Long-Term Changes in Climate Changes

by Andrew Nguyen, Taylor Canfield, and Chase Saeger

Studying Climate Change•Scientists follow an important principle: If plants or animals today need certain conditions to live, then similar plants and animals in the past also required those conditions.

•Scientists use fossils, tree rings, and pollen records to find climates of the past.

Tree Rings

•Every summer, trees grow a new layer of bark.

•You can see these as tree rings.

•Thick rings indicate a warm or wet summer.

•Thin rings indicate a cold or dry summer.

•Scientists count backwards from the outmost ring to see how old a tree is.

Pollen Records

•Scientists can also gather data through pollen records.

•Each type of plant has a particular type of pollen.

•Scientists can use records to tell which types of plants lived in a certain area.

Ice Ages•Ice Ages-glacial episodes•During each ice age, huge sheets of ice called

glaciers covered large parts of Earth’s surface.•There have been at least 4 ice ages in the last

2 million years.•Each of the last four ice ages lasted at least a

100,000 years.•Inland, large lakes were formed.

Causes of Climate Change

•Possible explanations for major climate changes include variations in the position of Earth relative to the sun, changes in the sun’s energy output, and the movement of continents.

Earth’s Position (Causes of Climate Change)

•As Earth revolves around the sun, the time of year when the Earth is closest to the sun shifts from January to July and back again over a period of about 26,000 years.

•The angle at which Earth’s axis tilts and the shape of Earth’s orbit around the sun also changes slightly over long periods of time.

Solar Energy (Causes of Climate Change)

•Sunspots- dark, cooler regions on the surface of the sun. Sunspots can be changed by the output of the sun’s energy.

•Satellite measurements have shown that the amount of energy the sun produces increases slightly from year to year

Movements of Continents (Causes of Climate Change)

•About 225 million years ago, most of the land on Earth was part of a single continent called Pangaea.

•The movement explains how tropical plants, such as palm trees, could have once existed on Greenland.

•The changes of the continents affected the global patterns of winds and ocean currents, which slowly changed climates.

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