 Axial procession, or wobble, refers to the direction the axis of rotation is pointed. As the earth rotates, it wobbles slightly upon its axis, similar to an off-center spinning top. This wobble is due to tidal forces caused by the gravitational influences of the sun and moon. The cycle of axial procession spans around 26,000 years. Axial procession makes seasonal contrasts more extreme in one hemisphere and less extreme in the other. Currently, southern hemisphere seasonal variations are extreme, while in the northern hemisphere seasonal variation is more moderate. In about 13,000 years, axial procession will cause these conditions to flip, with the northern hemisphere seeing more extreme seasonal variations and the southern hemisphere experiencing more moderate seasonal variations. Together, the cycles of earth's eccentricity, obliquity and procession are known as the Malankovitch cycles after the scientists that studied them. They are responsible for long-term changes in earth's climate, such as glacial interglacial cycles. However, it is important to note that these cycles are not responsible for earth's current warming trends.