By Javier
The existence of a ~ 2400-year climate cycle, discovered in 1968 by Roger Bray, is supported by abundant evidence from vegetation changes, glacier re-advances, atmospheric changes reflected in alterations in wind patterns, oceanic temperature and salinity changes, drift ice abundance, and changes in precipitation and temperature. This is established with proxy records from many parts of the world.
Introduction
In our attempt to better understand the nature of our planet’s abrupt climate changes I have already reviewed the glacial-interglacial cycle, and the Dansgaard-Oeschger cycle’s that take place during glacial periods. I now start reviewing the millennial climate cycles that abruptly impact the slowly changing Holocene climate. The most significant and regular one is the ~ 2400-year Bray cycle.
Recently, the Bray (Hallstatt) Cycle was reviewed by analyzing the main findings of some of the most significant articles by researchers who have studied it. That article summarizes the current scientific understanding of the ~ 2400-year cycle. In part A of this article, we are going to review, in detail, the evidence for the existence of the ~ 2400-year climate cycle. In part B, we will go over the arguments that the ~2400-year cycle of the production of cosmogenic isotopes 14C and 10Be represents a cycle in solar activity. In part C, we will discuss what it is considered the most likely mechanism by which solar variability could affect climate, as proposed by the authors researching the subject. Afterwards we recommend that the interested reader read the post “Impact of the ~ 2400 yr solar cycle on climate and human societies.” The post explores, in detail, the climatic effects and their impact on human civilization in each of the Bray cycle lows during the Holocene.
The biological 2400-year climate cycle
Over a century ago Scandinavian botanists started to reconstruct the climate of the Holocene from peat bog stratigraphy. They could distinguish the sediment layers into wet/dry, cold/warm, periods, and developed crude dating methods. Their efforts resulted in an understanding that the Holocene climate could be subdivided into periods of different climatic conditions, like in a diagram by Rutger Sernander from 1912 (figure 50 A, upper diagram).
Figure 50. Postglacial vegetation and climate periods as understood during the first half of the 20th century. A). Upper diagram, Rutger Sernander’s view of postglacial warm climate periods in southern and central Sweden, showing his proposed abrupt climate degradation at the Sub-Boreal/Sub-Atlantic transition, termed “fimbulvintern.” The dashed line indicates G. Andersson’s opposite view of continuous temperature evolution. Lower diagram, Late Glacial/Postglacial temperature evolution in southern and central Sweden based on biological evidence, after Magnus Fries, showing the temporal disposition of the nine pollen zones in Roman numbers. The thin line represents a near-millennial oscillation in humidity. Dates in calendar years. Source: T. Bergeron, 1956. Fornvännen, 51, 1-18. B). Analytical pollen zones defined by Knud Jenssen and Johs. Iversen for southern and central Sweden confirming Sernander’s climatic reconstruction. Dates in calendar years. Source: O.K. Davis, 2009. Introduction to Quaternary ecology.
The development of palynology (pollen studies) by Lenart von Post in the 1930’s allowed Knud Jenssen and Johs. Iversen to improve the postglacial period zonation (figure 50 B), and develop a summer vegetation-based temperature scale for the Scandinavian Holocene by the 1940’s. This temperature scale allowed reconstructions of the Holocene climate very similar to our current understanding by 1950 (figure 50 A, lower diagram).
Figure 50 summarizes decades of work by botanists to establish vegetation stages in the Northern Hemisphere Holocene. These stages allow us to distinguish a 2500-year vegetation and faunal cycle. Some botanists, like Rutger Sernander, proposed that these transitions were abrupt and not gradual. In particular, he proposed that the last transition between the Sub-Boreal and the Sub-Atlantic, at around 650 BC corresponded to the “Fimbulvintern” or Great Winter of the Sagas that marks the end of the Nordic Bronze Age (figure 50 A), and made the Nordic countries a colder place.
The glaciological 2400-year climate cycle
In the early 1950’s, researchers noticed a correlation between glacier movements in North America and sunspots for the previous 300 years. In the 1960’s James Roger Bray constructed a solar index starting in 527 BC by combining telescopic sunspot observations with naked-eye sunspot and auroral observations. He also constructed an index for postglacial major ice re-advances from glaciers all over the world. He compared these two observations and found a high degree of correlation, and good agreement with Icelandic sea-ice, and 14C production variations. He observed in the data a possible 2300-2700-year cycle, that he projected into the past from the Little Ice Age, finding that a 2600-year period closely matched both vegetation transitions like the Atlantic/Sub-Boreal, or the Sub-Boreal/Sub-Atlantic transitions, and significant glacier re-advances from the past after the Younger Dryas (Bray, 1968). Since he was the first to correctly identify and describe the ~ 2400 year climatic and solar cycles they should carry his name as this is the tradition.
Bray’s glaciological and solar studies were reproduced in 1973 by Denton and Karlén who did a more detailed study of world glacial advances and came up with essentially the same periodicity, 2500 years (figure 51 A). By then Hans Suess had determined the short-term fluctuations in 14C levels for the past 7000 years from tree rings. Even then, they were thought to represent variations in solar activity. As Bray had done previously, Denton & Karlén (1973) correlated periods of major glacier advances to periods of high 14C production (low solar activity).
Figure 51. Holocene glacier fluctuations. A). Synthesis of Holocene worldwide glacier fluctuations showing three broad intervals of glacier expansion within the last 6000 years and a fourth one recognized in Scandinavia. Source: G. Denton & W. Karlén, 1973. Quat. Res., 3, 155-205. B). Holocene subdivisions and glacier fluctuations in the European Alps showing the complex pattern of advances and retreats that do not always correspond between Austrian and Swiss Alps. The uncalibrated radiocarbon dates scale is shown together with the corresponding calibrated scale in calendar years BP. In this and following figures, blue bars mark the position of the lows of the ~ 2400-year Bray cycle. Source: D. Bressan, 2011. Scientific American.
Since then glaciologists have reconstructed Holocene glacier movements from hundreds of glaciers all over the planet, and glacier variability has become more complex (figure 51 B). Today we still recognize the major global advances that define the 2400-year cycle (Mayewski et al., 2004; figure 47), but there is hardly a century, especially during the Neoglacial, when glaciers were not advancing somewhere.
By the mid-70’s the scientific community was aware of the existence of a 2500-year climatic cycle that caused glacier advances and recessions, and that separated significantly different vegetation stages and cultural phases (figure 51B). Due to its coincidence with 14C fluctuations, it was inferred that its cause was solar variability. Throughout this work both the climatic and solar cycle are referred to as the Bray cycle, and the lows of the cycle, associated with enhanced 14C production, and climatic changes manifested by cooling, glacier advances, increased drift ice in the North Atlantic, and atmospheric, oceanic, and precipitation changes, are numbered from more recent backwards as B1, B2, …, with B1 the Little Ice Age.
The atmospheric 2400-year climate cycle
The next great advance in the characterization of the 2400-year climatic cycle came from the study of ice cores. Paul Mayewski, one of George Denton’s students, was the scientist in charge of coordinating the effort of over 200 scientists in the American Ice Core Program that in 1993 completed the Greenland Ice Sheet Project II (GISP2). He described this effort and its fruits in his 2002 book “The Ice Chronicles: The Quest to Understand Global Climate Change.” While other researchers took on studying gases, isotopes, or dust in the GISP2 ice core, Mayewski and colleagues studied the chemical composition of major ions brought to the ice by the wind, using them as tracers for atmospheric circulation. They discovered a strong association between expansions of northern hemisphere polar atmospheric circulation systems and the 2500-year cycle previously described by his former teacher (O’Brien et al., 1995; figure 46 F & G; figure 52 a & b). An increase in salt deposition is associated with winter atmospheric conditions today. This is when the north polar vortex expands and meridional circulation increases, and thus represents an increase in cold and windy conditions. The periodicity found by Mayewski and colleagues (O’Brien et al., 1995) in GISP2 salts is close to 2600 years (figure 52 b). They noticed a good correlation between the atmospheric maxima and clusters of three grand solar minima (GSM) of the Maunder- and Spörer-type patterns, with the most recent one taking place during the LIA (O’Brien et al., 1995; figure 52 c).
Figure 52. Holocene North Atlantic and Arctic atmospheric changes. a). GISP2 polar circulation index, a time series of the dominant empirical orthogonal function, EOF1, of the major ions in the ice core, that provides a relative measure of the average size and intensity of polar atmospheric circulation. PCI values increase (e.g., more continental dust and marine contributions) during colder portions of the record. b). Main periodic component of the sea salt Na flux in GISP2 ice core with a quasi-2600-year periodicity. c). ∆14C intervals that present Maunder- and Spörer-type patterns occurring in clusters. Sources: S.R. O’Brien et al., 1995. Science, 270, 1962-1964. Ice Core Working Group. The National Ice Core Laboratory. d). Mean grain size of eolian soil deposition at Hólmsá, Iceland, indicative of wind strength. Windy periods, indicated by the transport and deposition of coarse sediments, are coeval with cool, stormy periods recorded in GISP2 ice and North Atlantic sediment cores. Source: M. G. Jackson et al., 2005. Geology 33, 509-512. e). Dark grey trace, reconstruction of time coefficient by singular spectrum analysis of detrended and normalized alkenone based SST variance, from a NW Africa marine sediment core, as a proxy for AO/NAO oscillation. Black curve, main periodic component of the data. Source: J-H. Kim et al. 2007. Geology 35, 387-390. Light grey trace, inferred NAO circulation pattern from the principal component analysis of redox parameters (Ca/Ti and Mn/Fe ratios) from a Greenland lake sediment record. Source: J. Olsen et al. 2012. Nature Geoscience, 5, 808-812.
The atmospheric reorganization that takes place at the lows of the Bray cycle and causes increased polar circulation is partially evident in eolian soil sediments in southern Iceland (Jackson et al., 2005; figure 52 d). Some of the biggest grain sizes transported by the strongest winds are associated with cold periods and coincide with some of the lows of the Bray cycle (B3 & B4, figure 52 d). The authors of the work underscore the wind pattern similarity to the North Atlantic drift-ice Bond record.
The changes in polar circulation and wind strength are suggestive of the Arctic Oscillation/North Atlantic Oscillation (AO/NAO). The AO reflects the state of the atmospheric circulation over the Arctic, through a positive phase, featuring below average geopotential heights, and a negative phase in which the opposite is true. In the negative phase, the polar low-pressure system (also known as the polar vortex) over the Arctic is weaker, which results in weaker upper level winds (the westerlies). Therefore, cold Arctic air and storm tracks move farther south, causing a drop in northern hemisphere temperatures and changes in precipitation patterns. The AO often shares phase with the NAO, that reflects differences in the strength of two pressure centers in the North Atlantic: the low pressure near Iceland, and the high pressure over the Azores. Fluctuations in the strength of these pressure centers alter the alignment of the jet stream affecting temperature and precipitation distribution. A NAO negative phase is produced when the weakening of the Iceland low and the Azores high reduces the pressure gradient resulting in weaker more southern westerlies producing colder conditions over much of North America and Northern Europe while moving the storm tracks southward towards the Mediterranean. A NAO negative phase usually features more frequent and longer blocking conditions when a stationary pressure pattern allows cold Arctic air to spill over mid-latitudes.
The Holocene NAO patterns have been reconstructed from a marine sediment core whose alkenone content has been shown to depend on trade winds intensity-dependent upwelling near the coast of NW Africa (Kim et al., 2007; figure 52 e). For the last millennia, the NAO intensity has also been reconstructed from lake sediments in Greenland, showing the very low NAO values that characterized the LIA (Olsen et al., 2012; figure 52 e). The evidence indicates a 2400-year periodic variation in SST and upwelling intensity off NW Africa that is associated with a climatic cycle in oceanic circulation that reflects periodic NAO conditions. The lows of this NAO cycle are characterized by NAO negative dominant conditions that produce northern hemisphere cooling and precipitation changes. Rimbu et al. (2004), have argued that during the Holocene, the AO/NAO atmospheric circulation was the dominant climate mode at millennial time scales.
The oceanic 2400-year climate cycle
Given the strong coupling between atmospheric and oceanic variability, it is not surprising that the ~ 2400-year climate cycle is prominently displayed by some oceanic current proxies, particularly in the North Atlantic. Oppo et al. (2003) used an established deepwater proxy, the carbon-isotope composition of benthic foraminifera, to evaluate Holocene deepwater variability at a sediment core in the NE subpolar Atlantic. Low 13C values are indicative of a reduction in the 13CO2 rich North Atlantic Deep Water (NADW) contribution. Oppo et al. (2003) identify the largest reductions in NADW at 9.3, 8.0, 5.0 and 2.8 kyr ago. The latest three periods correspond with Bray lows 2 to 4 (figure 53 a). Significant reductions in 13C indicative of reduced NADW production have also been reported at 10,300 BP (B5) by Bond et al. (1997), and at the LIA (B1) by Keigwin and Boyle (2000). This means that all the lows in the Bray cycle had been identified as periods of reduced NADW contribution by different authors. Such periods might see a reduction in the northward flux of warm near surface waters in the North Atlantic to maintain mass balance (that could be the cause of the NADW reduction), and would result also in the cooling of North Atlantic high latitudes.
