In the United States, people began keeping weather records regularly in 1895. That seems like a long time ago, but compared to the age of the earth, it is a very, very short period of time.
Paleoclimatologists are scientists who figure out what the earth’s climate was like before written records existed. They find clues in pollen from trees and plants at archeological sites and in ice, soil, and lake beds. Fossils of plants and animals also can hold clues about what the climate was like hundreds, thousands, millions, or even billions of years ago.
Tales of Trees
One way scientists study the paleoclimate is through looking at tree rings. If you have ever seen a tree that has been cut down, you might have noticed that inside the trunk of the tree, circles or rings expand out from the middle of the trunk. Each ring signals a year that the tree was alive. The distance between each ring shows how much the tree grew in a single year. The farther apart the rings are, the more the tree grew. If the rings are closer to each other, we know that the tree didn’t grow very much in those years.
During droughts, trees don’t grow as much as they do during years of normal precipitation. So if a number of rings are close together, that indicates several years of drought when the tree did not get enough moisture to grow.
Let’s think about it this way: Imagine that you measure how tall you are each year on your birthday by marking it on a wall or door in your house. The distance between those measurements shows how much you grew during that year. You grow more in some years than in other years. If you were a tree, those marks would be the rings in your trunk.