Public Presentation

The Climate of Early Earth

Dr. James F. Kasting

Penn State University

Wednesday, November 12, 2003

7:30 pm Bluebonnet Ballroom, University Center

Free Admission

Abstract

Earth’s climate appears to have been warm early in its history despite the faintness of the young Sun. High CO₂ concentrations may have provided the necessary greenhouse warming at first, but once life had evolved, methane was probably an important part of the climate story as well. CH₄ concentrations exceeding 1000 ppmv are predicated prior the rise of O₂ at ~2.3 Ga, provided that the flux of methane into the atmosphere was comparable to that today. This could have provided sufficient greenhouse effect to compensate for low solar luminosity even if CO₂ levels were no higher than today. If the CH₄ concentration exceeded that of CO₂, however, hydrocarbon smog should have formed in the stratosphere. This would have cooled the Earth by creating an anti-greenhouse effect. Climate during the Archean and early Paleoproterozic may well have been stabilized by a negative feedback loop involving methane production and have optical depth. The rise of atmospheric O₂ at 2.3 Ga wiped out most of this methane and probably triggered the widespread glaciations observed at that time.

For questions, contact Dr. Manfred Cuntz at 817-272-2467 or cuntz@uta.edu

Refreshments will be served in the lobby at 7:00 pm.