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On the insignificance of Herschel's sunspot correlation

Geophysical Research Letters

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DOI: 10.1002/grl.50846

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Abstract

We examine William Herschel's hypothesis that solar-cycle variation of the Sun's irradiance has a modulating effect on the Earth's climate and that this is, specifically, manifested as an anticorrelation between sunspot number and the market price of wheat. Since Herschel first proposed his hypothesis in 1801, it has been regarded with both interest and skepticism. Recently, reports have been published that either support Herschel's hypothesis or rely on its validity. As a test of Herschel's hypothesis, we seek to reject a null hypothesis of a statistically random correlation between historical sunspot numbers, wheat prices in London and the United States, and wheat farm yields in the United States. We employ binary-correlation, Pearson-correlation, and frequency-domain methods. We test our methods using a historical geomagnetic activity index, well known to be causally correlated with sunspot number. As expected, the measured correlation between sunspot number and geomagnetic activity would be an unlikely realization of random data; the correlation is “statistically significant.” On the other hand, measured correlations between sunspot number and wheat price and wheat yield data would be very likely realizations of random data; these correlations are “insignificant.” Therefore, Herschel's hypothesis must be regarded with skepticism. We compare and contrast our results with those of other researchers. We discuss procedures for evaluating hypotheses that are formulated from historical data.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
On the insignificance of Herschel's sunspot correlation
Series title:
Geophysical Research Letters
DOI:
10.1002/grl.50846
Volume
40
Issue:
16
Year Published:
2013
Language:
English
Publisher:
Wiley
Contributing office(s):
Geomagnetism Program
Description:
6 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Geophysical Research Letters
First page:
4171
Last page:
4176