Variations in the average annual tree rings of 11 sequoia trees for 2189 years are studied. The power spectrum of tree ring variations, calculated by the Maximum Entropy Method (MEM), is power-law in character with the coefficient β close to -1.00, suggesting the fractal character of the considered time series. The calculations of the coefficient β in a 200-year sliding window showed that this coefficient rapidly drops to zero or very small positive values, indicating a break in the fractal structure in some intervals. We identified seven such episodes, two (the latest) of which correspond to Spörer and Maunder solar minima. The other five episodes, which occurred around 100 BC and 500, 700, 820, and 880 AD, i.e., before regular sunspot observations, may also correspond to climate changes. By combining methods aimed at identifying the specific spectral components, such as the Schwabe cycle and behavior of the 1/f dependence as a chaos characteristic, the chronobiologic (chronomics) approach can be used to study the global climatic processes-such as cycles of about 500 years-bearing on global warming.
- Fractal scaling (1/f dependence)
- Spörer and Maunder minima of solar activity