  We examine anharmonic contributions to the optical phonon modes in bulk
$T_d$-MoTe$_2$ through temperature-dependent Raman spectroscopy. At
temperatures ranging from 100 K to 200 K, we find that all modes redshift
linearly with temperature in agreement with the Gr\"{u}neisen model. However,
below 100 K we observe nonlinear temperature-dependent frequency shifts in some
modes. We demonstrate that this anharmonic behavior is consistent with the
decay of an optical phonon into multiple acoustic phonons. Furthermore, the
highest frequency Raman modes show large changes in intensity and linewidth
near $T\approx 250$ K that correlate well with the $T_d \to 1T^\prime$
structural phase transition. These results suggest that phonon-phonon
interactions can dominate anharmonic contributions at low temperatures in bulk
$T_d$-MoTe$_2$, an experimental regime that is currently receiving attention in
efforts to understand Weyl semimetals.
