A somewhat forgotten paper by Glenn Brier from 1989 demonstrates that ENSO is not as random as some think

http://contextEarth.com/2016/09/09/obscure-paper-on-enso-determinism/

Brier finds 6.75 and 14 year periods in the historical data going back to the 1525. My model finds the strongest periods at 6.5 and 14 years from 1880 until current.

Brier's paper only has 10 citations. That's probably why I didn't uncover it until now, and only thought to look more deeply because Brier always has interesting ideas.