Milankovitch Cycle

Diagram detailing Earth’s precession, and the effect over time. Source

As we all know, the Earth experiences seasons each year. These are due to the tilt of Earth’s rotational axis, which causes certain areas of the earth to receive more direct sunlight during parts of the year, which has obvious effects on yearly climate.

Interestingly, the Earth’s seasons also shift around on the calendar year. Eventually, summer in the Northern Hemisphere will take place during December and January and the winter solstice will take place in July. This phenomenon is known as the Milankovitch Cycle.

Over a long period of time the Earth’s eccentric orbit around the Sun changes orientation due in part to the Apsidal precession of the Earth. In a normal orbit, the Earth is closest to the Sun during January but over time this will change. When the Earth is closer to the Sun, it receives a larger amount solar radiation. This small difference in solar radiation the Earth receives at the closest and furthest points creates a slight change in overall climate patterns. In a single year, this change is not terribly noticeable, but over the scale of 100,000 years, the changes in climate become more significant.

So what does solar radiation have to do with the Milankovitch cycle? As Earth’s eccentric orbit changes its orientation, different parts of the Earth receive the more direct solar radiation. This matters because it has a huge long term effect on global climate processes such as glaciation. Understanding that the position of Earth’s tilt will change over time can lead scientists to study periods of Earth’s history (such as the Ice Ages) in a different light, or make predictions about the long term climate future of the planet.