Figure 53. Holocene North Atlantic and Arctic oceanic currents changes. a). Benthic Cibicidoides wuellerstorfi δ13C variations, at a marine sediment core in the subpolar NE Atlantic, record variations in δ13C of the total amount of CO2 in bottom waters, as a proxy for δ13C-rich North Atlantic deepwater (NADW) contribution. The lows in the Bray cycle (blue bars), correspond to periods of reduced NADW contribution. Source: D.W. Oppo et al., 2003. Nature, 422, 277-278. b). Salinity reconstruction at the base of the thermocline by paired Mg/Ca–δ18O measurements from Globigerina inflata from a marine sediment core south of Iceland. During the early Holocene, the sub-thermocline was saltier, but underwent a freshening at a time when the ice sheets were still contributing meltwater. The glacial freshwater discharge event of 8.2 kyr ago can be recognized. Warm saline sub-thermocline conditions took place at 0.3, 1.0, 2.7 and 5.0 kyr ago, coinciding with known climatic perturbations in the North Atlantic region. Source: D.J.R. Thornalley et al., 2009. Nature, 457, 711-714. c). Quantitative wt% mineralogical (quartz and feldspars) detrended variations from 16 cores from the Iceland shelf (thick line), as a proxy for drift ice from the Arctic Ocean and East Greenland, fitted to a fourth-order polynomial (thin line). Five peaks in residuals from the data are defined by the 2500-year cycle. Source: J.T. Andrews, 2009. J. Quat. Sci. 24, 664-676. d). Detrended (grey) and smoothed (black) Gephyrocapsa muellerae abundance (nº x 108/g) record as a proxy of warmer Atlantic water flow through the Iceland-Scotland strait of the Nordic Seas from a sediment core off Norway. The low abundance during the LIA (B1) might be due to Atlantic waters being too cold during summers for this warm-loving species. Source: J. Giraudeau et al., 2010. Quat. Sci. Rev. 29, 1276-1287.
Temperature and salinity analysis of the Atlantic Meridional Overturning Circulation (AMOC) using a sediment core south of Iceland, where the Faroe and Irmingen currents branch out of the North Atlantic current, shows that episodes of warm saline sub-thermocline conditions are centered at 0.3 (B1), 1.0, 2.7 (B2) and 5.0 (B3) kyr ago, coinciding with known climatic perturbations in the North Atlantic region (Thornalley et al., 2009; figure 53 b). The authors show evidence that the increased salinity, temperature, and water stratification, at times of abrupt climate change, are due to an increase in the Atlantic inflow of warmer saline subtropical gyre waters at the expense of the fresher and colder subpolar gyre waters. They interpret it as a negative feedback from the subpolar gyre, that stabilized the AMOC, at times of freshwater inputs, particularly during the early Holocene when the ice sheets were still melting rapidly, and at the 8.2 kyr event when the outbreak of proglacial Lake Agassiz took place (Thornalley et al., 2009; figure 53 b). They propose solar variability as the forcing behind these oscillations. The increased salinity of the Atlantic inflow observed at the times of reduced NADW formation identified by Oppo et al. (2003; figure 53 a) may have limited the reduction, or helped restart a stronger AMOC.
Andrews (2009) analyzed the distribution of foreign mineral species by drift ice in Icelandic shelf waters. While drift ice has been increasing in the past 6,000 years of Neoglacial conditions off Northern Iceland, the detrended data supports the existence of a 2400-year climatic periodicity. Periods of high drift ice coincide with the lows of the Bray cycle (Andrews, 2009; figure 53 c). As is the case with the Bond series, there is variability in drift ice records, since some cold events do not belong to the Bray cycle.
A more detailed look at millennial-scale oceanic transport changes that took place at the Iceland-Scotland Ridge further confirms the oceanic ~ 2400-year cycle. Abundance of coccolith species in a marine core off Norway reflects major Holocene changes in Atlantic water transfer to the Nordic Seas with a 2400-year periodicity (Giraudeau et al., 2010; figure 53 d). Millennial-scale Holocene episodes of increased advection of heat by Atlantic waters off Norway are associated with enhanced winter precipitation over Scandinavia, increased sea-salt fluxes over Greenland, and strengthened wind over Iceland. Thereby suggesting common atmospheric forcings. This may be the location and intensity of the westerlies and the associated changes in mid- to high-latitude pressure gradients. Such atmospheric processes are thought to explain the observed coupling between periods of excess drift ice delivery to Northern Iceland (Andrews, 2009; figure 53 c), and intervals of maximum inflow of warm Atlantic water to the Norwegian Sea (Giraudeau et al., 2010; figure 53 d) throughout the last 11,000 years.
The hydrological 2400-year climate cycle
Precipitation is affected by multiple factors, and in many cases determined by regional or even local climatic and weather patterns. It is clear however that the atmospheric reorganizations that have accompanied the 2400-year Bray climate cycle are reflected in precipitation changes in several locations. For decades Michael Magny has been studying Holocene mid-European lake level fluctuations and their impact on prehistoric human settlements (Magny et al., 2004). His research shows very clearly the impact of Holocene climatic change. There is a general trend to increasing dryness during the Neoglacial, after a wetter HCO. Overlapping this general trend attributable to Milankovitch forcing, the 2400-year cycle is characterized by strong transitions from low to high lake levels (Magny et al., 2004; figure 54 a), indicating greatly increased precipitation at the lows of the Bray climatic cycle.
Figure 54. Holocene northern hemisphere precipitation changes. a). Holocene mid-European lake-level reconstruction from a data set of 180 radiocarbon, tree-ring and archaeological dates of higher and lower lake-level events based on multiple lines of evidence, obtained from sediment sequences of 26 lakes in the Jura mountains, the northern French Pre-Alps and the Swiss Plateau. The score indicates how well registered the lake-level event is, not its intensity. With a resolution of 50 years, episodes of higher lake-level are defined by a collapse of lower lake-level scores followed by a peak in higher lake-level scores. Source: M. Magny, 2004. Quat. Internat. 113, 65-79. b). Winter precipitation reconstruction at Bjørnbreen glacier in Jotunheimen, southern Norway. Precipitation is reconstructed from the known relation between variations in the equilibrium line altitude (ELA, the boundary between the ablation and accumulation areas) and mean July temperature variations reconstructed from palynological data. Winter precipitation is more important than summer temperature for glacier expansion episodes. Source: J.A. Matthews et al., 2005. Quat. Sci. Rev. 24, 67-90. c). Holocene summed probability plot for Spanish fluvial system paleofloods, fine to medium sands deposits on the sides of narrow bedrock canyons that resulted from floods of similar or greater magnitude to those of the largest floods recorded in the instrumental series and are considered evidence of past extreme floods. Source: V.R. Thorndycraft & G. Benito, 2006. Quat. Sci. Rev. 25, 223–234. d). Irish bog-grown oaks (Quercus spp.) and pines (Pinus sylvestris L.) frequency (inverted scale) during the Holocene as evidence of changes in moisture delivery to Ireland. Under humid conditions trees were unable to grow on wetter bogs. Source: C. Turney et al., 2005. J. Quat. Sci. 20, 511-518. e). 25-year average sedimentary varve thickness record at a marine core in the Santa Barbara Basin as a proxy for annual rainfall in the area. Thin line represents lowpass filter to emphasize millennial scale fluctuations. Data is missing around the 8.2 kyr event when the basin entered a bioturbated non-varved interval similar to glacial stadials. Source: A.J. Nederbragt & J. Thurow, 2005. Palaeo. 221, 313-324. f). 5-year-resolution δ18O isotope record from Dongge Cave (southern China) stalagmite DA as a proxy for the strength of the Asian monsoon over the past 9000 years. Yellow bars denote the timing of Bond events 0 to 5 in the North Atlantic. Two grey bars indicate two other notable weak Asian monsoon events that can be correlated to ice-rafted debris events. Source: Y. Wang et al., 2005. Science 308, 854-857.
A winter precipitation reconstruction from Norway’s coastal glaciers shows periods of increasing precipitation at the lows of the Bray cycle (Matthews et al., 2005; figure 54 b). Besides feeding glacier advances at these times (figure 51 a), the Norway glacier-derived winter precipitation record matches almost exactly the Norway marine-derived Atlantic warm-water inflow record (figure 53 d), supporting a causal relationship.
Spanish fluvial chronology also supports a 2400-year cycle in precipitation (Thorndycraft & Benito, 2006; figure 54 c). Three of the five main flooding periods highlighted by the authors coincide with B1, B2, and B5 lows in the Bray cycle. In addition, B3 and B4 lows are also characterized by significant episodes of slackwater floods or paleofloods, that record periods of increased flood frequency related to Holocene climatic variability (Thorndycraft & Benito, 2006; figure 54 c). They are fine-grained sediments produced by large magnitude floods, preserved in valley side rock shelters in bedrock gorge reaches. The last 1300 years register a large increase in the frequency of floods in Spanish rivers. The authors propose an increased preservation potential and/or increased human impact on the landscape as likely cause.
Holocene Ireland hydrology has been reconstructed from oaks and pines collected from bogs. These trees, accurately dated through dendrochronology (oaks) and carbon-dating (pines), provide a record of dry conditions when the decreased water table levels allowed the colonization of these marginal environments by trees (Turney et al., 2005). Although Ireland hydrology shows a complex pattern over the increasingly wet Neoglacial trend, lows in the Bray cycle are associated with periods of increased precipitation (figure 54 d). This is in contrast with a Neoglacial drying trend in much of the rest of Europe and the world
The hydrological changes caused by the 2400-year climatic cycle are not restricted to the North Atlantic region. The same pattern can be found in the Santa Barbara Basin (California), reflected in varve thickness variability, that is known to depend on annual precipitation, and inversely correlates with wind strength (Nederbragt & Thurow, 2005). The described ~ 2750-year cycle in varve thickness correlates very well with the Bray climate cycle (figure 54 e), with periods of higher varve thickness (increased precipitation) at the Bray lows.
A high-resolution record of the strength of the Asian monsoon was obtained from oxygen isotopic analysis of stalagmite “DA” in Dongge Cave (China; Wang et al., 2005). The record supports episodes of monsoon weakness (dryness) at every one of the Bray lows, most of them highlighted by the authors of the work (figure 54 f). Most of the centennial and millennial variability in the Asian and Indian monsoons has traditionally been linked by multiple authors to solar variability (Wang et al., 2005; Neff et al., 2001).
The temperature 2400-year cycle
Although temperature variations should not dominate climate change analysis, they are an important indicator of abrupt climate changes, and therefore one would expect to find traces of the 2400-year climatic cycle in temperature proxy records. And indeed, they are clearly there. In the previous article I reviewed the 73 global proxies analyzed by Marcott et al. (2013; Holocene climate variability). When properly averaged every low of the Bray cycle coincides with a period when temperatures were experiencing a significant decrease when compared to the previous trend (figure 55 a). Even B5, when the world was still experiencing the fast warming that led to the HCO, shows a significant departure from the warming trend of the previous centuries.
Figure 55. Holocene temperature proxies and reconstruction. a). Global average temperature reconstruction from Marcott et al., 2013, using proxy published dates, and differencing average, with temperature anomaly rescaled as discussed here. Source: Marcott et al., 2013. Science 339, 1198-1201. b). Earth’s axis obliquity is shown to display a similar trend to Holocene temperatures. c). Holocene reconstruction of intermediate-water temperatures at 500 m depth from a suite of sediment cores in the Makassar Strait and Flores Sea in Indonesia, at the Indo-Pacific Warm Pool. Temperatures expressed as anomaly relative to the temperature at 1850-1880 CE. Shaded bands represent ±1 SD. Source: Y. Rosenthal et al., 2013. Science 342, 617-621. d). Sea Surface Temperature reconstruction at the Davao Gulf, south of Mindanao, from Mg/Ca levels in the surface foraminifer Globigerinoides ruber. Dark grey band corresponds to the 2000–3000 years band-pass filter of the data, with the light grey area the 90% confidence level. Source: D. Khider et al. 2014. Paleoceanography 29, 143–159. e). Holocene variations in subtropical Atlantic SST from marine sediment core 658C. The record documents a well-known shift in African monsoonal climate at 5.5 kyr, when changes in the earth’s orbit displaced the African monsoon southward, bringing much drier and warmer conditions to subtropical Africa and ending the African Humid Period. Superimposed on this trend are millennial-scale SST variations coherent with some of the North Atlantic ice-rafting events defined by Bond et al. 2001, including the lows of the Bray cycle (blue bars). Source: P. deMenocal et al., 2000. Science 288, 2198-2202. f). Ice-rafted debris stack (inverted) from four North Atlantic sediment cores. It is proposed that the increase in iceberg activity in the North Atlantic is tied to the increase in cold water advection from the Arctic and Nordic seas. Source: G. Bond et al., 2001. Science 294, 2130-2136.
