What is the primary cause of global temperature variations?

Written by Monte Heib, P.E.

Natural variations in global temperatures may occur in roughly 500-year cycles:

The primary cause of variations in global temperature is the cycles of the sun and Earth's orbit about the sun. In addition to 40-year cycles and 500-year cycles, other temperature cycles include:

• 21,000 - year cycle: Elliptical orbit of the Earth around the Sun (precession of the equinoxes)
• 41,000 - year cycle: Cycle of the +/- 1.5 degree wobble in Earth's orbit
• 100,000 - year cycle: Variations in the shape of Earth's elliptical orbit (cycle of eccentricity)