GEOCARB II: A revised model of atmospheric CO[sub 2] over phanerozoic time

Journal Article · Sat Jan 01 00:00:00 EST 1994 · American Journal of Science; (United States)

DOI:https://doi.org/10.2475/ajs.294.1.56· OSTI ID:6912275

Berner, R A ^[1]

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1. Yale Univ., New Haven, CT (United States)

Revisions of the parameters in the model of Berner (1991) (henceforth GEOCARB I) for the long term geochemical carbon cycle have been made. Principal changes are: (1) inclusion of the effects of the variation of solar radiation in the feedback functions for continental weathering; (2) distinction between the feedback functions for silicate weathering and carbonate weathering; (3) exclusion of land area from the expression for Ca-AM silicate weathering and its replacement by an uplift factor; (4) consideration for carbonate weathering of changes in land area underlain by carbonate rocks; (5) use of new data on the rate of seafloor subduction and spreading over the past 150 my; (6) use of new data on the temperature coefficient of silicate dissolution and the relation between river runoff and rates of silicate weathering; (7) application of a parameterization of global runoff over time; (8) consideration of a model where total crustal carbon varies with time. Results indicate that: (1) increase in the solar constant over the past 570 my has brought about a drop in atmospheric CO[sub 2] from values much higher during the Paleozoic; (2) high CO[sub 2] values during the Mesozoic and a decrease in CO[sub 2] during the Cenozoic are due largely to low Mesozoic relief and Cenozoic mountain uplift with decreasing metamorphic/volcanic degassing of CO[sub 2] during the Cenozoic; (3) changes in river runoff and carbonate land area are relatively unimportant; (4) variable degassing was not a major control on atmospheric CO[sub 2] during the Paleozoic; (5) calculated Phanerozoic CO[sub 2] is sensitive to the proportion of carbonate deposition in shallow water versus the deep sea; (6) letting total crustal carbon vary has little effect on results. Over Phanerozoic time a major control on global climate has been the CO[sub 2] greenhouse effect, and changes in CO[sub 2] have been a consequence of a combination of geological, biological, and astronomical factors. 46 refs., 20 figs.

• OSTI ID: 6912275
• Journal Information: American Journal of Science; (United States), Vol. 294:1; ISSN 0002-9599
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
CARBON DIOXIDE
GEOCHEMISTRY
PALEOCLIMATOLOGY
CLIMATE MODELS
CARBON CYCLE
CARBONATE MINERALS
COMPUTERIZED SIMULATION
G CODES
GEOLOGIC AGES
GREENHOUSE EFFECT
SILICATE MINERALS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMISTRY
CLIMATIC CHANGE
COMPUTER CODES
MATHEMATICAL MODELS
MINERALS
OXIDES
OXYGEN COMPOUNDS
PALEONTOLOGY
SIMULATION
540120* - Environment
Atmospheric- Chemicals Monitoring & Transport- (1990-)
540220 - Environment
Terrestrial- Chemicals Monitoring & Transport- (1990-)