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The Maunder Minimum shown in a 400-year history of sunspot numbers
The Maunder Minimum, also known as the "prolonged sunspot minimum", is the name used for the period around 1645 to 1715 during which sunspots became exceedingly rare, as was then noted by solar observers.
The term was introduced after John A. Eddy published a landmark 1976 paper in Science. Astronomers before Eddy had also named the period after the solar astronomers Annie Russell Maunder (1868-1947) and her husband, Edward Walter Maunder (1851-1928), who studied how sunspot latitudes changed with time. The period which the spouses examined included the second half of the 17th century.
Two papers were published in Edward Maunder's name in 1890 and 1894, and he cited earlier papers written by Gustav Spörer. Because Annie Maunder had not received a university degree, restrictions at the time caused her contribution not to be publicly recognized. Spörer noted that, during a 28-year period (1672-1699) within the Maunder Minimum, observations revealed fewer than 50 sunspots. This contrasts with the typical 40,000-50,000 sunspots seen in modern times (over similar 25 year sampling).
The Maunder Minimum occurred with a much longer period of lower-than-average European temperatures which is likely to have been primarily caused by volcanic activity.
Visibility is somewhat affected by observations being done from the ecliptic.
The ecliptic is inclined 7° from the plane of the Sun's equator (latitude 0°).
Little Ice Age
Comparison of group sunspot numbers (top), Central England Temperature (CET) observations (middle) and reconstructions and modeling of Northern Hemisphere Temperatures (NHT). The CET in red are summer averages (for June, July and August) and in blue winter averages (for December of previous year, January and February). NHT in grey is the distribution from basket of paleoclimate reconstructions (darker grey showing higher probability values) and in red are from model simulations that account for solar and volcanic variations. By way of comparison, on the same scales the anomaly for modern data (after 31 December 1999) for summer CET is +0.65oC, for winter CET is +1.34oC, and for NHT is +1.08oC. Sunspot data are as in supplementary data to  and Central England Temperature data are as published by the UK Met Office  The NHT data are described in box TS.5, Figure 1 of the IPCC AR5 report of Working Group 1.
The Maunder Minimum roughly coincided with the middle part of the Little Ice Age, during which Europe and North America experienced colder than average temperatures. Whether there is a causal relationship, however, is still under evaluation. The current best hypothesis for the cause of the Little Ice Age is that it was the result of volcanic action. The onset of the Little Ice Age also occurred well before the beginning of the Maunder minimum, and northern-hemisphere temperatures during the Maunder minimum were not significantly different from the previous 80 years, suggesting a decline in solar activity was not the main causal driver of the Little Ice Age.
The correlation between low sunspot activity and cold winters in England has recently been analyzed using the longest existing surface temperature record, the Central England Temperature record. They emphasize that this is a regional and seasonal effect relating to European winters, and not a global effect. A potential explanation of this has been offered by observations by NASA's Solar Radiation and Climate Experiment, which suggest that solar UV output is more variable over the course of the solar cycle than scientists had previously thought. In 2011, an article was published in the Nature Geoscience journal that uses a climate model with stratospheric layers and the SORCE data to tie low solar activity to jet stream behavior and mild winters in some places (southern Europe and Canada/Greenland) and colder winters in others (northern Europe and the United States). In Europe, examples of very cold winters are 1683-84, 1694-95, and the winter of 1708-09.
The term "Little Ice Age" applied to the Maunder minimum is something of a misnomer, as it implies a period of unremitting cold (and on a global scale), which was not the case. For example, the coldest winter in the Central England Temperature record is 1683-1684, but summers during the Maunder minimum were not significantly different from those seen in subsequent years. The drop in global average temperatures in paleoclimate reconstructions at the start of the Little Ice Age was between about 1560 and 1600, whereas the Maunder minimum began almost 50 years later.[original research?]
Solar activity events recorded in radiocarbon.
Graph showing proxies of solar activity, including changes in sunspot number and cosmogenic isotope production.
Past solar activity may be recorded by various proxies, including carbon-14 and beryllium-10. These indicate lower solar activity during the Maunder Minimum. The scale of changes resulting in the production of carbon-14 in one cycle is small (about one percent of medium abundance) and can be taken into account when radiocarbon dating is used to determine the age of archaeological artifacts. The interpretation of the beryllium-10 and carbon-14 cosmogenic isotope abundance records stored in terrestrial reservoirs such as ice sheets and tree rings has been greatly aided by reconstructions of solar and heliospheric magnetic fields based on historic data on Geomagnetic storm activity, which bridge the time gap between the end of the usable cosmogenic isotope data and the start of modern spacecraft data.
Other historical sunspot minima have been detected either directly or by the analysis of the cosmogenic isotopes; these include the Spörer Minimum (1450-1540), and less markedly the Dalton Minimum (1790-1820). In a 2012 study, sunspot minima have been detected by analysis of carbon-14 in lake sediments. 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.
A paper based on an analysis of a Flamsteed drawing, suggests that the Sun's surface rotation slowed in the deep Maunder minimum (1684).
During the Maunder Minimum aurorae had been observed seemingly normally, with a regular decadal-scale cycle. This is somewhat surprising because the later, and less deep, Dalton sunspot minimum is clearly seen in auroral occurrence frequency, at least at lower geomagnetic latitudes. Because geomagnetic latitude is an important factor in auroral occurrence, (lower-latitude aurorae requiring higher levels of solar-terrestrial activity) it becomes important to allow for population migration and other factors that may have influenced the number of reliable auroral observers at a given magnetic latitude for the earlier dates. Decadal-scale cycles during the Maunder minimum can also be seen in the abundances of the beryllium-10 cosmogenic isotope (which unlike carbon-14 can be studied with annual resolution)  but these appear to be in antiphase with any remnant sunspot activity. An explanation in terms of solar cycles in loss of solar magnetic flux was proposed in 2012.
The fundamental papers on the Maunder minimum have been published in Case studies on the Spörer, Maunder and Dalton Minima.
^ abMiller et al. 2012. "Abrupt onset of the Little Ice Age triggered by volcanism and sustained by sea-ice/ocean feedbacks" Geophysical Research Letters39, 31 January; see press release on AGU website (retrieved 16 July 2015).
^Owens; et al. (2017). "The Maunder Minimum and the Little Ice Age: An update from recent reconstructions and climate simulations". Space Weather and Space Climate. 7 (A33): A33. doi:10.1051/swsc/2017034.