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.
Click on image for full size
Image courtesy of UCAR Digital Image Library
Climates of the Past
Earth's climate has been changing for billions of years. It warmed and cooled many times long before humans were around.
There weren’t any people on Earth millions and billions of years ago to describe what climate was like, but the Earth kept records of past climates in special ways. Sediments and fossils deposited millions of years ago provide a record of ancient environments. Thin layers of mud and sand that form at the bottom of lakes record seasonal changes. Bubbles of ancient air trapped inside glaciers record what the atmosphere was like. Tree rings show what climate was like for each year of a tree’s life.
If climate has always changed, then why are people concerned about global warming? People are concerned because the Earth is warming faster now than it has in the past as more greenhouse gases are released into the atmosphere. Warming is happening faster and life on Earth, including humans, may not have time to get used to the warming planet.
Click on the links below to learn more about how climate has changed in the past.
Shop Windows to the Universe Science Store!
The
Summer 2010 issue of The Earth Scientist, available in our
online store, includes articles on rivers and snow, classroom planetariums, satellites and oceanography, hands-on astronomy, and global warming.
You might also be interested in:
Fossils are evidence of ancient life preserved in sedimentary rocks. On Earth, they are clues to what living things, ecosystems, and environments were like in the past. The oldest fossils are from mats
...more
When water or wind loses energy and slows down, sediment can no longer be carried in it. The particles fall through the water or air and form a blanket of sediment on the bottom of a river, a lake, ocean,
...more
The Little Ice Age was a time of cooler climate in most parts of the world. Although there is some disagreement about exactly when the Little Ice Age started, records suggest that temperatures began cooling
...more
Studying tree rings doesn't only tell us the age of that tree. Tree rings also show what climate was like for each year of a tree's life, which means they can tell us about climates of the past and about
...more
Earth’s climate is warming quickly now. We know that this has to do with additional greenhouse gases in the atmosphere and other global changes. But there is a lot we don’t yet know about how warming will
...more
Sometimes, a small change in the Earth can lead to a big change in climate. A new study shows that changes in the Bering Strait might have affected ocean currents and climate worldwide thousands of years
...more
An international team of scientists is currently studying the equatorial Pacific Ocean, and a second expedition will happen in May 2009. They are part of a science program called the Pacific Equatorial
...more
