Solar Cycle

The sun goes through a cycle of approximately 11-years between successive peaks (and troughs) in sunspot activity. During a so-called Solar Maximum, the greater sun spot activity causes more ultraviolet radiation to reach Earth, which is thought to enhance the strength of westerly winds in the stratosphere. Conversely, during the Solar Minimum phase, stratospheric westerlies have been seen to be weakened somewhat. This can influence the strength of the jet stream; and, while there are many other factors, the Solar Cycle is one which can impact on the likelihood of cold winters in mid-latitudes.