  A Galton-Watson process in a varying environment is a discrete time branching
process where the offspring distributions vary among generations. It is known
that in the critical case, these processes present a Yaglom limit, that is, a
suitable normalization of the process conditioned on non-extinction converges
in distribution to a standard exponential random variable. In this manuscript,
we provide the rate of convergence of the Yaglom limit with respect to the
Wasserstein metric.