That the global temperature reconstruction truly reflects global temperature changes and is not dominated by northern hemisphere records is confirmed by the Rosenthal et al. (2013) reconstruction of intermediate water temperatures at the equatorial Indo-Pacific Warm Pool, the warmest oceanic region in the world. Their reconstruction displays a very similar profile to the global reconstruction of Marcott et al. (2013), and shows that every Bray cycle low coincides with a significant downward departure from the general temperature trend (figure 55 c). This is confirmed also by the finding in the same area (south of Magindanao) that Holocene SST display variability in the 1000, 1500, and 2500 periodicities, and the 2500 periodicity coincides very well with the Bray cycle (Khider et al., 2014; figure 55 d). Khider et al. measure the water surface temperature changes associated with the Bray cycle at the Indo-Pacific Warm Pool as 0.3°C, and calculate a climate sensitivity to millennial solar cycles of 9.3-16.7 °C/Wm–2, an order of magnitude higher than the estimated sensitivity to the 11-year solar cycle.
Temperature proxies at the West African sea indicate that SST were over 2° C lower during the African Humid Period (de Menocal et al., 2000; figures 40 & 55 e), after which the lack of precipitation due to the southward displacement of the African monsoon produced an abrupt warming of the sea surface before joining the global cooling trend of the Neoglacial. Within this complex general pattern, the lows of the Bray cycle are once more associated with a significant temporal reduction in SST (figure 55 e).
A more complete analysis of SST temperatures in the tropical oceans and the North Atlantic region, the Mediterranean, and Red Sea, was performed by Rimbu et al. (2004), using 18 alkenone records. The principal mode of variability reflects Milankovitch forcing, delayed in the case of the North Atlantic by the melting of the ice sheets. The secondary mode of variability (principal temporal component from the second empirical orthogonal function) shows in both regions as a ~ 2300-year cycle that agrees well with the Bray cycle (Rimbu et al., 2004; figure 56). The main disagreement is with B4 due to the 8.2 kyr event, that affected SST in the North Atlantic as early as 8.4 kyr BP, but seems to have had a delayed effect in the tropics around 8.1 kyr BP, possibly preempting the effect of B4 a few centuries later. By analogy with the instrumental period records and the analysis of a long-term integration of a coupled ocean-atmosphere general circulation model, the authors suggest that the AO/NAO is one dominant mode of climate variability at millennial time scales. This conclusion agrees well with the other evidence shown here for the Bray climate cycle.
Figure 56. Holocene millennial-scale sea-surface temperature variability. a) and c). Marine sediment core positions for the 8 tropical region (25°S to 25°N) cores and the 10 North Atlantic realm cores analyzed, respectively. b) and d). Time coefficient (Principal Component Analysis) for the second empirical orthogonal function of the alkenone-based SST variability. The dominant modes of tropical and North Atlantic Holocene SST display a 2.3 kyr cycle linked to the strength of AO/NAO during the Holocene, showing that this cycle has a global character. Source: N. Rimbu et al., 2004. Clim. Dyn. 23, 215-227.
The Bond record of drift-ice petrological deposition in the North Atlantic is also generally considered to correlate to colder conditions in the North Atlantic region that favor more frequent southward moving icebergs (Bond et al., 2001). Most, if not all, Bond events have been linked to cooling and abrupt climate change outside the North Atlantic area. The Bond record also reflects the 2400-year Bray cycle as the lows in the Bray cycle coincide with Bond events 0 (LIA), 2a, 4a, 5a, and 7 (figure 55 f).
We can conclude that the 2400-year Bray climate cycle is very well established in the proxy record of past climate changes in the North Atlantic region, but affects the entire planet. It is the most important climatic cycle of the Holocene. Although the Bray climate cycle is present in the chemical record of Greenland ice cores, it is not easily seen or, maybe, absent in the Greenland and Antarctic ice core temperature records. This is one of the reasons why it has been ignored for so long despite being present in multiple proxies and recognizable since 1912. Paleoclimatology has come to depend too much on the very reliable and precisely dated polar ice cores at the expense of the often contradictory, unreliable, and imprecisely dated climate proxies. This has had the result that whatever is not prominently displayed in polar ice cores is considered unreal. Another complicating factor is that the Bray cycle is not the only cause of climate change during the Holocene and thus proxies are full of signals whose origin is often difficult to ascertain, creating much confusion among researchers that results in contradictory reports.
Continues in Part B.
Conclusions
1) A 2600-year climate cycle was first proposed in the late 1960s by Roger Bray based on vegetation transitions and major glacier re-advances, and linked to solar activity.
2) This climate cycle is clearly evident in numerous proxies from the North Atlantic region and other places in the world that reflect ~ 2400 year-periodic changes in wind patterns, oceanic currents strength and salinity, drift ice, precipitation, and temperatures.
Acknowledgements
I thank Andy May for reading the manuscript and improving its English.
Bibliography [link]
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I prefer to think of them as shifts in the multidimensional climate state space. Internal variability when pushed by small changes in orbits, the sun, greenhouse gases…
Javier, Thanks for the post, I’ve been looking forward to it. It’s too long for me to read in one sitting. I do have a question though.
Most of what we read about in climate is short range of say 30 to 60 to 100 years. What, if any, are these long term cycles teaching us about the short term, or has it no bearing?
Hi Ordvic,
The quality of our data goes down quickly as we go back in time, so our knowledge is much better for the most recent decades. And due to our lifespan, for most people anything longer than a century has little relevance. Short cycles have therefore a practical interest, while long ones have a theoretical interest.
Most, but not all, centennial to millennial climate cycles are due to solar variability. As far as I know all solar cycles appear to produce the same effects, but the amplitude of the effect is generally proportional to the length of the cycle, probably due to being cummulative. Small atmospheric effects linked to the 11-year solar cycle from models, observations and reanalysis, appear to be also responsible for the effects of longer cycles, only multiplied by an order of magnitud or more when the effect accumulates over several decades. I go over that in more detail in part C.
Javier
Forgive me for beating the same old drum again, but If you mean to say that the ‘quality of our instrumental data is much better for recent decades’, I think you are incorrect – again provided you mean the data after adjusting and homogenizing. There’s a case to be made that the only surface temperature data worth worrying about are those emanating from a relatively small number of national weather services before they get into the hands of the adjusters. If true, that adds weight to what you are implying in this very nice post.
Alan Longhurst
Hi Alan,
Try not to limit yourself to a few controversial temperature datasets. We are now taking continuous measurements on thousands of atmospheric, oceanic, solar and geological variables.
As an example for solar activity we have continuous measurements of TSI, spectral variance, solar wind, neutrons, magnetic changes, and a dozen more variables. Just a few decades ago we only had the number of sunspots. And a few centuries ago we have to attempt controversial reconstructions from cosmogenic isotopes records. The improvement in the amount and quality of the data has been enormous.
Now we can attempt to answer questions, like the effect of solar activity changes on atmospheric conditions, that 50 years ago were impossible to answer.
“As far as I know all solar cycles appear to produce the same effects, but the amplitude of the effect is generally proportional to the length of the cycle, probably due to being cummulative.”
Simply due to major grand solar minima being less frequent. There is no fixed frequency for major GSM’s through the Holocene, their periodicity varies greatly from around 400 years to around 1200 years. Purely because multi-body synodic periods have phase slips, and because orbits are not circular.
I have looked at every GSM recognizable in Holocene cosmogenic records, and all but three take place at or close to the lows of the Bray and Eddy solar cycles. The probability of a GSM outside one of these lows is quite small.
To a certain degree then, SGMs can be predicted, and none is expected for at least another 500 years. This is in stark contrast with what several researchers have published regarding a coming SGM. I wonder if they have carefully studied SGM distribution in terms of cyclical solar activity during the Holocene.
My empirical model shows a grand solar minimum triplet through the next three solar minima, from the 2090’s, from around 2200 AD, and from around 2310 AD, with the first two both longer than the Maunder Minimum.
That would double the number of GSM not associated to Bray or Eddy lows for the past 11,700 years. It is highly unlikely. It is a lot more probable that your empirical model is incorrect. The Eddy solar cycle indicates an increased probability of the next SGM starting ~ 2500-2600 AD.
Your empirical model appears to be a rehash of the de Vries cycle during the Wolff-Spörer-Maunder period, but you are not taking into account that said period took place during the last Bray cycle low and the next Bray low is not coming until ~ 4000 AD.
That would double the number of GSM not associated to Bray or Eddy lows for the past 11,700 years. It is highly unlikely. It is a lot more probable that your empirical model is incorrect. The Eddy solar cycle indicates an increased probability of the next SGM starting ~ 2500-2600 AD.
Your empirical model appears to be a rehash of the de Vries cycle during the Wolff-Spörer-Maunder period, but you are not taking into account that said period took place during the last Bray cycle low and the next Bray low is not coming until ~ 4000 AD.
By your own reference, a cluster of three protracted solar minima is just one GSM. My model would account for all the solar downturns discretely without need to reference hypothetical Bray or Eddy solar cycles. And no the model is not a rehash of anything. It does though agree with what Leif Svalgaard said, that the only regular longer cyclic behaviour in solar activity [that he was aware of] are solar minima occurring roughly every ten solar cycles, with a long term average of every 107 years. The very long term astronomical mean by the model is every 108 years. Certainly the sequence of Holocene GSM’s are very irregular, with intervals of between ~400 years and ~1200 years, but there should be longer term periodic repeats of the sequence.
Hypothetical but supported by abundant evidence, as I am showing. Your empirical model has its next prediction in 70 years. That makes it irrelevant to explain anything, to increase our knowledge, or to have any practical effect.
“Your empirical model has its next prediction in 70 years. That makes it irrelevant to explain anything, to increase our knowledge, or to have any practical effect.”
That is all irrationally disparaging considering the quality of the hindcasts. It will greatly improve the forecast for the timing and intensity of the FFT component on the Steinhilber and Beer (2013) prediction of solar activity for the next 500 years.
http://onlinelibrary.wiley.com/store/10.1002/jgra.50210/asset/image_n/jgra50210-fig-0004.png?v=1&t=j51a24f6&s=b7e5a5d5e0568281b9295a97edc08e2997d65b0d
Hindcasts are not science, but skill.
It shouldn’t be difficult to greatly improve Steinhilber & Beer 2013 forecast, as they predict a low for 2100, when it corresponds to a high in the millennial cycle (1100 AD Medieval Warming Period -> 2100 AD Modern Warming Period).
Demonstrating the precise ordering of solar cycles and of solar minima certainly is science, the skill is in identifying the components and their relationships. We are not talking something like analogue years for weather synoptics here, but rather a very well defined set of fixed rules.
I am not impressed with this millennial cycle.
https://judithcurry.com/2016/09/20/impact-of-the-2400-yr-solar-cycle-on-climate-and-human-societies/#comment-813095
Leave Leif out of it… There’s a man who believes that the oceans equilibrate as fast as a mercury filled glass thermometer. (he’s not exactly the brightest bulb on the tree)…
“This means that all the lows in the Bray cycle had been identified as periods of reduced NADW contribution by different authors. Such periods might see a reduction in the northward flux of warm near surface waters in the North Atlantic to maintain mass balance (that could be the cause of the NADW reduction), and would result also in the cooling of North Atlantic high latitudes.”
Since the mid 1990’s negative NAO has increased, and the AMO has warmed. In the weak solar minimum of the 1880-90’s, negative NAO increased, and the AMO was in a warm phase.
Ulric,
That paragraph reflects the most common interpretation found in the literature to the effect of NADW changes on AMOC strength. This is an important issue as changes in AMOC could be responsible for important climatic changes. In fact scientists like Wally Broecker put forward the hypothesis (incorrect in my view) that global warming could produce a shut down of AMOC (unsupported so far by evidence) causing an abrupt cooling of Eastern US and Western Europe, that was reflected in the 2004 movie “The day after tomorrow.”
I also reflect an opposing view in the article above, which in my opinion is more correct:
“The authors show evidence that the increased salinity, temperature, and water stratification, at times of abrupt climate change, are due to an increase in the Atlantic inflow of warmer saline subtropical gyre waters at the expense of the fresher and colder subpolar gyre waters. They interpret it as a negative feedback from the subpolar gyre, that stabilized the AMOC, at times of freshwater inputs.”
