New evidence links Arctic warming with severe weather

http://www.eurekalert.org/pub_releases/2015-05/uos-nel052015.php

Public Release: 20-May-2015
University of Sheffield

New evidence has linked Arctic warming with severe weather in countries including the UK and US.

Professor Edward Hanna and PhD student Richard Hall, from the University of Sheffield's Department of Geography, are part of a select group of international climate scientists investigating links between Arctic climate change and extreme weather in the northern mid-latitudes.

They have found that while it is too soon to know for certain whether the Arctic played a role in persistent cold events during the extreme wet UK winter of 2013/14 and recent USA East Coast winters, new studies are adding to the growing weight of evidence linking increased Arctic temperatures with changes in mid-latitude weather patterns.

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Arctic temperatures are increasing two to three times faster than those at the mid-latitudes. Some scientists have suggested that warming Arctic temperatures contribute to weaker upper level westerly winds and a wavier jet stream. This wavier path may have caused cold weather conditions to stall over the eastern seaboard and midwest United States during recent winters, according to these theories.

Professor Hanna and Richard Hall note increased variability of the jet stream in winter and high pressure over Greenland, which has given more variable UK winters in the last few years. This includes the exceptionally stormy winter of 2013/14 which could have been partly influenced by climate change in the Arctic.

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A way to advance research from a pre-consensus stage is to further investigate the meandering jet stream and the connection between the warmer Arctic and the negative phase of an index showing the dominant pattern of sea level air pressure in the Arctic.

"We are where other major theories such as plate tectonics and El Niño were before they were widely accepted," said Professor Overland.

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