Atmospheric carbon dioxide efficiently warmed early Earth before plate tectonics began, a study finds. Less light radiated from the young Sun compared with present times, and climate modelers have found it challenging to explain why early Earth was not freezing cold. Daniel Herwartz and colleagues provide a possible explanation for this faint young Sun paradox. The authors modeled the effects of intense carbonate and silica formation in the oceanic crust on δ18O, the ratio of stable isotopes oxygen-18 (18O) and oxygen-16 (16O), in ancient seawater. The results revealed that the δ18O of ancient seawater increased from about -5 per mille 3.2 billion years ago, before the onset of plate tectonics, to a new steady-state value close to -2 per mille around 2.6 billion years ago. The moderately low δ18O values imply a warm but not hot climate on early Earth, as well as high concentrations of carbon dioxide during this period. Together, the findings suggest that the young Sun's low luminosity was efficiently counterbalanced by carbon dioxide greenhouse warming more than 3 billion years ago, according to the authors.
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Article #20-23617: "A CO2 greenhouse efficiently warmed the early Earth and decreased seawater 18O/16O before the onset of plate tectonics," by Daniel Herwartz, Andreas Pack, and Thorsten J. Nagel
MEDIA CONTACT: Daniel Herwartz, University of Cologne, Cologne, GERMANY; tel: +49 221-470-3240; email: d.herwartz@uni-koeln.de
Proceedings of the National Academy of Sciences