Spaceborne radiometric measurements of the L band brightness temperature over the oceans make it possible to estimate sea surface salinity. However, Faraday rotation in the ionosphere disturbs the signals and must be corrected. Two different ways of assessing the disturbance directly from the radiometric measurements, and hence enabling a correction for the effect, are being discussed. Also, a method, which aims at circumventing the problem by using the first Stokes parameter in the salinity retrieval, is being discussed.