qOrbital-scale climate changes are
caused by subtle shifts in Earth’s orbit.
qThree features of Earth’s orbit around the Sun have changed over
time:
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(1) the tilt of Earth’s axis,
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(2) the shape of its yearly path of revolution around the Sun
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(3) the changing positions of the seasons along the path.
qOrbital-scale climate changes have typical cycles from 20,000 to
400,000 years.