Since 88% GSM occur during an Eddy or Bray low, it is unlikely that the next GSM will take place before ~ 2600 AD, when the next Eddy cycle low is expected.

speleothems dating website-72

W/S/M correspond to the Wolff, Spörer, and Maunder minima. a) Lomb-Scargle spectrogram on C solar activity reconstruction data grouped in 2000-yr windows, showing the distribution of spectral power for the 50-125 year range. This explains why the cycle cannot be detected in the sunspot record.

The 208-year de Vries solar cycle As previously described (see The 2400-year Bray Cycle), the de Vries solar cycle is strongly modulated by the Bray solar cycle.

Until the advent of computers, tides were predicted by complex “brass brain” machines. This periodicity is interesting in that it could be related to the pentadecadal variability described in sea level pressure and temperatures in the North Pacific (Minobe 2000). Of the spectral predictions, the one published (Clilverd et al., 2006) used a low-frequency modulation model that has some clear inadequacies, like including the Gleissberg 88-year cycle that is no longer observable, assigning an extremely low amplitude to the 208-year de Vries cycle, and not including the modulation by the ~ 2400-year Bray cycle that we have discussed previously.

The first of these was built by Lord Kelvin in 1873. Besides having the same length, the pentadecadal solar change that took place at SC20 was shortly followed by the well-known and studied Pacific climate shift that took place in 1976 (Miller et al., 1994). However, since it included the 104-year Centennial periodicity, it predicted very low activity for SC24 (figure 88 c).

Wavelet analysis shows the ~ 1000-year periodicity having a strong signal between 11,500 and 4,000 yr BP, and between 2,000 and 0 yr BP, but a very low signal between 4,000 and 2,000 yr BP (figure 79; Ma 2007; Kern et al., 2012). Several authors have noticed this solar forcing dominance during the early Holocene (figure 41; Debret et al., 2007; Simonneau et al., 2014). b) Holocene record of North Atlantic iceberg activity determined by the presence of drift-ice petrological tracers. When the amplitude of the 1000-year solar signal is adjusted by its wavelet power (figure 81), a high correlation between North Atlantic iceberg activity and the 980-year Eddy solar cycle corresponds to the periods when the 1000-year solar signal is high, while the correlation is low at periods of weak 1000-year solar signal, strengthening the relationship between climatic Bond events and solar activity, that has been acknowledged by multiple authors, starting with Gerald Bond himself (Bond et al., 2001). Black curve, a 1000-year frequency cycle representing solar activity for that periodicity, whose amplitude reflects the relative power (colored bar) of that frequency in a solar activity reconstruction wavelet analysis. Two of these GSM, at 10,165 and 5,275 years BP, also coincide with the Eddy cycle, as both cycles tend to coincide in phase when two Bray cycles (4,950 years), and five Eddy cycles (4,900 years) have passed. The name refers in some cases to a GSM cluster (cl.). As originally described, the Gleissberg cycle is unacceptable by modern scientific standards (and I would dare to say inexistent), and due to it the term Gleissberg cycle means different things to different authors.

The average duration of the ~ 1000-year cycle can be calculated from the grand solar minimum at 11,115 yr BP to the one at 1,265 yr BP (dates from Usoskin et al., 2016) for ten periods at 985 years, a span in very good agreement with the calculated 970 years from frequency analysis (Kern et al., 2012) and the calculated 983.4 years from astronomical cycles (Scafetta, 2012). The 980-year Eddy cycle in solar activity reconstructions. The Bond series of North Atlantic drift-ice record reflects a clear ~ 1000-year periodicity during the first 6,500 years of the Holocene that correlates with the 980-year Eddy solar cycle (figures 48 & 80; Debret et al., 2007). The 980-year Eddy cycle correspondence to Bond events. The unusually long Roman Warm Period (2500-1600 BP; Wang et al., 2012) coincided with the final part of this interval of low Eddy solar cycle activity, while known warm and cold periods have faithfully followed the since strengthened 980-year Eddy solar cycle (figure 81). North Atlantic iceberg activity and the Eddy solar cycle. The cycle states if the GSM shows a temporal coincidence with a low from the Bray (B), or Eddy (E) cycle. For some authors it is a frequency peak of ~ 88 years that appears in frequency analysis of the cosmogenic record (Mc Cracken et al., 2013b; Knudsen et al., 2011; figure 86).

In 1862 Rudolf Wolf, after completing the first continuous record of sunspot numbers, “concluded from the sunspot observations available at that time that high and low maxima did not follow one another at random: a succession of two or three strong maxima seemed to alternate with a succession of two or three weak maxima”. Despite this precedent, most solar physicists were expecting SC24 to have a slightly lower level of activity than SC23 and were surprised by the depth and duration of the 2008 minimum and the subsequent low activity of SC24. Despite a low bias, the model predicted the current centennial minimum for cycles 24 and 25. Importantly, the model also predicted in 2006 that SC25 will again be a below average cycle of similar amplitude to SC24.

That observation lead to the suggestion of the existence of a long cycle, or secular variation, the length of which was estimated at that time to be equal to 55 years (Peristykh & Damon, 2003). Of the 54 SC24 predictions published or submitted to the SC24 Prediction Panel in six general categories, spectral analysis predictions (figure 88 a, light blue; Pesnell, 2008) based on Fourier, wavelet, or autoregressive-based forecasts, outperformed all other categories, predicting below average SC24 activity (figure 88 b). As we approach the 2019-2020 solar minimum the polar field method appears to confirm that SC25 will again be a below average solar cycle.

After identifying the spectral harmonic components from a long tidal data series at a specific port, machines that could handle up to 40 tidal constituents would produce a year of tidal predictions for that port in a few hours (Parker, 2011). However, their relation at this time is speculative. Indeed, SC24 turned out to be the least active cycle in 100 years.

The Centennial (Feynman) and Pentadecadal solar cycles. The Centennial solar cycle appears as a peak of ~ 104 years in cosmogenic isotopes frequency analysis, and as a decrease in maximum and minimum sunspot numbers at the beginning of each century since there have been telescopic sunspot observations. b) Solar Cycle 24 Panel consensus high (red curve) and low (orange curve) predictions, with the final sunspot number being lower than both. c) Average sunspot number prediction by a low-frequency modulation model (dotted curve) based on frequency analysis from sunspot and cosmogenic isotope records, compared to the average sunspot number since 1750 (continuous curve). With its faults corrected the model would have predicted accurately slightly more activity for SC24 than for SC14 (in 1904), instead of less.

The ~ 208-year de Vries cycle has been detected in ice-cores for at least the past 50,000 years (Raspopov et al., 2008b).