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MILANKOVITCH CYCLES

In May 2021, I collaborated with scientific writer Rebecca Lindsay of NOAA’s Climate.gov (now Climate.us) to illustrate Milankovitch Cycles—orbital variations that affect how much of the sun’s energy reaches planet Earth. While crucial for driving natural climate changes, these orbital shifts are very slow and are not the cause of rapid modern global warming.

The most significant changes in Northern Hemisphere solar exposure come from three variations in Earth’s orbit:

  • eccentricity (every ~100,000 years): how far Earth’s orbit is from being a perfect circle.
  • precession ( every ~26,000 years): a slow rotation or “wobble” in the Earth’s axis of rotation, which changes where in the annual orbital path Northern Hemisphere summer solstice occurs
  • obliquity (every ~41,000 years): how tilted Earth’s axis of rotation is

The illustrations below help visualize the concepts.

Milankovitch Cycles: Eccentricity
Milankovitch Cycles: Precession in summer
Milankovitch Cycles: Precession in winter
Milankovitch Cycles: Tilt

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