So instead of a reduction of warm waters we would see an increase in the proportion of subtropical warm waters at the expense of colder subpolar waters. The AMOC then would not shut down, but adapt to different conditions. The evidence appears to support that the AMOC might have seen reductions in strength, but no evidence supports that it might have shut down.
As usual, incorrect catastrophic hypotheses make better movies filled with drama and strong scientist characters.
Javier,
My frame of reference is that increased forcing of the climate increases positive North Atlantic Oscillation states, driving a faster overturning, thereby reducing the warm water transport to the far North Atlantic and Arctic Ocean.
Yes, Ulric,
That is also my view of that matter based on the evidence I have read about.
https://www.iceagenow.info/sun-might-change-climate/
Solar up to 2005 despite it becoming lower since mid last century was still high and it should have caused warming which is what happened. Only since 2005 has solar activity been in an inactive mode which will promote global cooling.
I expect global cooling to begin (I think it has ) this year not 5 years from now.
Solar criteria is now moving to the values I had said would be significant enough to cause global cooling, following 10+ years of sub solar activity(2005-present) in general. Duration is now needed for my low average value solar parameters. I am of the opinion that if solar conditions are extreme enough it could move the terrestrial items which govern the climate to threshold values to one degree or another. This is perhaps part of the reason why abrupt climate change has occurred in the past.
TERRESTRIAL ITEMS
global cloud cover global
snow cover/sea ice cover
volcanic activity major
sea surface temperatures
atmospheric circulation
LOW AVERAGE VALUE SOLAR PARAMETERS NEEDED TO CAUSE GLOBAL COOLING
SOLAR FLUX SUB 90 IS IN PLACE
SOLAR WIND SUB 350 KM/SEC GETTING TOWARD THIS
COSMIC RAY COUNTS 6500 UNITS + IS IN PLACE
AP INDEX 5 OR LOWER COMING DOWN OF LATE
EUV/UV LIGHT- EUV 100 UNITS OR LOWER IS IN PLACE- UV LIGHT DOWN
IMF 4.2 NT NOT REACHED YET ON A REGULAR BASIS.
SOLAR IRRADAINCE OFF .15% not reached yet.
All given solar effects enhanced by a weakening geo magnetic field.
My solar /climatic play is very low sustained solar activity will result in an increase in the earth’s albedo ,while at the same time lowering sea surface temperatures the result is global cooling.
I expect global cooling to begin (I think it has ) this year not 5 years from now.
No way! We are in a natural, normal and necessary warm period that is the same kind of warm period as the Roman and Medieval Warm periods. This warm period will end after this warm period with open polar oceans promotes enough snowfall to rebuild ice volume on land to advance into another little ice age. This takes a few hundred years. This is a Northern Hemisphere cycle and the Southern Hemisphere cycle may stay warm and cool in phase or not in phase with this Northern Hemisphere cycle. This is about a thousand years cycle. There are shorter cycles in the data that confuses and causes most climate people, consensus and skeptic, to miss the longer cycles.
It can be demonstrated that global cooling started on March 2016. Nobody knows for how long it will proceed or how intense it will be. However very few people expect that the annual average GST will get lower than the 1981-2010 average. That the 1991-2020 average will be higher than the 1981-2010 appears a given at this point.
https://oz4caster.files.wordpress.com/2017/07/d4-cfsr-gta-daily-2014-2017-07-12.gif
https://oz4caster.wordpress.com/cfsr/
https://www.youtube.com/watch?v=5zIcR7ZNieE&feature=youtu.be
Javier you should watch this video.
Why? 55 minutes long and has nothing new in it. A power point version would take me 2 minutes to peruse. Being a fast reader I hate videos. They are such a waste of time.
Reblogged this on Floating-voter.
Thanks Javier. Further to your detailed review, see:
Nicola Scafetta et al. On the astronomical origin of the Hallstatt oscillation found in radiocarbon and climate records throughout the Holocene Earth-Science Reviews 162 (2016): 24-43.
Hi David,
As we will see in part B, the Bray solar cycle has a period of 2450-2500 years. Nine lows can be identified in the past 20,500 years. Scafetta’s cycle has 2300 years, and Chárvátova’s cycle has 2400 years. Both are too short and would get rather quickly out of phase. Even Chárvátova’s cycle would get shifted by at least 450 years in nine cycles and this is just not possible.
In planetary theory you can get different cycles using different planets, using baricenter movements, using solar inertia, or using planetary torque. However there is zero evidence supporting any of them, and it all appears as a game of matching two numbers. One is left with the impression that there is no particular reason why any of the many possible cycles should have an effect, and all the rest don’t.
Solar minima occur regularly roughly every ten sunspot cycles, with a duration of between one to five sunspot cycles from max to max, with the latter being major grand solar minima. This progression maps the start and duration of every one of them. The theory should be arrived at after the observation and not before.
https://snag.gy/Sivgtm.jpg
That’s the centennial ~ 105 year solar cycle, that appears to be a harmonic of the de Vries ~ 210 year solar cycle. This cycle is not constant in time, but is strongly modulated by the Bray cycle, as we will see in Part B, and it has been decreasing in amplitude for the past 400 years.
I have the suspicion with planetary theory, that any number that we could come up for one of these cycles could be matched to some orbital interference or other. Given my natural and trained skepticism, I will believe when evidence is provided, and not a minute before.
“That’s the centennial ~ 105 year solar cycle, that appears to be a harmonic of the de Vries ~ 210 year solar cycle. This cycle is not constant in time, but is strongly modulated by the Bray cycle..”
It has nothing to do with a ~ 210 year cycle, it is not 105 years, and the triple clusters of solar minima in GSM would go against a 210 year cycle. The intervals between minima can vary +/- 2 sunspot cycles, with a mean of ten sunspot cycles over very long periods. The occurrence of GSM’s is inherent to the nature of the progression, it does not require modulation by any long period cycle as an explanation.
“I have the suspicion with planetary theory, that any number that we could come up for one of these cycles could be matched to some orbital interference or other. Given my natural and trained skepticism, I will believe when evidence is provided, and not a minute before.”
I have provided a brief account, so rest your suspicions and inspect it for yourself.
Javier, I fully understand your position on planetary theory, there are so many cycles that can be massaged to fit a particular outcome, and there are so many “quacks” out there pushing their form of this nonsense.
But I fear your are missing one very clear cycle in solar proxy record across the Holocene, the 4267 year cycle.
http://www.landscheidt.info/images/INTCAL13_GRIP.png
Pick any spot in the Holocene record and move back or forward 4267 years and you will find a mirror image of the solar record.
The 4 outer planets only repeat their position in relation to each other every 4267 years (this is a given and backed up by our best planetary data, JPL etc). The Bray cycle is a secondary cluster that occurs during the 4267 year cycle where the positions are close to LIA type events but not as strong. These events are not quite in the middle of the 4267 year cycle which explains why the Bray cycle varies from 2100 – 2600 years.
This is solid evidence for planetary influence being the major driver of grand minima clusters, the 4 outer planets are in the same position when these events occur.
If you have any doubts, a simple solar system viewer by date will prove my falsifiable point. We have discussed this before, obviously my point didn’t cut through?
Apologies, that should read “4627” year cycle.
Geoff,
I might be a bit slow, but I have trouble distinguishing a planetary cycle from another. I’ll try to keep an eye on the 4627 year cycle. However it has the same problem with regard to the Bray cycle. It is too short. Two Bray cycles should be around 4900-5000 years. Otherwise they get out of phase rather fast.
Do you have any bibliography on this periodicity?
Hi Javier, there is no bibliography on this period that I know of other than the JPL database. But we have an ephemeris that is 20,000 years long that I have tested with some diligence.
The simple fact is that the outer 4 planets do not repeat their positions in relation to each other for 4627 years. What we need to do is throw out the Bray Cycle and look what happens in regard to clusters of grand minima across the 4627 period. If the LIA is at the end of the period there is a similar cluster 4627 years before (and 4627 years before that). But during this period there is another cluster not quite as strong that occurs around 2100 years from the start of 4627 year period if aligned with LIA type clusters.
That is why the Bray Cycle is quasi and not consistent, we need to change our thinking.
It is interesting that we both have the same predictions for solar grand minima going forward 1000’s of years. Yours is based on patterns from the past and mine is solely on planet positions. The coincidence is not by chance.
BTW, my paper has been reproduced by McCracken, Beer and Steinhilber, they are in complete agreement with me and reference me several times. Scafetta who also referenced my work backs up the JPL data in his Hallstatt paper.
One day this theory will be debated properly. I look forward to that day.
I am not very attached to hypotheses, not even my own, because I am very attached to evidence. And I’ll be willing to throw out the Bray Cycle when there is more evidence against it than for it. Meanwhile the evidence for the Bray cycle is pretty strong, with a very good correlation of climatic effects and solar activity. And I have yet to see any evidence for any of the multiple planetary hypotheses around. I have an open mind, and I am not closed to the idea that the planets could have an influence on solar activity through a completely unknown mechanism. But without any evidence, that proposition remains a path that leads nowhere.
Geoff~
Your chosen Jovian configuration occurred in 1830, well after the Dalton Minimum. And there are a string of them one third of the 4627 year period back from the LIA, during the the Roman Warm period. At 76 BC, 104 AD, and 283 AD.
“The Bray cycle is a secondary cluster that occurs during the 4267 year cycle where the positions are close to LIA type events but not as strong. These events are not quite in the middle of the 4267 year cycle which explains why the Bray cycle varies from 2100 – 2600 years.”
There is a pair in the middle, 179 years apart. So going forward from e.g. 1306 where all four are in inferior conjunction, the pair occurs 2224 and 2403 years later in 3530 and 3709 AD. The latter in this case is a tighter alignment, but that would vary on the starting point as the orbits are not circular.
(set date and click ‘update’)
https://www.fourmilab.ch/cgi-bin/Solar/action?sys=-Sf
Javier,
The solar proxy record is clear, there is no recurring 2400 year cycle when it comes to clusters of solar grand minima. But there is evidence of a 4627 year cycle as I have shown. The smaller clusters are what leads one to think there is a smaller cycle but in reality the gaps are roughly 2100, 2500, 2100, 2500, 2100, 2500 etc going on for thousands of years.
Of interest is that the 4627 year cycle will break down in time as Jupiter moves out of phase with the other 3 planets by about 2 deg every 4627 years.
Also of interest is that in my original work I used the INTCAL98 14C record to check my theory against, and at the time if we went back 4627 years from the LIA there was no corresponding LIA type event occurring. There was a 340 year error.
http://www.landscheidt.info/images/11000c14.png
At the time I suggested either the Dendrochronology record was wrong or my theory was busted. Guess what, the Dendrochronology record was wrong and now has been amended as shown in the INTCAL13 record where the mysterious 340 year error vanished silently. The 10Be record has also been amended as it uses the tree ring record for dating purposes.
There are two papers covering this theory, I suggest you read them carefully as they are closely coupled with your work.
http://www.scirp.org/journal/PaperInformation.aspx?paperID=36513&#reference
http://link.springer.com/article/10.1007/s11207-014-0510-1
If you don’t have access to the paper in Solar Physics let me know and I can send you a copy.
Geoff,
I agree that the solar proxy record is clear, but on stating the opposite that you defend. The solar data will be presented in part B showing very clearly the 2475-year solar cycle. And I also use IntCal13. The question is if you will then accept the evidence presented in figure 57 that is absolutely clear for anybody to see. In the meantime, regarding the question of the clustering of SGM at the lows of the Bray cycle, I refer to figure 8A of:
Usoskin, I. G., et al. “Solar activity during the Holocene: the Hallstatt cycle and its consequence for grand minima and maxima.” Astronomy & Astrophysics 587 (2016): A150.
https://www.aanda.org/articles/aa/full_html/2016/03/aa27295-15/F8.html
“figure 8A of: Usoskin, I. G., et al.”
Less than half within +/- 250 years of 2400 years. A 2400 year interval gives only five GSM’s through the whole Holocene. I can see five in the last 4000 years. The LIA, the Antique LIA, the Greek Minimum, the late Bronze and Mediterranean collapse around 1200 BC, and a fifth around 2000 BC, also noted for its desiccation of the Med region. To make sense of these events, we need to understand why they each happened when they did. Probabilities are of no worth for predicting events of such variable frequency, especially over such large time scales.
The solar data will be presented in part B showing very clearly the 2475-year solar cycle.
This I got to see…
Geoff says:
“Of interest is that the 4627 year cycle will break down in time as Jupiter moves out of phase with the other 3 planets by about 2 deg every 4627 years.”
