  We employ the Delta-variance analysis and study the turbulent gas dynamics of
simulated molecular clouds (MCs). Our models account for a simplified treatment
of time-dependent chemistry and the non-isothermal nature of the gas. We
investigate simulations using three different initial mean number densities of
n_0 = 30, 100 and 300 cm^{-3} that span the range of values typical for MCs in
the solar neighbourhood. Furthermore, we model the CO line emission in a
post-processing step using a radiative transfer code. We evaluate
Delta-variance spectra for centroid velocity (CV) maps as well as for
integrated intensity and column density maps for various chemical components:
the total, H2 and 12CO number density and the integrated intensity of both the
12CO and 13CO (J = 1 -> 0) lines. The spectral slopes of the Delta-variance
computed on the CV maps for the total and H2 number density are significantly
steeper compared to the different CO tracers. We find slopes for the
linewidth-size relation ranging from 0.4 to 0.7 for the total and H2 density
models, while the slopes for the various CO tracers range from 0.2 to 0.4 and
underestimate the values for the total and H2 density by a factor of 1.5-3.0.
We demonstrate that optical depth effects can significantly alter the
Delta-variance spectra. Furthermore, we report a critical density threshold of
~100 cm^{-3} at which the Delta-variance slopes of the various CO tracers
change sign. We thus conclude that carbon monoxide traces the total cloud
structure well only if the average cloud density lies above this limit.
