  In this paper, we have studied a 5-dimensional warped product space-time with
a time-dependent warp factor. This warp factor plays an important role in
localizing matter to the 4-dimensional hypersurface constituting the observed
universe and leads to a geometric interpretation of dynamical dark energy. The
five-dimensional field equations are constructed and its solutions are
obtained. The nature of modifications produced by this warp factor in the bulk
geometry is discussed. The hypersurface is described by a flat FRW-type metric
in the ordinary spatial dimension. It is found that the effective cosmological
constant of the four-dimensional universe is a variable quantity monitored by
the time-dependent warp factor. The universe is initially decelerated, but
subsequently makes a transition to an accelerated phase at later times.
