What Is the Role of Carbon Dioxide in Climate Change during Earth History?

Eric J. Barron
Jackson School of Geosciences, University of Texas at Austin, Austin, TX

Three distinct factors can alter the energy balance of the Earth system: (1) changes in the amount or distribution of incoming solar energy, (2) changes in the composition of the Earth’s atmosphere influencing energy absorption or reflection, and (3) changes in the Earth’s surface, independent of climate, that influence the Earth’s albedo or reflectivity. These external factors (external to the climate system - e.g. solar variability, orbital changes, volcanism, plate tectonics, etc) are termed “forcing factors.” In addition, the response of the Earth’s climate system to external forcing may result in changes to the energy budget - the cooling associated with a decrease in solar energy could result in glaciation (a higher surface reflectivity) and decreased water vapor (a greenhouse gas) content in the atmosphere, thus amplifying the cooling. Such changes are termed “feedbacks.” In Earth history, greenhouse gases such as carbon dioxide, have influenced climate both as a forcing factor and as a feedback. Changes in carbon dioxide can be a forcing factor if they involve the balance between inputs from the Earth’s interior (volcanism) and continental weathering and burial of organic matter. On other time scales, climate change itself has a significant impact on plant productivity and burial of organic matter that then alters the carbon dioxide content of the atmosphere - a feedback process. The distinction is critical to understand the role of carbon dioxide in climate change. Interestingly, carbon dioxide, either as forcing agent or feedback, appears to have played a dominant role in climate throughout Earth history.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas