Latest news with #vanWesten
Yahoo
2 days ago
- Science
- Yahoo
Scientists mapped what happens if a crucial system of ocean currents collapses. The weather impact would be extreme
The collapse of a crucial network of Atlantic Ocean currents could push parts of the world into a deep freeze, with winter temperatures plunging to around minus 55 degrees Fahrenheit in some cities, bringing 'profound climate and societal impacts,' according to a new study. There is increasing concern about the future of the Atlantic Meridional Overturning Circulation — known as the AMOC — a system of currents that works like a giant conveyor belt, pulling warm water from the Southern Hemisphere and tropics to the Northern Hemisphere, where it cools, sinks and flows back south. Multiple studies suggest the AMOC is weakening with some projecting it could even collapse this century as global warming disrupts the balance of heat and salinity that keeps it moving. This would usher in huge global weather and climate shifts — including plunging temperatures in Europe, which relies on the AMOC for its mild climate. What's less clear, however, is how these impacts will unfold in a world heated up by humans burning fossil fuels. 'What if the AMOC collapses and we have climate change? Does the cooling win or does the warming win?' asked René van Westen, a marine and atmospheric researcher at Utrecht University in the Netherlands and co-author of the paper published Wednesday in the Geophysical Research Letters journal. This new study is the first to use a modern, complex climate model to answer the question, he told CNN. The researchers looked at a scenario where the AMOC weakens by 80% and the Earth is around 2 degrees Celsius warmer than the period before humans began burning large amounts of fossil fuels. The planet is currently at 1.2 degrees of warming. They focused on what would happen as the climate stabilized post-collapse, multiple decades into the future. Even in this hotter world, they found 'substantial cooling' over Europe with sharp drops in average winter temperatures and more intense cold extremes — a very different picture than the United States, where the study found temperatures would continue to increase even with an AMOC collapse. Sea ice would spread southward as far as Scandinavia, parts of the United Kingdom and the Netherlands, the research found. This would have a huge impact on cold extremes as the white surface of the ice reflects the sun's energy back into space, amplifying cooling. The scientists have created an interactive map to visualize the impacts of an AMOC collapse across the globe. London, for example, could see winter cold extremes of minus 2.2 Fahrenheit , while Oslo could see temperatures as low as minus 55 Fahrenheit and endure maximum temperatures below 32 Fahrenheit for 46% of the year. Parts of Europe will also become stormier, the study found. The increased temperature difference between northern and southern Europe will strengthen the jet stream and increase storm intensity over northwestern Europe. It 'completely shifts the narrative, right?' van Westen said. 'Because now policy is planning for a warmer future, but maybe instead, we need to also prepare for a colder future.' While cooling on an ever-hotter planet may sound like good news, van Westen warns it's anything but. Society in many parts of the Northern Hemisphere 'is not built for these kind of cold extremes,' he said. Crops would die, threatening food security, and infrastructure could buckle. What's more, the impacts of an AMOC collapse would mostly be felt in Europe's winter; it would still endure increasingly deadly heat waves in the summer as the climate crisis intensifies. The Southern Hemisphere, meanwhile, is projected to experience increased warming. The scientists also looked at the impacts of an AMOC collapse in an even hotter world. If global temperatures reach around 4 degrees Celsius above pre-industrial levels, the heat outweighs the cooling impact of an AMOC collapse in Europe , van Westen said. 'The warming signal actually wins.' But, he added, an AMOC collapse won't only affect temperatures. Other impacts include increased sea level rise, which will particularly affect the US, where a weaker AMOC is already driving significantly increased flooding on the northeastern coast, according to recent research. Stefan Rahmstorf, a physical oceanographer at Potsdam University in Germany who was not involved in the latest research, said the study confirms 'an AMOC collapse would have massive impacts on European climate.' The research uses only one climate model; others will rely on different models and will likely come up with a variety of scenarios, he told CNN. What ultimately happens will depend on the how the two opposing trends play out: AMOC-induced cooling and climate change-induced heating. A 'large uncertainty' remains, he said. The study is 'by no means the last word' especially as huge questions remain over whether the AMOC could be on course to collapse, said Richard Allen, a climate science professor at the University of Reading, also not involved in the research. 'But even the mere possibility of this dire storyline unfolding over coming centuries underscores the need to forensically monitor what is happening in our oceans,' he said. What is crystal clear is that an AMOC collapse would be very bad for society, van Westen said. 'We want to avoid it at all costs.'
