Discovering Past

Climates

Grade 9 and 10 Science

Mr. MacMillan

A Scientist who studies past climates on Earth

Paleoclimatologists

What Can Tree Rings Reveal About Climate?

• As trees grow, rings of new growth form within the trunk• A wide tree ring indicates wet and cool weather, which allows trees to grow

rapidly

Ice Cores: Records of past Climates

• Ice cores are long cylinders of ice obtained by drilling into a glacier• Ice sheets over Greenland and Antarctica have built up over hundreds of

thousands of winters.• Ice Coring in Antarctica obtained climate records from Antarctic ice that date

back 800 000 years ago.

Evidence of Past Climates Obtained from Ice Cores

1. Dissolved and particulate matter in the icedust, ashes, salts, pollen and other matter are brought to the Earth’s surface when it rains or snows. Frozen samples of these materials give clues about conditions

2. Physical characteristics of the Icephysical characteristics of the ice crystals indicate the condition of the temperature and humidity at the time the crystals formed.

3. The composition of trapped air bubblesanalysis or air locked inside ice cores gives scientists a record of atmospheric concentration of greenhouse gases over the years

4. The composition of Iceconcentration of isotopes in different layers of ice indicates the temperature at the time the ice formed.

Other Evidence of Past Climates: Sedimentary Rock

• A rock type that is formed by the deposition of sediment• Every year, billions of tonnes of sediment (fragments of rock) wash from the land and

accumulate in thick layers on ocean floors and lake beds. Over long periods of time, this deposited material becomes compressed and hardened into sedimentary rock.

Other Evidence of Past Climates: Fossils

• The traces or remains of a once-living organism• Fossils can be analyzed to obtain information about the composition of the oceans

and atmosphere at the time the organism lived.