Exeter University, said “They say it suggests that ‘the present day AMOC is on route to tipping’.
‘Push it quite hard’
“This sounds alarming, but it’s important to note that this is not the same as saying collapse is going to happen imminently. They have to run their model for a long time (1,700 years) and push it quite hard to make the collapse happen.
“Models are not reality. The real system may be more, or less, prone to collapse than this model suggests.”
The authors said that the collapse of the AMOC would result in the “very strong and rapid cooling of Europe” by about 3C per decade, which they said ‘no realistic adaptation measures’ would be able to mitigate.
They said their study had picked up an early warning signal that the collapse was just 25 years away, when the movement of freshwater flowing through the southern Atlantic slows to a minimum.
Other experts said the research was a reminder of the possible unexpected impacts of uncontrollable global warming, which could actually plunge the world into a new ice age.
Prof Jeffrey Kargel, senior scientist at the Planetary Science Institute in Arizona, said: “A shut down of the AMOC would be felt globally, according to the model, from Europe to Antarctica.
‘Sea ice has diminished drastically’
“Sea ice in the Arctic, which has diminished drastically in recent decades, would expand in winter to the latitudes of Ireland, the UK and Denmark.
“The projected changes in climate in Scandinavia and parts of Greenland and the United Kingdom and elsewhere may threaten those countries’ humanly habitability if glacier and ice sheet growth extends from the mountains and hill terrains to lowlands.”
Last year a paper published in the journal Nature suggested the AMOC was likely to collapse by 2057, and possibly as early as 2025.
But the study was criticised as “far too simplistic” by the Met Office, which warned readers not to despair.
A climate model predicting a devastating ‘Day After Tomorrow’ collapse of ocean systems has been criticised for relying on ‘entirely unrealistic’ scenarios.
A Dutch team from Utrecht University published work in the journal of Science Advances this week suggesting that the Atlantic Meridional Overturning Circulation (AMOC) could reach a tipping point, triggering a new ice age.
The AMOC transports heat and salt throughout the world’s oceans and helps regulate the global climate, driving the Gulf Stream that keeps Britain warmer than it should be for its northerly latitude.
In the apocalyptic science fiction film The Day After Tomorrow, the ocean system is disrupted by climate change, plunging the northern hemisphere into a permanent winter.
Although ice-core data suggests the AMOC can switch off, recent sophisticated modelling has not been able to reproduce the effect, leading many scientists to think a collapse is unlikely to happen.
The new study claims to have shown that AMOC is “on route to tipping”, a prospect that the authors say is “bad news for the climate system and humanity”.
However British scientists warned that the outcome had been “forced” by using unlikely variables, such as assuming large influxes of freshwater into the Atlantic.
Prof Jonathan Bamber, director of the Bristol Glaciology Centre at Bristol University, said: “They did this by imposing a huge freshwater forcing to the North Atlantic that is entirely unrealistic for even the most extreme warming scenario over the next century.
“Their freshwater forcing applied to the North Atlantic is equivalent to six cm/year of sea level rise by the end of the experiment, which is more than seen during the collapse of the ice sheet that covered North America during the last glaciation.”
The UN’s Intergovernmental Panel on Climate Change has said that the AMOC is unlikely to collapse this century, and many scientists do not believe it will fail even if the climate continues to warm.
Observational data for the ocean system only goes back to 2004, making it difficult to predict, and because it spans the globe, most models cannot account for all the nuances and influences.
Commenting on the new research, Prof Andrew Watson, of Exeter University, said “They say it suggests that ‘the present day AMOC is on route to tipping’.
‘Push it quite hard’
“This sounds alarming, but it’s important to note that this is not the same as saying collapse is going to happen imminently. They have to run their model for a long time (1,700 years) and push it quite hard to make the collapse happen.
“Models are not reality. The real system may be more, or less, prone to collapse than this model suggests.”
The authors said that the collapse of the AMOC would result in the “very strong and rapid cooling of Europe” by about 3C per decade, which they said ‘no realistic adaptation measures’ would be able to mitigate.
They said their study had picked up an early warning signal that the collapse was just 25 years away, when the movement of freshwater flowing through the southern Atlantic slows to a minimum.
Other experts said the research was a reminder of the possible unexpected impacts of uncontrollable global warming, which could actually plunge the world into a new ice age.
Prof Jeffrey Kargel, senior scientist at the Planetary Science Institute in Arizona, said: “A shut down of the AMOC would be felt globally, according to the model, from Europe to Antarctica.
‘Sea ice has diminished drastically’
“Sea ice in the Arctic, which has diminished drastically in recent decades, would expand in winter to the latitudes of Ireland, the UK and Denmark.
“The projected changes in climate in Scandinavia and parts of Greenland and the United Kingdom and elsewhere may threaten those countries’ humanly habitability if glacier and ice sheet growth extends from the mountains and hill terrains to lowlands.”
Last year a paper published in the journal Nature suggested the AMOC was likely to collapse by 2057, and possibly as early as 2025.
But the study was criticised as “far too simplistic” by the Met Office, which warned readers not to despair.
