The question of the existence of millennial-scale climate variability and its possible impacts is important for interpreting long-term climate changes and predicting its future. In the present work a statistical analysis of the seven most recent annual reconstructions of the Northern Hemisphere temperature, covering time intervals with a length from 1260 to 2016 years, was carried out. The analysis included data of different types - both tree-ring paleo reconstructions and multi-proxies. The study was carried out using both methods of Fourier and wavelet analysis. It is shown that the yearly resolved modern temperature reconstructions indicate that in the temperature of the Northern Hemisphere of the Earth in the last 1-2 millennia there is a strong variation with a period close to 900 years. The 1400-year variation appears only in a few temperature reconstructions. Thus, the presence of a weaker 1400-year variation in the temperature of the Northern Hemisphere is not excluded but this is uncertain. The obtained difference in the spectral compositions of different data sets can be associated with: (a) the difference in the geographical location of the individual temperature indicators used, (b) the difference in the methods of standardization and generalization of the used individual proxies, (c) the difference in the seasonality of the temperature reconstructions. Although the evidence obtained for the existence of the millennial-scale variability in the climate of the Northern Hemisphere is sufficiently convincing, a concluding answer to the question of its character requires the analysis of more reconstructions that: (a) are at least several millennia-long, (b) have high time resolution, (c) use a network of individual indicators covering the largest part of the Northern Hemisphere.