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Greenhouse warming by CH4 in the atmosphere of early Earth
Department of Geosciences, Pennsylvania State University, University Park
Department of Geosciences, Pennsylvania State University, University Park
Department of Geosciences, Pennsylvania State University, University Park
Space Physics Research Institute, NASA Ames Research Center, Moffett Field, California
Space Physics Research Institute, NASA Ames Research Center, Moffett Field, California
Earth appears to have been warm during its early history despite the faintness of the young Sun. Greenhouse warming by gaseous CO2 and H2O by itself is in conflict with constraints on atmospheric CO2 levels derived from paleosols for early Earth. Here we explore whether greenhouse warming by methane could have been important. We find that a CH4 mixing ratio of 10−4 (100 ppmv) or more in Earth's early atmosphere would provide agreement with the paleosol data from 2.8 Ga. Such a CH4 concentration could have been readily maintained by methanogenic bacteria, which are thought to have been an important component of the biota at that time. Elimination of the methane component of the greenhouse by oxidation of the atmosphere at about 2.3 – 2.4 Ga could have triggered the Earth's first widespread glaciation.
Received 29 June 1999; accepted 4 January 2000; .
Citation: (2000), Greenhouse warming by CH4 in the atmosphere of early Earth, J. Geophys. Res., 105(E5), 11,981–11,990.
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