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]
| 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 |
| Little Ice Age [3][4][5][6] | 1350 | 1850 |
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.[7] Though a specific mechanism by which solar activity results in climate change has not been established,[3] one theory is modification of the Arctic Oscillation/North Atlantic Oscillation due to a change in solar output.[8]
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.