  Symbolic expressions for cosmic backreaction and mean redshift drift in a
range of 2-region models in terms of average quantities are presented. The
demonstration that these expressions can be obtained constitutes the opening of
a new avenue towards understanding the effects of cosmic backreaction in our
universe: With a symbolic expression for the redshift drift at hand, the
redshift drift can be used to constrain cosmological parameters including the
large-scale expansion rate and backreaction. In addition, by introducing
symbolic expressions for cosmic backreaction, this quantity can be constrained
with observations such as redshift-distance measures.
