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.

by Javier Summary: Holocene climate has been affected in different periods by several centennial to millennial solar cycles. The 980-year solar cycle was named the Eddy cycle by Abreu et al. For about a millennium centered in each Bray cycle low, the de Vries cycle reduces solar activity every ~ 208 years, and when a cluster of GSM takes place, it establishes the average spacing between them (figure 61). The modulation of the de Vries cycle by the Bray cycle is also apparent in the climatic data. (2012) analyzed the ~ 200-year periodicity during the past two millennia using seventeen near worldwide distributed tree chronologies, and found significant periodicities in the 208-year frequency band, corresponding to the De Vries cycle of solar activity, indicating a solar contribution in the temperature and precipitation series.

speleothems dating website-2

c) The spectral power distribution of a 2000-yr window centered at 4,525 BP, showing the Gleissberg cycle (~ 88 yr) as the most dominant feature in this frequency range for the 3,500-6,500 BP period. It is also very unlikely that we will be able to determine if it played a significant role in the climate of the period.

The result is reproduced using a Be solar activity reconstruction. As the evidence indicates this periodicity is not currently relevant, we will not consider it further.

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.

a) Solar sunspot number reconstruction from cosmogenic C isotopes. b) Wavelet analysis of the sunspot number reconstruction, with the Eddy periodicity indicated by a continuous line, and the Bray periodicity by a dashed line. a) Solar sunspot number reconstruction from cosmogenic C isotopes. Blue curve, inferred iceberg activity in the North Atlantic (inverted) from petrological tracers. Other researchers have found that applying the trapezoidal filter of Gleissberg separately to dates of solar cycle minima and maxima from sunspot records then merging them, one also obtains an ~ 80-year time domain periodicity (Peristykh & Damon, 2003).

A regularly spaced 980-year periodicity is shown as arches above. c) Scale-averaged wavelet power for the 800-1200 years band (Eddy periodicity, continuous line, left scale), and the 1700-2800 years band (Bray periodicity, dashed line, right scale). A regularly spaced 980-year periodicity is shown as arches above. They interpret this result as confirmation of the cycle, that would simultaneously regulate the 11-year cycle amplitude and period.

Despite this lack of a solid theoretical framework, paleoclimatologists keep publishing article after article where they report correations between solar proxy periodicities and climate proxy periodicities, and the observational evidence is now so abundant as to obviate the lack of a theory or well defined mechanism. The correspondence is very clear for the periods when the Eddy cycle has high power. E6 (6,300 BP) is less well established in the literature, although clearly identified as a dry event in Oman caves speleothems (Fleitmann et al., 2007). Climatic and solar proxy records, spanning the early Holocene, 250-year smoothed and 1800-year high-pass filtered. Those GSM are assigned to the Eddy cycle given the good temporal coincidence (figure 83 b). In 1944, Wolfgang Gleissberg, working at the University of Istanbul observatory, described a long solar cycle that could only be revealed by applying what he called a “secular smoothing” (a trapezoidal 1-2-2-2-1 filter) to a numerical sequence formed by the maximum sunspot values of the known 11-year solar cycles.

The millennial Eddy solar cycle Every frequency analysis of Holocene solar activity reconstructions shows a strong peak at ~ 1000 year (figure 62 A & C, Darby et al., 2012; Kern et al., 2012). The 980-year solar cycle, despite its shorter period and variable amplitude compared to the Bray solar cycle, seems to have dominated Holocene climate variability between 11,500 yr BP and 4,000 yr BP. The 1000-year periodicity displays very low power in solar activity wavelet analysis during several millennia (figures 79 & 81; Ma 2007; Kern et al., 2012; Steinhilber et al., 2013). E5 (5,200 BP) has been well described worldwide as an abrupt cold event (figure 44; Thompson et al., 2006). Records are Soledad Basin O (Indian monsoon proxy, green), and North Atlantic stack of IRD petrologic tracers (North Atlantic iceberg activity proxy, red). Next, we have 9 GSM that coincide with the lows of the 2,475-year Bray cycle, and in fact define it (figure 83 b). a) Conservative list with approximate dates (in -BC/AD and BP) of grand minima in reconstructed solar activity. According to him this numerical procedure revealed The cycle thus described is not apparent in the sunspot record, and cannot be produced from it by frequency analysis.

Additional periodic climate variability in the centennial to millennial range is produced by the 1500-year oceanic cycle, and by several solar activity periodicities that, according to numerous authors, correlate well with climate variability. E8 (8,300 BP) coincided with the outbreak of Lake Agassiz, and researchers are trying to differentiate the relative climatic contribution to the 8.2 kyr event from the solar minimum and the proglacial lake outbreak (Rohling & Pälike, 2005). Usoskin (2017) gives a conservative list of 25 GSM that were identified in previous studies by different researchers for the past 11,500 years. Since the Eddy cycle is so close to one thousand years, all the lows of the cycle take place at ~ X,300 yr BP, with X being every millennia of the Holocene. a) Left scale: Reconstructed Northern Hemisphere mean MJJA temperature anomaly time series (black line), smoothed with a 30-year Gaussian filter. A continuous in phase coherence between tree-ring temperatures and solar activity is seen at the de Vries periodicity. The synchronization, and in some cases amplitude, of the climatic signal correlates with the strength of the solar signal, indicating that the modulation of the de Vries cycle by the Bray cycle extends to its climatic effect. The 88-year Gleissberg solar cycle Despite the popularity of the Gleissberg solar cycle in the literature I have not been able to unambiguously identify this cycle as important for solar-climate effects.

The study of solar cycles and their climatic effect is hampered by a very short observational record (~ 400 years), an inadequate understanding of the physical causes that might produce centennial to millennial changes in solar activity, and an inadequate knowledge of how such changes produce their climatic effect. E7 (7,300 BP) coincides with the last cold, humid phase of the sixth millennium BC (Berger et al., 2016). We can observe in the list of GSM that 15 of them take place at ~ X,300 ± 80 yr BP (figure 83 a; Usoskin, 2017). Right scale: Solar forcing relative to the period 1976-2006 CE, with the pink shaded region showing the range of the forcing reconstructions compiled by Schmidt et al. This is due to the Gleissberg cycle being different things for different researchers.

Introduction In a recent review of Holocene climate variability (Part A, and Part B) it was shown that Milankovitch forcing was likely the primary driving force behind the general climate evolution from the Holocene Climatic Optimum to the Neoglacial period, for the past 12,000 years. The last three warm periods (orange bars) and 2 cold periods (blue bars) are indicated. E12 (11,250 BP) coincides with a particularly humid phase in northwestern and central Europe towards the end of the Preboreal oscillation (van der Plicht et al., 2004; Magny et al., 2007). This finding has been confirmed for tree-rings, which reflect changes in temperature or precipitation, in several regions of the planet. (2017) have constructed a tree-ring multi-proxy (54 series), extra-tropical Northern Hemisphere, warm season (MJJA), temperature record spanning 1,200 years (750-1988 AD). Arrows indicate the phase of the relationship where coherence 0.65. Band-pass filtered total solar irradiation (dotted red line) and tree-ring-derived climate data series in the range of periods 180–230 years for (a) Asia, and (b) Europe. Other studies link the 208-year de Vries cycle to climate change, including Central Asian ice-cores (Eichler et al., 2009), Asian (Duan et al., 2014) and South American (Novello et al., 2016) monsoon-record speleothems, Mesoamerican lake-sediment cores as drought proxies (Hodell et al., 2001), and Alpine glaciers (Nussbaumer et al., 2011).