Ah that was my apparent hand waving, sarc/
It’s more than 2 deg.
https://judithcurry.com/2016/09/20/impact-of-the-2400-yr-solar-cycle-on-climate-and-human-societies/#comment-813103
That’s pretty much what we have in paper, published in the journal Environment Pollution and Climate Change. It’s all about the sun, irrespective of the composition of the atmosphere and more specifically, “top-of-the-atmosphere solar irradiance and total surface atmospheric pressure. The hereto discovered interplanetary pressure-temperature relationship is shown to be statistically robust while describing a smooth physical continuum without climatic tipping points. This continuum fully explains the recently discovered 90 K thermal effect of Earth’s atmosphere… the atmospheric ‘greenhouse effect’ currently viewed as a radiative phenomenon is in fact an adiabatic (pressure-induced) thermal enhancement analogous to compression heating.”
.
Not the best choice of venue for publishing.
(Wikipedia) OMICS Publishing Group is widely regarded as predatory.
“the U.S. National Institutes of Health does not accept OMICS publications for listing in PubMed Central”
(Statnews) Are ‘predatory’ publishers’ days numbered?
“According to the US Federal Trade Commission, at least one of these mimics, called the OMICS Group, is a “predatory” publisher.”
You mean, pigs can’t fly? Say it ain’t so– that this paper has no more credibility than claims by Cook and Orsekes’ conclusion that 97% of all climate scientists agree with AGW theory?
Wagathon,
I can’t attest to your article’s credibility as it is far removed from anything I have knowledge, although some aspects of it are troubling:
” Some parameter values reported in the literature did not meet our criteria for global representativeness and/or physical plausibility and were recalculated using available observations as described below.”
However it is the publishing venue chosen that it is damning. For somebody publishing in a scientific predatory journal, one has to either not know or don’t care, and both are bad indicators.
Predatory journals would publish anything for a price. Even garbled meaningless texts, as it has been demonstrated.
I rather prefer an honest unreviewed internet article, that an article published in a dishonest predatory journal. People should be aware that these type of journals exist and learn not to trust things just because they have been published somewhere. And since I can’t comment on your article, I have nothing further to say about this issue.
So, all recalculations are per se troubling, even when explained? What we don’t like is unexplained adjustments and worse yet data that has simply gone missing when it does not fit the narrative.
–e.g.,
Javier
Another great very interesting and timely post.
From recent analysis, an increase temperature increases hemisphere pressure, and importantly the volume of atmosphere available for transport. Primarily driven by NH events.
Ultimately any increase in atmospheric volume affects the poles with increased intrusion, also transporting heat. Seasonal influences control hemisphere destination bias. This has been most noticable in the Arctic with decline.
One of the areas of my focus was determining and recording the volume and pressure of atmosphere entering the Arctic. Results confirm that his has been the cause of change in Arctic sea ice area.
On a larger scale, I believe that these drivers could play a larger role in glacial to interglacial transition than currently thought.
I expect to have a summary out by early September.
Regards
I am sure it will be interesting. I’m looking forward to reading it.
Javier points of disagreement
Co2 has no influence on the climate. You incorrectly think it does.
Galactic cosmic rays do influence the climate by promoting more cloud coverage.
There is a volcanic /solar link.
Chances are solar activity will be at Dalton Levels going forward.
Global temperatures look like they are now starting tor decline in response to very low solar conditions.
The question is will solar cycle 24 be long, if so this period between solar cycle 24 and solar cycle 25 is going to be very long and deep.
Javier
thank you very much for this very interesting article. There is a lot of material in there so it warrants several reads.
Can you clarify when the 2400 year cycle last had its effect as you have a mass of graphics?
Also how long does it take for the effect to wear off? That is to say, would any other lesser climate cycles cancel out the 2400 year effect after say 50 or 100 years?
tonyb
Hi Tony,
According to 14C data the last Bray cycle low was centered at 600-400 BP (1350-1550 AD). The climatic effects can last longer as solar activity decreases toward the low and there is a slow recovery afterwards, so the climate is affected for 400-600 years. The LIA was longer because right after the Bray low took place the Eddy ~ 1000 year cycle low centered at the Maunder minimum, and made worse by the effect of the non-solar ~ 1500-year climate cycle. Together with the declining Milankovitch insolation that made it the coldest Holocene period so far, well attested by glaciers.
My view is that as solar activity decreases below a threshold, an atmospheric reorganization starts slowly contracting the Hadley cells and expanding the polar cells (supported by evidence). This is a slow incremental process that reverses the moment solar activity goes above the threshold, so the effect on the 11-year solar cycle is averaged and has a very small climatic effect. When the low in the Bray cycle approaches, the time expent below the threshold is longer than above, so the atmospheric reorganization proceeds at stretches producing an incremental noticeable effect, like the cooling between 1100-1350 AD. At the same time the effect of the de Vries ~ 210 year cycle, that is modulated by the Bray cycle, increases, creating periods every 105 and 210 years when solar activity goes even lower for longer. At the Bray low the de Vries cycle causes solar activity to collapse to a basal level well below the threshold for ~ 80 (Maunder type) or ~ 150 (Spörer type) years. This is a solar grand minimum during which the atmospheric reorganization proceeds uninterrupted towards a colder state. But three things cause the climatic effect to be irregular. First, solar activity increases between these periods, sometimes to normal levels, so the process reverses sometimes for several decades. Second, the climatic effect is probabilistic, not deterministic. The chances of very cold winters are increased, but warm winters can still occur. Third, the climatic system oscillates (the Stadium Wave effect), sometimes increasing, sometimes decreasing the solar effect. The result, as you very well know, is that you can find warm periods within the Bray low. They just become less frequent.
This slow atmospheric reorganization explains why the high solar activity in the 18th century did not produce the same effect (temperatures) as similarly high solar activity in the 20th century. The starting conditions were very different so despite both producing warming, the final result is quite different.
Another important point is that climate sensitivity to solar variability forcing is not equally distributed in the planet. Some regions appear to be more sensitive than others, and the North Atlantic region is probably the most sensitive of all. While the LIA was a global phenomenon, its impact on Eastern US and Western Europe was very much enhanced.
Javier my thinking is very similar to your explanation here.
Spörer is actually two separate solar minima, one from around 1430, and another from around 1550. Regardless of what sunspot numbers may infer about the length of the Maunder Minimum, there was a sharp atmospheric shift to a strongly negative NAO regime largely confined to the period 1672 to 1705.
“At the same time the effect of the de Vries ~ 210 year cycle, that is modulated by the Bray cycle, increases, creating periods every 105 and 210 years when solar activity goes even lower for longer.”
Apart from the difficulty in explaining why it should produce a 105 period, when the origin of the 210 year period is unknown, it would be even harder for it to account for the intervals between solar minima regularly varying from between 8 to 12 solar cycles.
The proposition that the 105 and 210 year cycles are harmonics is just an hypothesis, since harmonics do happen.
That a cycle’s origin is unknown doesn’t mean it is not real. The knowledge of the seasons existed for many thousands of years before its origin could be determined.
The word ‘cycle’ in this case is an abstraction. There are solar minima varying between every 8 and 12 solar cycles, these are periodic events and not a cycle as such. A 210 (207?) year cycle would not produce a subharmonic *pulse* with such frequency variability, and it would not maintain phase integrity with solar minima as it is too short. I read that de Vries is not apparent in the last 400 years of sunspot numbers.
Of course the de Vries cycle is apparent in the last 800 years. As I will review the de Vries cycle in due term, there is no point in reviewing the evidence here.
Ulric Lyons, My limited understanding is that de vries is a radioactive isotope cycle not a sunspot cycle. You perhaps already know this? Sorry I can’t link with my Samsung phone. If you goggle de varies climate (more than one de vries) and go six links down you’ll see a science director article that explains it
It is supposedly a regional phenomenon. De Jager also has a pdf up. I’ll try to post some links if I go to the library tomorrow
Hi Ordvic,
de Vries is not a sunspot record cycle because the sunspot record only has 400 years, and you need more than two periods to identify a periodicity in the data.
Perhaps you refer to the Ogurtsov et al. 2016 article:
Ogurtsov, M., et al. “Possible solar-climate imprint in temperature proxies from the middle and high latitudes of North America.” Advances in Space Research 57.4 (2016): 1112-1117.
http://www.sciencedirect.com/science/article/pii/S0031018207005214
As I have said in one of the comments, the response to solar forcing changes on a regional basis. This regional variability has been modeled, so it is at least explainable. Central Asia is one of the regions that displays a strong response to solar forcing, and the de Vries cycle is very clear in tree ring climate reconstructions from that area.
Yeah that’s the one, thanks
Sorry, the reference above is incorrect (the link is correct). The reference is:
Raspopov, O. M., et al. “The influence of the de Vries (∼ 200-year) solar cycle on climate variations: Results from the Central Asian Mountains and their global link.” Palaeogeography, Palaeoclimatology, Palaeoecology 259.1 (2008): 6-16.
http://www.sciencedirect.com/science/article/pii/S0031018207005214
Low frequency spectral energy is enough to dismiss global warming. It means you have long trends related to nothing in particular.
To detect a particular cycle, it has to rise above the noise level by a great deal. The energy at any frequency has a negative exponential distribution from noise alone, so is very spikey (rayleigh distribution). With a real signal buried in it, you get a rice distribution, still noisy unless the signal is big.
As far as future solar activity my conclusion is we all do not know including myself.
However I am quite confident that if solar conditions are quiet enough for a long duration of time the result will be global cooling.
There is much ice on land in cold places in both hemispheres, much more in the Southern Hemisphere Antarctic than in the Northern Hemisphere. Ice provides cooling by reflecting and by melting and by dissolution. Ice melts at the freeze thaw point. Ice dissolves, which is different than melting, at temperatures below freezing, when contacted by salt water, providing even more cooling. This occurs on the underside of sea ice sheets and on the underside of ice shelves and glaciers that extent into salt water. This occurs around icebergs, even more as they flow into warmer oceans. Warm tropical ocean currents flow to Polar Regions and get chilled, some of it to below the freeze thaw point. This cold water sinks and flows back to the Tropics. This provides much cooling that is neglected by climate scientists. Graeme Stevens (JPL) and Jerry North (Texas A&M) told me that after Graeme gave a presentation at A&M. Dr Neil Frank also has mentioned to me it is not considered. I believe that this is a major flaw in consensus and skeptic climate theory and therefore in models. The Little Ice Age was colder than the Roman and Medieval warm periods. Cold periods are associated with more ice extent and warm periods are associated with less ice extent. I believe this is cause and not result. Ice volume on land grows due to ocean effect snowfall that falls on land when oceans are thawed and ice shelf and sea ice extent is small. Ice volume on land depletes when oceans are frozen due to lack of ocean effect snowfall that reaches land when ice shelf and sea ice extent is large. Ice advances as, and after, ice volume grows. Ice retreats as, and after, ice volume decreases. This is clearly shown by the ice core data. Ice core temperature is not the temperature of an ice core, it is the temperature of the oceans, determined by isotopes, that supplied the water for the snowfall. Ice cores are the best proxies for ocean temperatures in both hemispheres which is the best measure of earth temperature. This does not conflict with other theories, many factors influence temperature and sometimes correlate with temperature, other factors resonate in and out of phase with temperature, showing correlations, but if temperature tries to go out of bounds it snows more when oceans thaw and it snows less when oceans freeze. Ice extent resonates in phase with temperature, driving, not driven. Ice extent is always more in colder times and less in warmer times. That supplies bounding that has a set thermostat which is the freeze thaw point for oceans. This does not cause an equilibrium temperature; this creates a robust cycle. Temperature cycles toward an upper bound after it snows too much. Temperature cycles toward a lower bound after it snows too little. Then this repeats, in the same bounds, in both hemispheres, even while, over the past ten thousand years, almost 40 watts per square meter left the Northern Hemisphere above 60 degrees and entered the Southern Hemisphere below 60 degrees. These climate ice cycles are robust, resilient, self-regulating, and self-correcting. The NH and SH have cycled inside the same temperature bounds as each hemisphere regulated itself, not in phase with each other, for ten thousand years. Past, even warmer, periods, before twenty thousand years ago, occurred because there was more water in the oceans to be warmed. Major ice ages, before twenty thousand years ago, occurred because the more, warmer water promoted more massive ocean effect snowfall on land in cold and more temperate places. The major ice ages ended because the less water in the oceans was ice covered and could not provide enough snowfall to maintain the ice. Ice ages occurred because there was huge amounts of ice on land. The snowfall that put the ice on land only occurred when oceans were higher and warmer. The ice chest stays cold until the ice is depleted. The earth stayed cold until the ice was depleted. The earth warmed as the depleted and thinned ice sheets finally retreated. The amount of ice and water that took part in these cycles, increased over the past few million years until the last major warm period and last major ice age had removed enough water and sequestered it on the Antarctic, Greenland and the High Mountain Glaciers. Every warm cycle, even the little ones during the long cold ice age, placed some of the ice in cold places that did not reenter the next cycle. There is not enough water left in the oceans to promote another major warm period. Without another major warm period, there cannot be another major cold period.
