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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 105, NO. E5, PAGES 11,981–11,990, 2000

Greenhouse warming by CH₄ in the atmosphere of early Earth

Alexander A. Pavlov

Department of Geosciences, Pennsylvania State University, University Park

James F. Kasting

Department of Geosciences, Pennsylvania State University, University Park

Lisa L. Brown

Department of Geosciences, Pennsylvania State University, University Park

Kathy A. Rages

Space Physics Research Institute, NASA Ames Research Center, Moffett Field, California

Richard Freedman

Space Physics Research Institute, NASA Ames Research Center, Moffett Field, California

Abstract

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.

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Citation: Pavlov, A. A., J. F. Kasting, L. L. Brown, K. A. Rages, and R. Freedman (2000), Greenhouse warming by CH₄ in the atmosphere of early Earth, J. Geophys. Res., 105(E5), 11,981–11,990.

Copyright 2000 by the American Geophysical Union.