A study of seasonal records dating back to 1899 found while most seasons have not changed dramatically, winter has become much more unpredictable.
The results suggest the idea of a “typical” British winter is increasingly a myth, with wide swings from mild but stormy conditions like those which hit the UK this year to extremely cold temperatures and snow in another year becoming more common.
Researchers from the University of Sheffield, the University of East Anglia and the Met Office found seven out of the 10 most extreme winter conditions over the last 115 years have occurred in the last decade.
Yorkshire has borne the brunt of much of the severe conditions – from the Siberian snow and temperatures of late 2010 to last December’s devastating tidal surge which saw more than 1,100 properties flooded on the Humber.
Whether this winter will be extreme is too early to say, the Met Office said yesterday, adding it is not scientifically possible to give a detailed forecast more than a month ahead.
Professor Phil Jones, from the University of East Anglia, said: “British winters have become increasingly unsettled. If this trend continues, we can expect more volatile UK winter weather in decades to come.”
Winter conditions are commonly defined using North Atlantic Oscillation (NAO) – a system of barometric pressure variations which indicates the strength of westerly winds approaching the UK.
When westerly winds are strong, Britain experiences mild, wet and often stormy weather – like last winter.
Weaker or reverse airflow typically brings cold, snowy weather, such as that experienced in 2009/10 and 2010/11.
The variations were particularly noticeable in early winter. In November 2010, 30cm of snow fell at Copley in West Yorkshire, and three days later the mercury plunged to -20 degrees at Ravensworth, North Yorkshire.
Mr Jones said: “When we look at the month of December in particular, our data shows that over the last 115 years, three out of five all-time record high NAO values and two out of five record lows took place in the last decade.”
Last December England’s highest pub, the Tan Hill Inn at the head of Swaledale and Arkengarthdale, acquired a snow plough to make sure the remote watering hole is no longer unreachable when bad weather strikes. In the March, staff and guests had been cut off by snowdrifts as deep as 8ft, and in 2010 there was an “ultimate lock-in” after stranded guests were joined by motorists rescued from a snowbound A66.
Professor Edward Hanna, from the University of Sheffield, admitted it was too soon to say whether the increased volatility is linked to global warming.
But the study, published in the International Journal Of Climatology, states that it was extreme unlikely the clustering of extreme conditions had happened by chance.
The trend could be due to random fluctuations in the climate system but could equally be due to factors including changing pressure and weather systems over the Arctic, especially Greenland, and changes in energy coming from the sun.
Mr Hanna said: “We cannot use these results directly to predict this winter’s weather but, according to the long-term NAO trend, we can say that the probability of getting extreme winter weather – either mild/stormy or cold/snowy – has significantly increased in the last few decades.”