The most recent ten thousand years is the new normal. The Little Ice Age occurred after it snowed more during the Medieval Warm Period. Earth cooled as the ice advanced. The Little Ice Age ended after it snowed less during the Little Ice Age. Earth warmed as the ice retreated. We are in a temperature increase hiatus because oceans are thawed and it has snowed enough to increase ice volume that has halted the ice retreat. The ice volume that will advance into the next Little Ice Age is already growing. This warm period will last about as long as the Roman or Medieval warm periods lasted and then we will cool again. This warm period will stay warm until the ice volume is sufficient to advance, like it has in the past. This is a normal and necessary part of the natural cycle and we did not and cannot cause it. Read more on my website: http://popesclimatetheory.com/
Popes your theory would be good if it were not for all the sudden abrupt climatic changes as shown with Ice Core data.
You fail to address it. Your thinking suggest very slow gradual climate change in addition both hemispheres have cooled in sync with one another.
Salvatore
Popes your theory would be good if it were not for all the sudden abrupt climatic changes as shown with Ice Core data.
Sudden changes occurred because ice thawed, water was trapped and dumped into the oceans in surges at the end of the ice age as ice retreat and warming occurred..
I have explained that in different ways on different pages in my website.
https://wattsupwiththat.com/2013/06/02/multiple-intense-abrupt-late-pleisitocene-warming-and-cooling-implications-for-understanding-the-cause-of-global-climate-change/
This is where it’s at and I see NO explanations to explain it.
My best guess is solar changes bringing the climate to thresholds to put it in one sentence.
Javier, thank you for the essay.
http://www.pnas.org/content/97/4/1331.full
How fast the climate can change . Ice Core data.
I am a geologist who trained to some extent in glaciology, so I feel I have some creds to be impressed with this summary. And to sympathize with researchers who find regional time or event disconnects in studies. After all, if the monsoons move south, it is obvious that one region gets wetter while another gets drier: such things are contradictory only when the trees and not the forest are in your eyes.
And I have seen with my own eyes the clear evidence of glacial advance/retreat of the LIA in the Canadian Rockies and sea level variations from Florida to Abu Dhabi over the last 12,000 years. Cyclic variation is real; stability is an illusion created by the narcissism of our short human lives.
But …. as evidence against the CO2 monster, all this fails. The problem is what some geologists call “equifinality”: that more than one cause can produce the same effect. I call the impact on the CAGW alarmists the “Unique Solution Syndrome”: that a solution, once found, must necessarily be the correct one as there is only one solution possible (if only right now, in this instance under discussion).
For the alarmists three conditions cannot be refuted: 1) that on the time span in question, the solar cycles appear unimportant. The post 1850 period is only 5% of a Bray cycle. 2) anthropogenic CO2 has a solid increase since 1850. And 3) CO2 is a green house gas. These 3 combine the “specialness” with a warming element everyone agrees has some reality.
The best a red team/blue team or honest IPCC report can do with all this science is to admit another non-human cause could be contributing in a meaningful way. Not is but could be as the outcome of CO2 and nature is the same. Which in the continual use of conditional – could, might, may – is actually already what the “scientific” statements say! As a grudging sop to the skeptics, an increased admission might be acceptable but would not change the warmists ardor (except angering them by increasing doubt amongst the infidels).
However ….. doubt is a legitimate reason for governments to delay anti-CO2 measures. And delay gives us the time for challenges to data adjustments to sow doubt in even the current magnitude of the “problem”. And, more importantly, time for nature to slide into the cooling phase of the current warming cycle that many, including me, believe is significant today.
The moderate have no historic power to create movement, only interfer in the spead or direction of the movement. The extremes drive action. So Gore causes a panic while Morano disipates the energy until the reason for the panic is shown false (or, possibly, true, like Chamberlin in 1939). Unless the world catches fire soon, Gore will slide into irrelevance as Suzuki has already in Canada – a symbol rather than leader. Already it is noteworthy that neither has a replacement in the wings: time will remove the CAGW champions unless the sky falls in doon. And if the world cools or fails to warm for another 5 years, the technical dominance of computer models will be untenable.
Atmospheric CO2 will rise. Fossil fuels will be burnt. Developing countries won’t allow energy costs to prevent them competing economically. Developed country taxpayers don’t want to reduce their lifestyle to theoretically improve that of others any more than Gore or DiCaprio do. It is in the personal interests of all people to find a reason to at least delay anti-CO2 legislation. Doubt does that. Natural cooling would be more effective, but doubt is enough.
So science is the solution to one side – the skeptic – and the enemy to the other – the warmist. But science and in particular geo historical science is not where “resolution” will be found. The equifinality problem and unique solution syndrome will continue to plague us.
Very interesting comment, Douglas. I completely agree.
CO2 has zero effect upon the climate.
Interesting post. Have now read it twice. Had not come across the Bray cycle before.
Perhaps you know it by its improper name of Hallstatt.
Attempts to learn about climatic behavior over millennial time scales must necessarily rely upon proxy data of one kind or another. Understandably, the intrinsic limitations of the latter, relative to instrumented data, always need to be taken into account. Yet for the life of me, eyes that have seen and analyzed geophysical time-series of every variety, fail to see the evidence presented here for the Bray cycle as showing it to be truly quasi- periodic (narrow-band) in spectral structure. What is apparent is very much broad-band behavior inconsistent with a periodic driver. And, more importantly, the coherence between different proxies seems to be weak, at best.
Perhaps, working for nearly half a century in a far more rigorous field than paleoclimatology, I’m simply unequipped to appreciate the subtle indications it provides. Nevertheless, the serious doubt lingers that a much-too-sanguine view of the reliability of proxy data underlies it’s ambitious claims.
.
I suppose this matter is to be judged by journal editors and specialist referees, and indirectly by the entire field through citations. If you check the bibliography linked at the end of the article you can see that the quality of the journals suggests no serious doubt lingers in the field that the reliability of proxy data underlies its claims.
As an example the article:
Rimbu, Norel, et al. “Holocene climate variability as derived from alkenone sea surface temperature and coupled ocean-atmosphere model experiments.” Climate Dynamics 23.2 (2004): 215-227.
http://epic.awi.de/11125/1/Rim2004b.pdf
From which figure 56 has been extracted, in its abstract states:
” The dominant modes of Holocene SST variability emphasize enhanced variability around 2300 and 1000 years,” identifying in their proxy assortment the two main Holocene climate cycles. According to Google scholar the article has received 103 citations.
While you are entitled to your doubts, it must be made clear that the issues raised in this article are an important part of mainstream paleoclimatological discussions, and not some selected fringe, overstated, and niche issues.
When “mainstream paleoclimatological discussions” manifest little, if any, comprehension of data reliability issues and signal characteristics that are well-recognized in other, far-more-rigorous, fields of science, it’s not simply a matter of “some selected fringe, overstated, and niche issues.” It’s a much more fundamental matter of ill-founded paradigms that seem endemic throughout mainstream “climate science.”
Quite the contrary, paleoclimatologists appear to comprehend very well the nature of their data.
This is from:
Witt, A., & Schumann, A. Y. (2005). Holocene climate variability on millennial scales recorded in Greenland ice cores. Nonlinear Processes in Geophysics, 12(3), 345-352.
“3 Climate proxy data are awkward data
From the viewpoint of statistical data analysis climate proxy data based on lab measurements of ice cores are data with awkward sampling properties:
– Isotope-based age estimates that are affected by random and systematic errors cause uncertainties concerning the age axis. This property makes paleo climatic records fundamentally different to all data resulting from direct instrumental measurements as instrumental climate data, output of physical lab experiments or even medical data as ECG/EEG measurements. Moreover, these uncertainties along the time axis, i.e. the standard deviation of the random error concerning the estimated ages, grow backwards in time. An appropriate data analysis has to be performed.
– Due to the nonlinear age-depth relation the data are unevenly sampled. Further, the mass pressure of the ice leads to an increasing compression with growing overburden or age, hence, to a strong depletion of the lower, i.e. older, part of the ice sheet. Laboratory measurements are performed for core slices of constant thickness; consequently the data density (data per age interval) in the older part diminishes dramatically.
– As usual, amplitudes are disturbed by noise. The noise intensity of the GISP2 data varies for different paleo climatic periods and is further affected by changing sampling rates.
Standard time series analysis techniques and related software packages require evenly sampled and stationary time series, and implicitly, a well-defined time axis. Since data under consideration do not fulfill these assumptions alternative techniques are required.”
As I said, you are entitled to your opinion, but when coming from outside a scientific subfield, without much knowledge or experience about how they conduct their research, you adopt a disqualifying position, it is pretty clear to me that you have left behind your “far-more-rigorous” stance, as you are judging without knowledge.
There’s a profound irony in citing the astute critique of ice core data by nonlinear dynamicists Witt & Schumann as evidence that “paleoclimatologists appear to comprehend very well the nature of their data.” On the contrary, if that were the case, the critique would have come not from those who specialize well “outside [the] scientific subfield,” but from “climate scientists” who present their readings of the “awkward” proxy data to the world.
It’s also deeply ironic that, by applying suitable wavelet analysis methods to the GISP2 data, Witt & Schuman find strong evidence for a reasonably narrow-band 1.37kyr cycle, but none for the 2.4kyr Bray cycle that is touted here.
Everyone’s entitled to their opinion, but when it comes from mere visual impression of time series–a widely evident means of conducting paleoclimatological research–it is pretty clear to me that anything resembling rigorous science has been left behind in favor of bald presumptions about the knowledge of critics outside the all-too-arcane subfield.
Apparently you didn’t read the last paragraph of the post above. It is well known that the 2400 year Bray cycle does not reflect in Greenland ice cores 18O data, but it appears quite clearly in the chemical species data.
From Mayewski, Paul A., et al. “Major features and forcing of high‐latitude northern hemisphere atmospheric circulation using a 110,000‐year‐long glaciochemical series.” Journal of Geophysical Research: Oceans 102.C12 (1997): 26345-26366.
http://onlinelibrary.wiley.com/doi/10.1029/96JC03365/full
http://i.imgur.com/pgi79eb.png
The reasons why Greenland climate shows opposite response to solar forcing have been explained in detail by several authors, including:
Kobashi, T., et al. “On the origin of multidecadal to centennial Greenland temperature anomalies over the past 800 yr.” (2013).
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150002680.pdf
But your position on paleoclimatology as arcane, non-rigorous subfield prevents you from knowing this, and thus your opinion is based on lack of knowledge on the subject you criticize.
By pointing to results from the Mayewski et al. analysis of GISP2 “chemical species data,” the discussion is brought even further afield from the question of a Bray cycle in Holocene climate variations. In a companion paper it is stated:
They go on to claim evidence for 6500yr and 1450yr cycles in the North Atlantic, without any mention of the Bray cycle. Meanwhile, Kobayashi et al. seems irrelevant to the issue, because it treats only multi-decadal and centennial scales of variation. Anyone with professional understanding of geophysical power spectra will recognize that mechanisms that may be effective in some frequency interval need not be so throughout the entire baseband.
While I do not rule out the possibility of the existence of ~2400yr cycles in some climate variables, the absence of any evidence for such in the GISP2 δ18O record for the last 8 thousand years–perhaps the most carefully-reconstructed proxy data available–provides a strong caveat against claims of a globally effective quasi-periodic Bray cycle.
The spectral peaks shown by Rimbu et al., based upon a whole chain of mathematical decompositions of SST proxies, are simply much too wide-band to have been generated by a strictly periodic astronomical driver. Serious doubts about such attribution thus will persist in the minds of those who read paleoclimatological literature with a modicum of scientific insight.
I wonder if you have read the article given your lack of interest. It is an article dealing with 110,000 years, most of it about the last glacial period, where the 6200-year cycle represents the Heinrich cycle, and the 1450-year cycle the Dansgaard-Oeschger cycle, both glacial cycles. However these are exact quotes from the article:
“To investigate the possible role of solar variability in forcing changes in the PCI, we compare the spectrum of the ~11,500-year ∆14C residual series derived from tree rings and coral reefs [Stuiver and Braziunas, 1993] with the most recent 11,500 years of the 110,000-year-long PCI series.
…
For purposes of this study we chose only to investigate those periodicities which are common to both series and which we have thus far dealt with in this paper, namely those at 2300, 1450, and 512 years. They are all at the >99% significance level except for the 512-year periodicity for the PCI, which is >95% significant.
