Google search "History of earth" 3rd entry:

"Scientists have studied rocks using radiometric dating methods to determine the age of earth. Another really cool thing they've found in rocks that tells us more about the story of earth's past are the remains of living creatures that have been embedded in the rocks for all time. We call these fossils. It has been the careful study of earth's fossil record that has revealed the exciting picture about the kinds of creatures that once roamed this planet. Fossilized skeletons of enormous creatures with huge claws and teeth, ancient ancestors of modern day species (such as sharks) that have remained virtually unchanged for millions of years, and prehistoric jungles lush with plant life, all point to a profusion of life and a variety of species that continues to populate the earth, even in the face of periodic mass extinctions.

By studying the fossil record scientists have determined that the earth has experienced very different climates in the past. In fact, general climactic conditions, as well as existing species, are used to define distinct geologic time periods in earth's history. For example, periodic warming of the earth - during the Jurassic and Cretaceous periods - created a profusion of plant and animal life that left behind generous organic materials from their decay. These layers of organic material built up over millions of years undisturbed. They were eventually covered by younger, overlying sediment and compressed, giving us fossil fuels such as coal, petroleum and natural gas."
http://www.extremescience.com/earth.htm

Google search "History ice age" 2nd entry:
"A minor ice age occurred from 460 to 430 million years ago, during the Late Ordovician Period.

There were extensive polar ice caps at intervals from 350 to 260 million years ago, during the Carboniferous and early Permian Periods, associated with the Karoo Ice Age.
Sediment records showing the fluctuating sequences of glacials and interglacials during the last several million years.
Sediment records showing the fluctuating sequences of glacials and interglacials during the last several million years.

The present ice age began 40 million years ago with the growth of an ice sheet in Antarctica, but intensified during the Pleistocene (starting around 3 million years ago) with the spread of ice sheets in the Northern Hemisphere. Since then, the world has seen cycles of glaciation with ice sheets advancing and retreating on 40,000- and 100,000-year time scales. The last glacial period ended about ten thousand years ago."
http://en.wikipedia.org/wiki/Ice_age
Graph included:

Google search "ice age" 8th entry:

"Climatic Cooling from 60 million years ago to present day

Between 52 and 57 million years ago, the Earth was relatively warm. Tropical conditions actually extended all the way into the mid-latitudes (around northern Spain or the central United States for example), polar regions experienced temperate climates, and the difference in temperature between the equator and pole was much smaller than it is today. Indeed it was so warm that trees grew in both the Arctic and Antarctic, and alligators lived in Ellesmere Island at 78 degrees North.

But this warm period, called the Eocene, was followed by a long cooling trend. Between 52 and 36 million years ago, ice caps developed in East Antarctica, reaching down to sea level in some places. Close to Antarctica, the temperature of the water near the surface dropped to between 5 and 8 degrees Celsius. Between 36 and 20 million years ago the earth experienced the first of three major cooling steps. At this time a continental-scale temperate ice sheet emerged in East Antarctica. Meanwhile, in North America, the mean annual air temperature dropped by approximately 12 degrees Celsius.

Between 20 and 16 million years ago, there was a brief respite from the big chill, but this was followed by a second major cooling period so intense that by 7 million years ago southeastern Greenland was completely covered with glaciers, and by 5-6 million years ago, the glaciers were creeping into Scandinavia and the northern Pacific region. The Earth was once more released from the grip of the big chill between 5 and 3 million years ago, when the sea was much warmer around North America and the Antarctic than it is today. Warm-weather plants grew in Northern Europe where today they cannot survive, and trees grew in Iceland, Greenland, and Canada as far north as 82 degrees North.

We are still in the midst of the third major cooling period that began around 3 million years ago, and its effect can be seen around the world, perhaps even in the development of our own species. Around 2 and a half million years ago, tundra-like conditions took over north-central Europe. Soon thereafter, the once-humid environment of Central China was replaced by harsh continental steppe. And in sub-Saharan Africa, arid and open grasslands expanded, replacing more wooded, wetter environments. Many paleontologists believe that this environmental change is linked to the evolution of humankind. "
http://www.pbs.org/wgbh/nova/ice/chill.html