Variability of the Earth’s Orbit: Astronomical Theory
The astronomical theory is built on the fact that the solar input to high northern latitudes varies over many years due to “wobbles” in the Earth’s orbit, and these variations act as a controlling factor regarding the extent of northern ice sheets. The Earth’s orbit depends on the obliquity, the eccentricity and the precession of the equinoxes. As a result, the solar input to high altitudes goes through periodic oscillations every ~22,000 years, and the amplitude varies from cycle to cycle. Simple models have been derived that aim to show how this solar input leads to the observed cycles from Ice Ages to Interglacials, but these models are highly approximate because the 22,000-year solar oscillations differ from the observed pattern of ice volume versus year.