PaulP: "No evidence (QBO and ENSO are obviously hypercomplex multi-chaos cases)...by punting the football and suggesting that the solutions are chaotic means that one has prematurely eliminated all the non-linear possibilities"
The evidence is the large number of critically interacting multi-physics dimensions, resulting in noisy geophysical data that no simple model can well account for. The applicable math is canonically hypercomplex.
(Multi) Chaos is highly non-linear. Chaos science is hardly "punting", nor "premature elimination". It has a distinguished history in geophysical modeling, from Poincaré to Lorenz, to the present. Chaos may be computationally intractable for accurate long range geophysical prediction, but dismissing ENSO-QBO chaos by invoking football better suggests punting.