I refer to this article on nytimes.com: Every 202,500 Years, Earth Wanders in a New Direction
TLDR: Scientists believe the earth's orbit oscillates between circular and more elliptical due to the gravitational pull from Jupiter (big) and Venus (close). It takes 405k years to complete a cycle.
The big question: could this affect climate-change? Could it make colder winters, hotter summers or just more extreme weathers? Changing Gulf stream?