Thanks for load of reading guys,
I can't keep all this in my head so I'm having to summarise the El Nino paper refs. I cited above before I could possibly get a straight and up-to-date story.
> I am not comfortable at all with EOFs for instance.
Have you commented on this somewhere?
I agree that a volumetric model of the Pacific warm pool and its shearing of teleconnections seems like a necessary condition of a physical explanation. Do you know what arguments might be or are used to justify using the shallow water equations for changes in thermocline depth.
I took it as an implication of the Ludescher et al. paper that meridional effects are important in convergence of Rossby waves.
Wrt. neural networks I've only got as far as a list of the problems associated with trying to use them on 3D data.