Is the jet stream changing direction? Meandering air flow could lead to longer, harsher wintersThe jet stream controls weather over Northern Europe and North America Over the past two decades, scientists believe the jet stream has weakenedInstead of circling Earth in the north, the jet stream has begun to meanderThis could cause longer and colder winters over the northern hemisphere The fast-moving river of air that controls weather over Northern Europe and North America is undergoing a dramatic shift that could lead to harsher winters. Scientists believe the jet stream which girdles Earth is increasingly taken a longer, meandering path causing weather patterns to become ‘stuck’. This could result in longer and harsher winters over North America and northern Europe, according to researchers in Chicago. The jet stream is a ribbon of high altitude, high-speed wind in northern latitudes that blows from west to east. It is formed when the cold Arctic air clashes with warmer air from further south. The greater the difference in temperature, the faster the jet stream moves. According to Jennifer Francis, a climate expert at Rutgers University, the Arctic air has warmed in recent years as a result of melting polar ice caps. ‘The jet stream is a very fast moving river of air over our head,’ she said on Saturday at a meeting of the American Association for the Advancement of Science. ‘But over the past two decades the jet stream has weakened. This is something we can measure,’ she said. As a result, instead of circling the Earth in the far north, the jet stream has begun to meander, like a river heading off course. This has brought chilly Arctic weather further south than normal and warmer temperatures north. Perhaps most disturbingly, it remains in place for longer periods of time. The U.S. is currently enduring an especially bitter winter, with the midwestern and southern states experiencing unusually low temperatures. In contrast, far northern regions like Alaska are going through an unusually warm winter this year. This suggests ‘that weather patterns are changing,’ Professor Francis said. ‘We can expect more of the same and we can expect it to happen more frequently.’ Temperatures in the Arctic have been rising ‘two to three times faster than the rest of the planet,’ said James Overland, a weather expert with the National Oceanic and Atmospheric Administration (NOAA). Professor Francis added that it is premature to blame humans for these changes. ‘Our data to look at this effect is very short and so it is hard to get very clear signal,’ she said. ‘But as we have more data I do think we will start to see the influence of climate change.’ The meandering jet steam phenomenon, sometimes called ‘Santa's Revenge’, remains a controversial idea. ‘There is evidence for and against it,’ said Mark Serreze, director of the National Snowland Ice Data Centre in Boulder, Colorado. But he said rising Arctic temperatures are directly linked to melting ice caps. ‘The sea ice cover acts as a lid which separates the ocean from a colder atmosphere,’ Mr Serreze told the conference. But if the lid is removed, then warmth contained in the water rises into the atmosphere. This warming trend and the shifting jet stream will have a dire impact on agriculture, especially in the farm-rich middle-latitudes in the U.S.. ‘We are going to see changes in patterns of precipitation, of temperatures that might be linked to what is going on in the far north,’ said Mr Serreze. The main impact on agriculture and livestock will not come from small temperature changes, but rather from temperature extremes and the weather patterns that hold them in place for longer periods of time. This means there is now less of a difference in temperatures when it hits air from lower latitudes. http://www.dailymail.co.uk/sciencetech/article-2561218/Is-jet-stream-changing-direction-Meandering-flow-air-lead-longer-harsher-winters.html This and various other media outlets have printed versions of this story. Is it likely or just part of our normal weather over the centuries and these things just happen. I wonder if any one can comment on here ?