  We revisit the question of hemispherical power asymmetry in the WMAP and
Planck temperature sky maps by measuring the local variance over the sky and on
disks of various sizes. For the 2013 Planck sky map we find that none of the
1000 available isotropic Planck "Full Focal Plane" simulations have a larger
variance asymmetry than that estimated from the data, suggesting the presence
of an anisotropic signature formally significant at least at the $3.3\sigma$
level. For the WMAP 9-year data we find that 5 out of 1000 simulations have a
larger asymmetry. The preferred direction for the asymmetry from the Planck
data is $(l,b)=(212^\circ,-13^\circ)$, in good agreement with previous reports
of the same hemispherical power asymmetry.
