The ellipticity of the earth’s orbit varies over a 100,000 year cycle. This changes the solar flux received at the earth by as much as 30%. Milankovitch cycles Named after the man who proposed them as the explanation of the ice ages in the Pleistocene. These are variations in the Earth’s orbit and inclination.
Further, the tilt of the earth’s axis changes slightly over a 40,000 year cycle
The tilt angle of the Earth also show precession