The whole concept of 'oceanic-atmospheric oscillations' is one where the climate data community went off the rails a bit. In general climate models + observational data demonstrate convincingly that fossil-fuel-sourced CO2 and CH4 are steadily warming the planet at a rate best measured in decades - but the various 'oscillations' that were extracted from climate data aren't anywhere near as robust.
The heart of the problem is that the Fourier approach to time series analysis - which has worked extremely well is the astronomical domain, where the underlying physical model (planetary orbits) is definitely periodic, runs into problems when you apply it to data that has a more turbulent or chaotic character. Messing with the parameters can extract apparently periodic phenomena from large datasets that are really little more than artifacts.
Many of the supposed discoveries of periodic oscillations in the North Atlantic and the Pacific simply don't hold up over time, and as with ENSO, have zero predictive power over what phase/amplitude of the next 'period of the oscillation' will be. These phenomena are likely mostly chaotic in nature, not i.e. not subject to long-term predictability (unlike, say, the tides are) and should really be called 'fluctuations' instead of 'oscillations'.
The heart of the problem is that the Fourier approach to time series analysis - which has worked extremely well is the astronomical domain, where the underlying physical model (planetary orbits) is definitely periodic, runs into problems when you apply it to data that has a more turbulent or chaotic character. Messing with the parameters can extract apparently periodic phenomena from large datasets that are really little more than artifacts.
Many of the supposed discoveries of periodic oscillations in the North Atlantic and the Pacific simply don't hold up over time, and as with ENSO, have zero predictive power over what phase/amplitude of the next 'period of the oscillation' will be. These phenomena are likely mostly chaotic in nature, not i.e. not subject to long-term predictability (unlike, say, the tides are) and should really be called 'fluctuations' instead of 'oscillations'.