Recurring Drop in Solar Radiation Possible Reason for Cold Weather

In a new study, scientists have demonstrated a link between a recurring drop in solar radiation and the cold climate of the UK, northern Europe and parts of America.

The study, published in Nature Geoscience, explains why the UK has been gripped by such cold winters over the last few years. According to the results, the sun is just emerging from a so-called solar minimum, when solar activity is at its lowest.

The study was conducted by researchers from the Met Office, Imperial College London and the University of Oxford.

Our research establishes the link between the solar cycle and winter climate as more than just coincidence, said Dr. Adam Scaife from the UK's Met Office, one of the study's authors.

According to new satellite measurements from NASA's Solar Radiation and Climate Experiment (SORCE), differences in levels of UV light reaching the Earth during the 11-year solar cycle are larger than previously thought. The satellite, launched in 2003, is the first ever to measure solar radiation across the entire UV spectrum. The researchers were able to reproduce the effects of solar variability apparent in observed climate records by using this information in the Met Office's climate model.

Researchers said that during years of low UV activity, unusually cold air forms over the tropics in the stratosphere, about 50 kilometers up. This is balanced by a more easterly flow of air over the mid-latitudes - a pattern which then burrows its way down to the surface, bringing easterly winds and cold winters to northern Europe, according to a report in TG Daily.

When solar UV output is higher than usual, the opposite happens and there are strong westerlies which bring warm air and hence milder winters to Europe.

The UV levels may not be too forthcoming in providing information about what everyday weather pattens will be like. However, they may provide useful insights into better forecasts for winter conditions, allowing us to predict the onset of the cold season by months, maybe even years. These forecasts are key to durable contingency planning, said a climate scientist.

According to the Solar Cycle 24 Prediction, updated by the Space Weather Prediction Center every month, using the latest ISES predictions, the next solar cycle will be below average in intensity with a maximum sunspot number of 90. Given the predicted date of solar minimum and the predicted maximum intensity, solar maximum is expected to occur in May, 2013.

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