geomag.usgs.gov/downloads/publications/grl50846.pdfGEOPHYSICAL RESEARCH LETTERS, VOL. 40, 4171–4176, doi:10.1002/grl.50846, 2013
On the insignificance of Herschel’s sunspot correlation
Jeffrey J. Love
1
Received 23 June 2013; revised 8 August 2013; accepted 9 August 2013; published 27 August 2013.
[
1
] 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 pro-
posed 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 corre-
lation 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 proce-
dures for evaluating hypotheses that are formulated from
historical data.
Citation:
Love, J. J. (2013), On the insignifi-
cance of Herschel’s sunspot correlation,
Geophys. Res. Lett.
,
40
,
4171–4176, doi:10.10