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
Paleoclimates: Climates of the Past
Climate change has affected the Earth throughout its 4.6 billion year history. The Earth has repeatedly warmed and cooled and the changes affected the types of environments on Earth’s surface and the organisms that could survive.
Evidence of past climate change comes from many sources. The sediments 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 glacial ice record the characteristics of the atmosphere. Fossil plant pollen and tiny marine plankton provide clues the temperatures in the oceans and on the land. Tree rings show what climate was like over the life of the tree. The scientists who decipher these clues to ancient climates are called paleoclimatologists.
If climate has always changed, then why is global warming such a concern today? Humans are adding large amounts of greenhouse gas to our atmosphere by burning fossil fuels. This change in the concentration of greenhouse gases is increasing the speed of global warming. The rate of change today is increasing so rapidly that scientists are concerned that life on Earth, including humans, will not have time to adapt to the changing conditions.
Click on the links below to learn more about how climate has changed in the past.
Shop Windows to the Universe Science Store!
The Fall 2009 issue of The Earth Scientist
, which includes articles on student research into building design for earthquakes and a classroom lab on the composition of the Earth’s ancient atmosphere, is available in our online store
You might also be interested in:
Biomes are large regions of the world with similar plants, animals, and other living things that are adapted to the climate and other conditions. Explore the links below to learn more about some of the...more
When water or wind loses energy and slows down, sediment can no longer be carried in it. The particles of sediment fall through the water or air and form a blanket of sediment on the bottom of a river,...more
Fossils are evidence of ancient life preserved within sedimentary rocks. They are clues to what living things, ecosystems, and environments were like since life has existed on this planet. The oldest...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
Anyone who has ever cut down a tree is familiar with the rings radiating out from the center of a tree trunk marking the tree's age. Careful study of tree rings can offer much more: a rich record of history...more
In a vivid example of how a small geographic feature may have far-reaching impacts on climate, new research shows that water levels in the Bering Strait helped drive global climate patterns during ice...more
An abrupt release of methane, a powerful greenhouse gas, from ice sheets that extended to Earth's low latitudes some 635 million years ago caused a dramatic shift in climate, scientists funded by the National...more