Random observation, or an aside: Tierney, Haywood, Feng, Bhattacharya, and Otto-Bliesner have a paper accepted in _GRL_, which addresses, in the negative, the idea from Fedorov, _et_ _al_ (2006, 2010) of "permanent El Nino in the early Pliocene epoch". The paper is:

J. E. Tierney, A. M. Haywood, R. Feng, T. Bhattacharya, B. L. Otto-Bliesner, [Pliocene warmth consistent with greenhouse gas forcing](https://sci-hub.tw/10.1029/2019GL083802), _[Geophysical Research Letters](https://agupubs.onlinelibrary.wiley.com/journal/19448007)_ (2019).