Scientists study tree rings like these to figure out what climates of the past were like. Each year that the tree was alive it grew another ring, making its trunk wider. The thickness of a ring depends on what the weather was like during the year in which it grew.
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Image courtesy of UCAR Digital Image Library

Climates of the Past

The climate of Earth has been changing for billions of years! It warmed and cooled many times long before humans were on the planet.

How do we know what the climate was like a thousand years ago, a million years ago, or even a billion years ago? To figure out what climates used to be like, scientists work like detectives and look for clues around the planet to solve the mystery. They find clues inside sedimentary rocks, glaciers, fossils, trees and corals.

Today, people are worried because the Earth is warming faster than it has in the past. Faster warming is happening because more greenhouse gases are released into the atmosphere.

Click on the links below to learn more about how climate has changed in the past.

Last modified February 28, 2008 by Becca Hatheway.

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