Sunspots are temporary phenomena on the surface of the Sun (the photosphere) that appear visibly as dark spots compared to surrounding regions. They are caused by intense magnetic activity, which inhibits convection, forming areas of reduced sun-surface temperature.
The solar cycle, or the solar magnetic activity cycle, is approximately an 11-year periodic solar variation (changing the level of irradiation experienced on Earth) which drives variations in space weather and to some degree weather on the ground and possibly climate change.
Correlations between the solar magnetic activity, (reflected in the sunspot frequency) and climate parameters on Earth have led some scientists to hypotheses that sunspot activity may be subtly linked to the Earth's weather. Suggestive correlations between solar activity, global temperature, and rainfall have been observed, and analysis of tree-ring data spanning centuries seems to show the presence of an 11–13 year cycle.
There is also geological evidence that the solar cycle may have been affecting terrestrial weather since Precambrian times. However, all these data have been disputed on statistical grounds, and there presently no consensus among scientists as to whether sunspots actually affect the earth's weather or not, or if so, how.
Europeans commenced observations of sunspots in the early 1600’s and continuous daily observations were started at the Zurich Observatory in 1849.
(2) Long-term Variations in Solar Activity and their Apparent Effect on the