Orbital Forcing - The Changing Arctic Environment: The Arctic Messenger - page 382

3. Precession of the equinoxes:
To understand this cycle, I find it easier to temporarily forget about the variation in axial tilt.
Earth has a slow wobble as it spins on its axis. Although the angle of tilt remains the same,
the direction of tilt will vary with time around Earth's orbit (wobble) over a 23,000-year
cycle. At the present time, the direction of tilt is such that the North Pole is most inclined
away from the sun (winter solstice) at perihelion (when Earth is closest to the sun) and most
inclined towards the sun (summer solstice) at aphelion (when Earth is furthest from the sun).
However, in 11,000 years, the slow wobble will mean Earth will be most inclined away from
the sun at aphelion and most inclined towards the sun at perihelion.
The role of orbital forcing has been very important in the geological past. It is studied
today inlargepart because paleoclimate processes help usunderstand howEarth hasrespon-
ded to climate forcing. However, they do not operate on time scales that are relevant to the
climate warming that has been experienced over the last 50 or so years.