Global Warming

The Maunder Minimum is the name given to the period roughly spanning 1645 to 1715 by John A. Eddy in a landmark 1976 paper published in Science titled "The Maunder Minimum", when sunspots became exceedingly rare, as noted by solar observers of the time. Astronomers before Eddy had also named the period after the solar astronomer Edward W. Maunder (1851–1928) who studied how sunspot latitudes changed with time. The periods he examined included the second half of the 17th century. Edward Maunder published two papers in 1890 and 1894, and he cited earlier papers written by Gustav Spörer. The Maunder Minimum’s duration was derived from Spörer’s work. During one 30-year period within the Maunder Minimum, astronomers observed only about 50 sunspots, as opposed to a more typical 40,000–50,000 spots in modern times. Some scientists hypothesize that the dense wood used in Stradivarius instruments was caused by slow tree growth during the cooler period. Instrument maker Antonio Stradivari was born a year before the start of the Maunder Minimum. The lower solar activity during the Maunder Minimum also affected the amount of cosmic radiation reaching the Earth. The scale of changes resulting in the production of carbon-14 in one cycle is small (about 1 percent of medium abundance) and can be taken into account when radiocarbon dating is used to determine the age of archaeological artifacts. Solar activity also affects the production of beryllium-10, and variations in that cosmogenic isotope are studied as a proxy for solar activity. The existence of the Maunder minimum is interesting on purely astrophysical grounds, because it suggests that the regular rise and fall of sunspots observed from 1715 all the way through to the present day may not be a permanent, or even typical, aspect of solar behavior. It is possible to create a rough reconstruction of the sunspot record prior to the invention of the telescope, using indirect indicators of solar activity, and there is evidence for other Maunder minimum-like periods intermittently from about A.D. 1250 through 1715.

Other historical sunspot minima have been detected either directly or by the analysis of carbon-14 in tree rings; these include the Spörer Minimum (1450–1540), and less markedly the Dalton Minimum (1790–1820). In total there seem to have been 18 periods of sunspot minima in the last 8,000 years, and studies indicate that the sun currently spends up to a quarter of its time in these minima. One recently published paper, based on an analysis of a Flamsteed drawing, suggests that the Sun’s rotation slowed in the deep Maunder minimum (1684). The Maunder Minimum coincided with the middle — and coldest part — of the Little Ice Age, during which Europe and North America, and perhaps much of the rest of the world, were subjected to bitterly cold winters.

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