Comment on “Millennium Scale Sunspot Number Reconstruction: Evidence for an Unusually Active Sun Since the 1940s”

A Comment on the Letter by Ilya G. Usoskin et al., Phys. Rev. Lett. 91, 211101 (2003). The authors of the Letter offer a Reply.

Figure 1

${}^{10}\mathrm{Be}$ concentration in ice from the South Pole [2]. The horizontal line represents the average concentration in the samples representing ice from $\sim 1940–1984$.