Proxy Methods

A variety of independent tests of the modeling predictions as to levels of Phanerozoic atmospheric CO2 are available. Methods include determining (1) the S13C of carbonates in paleosols; (2) the stomatal density

Carbon Cycle
Figure 5.14. Input function for volcanic degassing of CO2 and for CO2 formed by the oxidation of CH4 from methane hydrate decomposition at the Permian-Triassic boundary. (After Berner, 2002.)
Carbon Cycle The Permian

Figure 5.15. Calculated plots of S13C of CaCO3 versus time at the Permian-Triassic boundary. The upper curve is for volcanic degassing associated with the eruption of Siberian basalts. The lower curve is for the input of CO2 from the oxidation of CH4 derived from methane hydrates. The return of the curves to the initial conditions represent dilution of the inputs as the long-term carbon cycle returns to a steady state. Actual measured values of S13C show changes of over -7%o during this same time span thereby supporting the methane source hypothesis. (Data from Berner, 2002.)

Figure 5.15. Calculated plots of S13C of CaCO3 versus time at the Permian-Triassic boundary. The upper curve is for volcanic degassing associated with the eruption of Siberian basalts. The lower curve is for the input of CO2 from the oxidation of CH4 derived from methane hydrates. The return of the curves to the initial conditions represent dilution of the inputs as the long-term carbon cycle returns to a steady state. Actual measured values of S13C show changes of over -7%o during this same time span thereby supporting the methane source hypothesis. (Data from Berner, 2002.)

of fossil leaves; (3) the degree of fractionation of carbon isotopes of specific compounds secreted by phytoplankton and preserved in sedimentary rocks; and (4) the boron isotopic composition of marine carbonate fossils. Each of the methods has its own problems (Royer et al., 2001a), but if certain precautions are taken, they provide reasonable estimates of ancient CO2 levels.

Organic Gardening

Organic Gardening

Gardening is also a great way to provide healthy food for you and your loved ones. When you buy produce from the store, it just isnt the same as presenting a salad to your family that came exclusively from your garden worked by your own two hands.

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