…
Finally, the presence of a possible solar-linked 2300-year periodicity, close to the global scale 2500-year cooling cycle suggested from Holocene glacier fluctuation records [Denton and Karlen, 1973] demonstrates that atmospheric circulation records may contain embedded evidence of solar-climate relationships.”
Kobayashi et al., 2013 is relevant to the study because they demonstrate that Greenland shows an inverse response to solar forcing, and therefore should not present a recognizable climatic signal for the Bray cycle given its solar origin. I guess you didn’t read that one either.
the absence of any evidence for such in the GISP2 δ18O record for the last 8 thousand years–perhaps the most carefully-reconstructed proxy data available–provides a strong caveat against claims of a globally effective quasi-periodic Bray cycle.
Or quite the opposite, a strong caveat about interpreting that GISP2 represents a global climate record when it doesn’t. It is a Central Greenland climate record.
I warned about that in the last paragraph of the article. Those that rely too much in a single proxy are bound to be wrong.
It’s amazing how quickly one’s own earlier words are forgotten in the face of criticism!
FYI, I did scan the entire Mayewski paper. Meanwhile, there is not even acknowldegement on your part of the substantive issues I’ve raised.
Merely citing published words without deeper comprehension just doesn’t cut it in mature debate. I have no interest in responding further to such polemical legerdemain.
Well, you didn’t get to the 2300 year periodicity part, because you said it wasn’t mentioned.
They are not for me to answer. They are for the scientists researching the issue. I just report on published peer-reviewed evidence that forms a coherent picture supporting a ~ 2500-year climate cycle of solar origin, that is the main climate cycle of the Holocene. I am not responsible in any way for the research or the data analysis.
You don’t find the evidence presented convincing? Fine with me. Opinions abound.
Well, I hope you do a better job of reporting than what is evident in the misrepresentation of my words: “without any mention of the Bray cycle.” By your own earlier statement, a 2300yr cycle is “too short” to be that.
The identification of the Bray cycle periodicity has been variable depending on the data, proxy, and method used. If you were to read the bibliography you would know that. Most studies identify the cycle as 2300-2600 years. Such variability with the type of data is understandable. The very well known and very well accepted 11-year Schwabe cycle is actually 9-14 years in length, and nobody comes doubting it for that. The 2475-year Bray cycle is actually 2250-2650 years in length. The sun is not as regular as you believe it should be.
The 2475-year Bray cycle is actually 2250-2650 years in length. The sun is not as regular as you believe it should be.
This is as perverse a response as your earlier pretense that I interpret the GISP2 record as a “global climate record.” You can’t claim that the Bray cycle is periodic and then provide a 400-year range without calling into question your knowledge of what the term “periodic” truly means scientifically. Nor can you presume to know what anyone’s unstated beliefs are.
Scientific novices, who have no idea why temperature-related proxies show no evidence for the fairly wide-band Bray cycle, might buy a non-scientist’s uncomprehending regurgitations of academic speculation about millenial-scale solar cycles as proven truths. Along with many others here, I refuse.
The Bray cycle is as periodic as the Schwabe (11-year) solar cycle that shows significant changes both in period and amplitude. And last time I checked everybody was talking about Solar Cycle 24. SC23 was 12.3 years long, while SC22 was only 10 years and I didn’t hear anybody complaining that it is not a cycle. I guess solar physicists understand that a cycle can have a variable periodicity, and they are scientists.
What you buy or don’t buy is your problem alone. I present the evidence available in the literature in favor of a climatic and solar ~ 2400 year cycle. As we will see in part C the evidence is self-consistent. It is what should be expected to be found if certain models based on instrumental data and reanalysis for the past decades were true. The regions that respond more clearly to solar forcing do it in a consistent manner to other solar cycles too.
After seeing the evidence presented you are welcome to believe what you want, but you should let others decide by themselves without calling them “scientific novices”. When in a scientific debate somebody claims that the scientific position is his, he is actually not debating but trying to diminish the opposing view. We know alarmists are abusing that fallacy. Anybody can check the linked bibliography and see by themselves that the position I present is reflected in the best journals, so go somewhere else with your accusations. Also, I am a scientist and I understand what I write about, so you are wrong on that too. Heck I doubt you have been right on anything you have wrote here. You even said you had no interest in responding further some comments ago and proved yourself wrong on that too.
The first paragraph should be italicized.
Nonsense! Neither is T-periodic in any strict scientific sense of f(t + T) = f(t) for all t. The power spectrum of the Schwabe cycle is, however, quite narrow band (aside from phase-locked higher harmonics due to nonlinear wave form). By strong contrast, the Bray cycle is wide-band, although the amateurish way of plotting the periodogram versus the log of period [sic!} makes that difficult to see in Mayewski’s graph–which shows an even stronger peak at ~2900yrs. Plainly unacquainted with the role of spectral bandwidth in signal characteristics you conflate it with changes in visually apparent “”period and amplitude.”
Even more distressing is your apparent premise that solar variability as expressed by these cycles is a driver of global temperatures. Instrumental data clearly show that is certainly not the case, at least for the Schwabe cycle.
The average Schwabe cycle is 11.06 years. However since 1700 we have seen cycles from 9.0-13.6 years. That’s 4.6 years range in an 11 year cycle, or ±21%.
The average Bray cycle is 2475 years. However we can detect cycles from 2250-2650 years.
That’s 400 years range in a 2475-year cycle, or ±8%.
If anything, the Bray cycle shows a lot less variability than the Schwabe cycle that is not controversial in the least.
I agree that the effect of the Schwabe cycle on global temperatures is very small. 0.1°K at most. However it is a non-sequitur that it follows that the Bray cycle cannot have an important effect on global temperatures. There is something called cumulative effect where a small forcing acting for a very long time can cause a much bigger change.
What narrow band? This?
http://i.imgur.com/icBRjN0.png
Looks to me more like four narrow bands. This type of behavior, taken to the bi-millennial scale instead of the decadal, cannot give a narrow band.
You are giving your opinion without a clear understanding of the nature of the data analyzed.
Clearly journal editors and referees have a different opinion to yours. And I will go with their opinion.
There is no bray cycle..
Steven Mosher: There is no bray cycle..
Maybe.
that’s it then. Next topic please.
tonyb
tonyb
Sarc on or Sarc off?
Scott
Mosher,
I’m thinking of switching to the warmist side.
The reading looks to be less time consuming.
Kidding – Thanks Javier, I enjoy your posts.
I thought your response to Tonyb was one of the best layouts I’ve read.
Steven,
Quite a few specialist scientists in paleoclimatology not only believe there is a 2300-2500-year climate cycle, but they believe the evidence supports it is related to solar variability.
Why should we think you are right since you have no expertise in the matter?
I suggest you say you believe there is no Bray cycle. As an English major you should know it is more correct, as you possess no knowledge on whether it exists or not.
Scott
It was sarc turned on to maximum volume.
tonyb
tonyb:
You let me braying with laughter.
That a set of peaks–far more narrowly clustered than Javier’s earlier claimed “periods”–appears in the raw amplitude spectrum of sunspots comes as no surprise to those who comprehend the inconsistencies of such analysis applied to finite-length, non-periodic data. This provides no contra-indication of a narrow-band random process. In a properly estimated power spectrum, they would blend into a single peak very close to 1/11yrs in frequency. And there is no intrinsic reason why a similar narrow-band process cannot exist at bi-millennial scale.
Alas, nothing has been presented here to show that the Bray cycle is as clearly quasi-periodic in its behavior. Certainly there is a wide-enough range of spectral peak frequencies to question whether different proxies are showing the same quasi-bi-millennial oscillations. Cross-spectrum analysis, which seems to be terra incognita in “climate science,” would resolve that question definitively. That is an objective matter of scientific analysis. To continue to argue with a student of the literature who considers such matters as “opinions” to be adjudicated by putative authorities is patently fruitless.
We have come full circle with my doubts expressed on July 12 that “a much-too-sanguine view of the reliability of proxy data underlies it’s ambitious claims.” I can only add my farewell to this thread.
“CO2 has zero effect upon the climate.” Really? del Prete, please explain why our atmosphere is warmer that it should be given the solar radiation that we receive.
“please explain why our atmosphere is warmer that it should be given the solar radiation that we receive.” It depends on who is doing the calculation. If you take into account a rotation of the planet, different albedos and heat capacities of oceans, clouds, deserts, and jungles, it is not a trivial task. Actually I have never seen it solved.
Since the physics is so complex and requires quite a few assumptions I take a different approach to the problem. I look at the whole system through time to determine if the present climatic situation is consistent with what has happened during the Holocene and compared to other interglacials. I will write with detail about it in the last article of the series, but I am convinced anthropogenic GHG emissions have contributed to the recent warming. I can’t determine how much, but clearly not enough to sustain an alarmist view of climate in the 21st century.
From a completely different approach I reach the same conclusion as Judith Curry, Nic Lewis, and many others.
We have a transgression (global warming) and we have found a suspect (CO2), and we have decided that our justice system should punish him. The problem is that we are not trying to determine his level of participation in the transgression, if there are more guilty ones, and who is the main culprit.
Our atmosphere is exactly as warm as it should be given the solar radiation that we receive.
“if there was no CO2 in the atmosphere the global climate would be significantly cooler.” from http://www.columbia.edu/~vjd1/carbon.htm
Let me know when you guys finish calculating how many angels can fit on the head of a pin.
It is Interesting to speculate about the cause of an hypothecated 2400 year cycle–e.g., the processional effects of our sun as it revolves around a dual star every 24,000 years (24,000 year zodiac calendar) — a tenth of which is 2,400 years — and, recent discussions of a 9th planet (way out there some 20 times farther from the sun than Neptune) — 10x bigger than Earth — replacing a dual star as the causative agent of the sun’s tilt… all amounting numerologists’ delight perhaps but no more fantastic than the mythical properties global warming alarmists ascribe to CO2.
Wag
How many angels dance on the head of a pin?
It is fun to speculate. I am worried about the civilazation killing asteroid and someone in gov is now starting to work on that?
But we need an urgent effort to revive the old star wars science efforts to imporve missile interseptions thanks to N Korea and Iran.
Scott
Here is the news from July 2017
https://www.sciencealert.com/nasa-is-planning-an-asteroid-deflection-test-mission-in-case-the-unthinkable-happens
Scott
Scott
I would be much more worried by a much more likely occurrence, another carrington event.
The last one happened at the very dawn of the electrification of our society. Another one would affect not just electricity but all the computers and the internet that now control the first world, whereby their demise would quickly ruin civilisation. I would give it two days before mass rioting broke out. And on that note I am just about to watch ‘ family guy’ which always seems to suggest that civilisation has already been ruined
Tonyb
tonyb
Thanks but doesn’t seem to be much to do about Carrrington events till after it happens. Keep some food on hand, gold and US secound ammendment resources for family protection.
Lots more at risk than 1-3 *C in 100 years.
I like asteroid study and tests cause we can do something useful if we can spot it.
I don’t see how one predicts Carrington events, earthquakes and large tidal waves. All lmore likely to harm 100’s of thousands than 1-3 * C in 100 years.
Scott
Scott
If govts and utilities are aware of the dangers, measures can be taken to protect our electronic infrastructure. It would cost a fraction of combating the real world impacts of that elusive scarlet pimpernel, CO2 .
This is an interesting article which, within the comments towards the end, clarifies what the UK government is currently doing to try to mitigate the effects of something very likely to happen
http://euanmearns.com/the-next-carrington-event/
Tonyb
Tonyb
THanks very much.
You are always interesting and informative.
I recall now reading about that plus the article.
Most likely at your last prompting.
I also enjoy you sarc on and sarc off comments to Moshpit
Scott
Tony, i lived through katrina. You would be surprised at how people respond to such a situation. Life goes on. People are resourceful. It brings out the best in all but the criminal element. Of course, we had a lot of outside help, perhaps unlike the fallout from a carrington event. (i’m just saying that your expectations won’t necessarily come to fruition)…
Reblogged this on Climate Collections.
Please consider the following reference link:
http://astroclimateconnection.blogspot.com.au/2013/08/the-vej-tidal-torquing-model-can.html
The VEJ Tidal Torquing Model can explain many of the long-term changes in the level of solar activity. II. The 2300 year Hallstatt Cycle (Bray Cycle)
23/08/2013
There are two steps in the proof that the VEJ Tidal Torquing Model can explain the 2300 year Bray Cycle:
STEP 1
Jupiter in a Reference Frame that is Rotating with the Earth-Venus-Sun Line
# The Movement of Jupiter with Respect to the Tidal-Bulge that is Induced in the Convective Layers of the Sun by Periodic Alignments of Venus and the Earth.
