ocr: The long ferm variatons in the fotal irradiance may have caused the ice ages. Also the changes in eccentricity in the Earth's orbit and the changes in Earth's axis' tilt infiuence the global long ferm weather (see Milankovitch - theo- ry). One move reason to ice ages is continental drifting (pushing continents toward polar regions) together with tectonic movements of large land masses to higher latitudes.
