evidence: Natural Causes of Climate Change The Milankovitch Theory explains the 3 cyclical changes in Earth’s orbit and tilt that cause the climate fluctuations that occur over tens of thousands of years to hundreds of thousands of years. You have learned about these orbital changes in the Temperature over Time module. These fluctuations include changes in the shape (eccentricity) of Earth’s orbit every ~100,000 years, the tilt (obliquity) of Earth’s axis every ~41,000 years, and the wobbling (precession) of Earth’s axis about ~23,000 years. Milankovitch proposed that glacial periods began when the three cycles align to favor an extended period of more solar radiation in the winter and less solar radiation in the summer at a latitude of 65°N. These conditions for the northern latitudes favor somewhat higher temperatures, but also more water vapor in the air – causing more snowfall. A relatively cool summer for the northern latitudes favors less melting of winter snow and glacier formation. [...] Variation in Solar Radiation