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    Richard Vines at |

    Bruce,

    An interesting and thoughtful piece.

    I would draw your attention also to the possible relationship between the 18.6 luni-solar cycle and the Pacific Decadal Oscillation (PDO) and Interdecadal Pacific Oscillation (IPO). An example of a publication that has aimed to draw attention to these phenomena is Impact of the astronomical lunar 18.6-yr tidal cycle on El-Niño and Southern Oscillation. See https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6185980/ .

    My late father (see – https://www.theage.com.au/national/scientist-embodied-early-csiro-values-20170616-gwsnap.html) was involved in Bushfire Research in the CSIRO in the 1960’s and early 1970s and became fascinated by the possibilities of quasi cycles across Eastern Australia. He published a very interesting paper with a US based colleague in the International JOurnal of Climatology (see https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/%28SICI%291097-0088%28199611%2916%3A11%3C1243%3A%3AAID-JOC85%3E3.0.CO%3B2-E) to hypothesise evidence for Luni-Solar and Solar Cycle signals in Australian Rainfall Data.

    Bob (my father) and Jim Noble – both ex CSIRO scientists had a short synopsis about aspects of rainfall patterns in Eastern Australia – also touching upon bushfire events in Eastern Australia – in the March 2011 Rangeland Journal newsletter (see https://web.archive.org/web/20150923124223/http://www.austrangesoc.com.au/pages/range-management-newsletter-111.html). In this there is reference to the 18.6 year cycle (if you read this, it can be noted that 2019.8 is a mid epoch year of this cycle).

    None of what I am saying here is refuted science, nor are any mechanisms understood. But as has been hypothesised

    “The 18.6-yr cycle is caused by the oscillation of the orbital surface of moon around the earth: the surface inclines 23.4° to the equatorial surface of earth on average and this inclination oscillates with the period of 18.613 years with the amplitude of 5.2°11. This 18.6-yr cycle causes the long-term modulation of oceanic tides where amplitudes of diurnal (semi-diurnal) components of K1 and O1 (M2) tides modulate by 11% and 19% (4%) respectively, and the amplitude modulation of the semi-diurnal M2 tide is out-of-phase from the diurnal (K1 and O1) tides11. This tidal modulation causes variations in oceanic vertical mixing variability” (Yasuda, 2018). See also the commentary on the 18.6 year cycle here https://en.wikipedia.org/wiki/Lunar_standstill .

    None of this is to cut across anything you are talking about in your piece. But perhaps the Luni Solar cycle adds an extra piece to your giant jig saw puzzle.

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