Variations in the annual radial growth of fossil trees (a palaeoclimatic indicator of the environment) that grew in the Gobi Desert (Mongolia) about 100–150 million years ago are considered. By using the method of combined spectral periodogriams of variations in the ring widths of fossil samples, quasi-harmonic components with the periods similar to basic solar activity cycles of our days have been revealed. This suggests that the Earth’s climate is influenced by the solar activity over large time scales.