Britons should brace themselves for more extreme winters as weather conditions become more volatile, scientists have warned. A study of seasonal records dating back to 1899 found that 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 becoming 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 East Anglia (UEA), University of Sheffield and the Met Office found that seven out of the 10 most extreme winter conditions over the last 115 years have occurred in the last decade.
Professor Phil Jones, from the University of East Anglia's climatic research unit, said: "This indicates that 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. 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."
Professor Edward Hanna, from the University of Sheffield's department of geography, said 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."
The National Trust, which cares for 742 miles of coastline in England, Wales and Northern Ireland, said the findings should be used as a catalyst for action. A spokesman added: "This new research is really important to understand how the weather will impact on the places that we care for.
"Last winter's storms were a major wake-up call on how extreme weather can rapidly change the nature of our coast with years' worth erosion at Birling Gap on the Sussex coast or bringing down hundreds of trees on a scale not seen since the Great Storm. It's essential that this data is used for careful long term planning and the management of change to provide an element of certainty for an uncertain future."