Variations Of Sunspot Activity Research Articles

Comment on ‘The Medieval Quiet Period’ – Implications arising from models of solar irradiance

The recent re-evaluation of sunspot data by Clette et al. strongly suggests that the total solar irradiance (TSI) values for the late 20th century were (apart from 1960) not significantly different from those of the periods of sunspot maxima in the 1780s and the 1840s–1860s in the latter part of the ‘Little Ice Age’. In effect, the re-evaluation removed the previously supposed sunspot maximum of the ‘modern’ period. That means that the supposed recovery of TSI levels to values significantly higher in the late 20th century than those of the ‘Medieval Quiet (or Warm) Period’ (Figure 1 of Bradley et al., 2016) must be an artefact of the solar data. Orbital data suggest that the northern hemisphere cooled significantly over the past 2000 years, a trend confirmed by global temperature proxies. Variations about that trend were driven by small variations in sunspot activity that led to the warmth of the ‘Medieval Quiet (Warm) Period’ and the subsequent cooling of the ‘Little Ice Age’. In fact, the ‘Little Ice Age’ contained several short warm periods when sunspots were at a maximum. It seems highly likely given the new sunspot calibration that the mid- to late 20th century warming was yet another of these ‘Little Ice Age’ warm episodes (e.g. no different from that in 1780) superimposed on which was a growing additional warming supplied by expanding emissions of greenhouses gases.

HOLOCENE CLIMATE OF NAMIBIA: A REVIEW BASED ON GEOARCHIVES

The Holocene palaeoclimates in Namibia are reviewed by discussing different palaeoclimate geoarchives. The available evidence suggests little climatic fl uctuations during the Holocene. There is evidence of more humidity compared to today during the early Holocene. Short dry episodes occurred around 8 14 C-ka BP and around 5-3 14 C-ka BP. Since 1000 years the northern Benguela Current sea surface temperatures show a decline and since ca. 500 years Namibia experienced in the Namib Desert and adjacent areas more arid condi- tions than before. Extreme fl ash fl oods occurred more frequently during the Little Ice Age, probably correlating to variations of sun spot activity.

Predictions of strengths of long-term variations in sunspot activity

Recently, using Greenwich data (1879-1976) and SOON/NOAA data (1977-2002) on sunspot groups we found a big or a moderate drop in the solar equatorial rotation rate, A, occurred after every four solar cycles suggesting theexistence of double cycle (DHC) and Gleissberg cycle (GC) in A. We also found the existence of Hale cycle (HC) and GC in the latitude gradient of the rotation, B (Javaraiah 2003). Using these results here we made forecasts for the following: (i) epochs of the forthcoming big and moderate drops in A; (ii) the epoch of maximum ‖B‖ during the current GC of B; (iii) the strengths of DHCs and HCs of sunspot activity which follow the big and the moderate drops in A; (iv) violation of the Gnevyshev & Ohl rule during the current HC 11 which consists of cycles 22 and 23; and (v) deduced the near complete absence of sunspot activity during the deep Maunder minimum.

Sizing up the Sun

Variations in sunspot activity affect the weather on Earth, but the underlying mechanisms are unknown. New measurements of the Sun's radius and luminosity may help pinpoint the source of the energy responsible.

On the triggering mechanism of the 11y solar-induced signal in surface air temperature

The surface air temperature recorded at Vesuvian Observatory has evidenced a significant 11y cycle related to total ozone variation, which in turn has been coherently linked to sunspot activity. Such a correlation has not been found in the series of Naples (few km apart), where it is masked by the large long-period variations related to the growth of the urban heat island. A physical mechanism involving variations in sunspot activity, ozone layer and surface air temperature has been proposed.

SECULAR VARIATIONS IN THE 14C CONCENTRATION OF DOUGLAS FIR TREE RINGS

Measurements of the 14C concentration in a Douglas fir from Vancouver Island indicate a maximum variation of 44‰, during the past 1 100 years. The magnitude and trend of these variations are similar to those observed by de Vries (1958) in oak from Germany and by Willis et al. (1960) in sequoias from California, confirming earlier observations that atmospheric mixing of CO2 takes place rapidly on a large scale.14C measurements of successive annual growth rings from the piths of two firs (346 years and 1 142 years old) show no variations beyond those attributable to the statistical counting error of ± 6‰. Thus, cyclic variations in sunspot activity and (or) climate, if present during these intervals, did not affect the 14C concentration in the biosphere appreciably.A mechanism, based on a climate-sensitive carbon pumping rate of the biosphere coupled with the temperature-dependent oceanic CO2 content is postulated to explain, qualitatively, the observed short-term (150 years or less) and long-term (1 000 years or more) 14C variations in the land biosphere. Short-term fluctuations are directly proportional to temperature because variations in the carbon fixation rate lead to a pulsating CO2 content of the atmosphere. Long-term changes are inversely proportional to temperature because large quantities of carbon, normally stored in deeper regions of the ocean, are exchanged between biosphere and hydrosphere.

An attempt to the explanation and to the prediction of the eleven-year cycle of solar activity

According to the author the reason of the subsistence of the 11 years' sunspot cycle is to be found in the conjunction of the planets. As a result of the investigations it has been stated that from among the nine planets the joint tidal effect of Venus-Jupiter-Earth is a decisive factor in the variations of sunspot activity. The above three planets are every 10.4 years and 12.0 years respectively, in a close conjunction. The mean value (11.2 years) is in an almost full accordance with the average cycle-period. The fluctuations of the period of the cycle come from the fact that the planets' getting into approximately one line takes a different time within each cycle. This time delay is the cause of the stronger or weaker sunspot activity, and of the shorter or longer cycles.

Variations in radiocarbon concentration and sunspot activity

Variations in cosmic-ray intensities will produce variations in C/sup 14/ production in the atmosphere. A comparison is made between variations in sunspot activity and fluctuations in C/sup 14/ concentration during the past 13 centuries. Although a definite conclusion is not reached, the evidence given suggests some correspondence between sunspot activities and C/sup 14/ concentration in the atmosphere. (auth)