1. The Greenhouse Effect
IB Topic 5.2

2. The greenhouse effect is natural …
It’s just intensifying due to human activity and pollution
Causing the overall temperature to increase
Called Global Warming

3. What is a greenhouse? Walls and roof are made of glass
Sunlight penetrates the glass and warms the plants inside
Sunlight is not that warm
Due to short wavelengths
Outer space between the Sun and Earth is hundreds of degrees below freezing

4. Greenhouse (cont.)
It’s only when sunlight hits an object that some of the energy is transferred to heat energy
Heat energy has longer wavelengths
The glass is not as transparent to heat
Heat is trapped inside
Result: the temperature is greater inside the greenhouse

5. This happens on Earth, too
The atmosphere’s ability to retain heat
Greenhouse gases
Carbon dioxide (CO2), methane, water vapor
Play the role of the glass
Less transparent to heat than light
As a result:
Some of the heat radiated from Earth’s surface is trapped
This keeps the atmosphere warm

6. How does it work?
1. Sunlight enters Earth’s atmosphere because gases are transparent to light
2. Most sunlight is reflected off of Earth’s surface and travel back out of the atmosphere (that’s why Earth can be seen from outer space)
3. Some of the light energy is transformed into heat energy – warms Earth’s surface – radiate much of the heat back to the atmosphere

7. How does it work?
4. Greenhouse gases retain some of the heat and trap it in the atmosphere
5. Result: Earth’s natural greenhouse effect keeps Earth warmer than outer space

8. SUN Heat Radiation Atmosphere Earth
Some of the heat energy from the Sun reflects off the atmosphere back into space
Atmosphere
Some heat enters the atmosphere
Earth

9. What happens when heat radiation hits the ground?
Some heat energy is reflected back into the atmosphere
Some heat energy is absorbed by the ground

10. What happens to heat radiation after it is reflected by the ground?
Some heat escapes back into space
…greenhouse gases
CO2
CH4
Some heat is absorbed by…

11. The higher the concentration of greenhouse gases in the atmosphere…
… the more heat is absorbed by the atmosphere.
The more heat radiation that is absorbed by greenhouse gases…
… the warmer the atmosphere becomes.

12. The greenhouse gases Carbon dioxide Methane Water vapor
Oxides of nitrogen
Concentrations of these gases are naturally low
Prevents too much heat retention

13. The problem is … Human activity
Demands for food, fuel, & space = excess production of waste gases
Burning fossil fuels (e.g. gas in cars)
Organic and commercial fertilizers
Industrial processes
Methane (CH4)
Cooking and heating
Cattle ranching
Waste disposal in landfills

14. Sources of Greenhouse Gases
Burning fuels produces…
Rotting vegetation produces…
… carbon dioxide
…methane
Animals produce…
Methane
Carbon dioxide
(Mostly burps, but also…
(Respiration)
…some farts!)

15. Plants remove carbon dioxide from the atmosphere, in a process called…
… photosynthesis
Chopping down trees…
…increases the amount of carbon dioxide in the atmosphere, by…
… reducing the rate of photosynthesis

16. In conclusion …
Rise in human population and activity = increased levels of greenhouse gases
These gases absorb heat
Intensifying Earth’s natural greenhouse effect
However, climate is a complex phenomenon
Not fully understood
From what is known, a rise in global temperatures:
Increase in photosynthetic rates
Changes in climate effecting ecosystems
Extinction of certain species
Melting glaciers
A rise in sea levels … flooding of costal area?

17. What’s Al Gore Up To?