One hint of a sunspot-climate connection is that when the sun is most spotted, its total energy output is about 0.1 percent greater than during the sunspot minimums. A second hint is what happens when sunspots virtually disappear. Without sunspots, long, severe winters and short, wet summers appear. Scientists still remained cautious about drawing a connection. The stratosphere extends from about 6 to 15 miles above sea level.
Temperatures are very, very cold but also stable.
At the AAAS meeting, Brian A Tinsley, of the University of Texas at Dallas, explained a theoretical multistep process that begins when solar activity associated with sunspots intensifies the solar wind - electrically charged particles thrown out by the sun. On contact with the earth's magnetic field, these particles trigger a cascade of lower-energy ions. Eventually, these charged particles hit droplets of water that make up high-altitude clouds. At cloud tops the droplets are generally supercooled, that is, at temperature below freezing but still liquid. A minute quantity of energy input can trigger freezing, as in cloud seeding.