Solar Activity during Two Millennia as Estimated from Annual Tree Rings

TL;DR

This study analyzes tree rings from Japan over two millennia to investigate solar activity's influence on climate, revealing periodic cycles and correlations with glacier fluctuations, thus providing long-term climate insights.

Contribution

It introduces a novel long-term solar activity reconstruction from tree rings across multiple Japanese sites, identifying specific periodicities and correlations with glacier data.

Findings

Fourier analysis revealed 12- and 25-year cycles during the Maunder minimum.

Consistent evidence of solar activity signals across different Japanese samples.

Correlation found between Swiss glacier fluctuations and Yaku tree ring growth.

Abstract

The relationship between solar activity and the global climate is not only an academically interesting issue, but also an important problem for human beings. Lean and Rind have analyzed a considerable amount of climate data from around the world from 1889 to 2006. According to their analysis, the global effect was estimated to be 0.17 plus-minus 0.01K between the solar maximum and minimum. However, they noticed that the effect strongly appeared in the zones between 70N and 30N, and between 25S and 50S. At its peak latitude (near 40), the effect was estimated to be 0.5 K. Therefore, we analyzed a tree that survived at the Murooji temple in Nara prefecture (34d32mN, 136d2mE) Japan, for 391 years. Quite surprisingly, Fourier analysis of the annual growth rate identified two cycles with periodicities of 12 and 25 years during the Maunder minimum. We have continued the analysis, using different samples from the Nagusa shrine in Hyogo Prefecture, Itayanagi City, Aomori Prefecture, Japan, and from Yaku Island in Kyusyu, Japan. An evidence of solar activity was found in all of the samples. In particular, we have discovered a correlation between Swiss glacier fluctuation and the growth rate of the Yaku tree ring.