How Arctic warming could be changing our weather
RECORD wet summers and severe snowy weather in winter seen in recent years in the UK could be linked to Arctic warming, scientists have said.
The UK has been hit by a number of extreme weather events in the past decade, including heavy rain in summer 2007 and 2012, the record wet and stormy winter of 2013-14 and cold and snowy winters in 2009-10 and 2010-11.
The winter of 2014 was notable for storms that battered the Welsh coast, with Aberystywth in particular bearing the brunt of ferocious waves pounding the promenade night after night, forcing mass evacuations at seafront buildings.
And the last “big freeze” in Wales hit the nation in 2010. Temperatures dipped to -17.3°C at Lysdinam near Llandrindod Wells that November, making it colder that Greenland. And Cardiff council used up to 700 tonnes of grit in just a week.
Researchers compared data of recent UK extremes with the position of the North Atlantic polar atmospheric “jet stream” – a giant current of air – using a measure called the North Atlantic Oscillation (NAO) index which indicates shifts north and south.
The exceptional wet summers, snowy cold snaps and mild stormy winters all corresponded with pronounced negative or positive spikes in readings of the index, showing more extreme north and southward movements of the jet stream.
The researchers also linked the jet stream’s altered path – its increasing “waviness” – with a rise in summer months of areas of high pressure remaining largely stationary over Greenland, distorting the path of storms across the North Atlantic.
While many factors influence the weather, the researchers from the University of Lincoln and the National Oceanographic and Atmospheric Administration in the US said global warming could be one of the causes.
The strength and path of the North Atlantic jet stream and the high pressure in Greenland appear to be influenced by increasing temperatures in the Arctic, which has been warming much faster than the global average in the past two decades.
Professor Edward Hanna, from the University of Lincoln’s School of Geography, said: “Arctic warming may be driving recent North Atlantic atmospheric circulation changes that are linked to some of the most extreme weather events in the UK over the past decade.
“Of course, weather is naturally chaotic, and extremes are a normal part of our highly variable UK climate, but globally there has recently been an increase in the incidence of high temperature and heavy precipitation extremes.
“The cold winter episodes we noted are not so intuitively linked to global climate change, but reflect part of a long-term trend towards more variable North Atlantic atmospheric circulation from year to year during winter months, especially early winter.”
He said the trend had led to extreme winter weather in the last decade.
There have also been no notably hot or sunny summers since 2006, with summers either average or exceptionally wet, which is linked to strong warming and more frequent high pressure over Greenland in the last decade, he said.
The wash-out summer of 2012 was particularly notable, marking the wettest June on record in Wales. Communities in Mid and West Wales were particularly badly hit that year, with Talybont, Dol-y-Bont and Borth near Aberystwyth all suffering destructive flooding.
But with strong Arctic warming only seen in the last 15 to 20 years, more years of data are needed to get a clearer picture of how rising temperatures at the top of the world are affecting the weather in the UK, he added.
The study was published in Weather, the magazine of the Royal Meteorological Society.