The Spörer Minimum was a period of low solar activity which lasted from about 1420 to 1570 (some say 1450 to 1550). It occurred before sunspots had been directly observed, and was discovered instead by analysis of the proportion of carbon-13 in tree rings, which is strongly correlated with solar activity. It is named for the German astronomer Gustav Spörer. 20 years of solar irradiance data from satellites Solar variation refers to fluctuation in the amount of energy emitted by the Sun. ... Events May 21 - Treaty of Troyes. ... Events January 23 - The assassination of regent James Stewart, Earl of Moray throws Scotland into civil war February 25 - Pope Pius V excommunicates Queen Elizabeth I of England. ... Events March - French troops under Guy de Richemont besiege the English commander in France, Edmund Beaufort, Duke of Somerset, in Caen April 15 - Battle of Formigny. ... Events February 7 - Julius III becomes Pope. ... 400 year sunspot history A sunspot is a region on the Suns surface (photosphere) that is marked by a lower temperature than its surroundings, and intense magnetic activity. ... Carbon-13 is a stable isotope of carbon. ... Pinus taeda Cross section showing annual rings Cheraw, South Carolina Dendrochronology or tree-ring dating is the method of scientific dating based on the analysis of tree ring patterns. ... Friederich Wilhelm Gustav Spörer (October 23, 1822 – July 7, 1895) was a German astronomer. ...

Like the subsequent Maunder Minimum, the Spörer Minimum coincided with a time when Earth's climate was colder than average. It appears that low solar activity is correlated with cooler than average global temperatures, although the mechanism by which solar activity results in climate change is not yet understood. The Maunder minimum in a 400 year history of sunspot numbers The Maunder Minimum is the name given to the period roughly from 1645 to 1715 A.D., when sunspots became exceedingly rare, as noted by solar observers of the time. ... The term climate change is used to refer to changes in the Earths climate. ...

For details on solar activity see: solar variation. 20 years of solar irradiance data from satellites Solar variation refers to fluctuation in the amount of energy emitted by the Sun. ...