There's an annual wobble component. What is that due to? Of course it's due to the annual solar cycle. End of that story because it can't be due to anything else. The non-annual wobble component is known as the Chandler wobble. That follows precisely from the synching of the moon and the sun. What are the odds that these two wobbles are PRECISELY predicted by the EXACT lunar and solar nodal cycles just by chance?
If I measured a 60 Hz hum in the output of an amplifier, I'm not going to waste my time trying to find a resonance in a circuit that matches 60 Hz when I know darn well that the 60 Hz is likely being picked up via the line voltage and passed to the output as a forced response. Let's use some common sense here -- the gyrations that these geophysicists go through to rationalize a root cause is laughable.