SUNSPOT ACTIVITY

(Climate) A theory which posits that weather patterns may be caused by the level and timing of sunspot activity. Sunspots represent increased solar (irradiance) activity on the sun's surface that occurs with periodic frequency of, on the average, once every 11.13 years. They last often a month, sometimes for several months, and their appearance is frequently accompanied by magnetic storms on earth. In research by the National Center for Atmospheric Research in Boulder, Colorado and the U.S. Geological Survey (USGS) in Lawrence, Kansas, researchers have shown a very high probability that the interior of the United States will be dominated by a low pressure system when there is little solar flare (sunspot) activity and the winds high above the equator are blowing from the west. This system results in cold weather in much of the country but warm weather in the Northeast. These researchers have also shown a much higher probability of wet weather in the West four years after a peak of solar irradiance, a peak that occurs, more or less, in conjunction with a peak in sunspot activity. The last recorded period of high sunspot activity was unusual as it was marked by a double peak, one in 1989 and one in 1991.