Orbital Forcing - The Changing Arctic Environment: The Arctic Messenger - page 381

2. Obliquity (axial tilt):
The tilt or inclination of Earth's axis of rotation in relation to the plane of the orbit around
the sun oscillates between 21.5 and 24.5° and with a periodicity of about 41,000 years. The
greater the tilt, the greater is the difference between our seasons. At present, we are located
roughly in the middle of the obliquity cycle.