Our good friend Vukcevic has just posted on a WUWT open thread this spectral analysis of the signed sunspot cycle (solar magnetic cycle) compared to land and sea surface temperature, and the Earth’s geomagnetism. I trust he will be along to explain a little further.
The red arrow specifies the length of the 18.6 year Lunar nodal cycle.
Vuk offers a possible explanation:
This is controversial, highly speculative, possible coincidence, so if any of this is not ‘your cup of tee’ then stop reading here and go to the next person’s comment.
I keep telling myself ‘don’t believe in coincidences, there must be reason for what we observe’.
Some time ago I plotted this graph of various spectral responses:
What is unusual here is the spectrum of the ‘Solar Magnetic Cycle’, which is derived from sunspot cycle (odd cycles negative polarity, even cycles positive polarity).
There is the obvious peak at just under 22 years as expected, and again as expected 11 year peak has disappeared.
Problem is the second strongest peak around 18.5 years. Some will recognize this as a luni-solar cycle, very prominent and important in the sea and ocean tides (induces an extra variability of about 7%).
Since moon can not affect sunspot count, question is what is going on here. There is only one possible explanation (excluding sunspot observers mental capacity, being affected by lunar phases) which I put as following:
Sunspot count is affected by the size of a sunspot (larger spots are given higher weighting).
If luni-solar cycles cause hydrosphere tidal distortions it wouldn’t be unreasonable to expect same effect on the atmosphere, this could cause kind of ‘lensing’ effect combined with the observing telescope optics resulting in all sunspots appearing a bit larger then normal, enhancing the sunspot count.
This may be totally irrelevant to solar max-min numbers, but may not be irrelevant to the climatic events if the Earth’s atmosphere is pulsating to the tune with 18.5 year period to an extent of 7% of its density. This would not be observed in the atmospheric pressure measurements since column of the air at the ‘high tide’ would increase its height but reduce its density, unlike water which is not ‘stretchable’ .