Beam me to Planet Gore !
It is the ultimate lib gob stopper. Astronomers and Physicists have relied upon the model for decades. Archaeologists know it. Paleontologists know it. Paleoclimatologists know it. The only people who don't know it are environmentalists of the liberal persuasion.
The "it" is that in it's cyclical travels around the sun, Earth's orbital shape changes, axial tilt changes, and polar precession changes. These multi-millenial cycles govern how much solar radiation reaches Earth, and where.