The CU-Boulder researchers are now looking at cloud composition and formation, the hydrological cycle, movements of continental masses over time and heat transport through Earth's system as other possible modes of keeping early Earth warm enough for liquid water to exist. Wolf gave a presentation on the subject at the annual American Geophysical Union meeting held Dec. 5-9 in San Francisco.
Toon said 1-D models essentially balance the amount of sunshine reaching the atmosphere, clouds, and Earth's terrestrial and aquatic surfaces with the amount of "earthshine" being emitted back into the atmosphere, clouds, and space, primarily in the infrared portion of the electromagnetic spectrum. "The advantage of a 3-D model is that the transport of energy across the planet and changes in all the components of the climate system can be considered in addition to the basic planetary energy balance."
In the new 3-D model, preventing a planet-wide glaciation requires about three times more CO2 than predicted by the 1-D models, said Wolf. For all warm climate scenarios generated by the 3-D model, Earth's mean temperature about 2.8 billion years ago was 5 to 10 degrees F warmer than the 1-D model, given the same abundance of greenhouse gases. "Nonetheless, the 3-D model indicates a roughly 55 degrees F mean temperature was still low enough to trigger a slide by early Earth into a runaway glacial event, causing what some scientists call a 'Snowball Earth,'" said Wolf.
"The ultimate point of this study is to determine what Earth was like around
|Contact: Eric Wolf|
University of Colorado at Boulder