Figure 2.

Diagram for the carbon cycle box model used in the present paper. Fv = flux of volcanic CO_2; Fm = flux of methane from methane hydrates (the methane is assumed to be oxidized to CO₂ essentially instantaneously); Fwc = uptake of CO₂ by means of the weathering of carbonates (twice this value is the flux of carbon to the oceans from carbonate weathering); Fwsi = uptake of atmospheric CO₂ by means of the weathering of Ca–Mg silicates with transfer of the carbon to the oceans; Fbg = burial flux of organic carbon in sediments; Fwg = weathering flux of ancient sedimentary organic carbon (kerogen); Fbio = flux of CO₂ caised by the mass mortality of terrestrial biota; Fbc = burial flux of marine carbonates ( = flux of CO₂ from ocean to the atmosphere). Modified from Beerling and Berner (18).