Introduction | A LONG LONG LONG time ago... | A LONG LONG time ago...
A LONG time ago... | Not so long ago...

Not so long ago...

About 1,000 years ago, the climate was warm and the North Atlantic Ocean did not have much sea ice in it. Without icebergs to stop them, the Viking people set out from northern Europe by boat and traveled across the Atlantic to places like Iceland, Greenland, and Labrador. The changing climate put a stop to their travels as the climate of Europe became cooler between 1300 and 1850 during a time called “The Little Ice Age”.

A group of Native Americans lived in the cliffs at Mesa Verde, in the U.S. Southwest, at almost the same time the Vikings were traveling across the sea. The artifacts they left behind tell us that they were farmers and had a very interesting culture. But around 1300, after a very long dry period, they left their homes in the cliffs and disappeared.

About 100 years ago, people worldwide began burning more coal and oil for homes, factories, and transportation. Burning these fossil fuels emits carbon dioxide and other greenhouse gases. Since then, Earth’s climate has warmed more quickly. Since 1850, the average global air temperature has risen more than 1 degree Fahrenheit (0.6 Celsius). Some places, like the Arctic, have warmed more quickly than others. The 1990s were the warmest decade of the last century.