«Bias might be introduced
in cases where the spatial coverage is not uniform (e.g., of the 24 original chronologies with data back to 1500, half are concentrated
in eastern Siberia) but this can be reduced by prior averaging of the chronologies into regional series (as was done
in the previous section)... Eight different methods have been used... They produce very similar results for the post-1700 period... They exhibit fairly
dramatic differences, however,
in the magnitude of multidecadal variability prior to 1700... highlighting the sensitivity of the reconstruction to the methodology used, once the
number of regions with data, and the reliability of each regional reconstruction, begin to decrease.