  Recent data from ATIC, CREAM and PAMELA indicate that the cosmic ray energy
spectra of protons and nuclei exhibit a remarkable hardening at energies above
100 GeV per nucleon. We propose that the hardening is an interstellar
propagation effect that originates from a spatial change of the cosmic-ray
transport properties in different regions of the Galaxy. The key hypothesis is
that the diffusion coefficient is not separable into energy and space variables
as usually assumed. Under this scenario, we can reproduce the observational
data well. Our model has several implications for the cosmic-ray
acceleration/propagation physics and can be tested by ongoing experiments such
as the Alpha Magnetic Spectrometer or Fermi/LAT.
