The sun's 11-year cycle of solar activity may have been behind the unusually long spells of cold weather seen in Britain over the past two winters, a study has found.
An exceptional period of low solar activity could have influenced the flow of air in the upper atmosphere, bringing cold easterly winds over northern Europe, scientists said.
Although the researchers emphasised that there could be several factors that influenced the recent cold winters, such as declining sea ice and El Niño, they said that satellite measurements of UV radiation in the upper atmosphere support the idea that low solar activity played a major role.
"There is a lot of different factors that affect our winter climate. However, the solar cycle would probably have been acting in a way that gave us those cold winters," said Sarah Ineson, a climate scientist at the Met Office Hadley Centre near Exeter.
The study, published in Nature Geoscience, was based on computer models of what happens to the temperature of the upper stratosphere over the tropics when there is such a dip in ultraviolet radiation, and how this colder-than-usual stratosphere can influence a change in wind patterns over the lower troposphere of the northern hemisphere.