Extreme weather more likely as Arctic warms, warn scientists
Scientists have long observed that the Arctic is more sensitive to global temperature changes than anywhere else on Earth – the Arctic has warmed more than twice as fast as the global average – a phenomenon known as ‘Arctic amplification.’ This has resulted in a smaller difference in temperature between the Arctic and the mid-latitudes, which has a major impact on the jet-stream, the high-speed current of air in the atmosphere that controls much of the weather across North America and Europe. When there is less of a temperature difference the jet-stream slows and weakens, making it follow a wavier route. This leads to more persistent weather patterns that cause extreme events.
Professor Francis’ analysis shows substantial increases in the occurrence of high-amplitude (wavy) jet-stream patterns during autumn, with large increases over North America and the Atlantic during winter and summer, which correspond with periods of high Arctic amplification.
Professor Francis will argue that the recent increase in extreme weather events throughout the Northern Hemisphere mid latitudes are likely to be partly due to the rapid pace of Arctic warming.
“While it is difficult to say with any certainty that Arctic amplification is the cause of any particular extreme weather event, these are the types of phenomena that are expected to occur more often as the world continues to warm and the Arctic continues to lose its ice,” said Professor Francis.
Examples of the persistent, “stuck” weather patterns that Professor Francis says are increasing include the deep troughs in the jet-stream that hung over the U.S. east coast and Western Europe during the winters of 2009/10, 2010/11 and 2012/13 causing extreme snow storms and cold weather. In contrast, during the winter of 2011/12 these same areas were under ridges in the jet-stream, which brought unusually warm weather.
Professor Francis’ presentation is part of a two-day discussion meeting on ‘Arctic sea ice: the evidence, models and global impacts’ being held at the Royal Society (22nd – 23rd September).
Professor Daniel Feltham, of the University of Reading, UK, one of the meeting organisers, said: “People in Europe and North America may wonder why, if greenhouse gas emissions are making the world warmer, we can still experience cool, wet summers or extremely cold winters.
“We know that the jet stream plays an important role in our weather, but we are still learning how climate change may be influencing the jet stream. This research suggests an elegant and plausible explanation of how dwindling levels of Arctic sea ice may be influencing the path of the jet stream and hence having a big impact on the weather in Britain, and other countries at similar latitudes.”
The full discussion meeting programme can be downloaded here: https://royalsociety.org/events/2014/arctic-sea-ice/
Notes
1. The Royal Society is a self-governing Fellowship of many of the world’s most distinguished scientists drawn from all areas of science, engineering, and medicine. The Society’s fundamental purpose, as it has been since its foundation in 1660, is to recognise, promote, and support excellence in science and to encourage the development and use of science for the benefit of humanity.
The Society’s strategic priorities emphasise its commitment to the highest quality science, to curiosity-driven research, and to the development and use of science for the benefit of society. These priorities are:
1. Promoting science and its benefits
2. Recognising excellence in science
3. Supporting outstanding science
4. Providing scientific advice for policy
5. Fostering international and global cooperation
6. Education and public engagement
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