  The universality of interstellar turbulence is examined from observed
structure functions of 27 giant molecular clouds and Monte Carlo modeling. We
show that the structure functions, dv=v0 l^gamma, derived from wide field
imaging of CO J=1-0 emission from individual clouds are described by a narrow
range in the scaling exponent, gamma, and the scaling coefficient, v0. The
similarity of turbulent structure functions emphasizes the universality of
turbulence in the molecular interstellar medium and accounts for the
cloud-to-cloud size-line width relationship initially identified by Larson
(1981). The degree of turbulence universality is quantified by Monte Carlo
simulations that reproduce the mean squared velocity residuals of the observed
cloud-to-cloud relationship. Upper limits to the variation of the scaling
amplitudes and exponents for molecular clouds are ~10-20%. The measured
invariance of turbulence for molecular clouds with vastly different sizes,
environments, and star formation activity suggests a common formation mechanism
such as converging turbulent flows within the diffuse ISM and a limited
contribution of energy from sources within the cloud with respect to large
scale driving mechanisms.
