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

Long Ago Climates

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

How do we know what the climate was like a thousand years ago, a million years ago, or even a billion years ago? That’s long before there were people keeping track of the weather!

To figure out what climates used to be like, scientists work like detectives and look for clues around the planet to solve the mystery. These scientists are called paleoclimatologists. They find clues in the sediments at the bottoms of lakes and oceans, in the ice of glaciers, in fossils, and inside trees and corals.

• Thin layers of mud and sand that form in lakes are clues to past climates.
• Fossils of tiny plankton that once floated through the seas contain clues to ancient ocean temperatures.
• Bubbles trapped inside the ice of old glaciers hold air from many thousands of years ago.
• Tree rings show what climate was like for each year of a tree’s life.
• The skeletons of corals contain clues to changing ocean temperatures.