LOLA is correct...this has been a repeating pattern for millions of years. There is a debate about man versus mother nature. There is also a debate about the chicken and the egg...is CO2 the cause of warming, or the result of it:
Warming trends and CO2 elevations have occurred throughout history in close proximity in time and have coincided with the earth's place in the solar system and orbital tilts. (The Milankovitch Cycles) When closer to the sun as it is now, warming occurs, and further away, ice ages occur. Warmer water cannot absorb as much CO2 and permafrost (frozen peat and decaying material) melts which gives off stored CO2. Many scientists believe the increased CO2 actually results from warming, not the other way around. If interested, here are some results from a google search to get you started:
http://www.google.com/search?hl=en&rls=com.microsoft:*:IE-SearchBox&rlz=1I7GGIH&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=milankovitch+cycles+environment+global+warming&spell=1