The Spörer Minimum was a 90-year span of low solar activity, from about 1460 until 1550, which was identified and named by John A. Eddy in a landmark 1976 paper published in Science titled "The Maunder Minimum". It occurred before sunspots had been directly observed and was discovered instead by analysis of the proportion of carbon-14 in tree rings, which is strongly correlated with solar activity. It is named for the German astronomer Gustav Spörer.
|Oort minimum ||1010||1050|
|Oort minimum (see Medieval Warm Period)||1040||1080|
|Medieval maximum (see Medieval Warm Period)||1100||1250|
Like the subsequent Maunder Minimum, the Spörer Minimum coincided with a time when Earth's climate was colder than average. This correlation has generated hypotheses that low solar activity produces cooler than average global temperatures. Though a specific mechanism by which solar activity results in climate change has not been established, one theory is modification of the Arctic Oscillation/North Atlantic Oscillation due to a change in solar output.
Wilfried Schröder published a table of observed aurora borealis during the Spörer Minimum which showed that the solar cycle was active (see: Wilfried Schröder, Annals Geophys. 1994)
For details on solar activity see: solar variation.
- Eddy, J. A., "The Maunder Minimum", Science 18 June 1976: Vol. 192. no. 4245, pp. 1189–1202, PDF Copy
- "History of Sunspot Observations". Retrieved 04-02-2009. Check date values in:
|accessdate=(help) The Spörer Minimum (1420 to 1570), named after the German astronomer Gustav Spörer.
- "The Sun's Chilly Impact on Earth". December 6, 2001. Retrieved 2009-04-04.
- "The Medieval Warm Period". Retrieved 04-02-2009. Check date values in:
- Shindell, T.; Schmidt, A.; Mann, E.; Rind, D.; Waple, A. (Dec 2001). "Solar Forcing of Regional Climate Change During the Maunder Minimum". Science 294 (5549): 2149–2152. Bibcode:2001Sci...294.2149S. doi:10.1126/science.1064363. ISSN 0036-8075. PMID 11739952.