• E-mail
• Print
• Comment
• Font Size
• Digg
• del.icio.us
• Discuss article

Sunspots and the price of wheat

Posted on: Friday, 26 March 2004, 06:00 CST

Back in 1610, Galileo Galilei spotted anomalous dark circles on the surface of the Sun. These "sunspots", as they came to be called, became a familiar sight to generations of astronomers, and it was soon common knowledge that they varied greatly over the years in numbers and in size.

It was also soon suspected that they might have an effect upon our weather. In 1801, for example, William Herschel, who had in his spare time discovered Uranus, reported that during five recent solar minima, or periods when the sunspots were few and far between, the price of English wheat had peaked. He concluded that sunspots must have affected agricultural output; but no one paid more than passing attention to his novel theory. More convincing, however, was the discovery by a team of American meteorologists in 1987 that a relationship appeared to exist between sunspot activity and the rise and fall of temperatures 25 kms or so above the polar ice-caps. Subsequent work uncovered similar temperature oscillations elsewhere in the upper atmosphere, and indeed it appeared that here and there, these temperature anomalies might percolate right down to ground level - causing, for example, an unseasonal chill in the US southern states around the solar sunspot maximum. Another team of scientists claimed to have found that in periods of high sunspot activity, depressions in the North Atlantic seemed to move on tracks that were slightly further north than usual.

Recently, there has been another interesting development. Two Israeli scientists, Lev Pustilnik and Gregory Yom Din, have analysed records of the price of wheat in England from 1259 to 1702. They have found that Herschel may have had a point; the cost of wheat was high in mediaeval England during periods when there were hardly any sunspots, and low during solar maxima.

The missing link has always been any convincing mechanism by which sunspot activity might affect the climate of our planet. In this context, some meteorologists have pointed out that cosmic radiation from outer space is modulated by the 11-year sunspot cycle. The solar wind, which consists of surges of particles emitted by the Sun, is weakest at a solar minimum; since the solar wind tends to protect the Earth from cosmic rays, our planet receives more cosmic radiation during sunspot minima.

The theory goes that these extra cosmic rays may react chemically with the atmosphere to produce greater cloud coverage, the extra cloud, in turn, warming or cooling the climate in different regions of the world.

More News in this Category