How does the earth know when to have an ice age and how does the earth create it? – Secondary 11

Question: How does the earth know when to have an ice age and how does the earth create it?
- Keywords:
  earth,
  ice age,
  world
Asked by kookieboi to Kate, Mark U, Tess, Yue on 2 May 2012. This question was also asked by cheese2000.
- Kate Davies answered on 2 May 2012:
  
  Hey kookieboi, an ice age is created by a significant and long term reduction of the earths surface temperature and results in the creation of a large number of ice sheets or more accurately glaciers (large bodies of ice) that cover the earths surface. From what we can determine from geographical and geological studies there have been 5 ice ages in the earths past. It is often reported that we continue to be in a form of ice age and will continue to be so whilst there is ice present on the earth, so greenland, antarctica and the arctic indicate this “current ice age” is over 2.4million years old.
  A number of factors are believed to contribute to the creation of an ice age, the common ones include atmosphere (greenhouse gases), fluctuation of ocean currents and the position of the continents. Hope this gives you some help, its all i know i’m afraid 🙂

Question: How does the earth know when to have an ice age and how does the earth create it?