  We analyse the spectral variability of MCG--06-30-15 with 600 ks of
XMM-Newton data, including 300 ks of new data from the joint XMM-Newton and
NuSTAR 2013 observational campaign. We use principal component analysis to find
high resolution, model independent spectra of the different variable components
of the spectrum. We find that over 99 per cent of the variability can be
described by just three components, which are consistent with variations in the
normalisation of the powerlaw continuum (~97 per cent), the photon index (~2
per cent), and the normalisation of a relativistically blurred reflection
spectrum (~0.5 per cent). We also find a fourth significant component but this
is heavily diluted by noise, and we can attribute all the remaining spectral
variability to noise. All three components are found to be variable on
timescales from 20 ks down to 1 ks, which corresponds to a distance from the
central black hole of less than 70 gravitational radii. We compare these
results with those derived from spectral fitting, and find them to be in very
good agreement with our interpretation of the principal components. We conclude
that the observed relatively weak variability in the reflected component of the
spectrum of MCG--06-30-15 is due to the effects of light-bending close to the
event horizon of the black hole, and demonstrate that principal component
analysis is an effective tool for analysing spectral variability in this
regime.