The Independent
26-02-2025
- Science
- The Independent
Critical ocean circulation won't entirely collapse because of climate crisis - but it's still in trouble
One of the world's most important ocean currents is dangerously weakening but new research suggests it is unlikely to stop entirely in the near future. The Atlantic Meridional Overturning Circulation, or AMOC, a massive system of ocean currents, helps regulate global weather patterns by transporting warm water north and cold water south. Concerns about its stability have grown, with recent studies warning the system might be approaching a tipping point that could prompt catastrophic climate shifts. However, a new study published in Nature on Wednesday suggests that while the AMOC is still in trouble, a key mechanism, wind-driven upwelling in the Southern Ocean, can prevent its total collapse this century. The study, led by researchers from the UK's Met Office and the University of Exeter, analysed 34 climate models under two extreme scenarios: a quadrupling of atmospheric Carbon dioxide and a major freshwater influx into the North Atlantic. While all models showed a weakening of the AMOC by 20-81 per cent over 90 years, none predicted a complete collapse. The main reason for this resilience is persistent upwelling in the Southern Ocean, driven by strong westerly winds, which compensates for AMOC weakening, the study says. A Pacific Meridional Overturning Circulation does develop in most models as the AMOC weakens, but it is too weak to completely replace the AMOC's role. Scientists say the findings do not imply that the AMOC is safe from dangerous weakening. 'The study's results should certainly not be interpreted as showing that AMOC is a resilient system, given it finds that the AMOC still reduces to (very) weak strengths under human-caused global warming,' Dr René van Westen, postdoctoral researcher at Royal Netherlands Meteorological Institute, says. The 'key message of this paper', he says, is that the AMOC may be partly stabilised by 'remote' feedback processes, such as those outside the Atlantic Ocean. While the AMOC does not shut down in the study's 150-year simulations, Dr van Westen says, this does not rule out a full collapse if simulations are extended further. He points out a key limitation of the study: 'Southern Ocean dynamics can only be adequately captured with high-resolution climate models in which large swirls (i.e., ocean eddies) are resolved. None of the 34 climate models used in this study have such a high resolution.' Several studies in recent years have found that AOMC is likely to shut down completely, and earlier than we previously expected. Dr Joel Hirischi, associate head of Marine Systems Modelling at UK's National Oceanography Centre says this new study provides 'counterbalance' to the debate. However, even without a complete collapse, a weaker AMOC could have serious economic and environmental consequences, experts warn. 'While they find no evidence for a switch-off or collapse of the AMOC, they do find a weakening in all cases, and this alone should be cause for concern,' Dr Jonathan Bamber, director of the Bristol Glaciology Centre, University of Bristol, says about the study. A recent study by the University of Hamburg's climate research group found that an AMOC slowdown could accelerate global heating by reducing CO2 absorption in the ocean. This would, in turn, intensify extreme weather events such as heatwaves, floods, and hurricanes, potentially costing the global economy trillions of euros by 2100. 'The formation of a new overturning circulation in the Pacific, as seen in this study, signals a major transformation in global ocean dynamics,' says Dr Sofia Palazzo Corner, a researcher at the Centre for Environmental Policy at Imperial College London. Observations from the National Oceanography Centre indicate that the AMOC has already slowed by about 15 per cent since the mid-20th century, and its continued weakening could disrupt weather patterns, sea level rise, and ocean ecosystems. Scientists say the AMOC's long-term stability depends on future emissions and warming trajectories. 'This is not a reason to relax - on the contrary, it's a warning that the AMOC is already in decline, and we need to act decisively to prevent worse outcomes,' Dr Rahmstorf says.
