Since man’s initial curiosity about the history of his earth, much has been discovered about the way the earth moves and changes, including its climate. Scientists have found geologic evidence of at least five ice ages. The first seemed to occur more than two billion years ago and the most recent peeked just 18,000 years ago (Hughes 1993, pg. 11). However, there is one mystery that has seemed to elude scientists from all over the world for quite some time. This mystery is the cause of the several eras of ice that have appeared many times throughout earth’s history. There have been numerous theories formulated to explain these “glacial epochs” (Hughes 1993, pg.13),

Croll began his research by becoming familiar with the studies of the French astronomer Urbain Leverrier (Imbrie 1986, pg. 80). This included calculating how the shape of the earth’s orbit and the degree of its axial tilt had varied over the past 100,000 years (Imbrie 1986, pg. 81). Using this information, Croll calculated “the orbital eccentricity for a sampling of dates over the past 3 million years” (Imbrie 1986, pg. 81). He also drew a curve to illustrate the changes. Croll discovered that “the eccentricity of the orbit changes cyclically” (Imbrie 1986, pg. 81). Also using this information, he decided that eccentricity affects the seasons. Therefore, if winter occurs when the earth is far from the sun, temperatures are colder that usual” (Imbrie 1986, pg. 83). Croll calculated that the tilt of the earth ranged from 22o to 25o. Croll also hypothesized that an ice age would be more likely to occur when the earth was closest to vertical, because the poles would receive less direct sun light at those angles (Imbrie1986, pg. 86). Imbrie writes:

Even though the Milankovitch model is well accepted, there are still problems with this theory. Many believe that the variations seem to be on too short a time scale to explain the timing of the long intervals related to glaciation (Anon, 2001). It is also though that orbital changes in themselves are not big enough to make or to melt ice sheets, but almost certainly serve as “glaciers’ pacemaker” (Watson, 1997). Croll himself worried that the magnitude of the variations was not enough to account for the vastness of the ice sheets (Imbrie 1986, pg. 84).

Some topics in this essay:
Leverrier Imbrie, Reduction CO2, REDUCTION CO2, SHIFT UPLIFT, David Rea, EARTH’S ORBIT, Polar Regions, Pole Anon, ERUPTION Scientists, Geological Survey, ice ages, imbrie 1986 pg, 1986 pg, imbrie 1986, ice age, carbon dioxide, anon 2001, hughes 1993, reduction co2, watson 1997, earth’s orbit, 1986 pg 81, hughes 1993 pg, 81 using information, changes earth’s orbit,