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China has turned on the world's most sensitive neutrino detector after more than a decade of construction. The Register reports: The Jiangmen Underground Neutrino Experiment (JUNO) is buried 700 meters under a mountain and features a 20,000-tonne "liquid scintillator detector" that China's Academy of Science says is "housed at the center of a 44-meter-deep water pool." There's also a 35.4-meter-diameter acrylic sphere supported by a 41.1-meter-diameter stainless steel truss. All that stuff is surrounded by more than 45,000 photo-multiplier tubes (PMTs). The latter devices are super-sensitive light detectors. A liquid scintillator is a fluid that, when exposed to ionizing radiation, produces light. At JUNO, the liquid is 99.7 percent alkylbenzene, an ingredient found in detergents and refrigerants. JUNO's designers hope that any neutrinos that pass through its giant tank bonk a hydrogen atom and produce just enough light that the detector array of PMTs can record their passing, producing data scientists can use to learn more about the particles. At this point, readers could sensibly ask how JUNO will catch any of these elusive particles. The answer lies in the facility's location -- a few tens of kilometers away from two nuclear power plants that produce neutrinos. The Chinese Academy of Science's Journal of High Energy Physics says trials of JUNO succeeded, suggesting it will be able to help scientists understand why some neutrinos are heavier than others so we can begin to classify the different types of the particle -- a key goal for the facility. The Journal also reports that scientists from Japan, the United States, Europe, India, and South Korea, are either already using JUNO or plan experiments at the facility.

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An anonymous reader quotes a report from The Guardian: The collapse of a critical Atlantic current can no longer be considered a low-likelihood event, a study has concluded, making deep cuts to fossil fuel emissions even more urgent to avoid the catastrophic impact. The Atlantic meridional overturning circulation (Amoc) is a major part of the global climate system. It brings sun-warmed tropical water to Europe and the Arctic, where it cools and sinks to form a deep return current. The Amoc was already known to be at its weakest in 1,600 years as a result of the climate crisis. Climate models recently indicated that a collapse before 2100 was unlikely but the new analysis examined models that were run for longer, to 2300 and 2500. These show the tipping point that makes an Amoc shutdown inevitable is likely to be passed within a few decades, but that the collapse itself may not happen until 50 to 100 years later. The research found that if carbon emissions continued to rise, 70% of the model runs led to collapse, while an intermediate level of emissions resulted in collapse in 37% of the models. Even in the case of low future emissions, an Amoc shutdown happened in 25% of the models. Scientists have warned previously that Amoc collapse must be avoided "at all costs." It would shift the tropical rainfall belt on which many millions of people rely to grow their food, plunge western Europe into extreme cold winters and summer droughts, and add 50cm to already rising sea levels. The new results are "quite shocking, because I used to say that the chance of Amoc collapsing as a result of global warming was less than 10%," said Prof Stefan Rahmstorf, at the Potsdam Institute for Climate Impact Research in Germany, who was part of the study team. "Now even in a low-emission scenario, sticking to the Paris agreement, it looks like it may be more like 25%. "These numbers are not very certain, but we are talking about a matter of risk assessment where even a 10% chance of an Amoc collapse would be far too high," added Rahmstorf. "We found that the tipping point where the shutdown becomes inevitable is probably in the next 10 to 20 years or so. That is quite a shocking finding as well and why we have to act really fast in cutting down emissions." "Observations in the deep [far North Atlantic] already show a downward trend over the past five to 10 years, consistent with the models' projections," said Prof Sybren Drijfhout, at the Royal Netherlands Meteorological Institute, who was also part of the team. "Even in some intermediate and low-emission scenarios, the Amoc slows drastically by 2100 and completely shuts off thereafter. That shows the shutdown risk is more serious than many people realize." The findings have been published in the journal Environmental Research Letters.

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