Fossil forest reveals sunspot activity in the Early Permian

Modern-day periodic climate pattern variations related to solar activity are well known. High-resolution records such as varves, ice cores, and tree-ring sequences are commonly used for reconstructing climatic variations in the younger geological history. For the first time we apply dendrochronological methods to Paleozoic trees in order to recognize annual variations. Large woody tree trunks from the early Permian Fossil Forest of Chemnitz, southeast Germany, show a regular cyclicity in tree-ring formation. The mean ring curve reveals a 10.62 yr cyclicity, the duration of which is almost identical to the modern 11 yr solar cycle. Therefore, we speculate and further discuss that, like today, sunspot activity caused fluctuations of cosmic radiation input to the atmosphere, affecting cloud formation and annual rates of precipitation, which are reflected in the tree-ring archive. This is the earliest record of sunspot cyclicity and simultaneously demonstrates its long-term stable periodicity for at least 300 m.y.