If you observe the sky on a axis which is perpendicular to the direction of travel of the light, (Sun in the south, look east or west) with a polarized lens you can see the polarization. This polarization is simply due the effect of observing the "side view" of "passing" rays. The only components you can observe are vertical, thus it appears to be polarized.
When light reflects from a NON CONDUCTIVE surface the component of the incident light which is normal to the surface is adsorbed by the material. While the component which parallel to the surface is reflected. Thus the reflected light is polarized.