Radiocarbon abundances in tree rings from the Spoerer minimum

Year-by-year measurements of the radiocarbon ( 14 C) content of tree rings formed during the Spoerer min- imum (1414-1534 AD) have been carried out with an accu- racy of 0.3 %. The measurements were made using the liquid scintillation method. Liquid benzene samples of 10 ml were prepared from single-year tree ring samples of 70 g taken from a 700 year-old Yaku cedar tree. The absolute year was determined using the bomb effect, which has its peak of ra- diocarbon content in 1964. Our first results of year-by-year measurements of 14 C con- tent in the tree ring samples between 1410 and 1480 AD agree well with the pioneering work of Stuiver et al., which was obtained by combining tree rings of 10 years.