Solar lows caused extreme European winters

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2010 saw the coldest November temperature in the UK since 1985, in Llysdinam, Wales(Image: Rex Features)

The link between extreme winter weather in North America and Europe – including the cold spells of the last three years – and the 11-year solar cycle is growing stronger.

Last year, New Scientist reported that physicists suspected events in the stratosphere linked solar activity to extreme winters in the UK.

Climate scientists at the UK Met Office have done a new analysis of fluctuations in the Sun’s UV radiation, which reinforces that link and suggests a mechanism for how solar activity may affect seasonal weather. The team emphasise that their findings do not suggest a link to long-term global warming.

The researchers used satellite measurements to show that fluctuations in solar UV radiationare five times as large as previously thought.

When they plugged the data into the Hadley Centre computer model – one of the leadingmodels of the world climate – they were able to show how these fluctuations affect regional weather.

The BBC’s Richard Black explains it nicely:

UV is absorbed in the stratosphere, the upper atmosphere, by ozone. So in the quiet bit of the solar cycle, when there is less UV to absorb, the stratosphere is relatively cooler.

The Hadley Centre model shows that the effects of this percolate down through the atmosphere, changing wind speeds, including the jet stream that circles the globe above Europe, North America and Russia.

The net change is a reduced air flow from west to east, which brings colder air to the UK and northern Europe and re-distributes temperatures across the region.

“Our research confirms the observed link between solar variability and regional winter climate,” Sarah Ineson, the lead author on the study, told International Business Times. “It’s more than just coincidence, there’s a real correlation between ultraviolet levels and meteorological variables.”

The authors emphasize that cooler temperatures in Northern Europe are accompanied by warmer ones further south, resulting in no net overall cooling. “It’s a jigsaw puzzle, and when you average it up over the globe, there is no effect on global temperatures,” Adam Scaife, head of the UK Met Office’s Seasonal to Decadal Prediction team, told BBC News.

The UV measurements could lead to better forecasting. “While UV levels won’t tell us what the day-to-day weather will do, they provide the exciting prospect of improved forecasts for winter conditions for months and even years ahead. These forecasts play an important role in long-term contingency planning,” Ineson told Reuters.

The scientists emphasised that several other factors, such as declining levels of sea ice and El Nino, may have played a role in the unusually chilly winters, reports The Independent, which quotes Ineson as saying: “There are 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.”

The weather seen around the Atlantic from 2009 to 2011 backs up the finding, but the scientists will further confirm their work with solar UV measurements taken over a longer period.

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~ by FSVSF Admin on 10 November, 2011.

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