  I review several different calculations, coming from string theory,
nonperturbative quantum gravity and analyses of black holes that lead to
predictions of phenomena that would uniquely be signatures of quantum
gravitational effects.
  These include: 1) deviations from a thermal spectra for evaporating black
holes, 2) upper limits on the entropy and energy content of bounded regions, 3)
suppression of ultra-high energy scattering amplitudes, consistent with a
modified uncertainty principle, 4) physical volumes and areas have discrete
spectra, 5), violations of $CPT$ and universal violations of $CP$, 6) otherwise
inexplicable conditions on the initial state of the universe or otherwise
inexplicable correlations between cosmological and microscopic parameters.
Consideration of all of these together suggests the possibility of connections
between perturbative and nonperturbative approaches to quantum gravity.
