Shop Windows to the Universe

The Spring 2011 issue of The Earth Scientist is focused on modernizing seismology education. Thanks to IRIS, you can download this issue for free as a pdf. Print copies are available in our online store.
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 werenít 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 treeís 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.

Last modified February 28, 2008 by Becca Hatheway.

Shop Windows to the Universe Science Store!

The Spring 2010 issue of The Earth Scientist focuses on the ocean, including articles on polar research, coral reefs, ocean acidification, and climate. Includes a gorgeous full color poster!

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Cool It! Game

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

What Is a Fossil?

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

Step 3: Sediments Settling Down!

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

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

Growth Spurt in Tree Rings Prompts Questions About Climate Change

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

Scientists Search for the Cause of Ancient Global Warming

Earthís 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 donít yet know about how warming will...more

Global Ice Age Climate Patterns Influenced by Bering Strait

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

Scientists to Investigate Role of Equatorial Pacific Ocean in Global Climate System

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

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF