ESS101C
Prof.
Jin-Yi Yu
Tilt Change (Obliquity Variation)
qOver time, the tilt angle varies
in a narrow range
(22.2° ~ 24.5°).
qThese variations are caused by
the gravitational
tug of large planets, such as Jupiter.
qThe present-day value of the
tile is decreasing.
qCyclic changes in the tilt angle
occur at a period of
41,000 years.
qChanges in tilt cause long-term
variations in seasonal solar insolation received on Earth.
qThe main effect of tilt changes
is to amplify or suppress the seasons: increase tilt amplifies seasonal differences, decreased
tilt reduces them.
(from Earth’s Climate: Past and Future)