Summary: A Statistical Study of the Relationship between
the Solar Cycle Length and Tree­Ring Index
Values
Zhou Keqian 1;2
and C.J. Butler 2
1 Institute of Geography, Henan Academy of Sciences, Zhengzhou, 450052, China
2 Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland
Abstract
We have determined the correlation coefficient between tree­ring index val­
ues and the sunspot cycle length for 69 tree­ring data sets from around the
world of greater than 594 years duration. A matrix of correlation coefficients
is formed with varying delay and smoothing parameters. Similar matrices,
formed from the same data, but randomly scrambled, provide a control against
which we can draw conclusions about the influence of the solar cycle length on
climate with a reasonable degree of confidence. We find that the data confirm
an association between the sunspot cycle length and climate with a negative
maximum correlation coefficient for 80% of the data sets considered. This
implies that wider tree­rings (i.e. more optimum growth conditions) are asso­
ciated with shorter sunspot cycles. Secondly, we find that the climatic effect
of the solar cycle length is smoothed and delayed by several decades and the

Source: Armagh Observatory

Collections: Physics