Why Did Earths Surface Cool?
There was both a long-term decline in temperatures, as well as an oscillation of glacial and interglacial stages. Any hypothesis for the cooling must consider both of these factors. A widely accepted hypothesis for the temperature fluctuations is related to Earth’s orbital oscillations. This hypothesis was developed by Yugoslavian mathemetician Milutin Milankovitch, and it is referred to as the Milankovitch cycles. The cyclic climatic changes result from changes in the distance and angular relationships between the Earth and Sun due to periodic fluctuations in Earth’s orbit. • Precession – Earth’s axis wobbles or moves in a circle like a spinning top over 26,000 years, affecting the amount of solar radiation received at the poles. • Orbital eccentricity – Earth’s orbit around the Sun changes from more circular to more elliptical by about 2% over about 100,000 years, moving the Earth closer to or farther from the Sun, and varying the amount of solar radiation received by the Earth. • An
