The Discovery of Global Warming

The Earth's climate is constantly changing. Many climatologists believe that the temperature of the Earth slowly fluctuates over time. In fact, several scientists estimate that between 15,000 and 30,000 years ago the Earth was covered by large sheets of ice. This period of time was known as the Ice Age. As the temperature of the Earth began to rise 7,000 years ago, the Ice Age came to an end.