As we've seen, it is the tilt of the Earth's axis which causes the height of the Sun's path to change.
(we; 've seen; ) (it; is; the tilt of the Earth's axis) (the tilt of the Earth's axis; causes; the height of the Sun's path)
we it the tilt of the Earth's axis
've seen is causes
the tilt of the Earth's axis
the height of the Sun's path