A study published in Environmental Research Letters suggests a link between low solar activity and jet streams could explain why regions North East of the Atlantic Ocean might experience more frequent cold winters in years to come.
Scientists say the UK and Europe could experience temperatures not seen since the end of the seventeenth century as a result of the changes in solar activity.
"This year's winter in the UK has been the 14th coldest in the last 160 years and yet the global average temperature for the same period has been the 5th highest," said Lead author Mike Lockwood of the University of Reading. "We have discovered that this kind of anomaly is significantly more common when solar activity is low."
The new theory differs from previous efforts to explain the UK's recent cold winters by comparing the most comprehensive, but regionally specific, temperature dataset available (the Central England Temperature dataset) to the long-term behavior of the Sun's magnetic field, and to trends across the entire Northern Hemisphere.
The researchers suggest that the anomaly in Northern Europe's winter temperatures could be to do with a phenomenon called 'blocking'.
'Blocking' is related to the jet stream which brings winds from the west, over the Atlantic, and into Northern Europe but, over the past couple of winters, could have lost its way, for weeks at a time, in an 'anticyclone' before it reaches Europe.
Strong correlations have been found between weak solar activity and the occurrences of 'blocking'. As the temperature is affected by a weak Sun so the wind's patterns also change and, as the warmer westerly winds fail to arrive, the UK is hit by north-easterlies from the Arctic.
The researchers, not wanting take any focus off the potentially world-ending consequnces of global warming, are keen to stress the regional and seasonal (European and winter) nature of their research.
The trends do not guarantee colder winters but they do suggest that colder winters will become more frequent, said Lockwood. "If we look at the last period of very low solar activity at the end of the seventeenth century, we find the coldest winter on record in 1684 but, for example, the very next year, when solar activity was still low, saw the third warmest winter in the entire 350-year record. The results do show however that there are a greater number of cold UK winters when solar activity is low."
Citation: Lockwood et al., 'Are cold winters in Europe associated with low solar activity?', April 2010, Environmental Research Letters, 5 024001; doi: 10.1088/1748-9326/5/2/024001
