Spörer Minimum

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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".[1] 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.[2]

Solar activity events recorded in radiocarbon. Values since 1950 not shown.
Solar activity events and approximate dates
Event Start End
Oort minimum [2] 1010 1050
Oort minimum (see Medieval Warm Period) 1040 1080
Medieval maximum (see Medieval Warm Period) 1100 1250
Wolf minimum 1280 1350
Spörer Minimum 1460 1550
Maunder Minimum 1645 1715
Dalton Minimum 1790 1820
Modern Maximum 1950 ongoing

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.[3] Though a specific mechanism by which solar activity results in climate change has not been established,[4] one theory is modification of the Arctic Oscillation/North Atlantic Oscillation due to a change in solar output.[5]

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.

References[edit]

  1. ^ Eddy, J. A., "The Maunder Minimum", Science 18 June 1976: Vol. 192. no. 4245, pp. 1189–1202, PDF Copy
  2. ^ a b "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.
  3. ^ "The Sun's Chilly Impact on Earth". December 6, 2001. Retrieved 2009-04-04. 
  4. ^ "The Medieval Warm Period". Retrieved 04-02-2009.  Check date values in: |accessdate= (help)
  5. ^ 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.  edit