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11:19
Measuring Carbon-based Contaminant Mineralization Using Combined CO2 Flux and Radiocarbon Analyses
Published on: October 21, 2016
Atmospheric carbon dioxide concentrations before 2.2 billion years ago
1Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
Nature
|December 7, 1995
Summary
Early Earth
Area of Science:
- Geosciences
- Paleoclimatology
- Atmospheric Science
Background:
- Earth's early atmosphere composition is debated.
- Higher carbon dioxide (CO2) may have been needed for warmth due to lower solar luminosity.
- Palaeosols provide constraints on early atmospheric oxygen (pO2).
Purpose of the Study:
- Constrain atmospheric carbon dioxide (pCO2) levels between 2.75 and 2.2 billion years ago.
- Investigate the role of CO2 in regulating early Earth's climate.
- Re-evaluate climate models for the late Archaean and early Proterozoic eras.
Main Methods:
- Analysis of well-studied palaeosols (fossil weathering profiles).
- Examining iron precipitation patterns within palaeosol profiles.
- Using iron silicate and iron carbonate formation to infer pCO2 levels.
Main Results:
- Atmospheric pCO2 was less than 10(-1.4) atm (approx. 100 times present levels).
- This level is significantly lower than predicted by climate models for early Earth.
- Iron reprecipitation as silicates, not carbonates, indicates limited CO2.
Conclusions:
- Early Earth's climate sensitivity to CO2 may be higher than previously assumed.
- Other greenhouse gases likely played a significant role in regulating ancient climate.
- The findings challenge existing models of Archaean and Proterozoic atmospheric composition and climate.
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