The slow revolution of the Earth-Venus-Sun alignment axis can be removed provided you place yourself in a framework that rotates by 215.5176 degrees in a pro-grade direction [with respect to the fixed stars as seen from the Sun] once every 1.59866 years. In this rotating framework, Jupiter moves in a pro-grade direction (with respect to the Earth-Venus-Sun line) by 12.9993 degrees per [inferior conjunction] VE alignment
The following table shows how Jupiter advances by one orbit + 3.9796 degrees every 28 VE alignments until the alignment of Jupiter with the Earth-Venus-Sun line progresses forward by 13 orbits in the VE reference frame plus 51.7345 degrees. This angle (see * in table) is almost exactly equal to the angle moved by Jupiter in 4 VE aligns (i.e. 4 x 12.99927 degrees = 51.9971 degrees).
VE_multiple______Angle of______Orbits_+__Degrees
of 12.9993_______Jupiter______________________
degrees
____ 28_________363.9796_______1__+___3.9796
____56_________727.9592_______2__+___7.9592
____84________1091.9387_______3__+__11.9387
___112________1455.9183_______4__+__15.9183
___140________1819.8979_______5__+__19.8979
___168________2183.8775_______6__+__23.8775
___196________2547.8571_______7__+__27.8571
___224________2911.8366_______8__+__31.8366
___252________3275.8162_______9__+__35.8162
___280________3639.7958______10__+__39.7958
___308________4003.7754______11__+__43.7754
___336________4367.7550______12__+__47.7550
___364________4731.7345______13__+__51.7345__*
This means that Jupiter returns to almost exact re-alignment with the Earth-Venus-Sun line after:
(364 – 4) VE aligns = 360 VE aligns = 575.5176 years
[i.e. 12.9993 orbits of Jupiter in a retro-grade direction in the VE reference frame, falling 0.2625 degrees short of exactly 13 full orbits].
STEP 2
Re-aligning the Movement of Jupiter in the Rotating VE Reference Frame with its Movement in the Reference Frame that is Fixed with the Stars
The the period of time required for Jupiter to precisely re-align with the Earth-Venus-Sun line in a reference frame that is fixed with respect to the stars is 4 x 575.52 years = 2302 years. This is the (Bray) Hallstatt-like cycle that is naturally found in the planetary configurations that are driving the VEJ Tidal-Torquing model for solar activity.
You also have the connection between the Extreme Perigean Spring Tides
and the Bray Cycle:
A Direct Connection Between the Venus, Earth and Jupiter Tidal-Torquing Cycles (a Proposed Driver of Solar Activity) and the Long-Term Strength of (Lunar) Perigean Spring Tides
http://astroclimateconnection.blogspot.com.au/2016/12/a-direct-connection-between-venus-earth.html
Results:
1. The Synodic (phase) cycle of the Moon precisely re-synchronises with the times of the Extreme Perigean Spring tides (EPST) once every 574.60 topical years.
2. Jupiter precisely re-synchronises itself in a frame of reference that is rotating with the Earth-Venus-Sun line once every 575.52 tropical years.
3. The orientation of Jupiter to the Earth-Venus-Sun line produce the tidal torques that act upon the base of the convective layers of the Sun which are thought to be responsible for the periodic changes in the level of magnetic activity on the surface of the Sun (i.e. the Solar Cycle).
4. The period of time required for Jupiter to precisely re-align with the Earth-Venus-Sun line in a reference frame that is fixed with respect to the stars is 4 x 575.52 = 2302 years. This is the Hallstatt cycle that is intimately associated with the planetary configurations that are driving the VEJ Tidal-Torquing model for solar activity.
5. Hence, the repetition period for strongest of the Extreme Perigean Spring tides appears to match that of the planetary tidal-torquing forces that are thought to be responsible for driving the Solar sunspot cycle.
Extreme Perigean Spring tides (EPST) occur when a New moon occurs at time when the Perigee of the lunar orbit points directly at the Sun or when a Full Moon occurs when the Perigee of the lunar orbit points directly away from the Sun (the latter are often called Extreme Super Moons). Figure 1 shows a schematic diagram an EPST occurring at a New Moon.
Figure 2, (see link above), has as its initial starting point (T = 0.0 tropical years), a New Moon taking place at the precise time that the Perigee of the lunar orbit points directly at the Sun. In addition, this figure shows the number of days to (negative values on the y-axis) or from (positive values on the y-axis) a New/Full Moon for each of the EPST’s that occur over the next 618.4 tropical years.
Figure 2 shows that the point representing the New Moon at T = 0.0 tropical years is part of a triplet of points with the other two points occurring at (-1.1274 tropical years, 1.64 days) and (+1.1274 tropical years, -1.64 days).
Hence, a point starting at (-1.1274 tropical years, 1.64 days), reaches the x-axis at (573.4727 topical years, 0.0 days), leading to an overall repetition cycle of 574.600 tropical years.
Remember:
Jupiter returns to almost exact re-alignment with the Earth-Venus-Sun line after: (364 – 4) VE aligns = 360 VE aligns = 575.52 years
[i.e. 12.9993 orbits of Jupiter in a retro-grade direction in the VE reference frame, falling 0.2625 degrees short of exactly 13 full orbits]
Hi Ian,
Thank you for your explanation of the 2302-year astronomical cycle that you have identified. It is one of the several planetary explanations that have been proposed for the Bray (Hallstatt) solar cycle, and it is good that you were able to publish it in the famous final special issue of Pattern Recognition in Physics
http://www.pattern-recogn-phys.net/special_issue2.html
Wilson, I. R. G. (2013). The Venus–Earth–Jupiter spin–orbit coupling model. Pattern Recognition in Physics, 1(1), 147-158.
While I am totally in favor of publishing and discussing planetary hypotheses of solar cyclic behavior as an obvious causal possibility, I am also unable to evaluate them. Given a single periodicity of 2300=2500 years, scientists have identified quite a few astronomical cycles with a periodicity in that range. Charvátová published in 2014 a 2402-year cycle
Charvátová, I., & Hejda, P. (2014). Responses of the basic cycle of 178.7 and 2402 yr in solar-terrestrial phenomena during Holocene. Pattern Recogn. Phys. 2, 21–26.
Geoff Sharp has published the basis of his 4627-year cycle to explain SGM according to the Jose cycle.
Sharp, G. (2010). Are Uranus & Neptune responsible for solar grand minima and solar cycle modulation?. International Journal of Astronomy and Astrophysics, 3, 260-273.
And with the same Jose cycle basis the 2314-year cycle of
McCracken, K. G., Beer, J., & Steinhilber, F. (2014). Evidence for planetary forcing of the cosmic ray intensity and solar activity throughout the past 9400 years. Solar Physics, 289(8), 3207-3229.
So the only important question here is how do we know if anyone of them has any effect on solar activity and climate.
And the problem for all these cycles is that they have been researched based on poorly defined solar activity evidence. As we can see in this article climatic evidence is very clear that the climate Bray cycle is close to 2500 years. And as we will see in the next part, the cosmogenic record is very clear that the solar activity Bray cycle is between 2450-2500 years. We are dealing with a ~ 2475-year cycle that can be identified directly in the cosmogenic record for the past 11,700 years, and indirectly through its modulation of the 208-year de Vries cycle in 10Be records for much longer, at least 20,500 years.
Although we don’t know the effect of the astronomical cycles identified by you and others, they cannot be responsible for the ~ 2475-year Bray cycle. Even a 75 year difference in period would lead to a phase shift of almost one millennium in the period analyzed that is unsupported by evidence.
I guess it is back to the drawing board to identify a ~ 2475-year astronomical cycle. Given the abundance of 2300-2400-year astronomical cycles found I remain confident that several 2500-year cycles will also be found. After all we have a lot of planets to play with.
Javier,
The JEV Tidal Torquing model is an hypothesis that tries to explain how Jupiter Venus and the Earth are able to influence solar activity through a spin-orbit coupling mechanism i.e. a coupling between rate of spin the Sun to the rate at which it orbits the Barycentre of the solar system. In this model the effects of the gravitational force of Jupiter upon the temporary tidal bulges created by alignments of Venus and the Earth naturally resets itself
once every 2302 years. This time period agrees wit the 2300 year (NOT 2475 year) period that is seen in the level of the Suns activity.
The most extreme Lunar Perigean Spring tides also exhibit the same 2300 year cycle.
If either solar activity – or extreme lunar tidal forces play a significant role in influencing the Earth’s climate they must do so with a cyclical time scale of ~ 2300 years not 2475 years.
https://2.bp.blogspot.com/-IK8WTNzmdqw/WLGgSigNzMI/AAAAAAAABHU/27JHpscjcaQYK5VtP65Td_mtHHCSy2IgwCLcB/s1600/Solar_Lunar.JPG
Where is your evidence that the Bray cycle is ~2475 years. I do not believe that you have proven your case. for this modified period.
Ian,
The evidence for the ~ 2475-year solar activity cycle comes from the correct identification of every low in the solar Bray cycle for the past 22,000 years. It has already been sent to Prof. Curry as part B of the three parts composing this article, so it will be posted in the near future.
The lows of the Bray cycle are:
B9: ~ 20,500 BP
B8: ~ 17,600 BP
B7: ~ 15,000 BP
B6: 12,800-12,650 BP
B5: 10,300-10,100 BP
B4: ~ 7,700-7,400 BP
B3: 5,350-5,200 BP
B2: 2,800-2,650 BP
B1: 600-400 BP
The periods are: (2900), (2600), (2275), 2525, (2600), (2325), 2550, 2225.
The dates between parenthesis are not very precise. The average is 2500 years. Using the best dated lows the average is 2445 years. Hence the cycle is 2450-2500 years. Less than 2450 years and B9 would fall out of phase.
This periodicity also coincides with the Bray climatic cycle, so it is consistent with a causal relationship.
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Javiar,
Sorry for the delayed response to your post OI have been away for a couple of days.
Here is a crude way to estimate the uncertainties of your claim using a specific example: I have a times series that lasts for 62 years. It contains a quasi-repetitive cycle that I believe could be either 8.85 years long or 9.02 years long. This means that that the time series contains at most 7 cycles.
I am having trouble distinguishing whether a 8.85 year or 9.02 can fit the very clear and pronounced sinusoidal minimums seen in the data. This tells me that this well defined quasi 9 year signal has an uncertainty of +/- 0.17 years i.e. the relative error is ~ 0.17/8.85 = 0.0192 ~ 2 %
You have a cycle that a rough period of 2445 years that evident over at least 20,500 years. That means that you have at least 8 cycles in your time series. This not much different to my time series above. Hence, I would expect that [even under the best of conditions – i.e. a very definite cycle length that effectively remains unchanged over duration of the time series and which easily visible in the data] you would expect an minimum error of
+/- 0.02 x 2500 years ~ +/- 50 years. Given that precise detection of Bray minimums are not the best, I wouldn’t be surprised if the error was 3 times the size i.e. more like +/- 150 years, which agrees well with the 1 sigma (r.m.s) uncertainty of 150 years if you ignore the first 2900 year period as an outlier.
In other words you have only shown that the repetition period lies somewhere between 2295 and 2595 years. If make the assumption that the Bray period is quasi-stationary then this does not rule out a period of 2300 years.
Hi Ian,
I understand that quite clearly. One cannot determine the average periodicity of the 11-year Schwabe cycle with certainty from only 8 cycles. But that is of little relevance to the question that matters here.
Astronomical cycles are not probabilistic, but deterministic. The relevant conjunctions and positions are determined with precision. If they don’t match what is known of these 8 Bray cycles then there is no correlation, and lack of correlation is pretty damning.
The astronomical dates are precise probably to a fraction of the year. 14C dates are as good as we can do as they are used for dating ancient biological materials for every discipline. Outside certain short periods, 14C dates have a precision of a few decades for most of the Holocene. Ice cores are the best dated proxies. 10Be dates from ice cores have a subdecadal precision.
The Bray solar cycle is defined not only by cosmogenic variability, but also from the clustering of SGM at its lows. Those SGM are very well dated.
Given the stated precision of the data, what is sorely missing from the people that research planetary cycles is the match between their astronomical cycles and solar activity from cosmogenic records for the entire Holocene. It is not enough that the periodicity is more or less (often tenuously) compatible. The astronomical and solar cycles have to be in phase. And the problem is that the cosmogenic Bray cycle presents irregularities that are matched by its climatic effects. If the astronomical cycle doesn’t match those irregularities then its causal proposition gets considerably weakened.
Until all the evidence for solar activity and climate change for the entire Holocene is carefully examined and matched to the astronomical cycles, to me they amount to little more than numerology where a frequency peak from a periodogram is chosen and an astronomical cycle involving a few planets that more or less agrees with the peak is picked. The problem is that if they do that check they are likely to come empty handed.
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