Sunspot cycle

The sunspot cycle is a periodic variation in the number of sunspots. Over the last, 23 of these have been observed with an average length of 11 years. A period of time when there are few sunspots is called a solar minimum. The longest one was the Maunder Minimum, and it corresponded with the Little Ice Age (1650 to 1850).

Sunspot cycles are important, because of their link to climate change on the earth. When there are few sunspots, the earth tends to get cooler, and vice versa. This may be the main driver of global warming and cooling.
 * ...there is some evidence that a lack of sunspots can cause moderate cooling because of the way the sun interacts with Earth's outer atmosphere, said Alexei Pevtsov, staff astronomer at the National Solar Observatory in Sunspot, N.M.

Links

 * Are sunspots to blame for climate change? - Paul MacRae, May 31, 2008