1. Geologic History: Climate Change
It’s a balancing act!

2. Climate during Earth’s history
Over the past 4.6 billion years, Earth’s climate has cycled between warm and cold periods.
What has caused these changes?

3. 1. Change in Earth’s Orbit
The amount of solar radiation from the Sun determines Earth’s temperature.
Over hundreds of thousands of years, Earth’s orbit changes, from circular (warmer Earth) to elliptical (cooler Earth)
In a circular orbit, Earth spends relatively more time closer to the Sun
In an elliptical orbit, Earth spends relatively more time further away from the Sun

4. 2. Greenhouse Gases
What do you notice about the relationship between carbon dioxide and temperature?

5. 2. Greenhouse Gases
Greenhouse gases are gases that are able to trap and hold heat energy from the Sun.
Fewer greenhouse gases = less heat trapped, colder temperatures
More greenhouse gases = more heat trapped, warmer temperatures
CARBON DIOXIDE and METHANE are two greenhouse gases

6. 2. Greenhouse Gases
Current scientific theory suggests that greenhouse gases have played a MAJOR role in changing climate in Earth’s history
Rising CO2 and methane levels have caused several long periods of warming in the past

7. 3. Volcanoes can cool Earth
Volcanic eruptions can send huge clouds of ash into the atmosphere
The ash can block some of the Sun’s rays from reaching Earth, causing the Earth’s temperature to drop

8. 3. Or, volcanoes can heat Earth!
Volcanoes release carbon dioxide gas into the atmosphere
Carbon dioxide is a greenhouse gas
In periods where there is a lot of volcanic activity, the increase in carbon dioxide can warm Earth

9. How do we know? Ice Core Data

10. How Does It Work?
Scientists drill deep into the ice at the poles, and extract long ice cores.
The ice can date back to almost a million years
The ice traps data about the climate of the time