As discussed in Wikipedia (Wikipedia, 2021), 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 Edward Walter Maunder (1851–1928), and his wife Annie Russell Maunder (1868–1947),who studied how sunspot latitudes changed with time. The period which the Maunders 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.
The strengthening solar output has been noted over the past 40-50 years reaching a peak coinciding with the second half of the 20th century. Entering the 21st century, solar activity appears to be falling off with a corresponding cooling effect on Earth’s climate.
Note that more intense solar activity over the period 1850-2000 presumably related to increased anthropogenic greenhouse gas emission of the industrial age also corresponds with more intense solar activity leading to the Modern Maximum peaking around the start of the 21st century.
Historically, the Sun exhibits centennial-scale activity variations. A grand solar minimum
occurs when solar activity becomes extremely weak and sunspots disappear for several decades. Such extreme solar weakening could cause severe climate, leading to massive reductions in crop yields in some regions.
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.
Indeed, the past decade saw the Sun’s activity decline.
In a recently published paper, Miyahara (2021) shows that the 11-year solar cycles were signifcantly lengthened before the onset of the Maunder Minimum (1645–1715 CE) based on unprecedentedly high-precision data of carbon-14 content in tree rings. This finding implies that fow speed in the convection zone is an essential parameter to determine long-term solar activity variations.
In fact, Myahar finds a 16 year long cycle occurred three solar cycles before the onset of prolonged sunspot disappearance, suggesting a longer-than-expected preparatory period for the grand minimum. Like the 17th century Maunder Minimum, the Sun has shown a tendency of cycle lengthening since Solar Cycle 23 (1996–2008 CE). That means the behavior of Solar Cycle 25 can be critically important to the later solar activity.
Miyahara, H., Tokanai, F., Moriya, T., Takeyama, M., Sakurai, H., Horiuchi, K., & Hotta, H. (2021). Gradual onset of the Maunder Minimum revealed by high-precision carbon-14 analyses. Scientific Reports, 11(1), s41598-021.
Wikipedia contributors. (2021, March 15). Maunder Minimum. Retrieved March 15, 2021, from Wikipedia, The Free Encyclopedia website: https://en.wikipedia.org/w/index.php?title=Maunder_Minimum&oldid=1012332673