Natural periodic processes and climate variability in the Northern Hemisphere

Decomposition of five different paleoclimatic reconstructions of regional and hemispheric scale into different frequency periodic components has been performed for the extratropical zone of the Northern Hemisphere using spectral analysis methods (Hilbert–Huang transformation, wavelet transform, Fourier transform). The presence of ~1000, ~500, ~350, and ~200-year quasi-cyclic periodicities has been established, which determines climatic variability over the last 2–4 millennia. The presence of similar cyclicities, manifested in climatic and other geological processes, has been noted by many researchers and has been explained, as a rule, by changes in solar insolation. Thus, there is every reason to believe that the revealed quasi-periodic components in the climate variability of the extratropical zone of the Northern Hemisphere are natural, conditioned by natural cyclical phenomena and can serve as a basis for long-term predictive climatic constructions.