Snowball Earth Hypothesis

Snowball Earth

600 to 750 million years ago Earth was incased in ice for prolong periods of time and each global glacial event ended under severe greenhouse conditions. This late Precambrian planet-wide glaciation is known as “Snowball Earth” and is an extension on Sturtian- Varangian glaciation.

Solar radiation and Earth's albedo

Solar luminosity at a distance of one AU (distance from earth to the sun) is about 1370 watts per square meter (Barkstrom, 2005). Earth receives most of its energy from the sun, about 343 watts per square meter (NASA, 2005). About one third of this energy is reflected into space by cloud cover and land surface, the other two thirds is absorbed by the atmosphere and the Earth's surface, raising the average temperature (Hoffman, 1999). Figure 1 depicts a more detailed breakdown of solar energy interaction between atmosphere and the Earth's surface.

(Figure 1)

The surface albedo is a measure of how much radiation is reflected, for example, snow has an albedo of 0.8, where as seawater has albedo of 0.1, the land surface albedo can very widely principally depending on flora (Hoffman, 1999). Average albedo of planet Earth is about .31. Figure 2 shows albedo values for different surfaces.

(Figure 2)