What Is Paleoclimatology?
The study of ancient climates is known as paleoclimatology. In much the same way that some researchers study the prehistoric past by examining fossils and other physical clues, paleoclimatologists study several types of evidence in an attempt to understand what Earth's climate was like in the past and how—and why—–it has changed. The more scientists learn about how the climate has varied over the past several million years, the better their predictions about future changes will be.
The most common sources of data for paleoclimatologists include ice cores, long, narrow cylinders of ice drilled from an icecap; sediment cores, cylinders of mud and other matter drilled from the floors of oceans and lakes; the fossilized remains of plants and animals; samples from coral reefs; plant remains obtained from peat bogs; and the growth rings of trees. By studying these kinds of evidence, researchers have been able to reconstruct a timeline of the prehistoric climate of Earth.
For example, researchers now know that the Earth has gone through many glacial periods, or ice ages, during which average global temperatures dropped and the polar icecaps expanded, spreading thick sheets of ice across vast regions of land and sea. The earliest known ice ages occurred more than 2 billion years ago. The last few began about 600,000 years ago and lasted close to 100,000 years each. After each glacial period, global temperatures rose and the icecaps receded. The spans between ice ages, called interglacial periods, lasted from 10,000 to 20,000 years. At the height of the last glacial episode—usually called the Ice Age—glaciers spread across much of northern Europe and North America. The Ice Age ended about 11,500 years ago, giving way to the present interglacial, known as the Holocene Epoch.