For well over a century there have been continuing efforts to establish links between events here on Earth and the changing activity of the sun. It is known that the sun goes through a regular cycle lasting about 11 years during which sunspots vary in size and number, and as we noted in Weather Eye earlier this week, researchers have tried to relate this cycle to changes in temperature, pressure or rainfall at various places on the Earth's surface.
Indeed, for many years sunspots fulfilled the scapegoat role that has now descended on the ubiquitous El Nino; they were blamed for every imaginable natural disaster, not to mention plagues in Africa, the ups and downs of the fashion hemline, or the number of Democrats elected to the US Senate.
Some effects, of course, are genuine and widely documented. Disturbances associated with sunspots cause the sun for a time to emit a greatly increased number of the tiny electrically charged particles that we call the "solar wind", and these surges are manifest on Earth as "magnetic storms". Strong electrical currents are created in the upper atmosphere, which in turn induce sympathetic bursts of electrical activity in long metal objects on the ground below - such as railways, pipelines and electric power lines; radio communications are interrupted, power cuts occur and compasses and computers are upset.
As far as meteorology is concerned, there was a resurgence of interest in sunspots about 10 years ago following the publication of a paper by two American scientists with the improbable names of Labitske and van Loon. They discovered - quite by chance, as it happened - that a relationship appeared to exist between sunspot activity and the rise and fall of temperatures 15 miles or so above the polar ice-caps.
On the troublesome question of the mechanism through which the solar influence might exert itself, it was pointed out that cosmic radiation is modulated by the solar cycle, and it was suggested that this radiation may cause chemical changes in the upper atmosphere which affects its transparency - and thus the terrestrial ebb and flow of solar radiation.
It was a link, a very tenuous one, between sunspots and the weather - and enough to set people thinking.
Of course, this exciting relationship has been disputed. Other scientists claim to have found that the atmosphere wobbles like a jelly with a natural frequency of about 10 years. They think it was this oscillation that Labitske and van Loon spotted - and that for the 30 years on which their calculations were based, this 10-year cycle happened, coincidentally, to be in phase with the sunspots.