Changes in Climate

1. Changes in Climate Pgs 83 - 87

2. Ice Ages • The geologic record indicates that the Earth’s climate has been much colder than it is today. • Ice ages are periods of time in which ice collects in high latitudes and moves toward lower latitudes. • Major ice ages have occurred during the Earth’s history. • The most recent one started about 2 million years ago.

3. Glacial and Interglacial Periods • There are periods of cold and warmth during ice ages. • They are glacial and interglacial periods. • Glacial periods have large sheets of ice covering large areas. • The amount of water involved in a glacial period causes the sea level to drop. • Warmer times that occur between glacial periods are interglacial periods. • The last interglacial period began 10,000 years ago and is still occurring.

4. Motions of the Earth • Once theory that attempts to explain the gradual cooling and warming of the Earth is the Milankovitch theory. • His theory proposes that the changes in the Earth’s orbit and tilt of the Earth’s axis cause ice ages.

5. Volcanic Eruptions • Catastrophic events, like volcanic eruptions can influence the climate. • Volcanic eruptions send large amounts of dust, ash, and smoke into the atmosphere. • These particles block out the sun’s rays and cool the Earth.

6. Plate Tectonics • The climate is influenced by plate tectonics and continental drift too. • One ice age theory proposes that when the continents are aligned in polar regions, there is a greater chance for a glacial period. • We had a glacial period like this with Pangea over 250 million years ago.

7. Global Warming • Global warming – a rise in the average temperature that can result from an increase in the greenhouse effect. • The green house effect – the Earth’s natural heating process in which the gases in the atmosphere trap thermal energy. • Greenhouse gases allow sunlight to pass through the atmosphere, but trap heat absorbed by air molecules. • Greenhouse effect can increase if there is an increase in the amount of greenhouse gases in the atmosphere, like carbon dioxide. • Deforestation, clearing forests, aides to global warming because trees remove CO2 from the atmosphere.

8. Consequences of Global Warming • Some scientists think that if the average global temperature continues to rise, the polar ice caps will melt. • If they do, then the global sea level will rise and flood coastal cities. • Global climate patterns would change due to the new ocean level and amount of water vapor in the air.