Up to now we have considered the effect of Raman scattering on Fraunhofer lines. These absorption lines in the spectrum of solar radiation result from absorptions that took place before the sunlight reached the Earth, generally in the Sun's atmosphere.

A second, more subtle effect of Raman scattering arises from the change of wavelength it causes after absorption processes have taken place in the Earth's atmosphere.

As differential absorption spectroscopy is based on the relative loss of photons at different wavelengths (the Beer-Lambert Law), a change in wavelength disrupts the proportionality between the number of absorbing molecules and the logarithm of the intensity. In effect, some photons of a particular wavelength that were not absorbed have their wavelength shifted as a result of Raman scattering and subsequently, therefore, are counted as not-absorbed photons at the new wavelength. Photons from outside the absorber wavelength range can be shifted by Raman scattering into that range and thus mask the true degree of absorption.

One could say that Raman scattered photons lose the 'memory' of the absorption that took place before the scattering process, and therefore the total amount of absorption is underestimated in an atmosphere with Raman scattering.