Retrospective evaluation of spectral irradiances obtained during the last 10 years at wavelengths relevant to the photodissociation of molecular oxygen provides an indication of the accuracy and precision of the information currently available. In the spectral region of wavelengths less than 175 nm corresponding to the O2 Schumann-Runge continuum which is absorbed in the thermosphere, all the observational results are not reliable since the global accuracy is of the order of ± 50%. In the spectral region 175-200 nm of the Schumann-Runge bands, mainly absorbed in the mesosphere, the uncertainties of all available data are not less than 20-30% and make it impossible to determine the exact solar activity effect on the O2 photodissociation rate. The available measurements for the spectral region associated with the O2 Herzberg continuum, 200-240 nm, relevant to the stratosphere have typical uncertainty limits reaching ± 10% with additional random errors of ± 10% for 1 nm intervals. The general accuracy is not yet sufficient to infer the exact part in the irradiance changes associated with solar variability. A consistent reference spectrum for a better assessment must be, therefore, adopted to describe the complex behavior displayed by the spectral solar irradiances in the spectral ranges of the photodissociation of O2.