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The effect on human societies can be postulated as higher frequency of food crises, population decrease, increased migration, increased violence, and higher chance of civilization regression or failure. Greenland and Tibetan ice cores display a d O isotope minimum (Björk et al., 2001, and references within).
It is so common that new civilizations emerge after climatic crises that some archaeologists have developed the theory that climate caused environmental stress is an engine to societal change (Weninger et al., 2009; Roberts et al., 2011). The increase in precipitation in the North Atlantic-European region is supported by the increase in lake levels in west-central Europe and central Italy (Magny et al., 2007; figure 3c), and the increased iceberg discharge (Bond et al., 2001). Upper panel shows the correlation between solar activity and cold phases reflected by highstands of mid-European lake levels (c). Periods of lower solar activity coincide with periods of higher production of the cosmogenic radionuclides 10Be (a) and 14C (b). Bottom panel (d) O speleothem (‰, inverted) from Qunf Cave (Southern Oman), a proxy for the strength of the Indian monsoon (as represented, weaker towards bottom).
Temperatures on Earth appear to depend mainly on orbital changes, firstly obliquity, but also precession and eccentricity, and oceanic cycles, and volcanic activity also play an important role at times, and therefore solar variability alone does not explain climate changes.
Let’s now review what has happened to the planet and people at the lows of the Bray cycle during the Holocene. Glacier readvances took place in Norway (the Erdalen event; Dahl et al., 2002) and Tibet (Seong et al., 2009). (e) GISP2 non-sea salt [K ] (ppb, inverted), a proxy for Siberian High polar conditions. The position of the two lows for the ~ 2400-yr Bray cycle in this period at 10.3 and 7.7 kyr BP is indicated by the two violet bars.
These have taken place around the following dates (kyr BP. (f) Relative abundance (%, inverted) of the cold-water dinocyst Spiniferites elongatus in the Aegean sea core SL21. indicates a strong biological response to the climatic deterioration and lower SST in the Eastern Mediterranean during the 10.3 kyr event (Marino et al., 2009; figure 3f).
Solar variability is quite small (about 0.1% of total irradiation), and there is no generally accepted mechanism by which the solar variability signal could be amplified by the climate system.
While progress is being made to solve these problems, there is a growing number of scientific paleoclimatology articles published every year that defend a significant role for solar variability in paleoclimate change.