You'd be wrong about that (although I agree with you overall). I've been posting for some years, here, for discussion, those graphs going back many hundreds of thousands of years, or even millions of years. Here's a link to one:
https://upload.wikimedia.org/wikipedia/commons/thumb/f/f7/Five_Myr_Climate_Change.svg/1280px-Five_Myr_Climate_Change.svg.png
(By Dragons flight (Robert A. Rohde), svg by Jo - svg-version of Five_Myr_Climate_Change.png; original image by User:Dragons flight, based on data (figure 4?) from Lisiecki and Raymo (2005), CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=5891468)
Note the change in cycle periods starting about 1 million years ago, and note the increasingly wild oscillations in general.
Oops - 1st line was supposed to be a quote...