What are Milankovitch cycles?

A:

The Milankovitch (or Milankovich) Theory describes the collective effects of changes in the earth's movements upon its climate. A cycle of precession lasts 26,000 years. At the same time, there is a cycle in which the earth's elliptical orbit rotates. The angle between Earth's rotational axis and the normal to the plane of its orbit oscillates between 22.1 and 24.5 degrees on a 41,000-year cycle. The combined effect of these and other cycles can produce a long-term cycle in the amount of warmth received from the sun.

Milankovitch cycles operate over the very long term and have great value as a theory to explain ice ages and long-term changes in the climate, but are unlikely to have very much impact on the decade-century timescale. Over several centuries, it may be possible to observe the effect of these orbital parameters, however for the prediction of climate change in the twenty-first century, these changes are considered far less important than radiative forcing from greenhouse gases.