  The compactification of M theory with time dependent hyperbolic internal
space gives an effective scalar field with exponential potential which provides
a transient acceleration in Einstein frame in four dimensions. Ordinary matter
and radiation are present in addition to the scalar field coming from
compactification. We find that we have to fine-tune the initial conditions of
the scalar field so that our Universe experiences acceleration now. During the
evolution of our Universe, the volume of the internal space increases about 12
times. The time variation of the internal space results in a large time
variation of the fine structure constant which violates the observational
constraint on the variation of the fine structure constant. The large variation
of the fine structure constant is a generic feature of transient acceleration
models.
