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Atmospheric carbon dioxide levels over phanerozoic time.
Science (New York, N.Y.)
|September 21, 1990
Summary
A new model reconstructs atmospheric carbon dioxide (CO2) levels over 570 million years. Results show high CO2 in the Mesozoic and early Paleozoic, and low CO2 in the Permo-Carboniferous and late Cenozoic, influencing ancient climates.
Area of Science:
- Geochemistry
- Paleoclimatology
- Earth System Science
Background:
- Atmospheric carbon dioxide (CO2) is a key driver of Earth's climate.
- Understanding long-term CO2 variability is crucial for paleoclimate reconstruction.
- Previous models often simplified complex geological and biological feedbacks.
Purpose of the Study:
- To develop a novel model for calculating atmospheric CO2 levels over the past 570 million years.
- To investigate the interplay of geological and biological processes influencing CO2 concentrations.
- To correlate reconstructed CO2 levels with Phanerozoic paleoclimates.
Main Methods:
- Utilized a series of successive steady states to model CO2 levels.
- Incorporated a feedback function for silicate mineral weathering.
- Calculated sediment burial rates using an isotope mass-balance model and carbon isotopic data.
- Estimated weathering rates based on continental land area, elevation, river runoff, and plant evolution.
- Assessed degassing rates from changes in seafloor generation and carbonate deposition patterns.
Main Results:
- The model indicates high atmospheric CO2 levels during the Mesozoic and early Paleozoic eras.
- Low CO2 concentrations were calculated for the Permo-Carboniferous and late Cenozoic periods.
- Reconstructed CO2 trends align with independently derived Phanerozoic paleoclimate data.
Conclusions:
- The atmospheric CO2 greenhouse mechanism significantly controls climate over geological timescales.
- The model provides a robust framework for understanding long-term carbon cycle dynamics.
- These findings support the link between atmospheric CO2 and long-term climate regulation.
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