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Geomagnetic Field Effects on Living Systems

FIGURE 6.6 Te easterly distribution of the Middle-Late Permian large igneous provinces (LIPs) in Pangea

(Isozaki, 2009). Paleogeographic base map is afer Maruyama et al. (1989). W. Austr., Western Australia; N. China,

North China. (Reproduced with permission from Isozaki (2009), Copyright 2009, Elsevier.)

Te estimated changes in СО2 concentrations during the Phanerozoic were shown by Rohde (2006).

Te СО2 concentration in the atmosphere started rapidly decreasing from the Late Ordovician and sub­

sequently never reached the Early Paleozoic (Cambrian) values during the Phanerozoic (Rohde, 2006).

Tree estimates are based on geochemical modeling: GEOCARB III (Berner and Kothavala, 2001),

COPSE (Carbon-Oxygen-Phosphorus-Sulfur-Evolution), (Bergmann et al., 2004), and another geo­

chemical model (Rothman, 2002). Tese are compared to the carbon dioxide (CO2) measurement data­

base of Royer et al. (2004), and a 30 Myr fltered average of those data (see Rohde, 2006; Cm, Cambrian;

O, Ordovician; S, Silurian; D, Devonian; C, Carboniferous; P, Permian; Tr, Triassic; J, Jurassic; K,

Cretaceous; Pg, Paleogene; N, Neogene). Direct determination of past CO2 levels relies primarily on the

interpretation of carbon isotopic ratios in fossilized soils (paleosols) or the shells of phytoplankton and

through interpretation of stomatal density in fossil plants (Rohde, 2006). Te Ordovician (O) green­

house climate was replaced by a glacial one with several glacial periods (Saltzman and Young, 2005).

Huge volcanoes occurred frequently in the Cretaceous (K) (Hofmann et al., 2000; Nordt et al., 2003).

As a result, volcanic activity released a large amount of CO2 into the atmosphere, causing the Earth’s

surface to warm greatly.

Tus, it has been explained that past cooling and warming conditions of the Earth’s surface are

caused by changes in the concentration of CO2 in the atmosphere. In addition, recent artifcial satellite

data suggest that the amount of clouds afected temperature changes of the Earth’s surface. It has been

found that the formation of the cloud requires the formation of a large number of cloud particle nuclei

by ionization of atmospheric molecules by GCRs (frst described by Svensmark and Friis-Christensen,

1997). When a large amount of GCRs enter into the atmosphere, clouds are generated over a wide area

and the Earth’s surface becomes cold, whereas when the infow is small, the Earth’s surface continues to

be sunny and warms. Te infux of GCRs into the atmosphere is determined by two factors: the strength

and distance of sources such as supernovae and the GMF strength. Te probability of encountering a

supernova explosion changes depending on the position of the solar system in the galaxy. On the other

hand, the GMF strength plays the role in the infux of GCRs into the atmosphere as a magnetic shield,

and therefore, when the GMF strength is sufciently high, GCRs cannot easily fow into the atmosphere

and vice versa (Ueno et al., 2019).

Kirkby (2007) speculated that GCRs forcing of the climate acts simultaneously and with the same

sign throughout the entire globe and operates on all time scales from days to hundreds of millions of

years. For this reason, even a relatively small forcing can lead to a large climatic response over time

(Kirkby, 2007). However, the hypothesis about this mechanism has not been proved (see discussion).