Minimum

¹⁴ C as an indicator of solar activity over the past 1100 years: After 20 to 60 years, the minima of ¹⁴ C formation caused by activity maxima can be detected using the radiocarbon method .

The Spörer minimum (after the German astronomer Gustav Spörer ) is a period of particularly low solar activity in the period between 1420 and 1570, with a focus between 1460 and 1550. Since the period lies before the observation of sunspots , the minimum can only be determined indirectly by the ¹⁴ Detect carbon content in tree rings from this period.

According to popular belief, the Spörminimum marks the beginning of the so-called Little Ice Age , a period with a cooler earth climate, which extended over the following Maunder minimum ( 1645–1715) to the Dalton minimum (1790–1830). Reduced solar intensity resp. large fluctuations in these are considered to be a possible factor for the cooling.

In addition to volcanic eruptions, the spor minimum was suspected to be the cause of several cold winters (see weather anomalies of the 1430s ), which caused crop failures and a famine in the years 1437–1439 . The cold lasted unusually long and began again in early autumn, so that the growing season was shortened considerably. Extensive crop failures caught Central Europe, which had not experienced anything like it for a century, unprepared and led to the worst European famine of the 15th century. The short summers of the years, however, were unusually warm. This contrast between winter and summer temperatures speaks against low solar activity as the cause of the weather anomalies and rather points to internal fluctuations in the climate system.

Individual evidence

↑ At the 24th General Assembly of the International Astronomical Union in 2015, a revised data series of the sunspot relative number from 1750 was presented after the observation conditions were checked again, which now gives less low and higher sunspot numbers around 1885 and 1945. This makes the time series less extreme. Corrected Sunspot History Suggests Climate Change since the Industrial Revolution not due to Natural Solar Trends. International Astronomical Union press release, iau1508, August 7, 2015 (iau.org, accessed August 20, 2015).

^ Christian Jörg: Expensive, Hunger, Great Dying . Famine and supply crises in the cities of the empire during the 15th century, Stuttgart (Hiersemann-Verlag) 2008.

↑ Chantal Camenisch u. a .: The 1430s: a cold period of extraordinary internal climate variability during the early Spörer Minimum with social and economic impacts in north-western and central Europe . In: Climate of the Past . 2016, doi : 10.5194 / cp-12-2107-2016 (Open Access).

[iau1508-1] At the 24th General Assembly of the International Astronomical Union in 2015, a revised data series of the sunspot relative number from 1750 was presented after the observation conditions were checked again, which now gives less low and higher sunspot numbers around 1885 and 1945. This makes the time series less extreme. Corrected Sunspot History Suggests Climate Change since the Industrial Revolution not due to Natural Solar Trends. International Astronomical Union press release, iau1508, August 7, 2015 (iau.org, accessed August 20, 2015).

[Quelle_1-2] Christian Jörg: Expensive, Hunger, Great Dying . Famine and supply crises in the cities of the empire during the 15th century, Stuttgart (Hiersemann-Verlag) 2008.

[camenisch2016-3] Chantal Camenisch u. a .: The 1430s: a cold period of extraordinary internal climate variability during the early Spörer Minimum with social and economic impacts in north-western and central Europe . In: Climate of the Past . 2016, doi : 10.5194 / cp-12-2107-2016 (Open Access).