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Thursday, March 21, 2024

Sunspots, Lunar Cycles and Weather Cycles | Louis M. Thompson

The occurrence of an 18- to 20-year cycle in weather in the U.S. Midwest is no longer controversial. The controversial issue is the cause. This article will present both sides of the issue, and will indicate why we will know more about the cause after the 1990s.


[...] The sunspot cycle has been associated with the “20-year drought cycle” in the western U.S. since about 1909, when A.E. Douglass started publishing his tree-ring studies. This scientist became so well known that he was able to establish the Laboratory for Tree Ring Research in Tuscon, Arizona, in 1938. 
 

[...] The sunspot cycle has averaged about 11 years since 1800. As the sun rotates on its axis, it makes a complete turn in about 27 days. Large and persistent spots appear to move from left to right for about two weeks, disappear, and return after about two weeks. The leading edges of spots or clusters of spots have a negative charge in one 11-year cycle and a positive charge in the next cycle. Hence, the term “double sunspot cycle.”


The conventional wisdom is that the drought cycle of about 20 years occurs near the end of the negative cycle and at the time of low solar activity. The drought periods of the 1910s, 1930s, 1950s, and 1970s occurred at the end of the negative cycle. The drought periods did not consistently follow that pattern from 1800 to 1900, although the severe droughts of the 1820s and 1840s occurred at the end of the negative cycle.

Quoted from:
Louis M. Thompson (1989) - Sunspots and Lunar Cycles: Their Possible Relation to Weather Cycles.
In: Cycles, September/October 1989, Foundation for the Study of Cycles.
 
See also:
William Stanley Jevons (1875) - Sunspots and the Price of Corn and Wheat.
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