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Well WHERE THE H*LL WERE THEY for the past billion years when the climate changed!?!?!?! We have had numerous climate changes on the earth over the millenniums and they didn't care before. They could have kept the glaciers COVERING the entire earth all these millions of years IF they had been more active from the beginning of time!

http://www.pbs.org/wgbh/nova/ice/chill.html

The Big Chill by Kirk A. Maasch

During the past billion years, the Earth's climate has fluctuated between warm periods - sometimes even completely ice-free - and cold periods, when glaciers scoured the continents. The cold periods - or ice ages - are times when the entire Earth experiences notably colder climatic conditions. During an ice age, the polar regions are cold, there are large differences in temperature from the equator to the pole, and large, continental-size glaciers can cover enormous regions of the earth. Ever since the Pre-Cambrian (600 million years ago), ice ages have occurred at widely spaced intervals of geologic time - approximately 200 million years - lasting for millions, or even tens of millions of years.

For the Cenozoic period, which began about 70 million years ago and continues today, evidence derived from marine sediments provide a detailed, and fairly continuous, record for climate change. This record indicates decreasing deep-water temperature, along with the build-up of continental ice sheets. Much of this deep-water cooling occurred in three major steps about 36, 15 and 3 million years ago - the most recent of which continues today. During the present ice age, glaciers have advanced and retreated over 20 times, often blanketing North America with ice.

Our climate today is actually a warm interval between these many periods of glaciation. The most recent period of glaciation, which many people think of as the "Ice Age", was at its height approximately 20,000 years ago. Although the exact causes for ice ages, and the glacial cycles within them, have not been proven, they are most likely the result of a complicated dynamic interaction between such things as solar output, distance of the Earth from the sun, position and height of the continents, ocean circulation, and the composition of the atmosphere. 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.

Possible Explanations for the Past 60 Million Years of Cooling Climate change on ultra-long time scales (tens of millions of years) are more than likely connected to plate tectonics. Plate motions lead to cycles of ocean basin growth and destruction, known as Wilson cycles, involving continental rifting, seafloor-spreading, subduction, and collision. Several explanations of the latest cooling trend that involve a climate-tectonic connection are summarized below.