The author explores the causes of Earth's cyclical temperature changes and shows how those temperature shifts touch off a chain of events in the atmosphere, in the oceans and on land. Cold temperature was the trigger; and the resultant reduction in carbon dioxide, he argues, was the bullet that killed off so many species. The re-warming released more carbon dioxide into the atmosphere and fueled a resurgence. This book provides significant long term background information to put global warming into perspective. In addition, the author describes the human responses to increases in atmospheric carbon dioxide after the last ice age and in the last 150 years. Near the end of the last ice age, atmospheric carbon dioxide was about half of what it is today. Due to the lack of carbon dioxide, most of the vegetation disappeared from the middle and high latitudes. Without plants to eat, many large animals became extinct; North America lost three-fourths of its large animals including the woolly mammoth, mastodon and saber tooth cat. Humans, too, had little to eat in these areas and their population declined dramatically. The book then explains how and why atmospheric carbon dioxide increased by about 50% after the last ice age ended, encouraging a population explosion among plants, animals and humans, all of which then migrated into many previously barren areas. More recently, the 28% increase in atmospheric carbon dioxide in the last 150 years has caused a six-fold increase in the human population. Changes in the next 300 years will reverse some of the current trends. This book has value for anyone interested in the ice age extinction; glaciers; the glacial cycle; the atmosphere and oceans and the past and future of plants, animals and humans. It provides long-term information on atmospheric carbon dioxide, global warming and cooling.