● The episodic nature of the Earth's glacial and interglacial periods within the present Ice Age (the last couple of million years) have been causedprimarily by cyclical changes in the Earth's circumnavigation of the Sun . ● Variations in the Earth's eccentricity, axial tilt, and precession comprise the three dominant cycles, collectively known as the Milankovitch Cycles . Hence option 3 is correct. ● It is of primary importance to explain that climate change , and subsequent periods of glaciation , resulting from the following three variables is not due tothe total amount of solar energy reaching Earth. ● The three Milankovitch Cycles impact the seasonality and location of solar energy around the Earth , thus impacting contrasts between the seasons.