  A two-wave dynamo model was recently proposed by Zharkova et al. (2015, Zh15
henceforth), which aims at long-term predictions of solar activity for
millennia ahead and backwards. Here we confront the backward model predictions
for the last 800 years with known variability of solar activity, using both
direct sunspot observations since 1610 and reconstructions based on cosmogenic
radionuclide data. We show that the Zh15 model fails to reproduce the
well-established features of the solar activity evolution during the last
millennium. This means that the predictive part for the future is not reliable
either.
