1. Topic 5.2 The Greenhouse effect
Topic 5: Ecology and Evolution

2. The Carbon Cycle

3. Carbon in the Environment
The element carbon is a basic element of all living organisms.
Its atoms combine easily with other atoms to form a huge variety of molecules.

4. Remember Photosynthesis: 6CO2 + 6H20  C6H12O6 + 6O2 Respiration
C6H12O6 + 6O2  6CO2 + 6H20

5. Remember Photosynthesis: 6CO2 + 6H20  C6H12O6 + 6O2 Respiration
C6H12O6 + 6O2  6CO2 + 6H20

6. Remember
Fossil fuels are made from the remains of dead plants and animals
Combustion of fossil fuel:
Fuel + O2  CO2 + H20

7. Carbon Dioxide in the air
Photosynthesis
Combustion
Respiration by decomposers
Respiration of plants and animals
Eaten by
Fossilisation
Fossil Fuel

8. Carbon Dioxide in the air
Photosynthesis
Combustion
Respiration by decomposers
Respiration of plants and animals
Eaten by
Fossilisation
Fossil Fuel

9. Human effect on the carbon cycle
Facts
Humans cut down forests.
Humans burn fossil fuels

10. What happens next??

11. Carbon Dioxide in the air
Photosynthesis
Combustion
Respiration
Eaten by
Fossilisation
Fossil Fuel

12. Effect of increased CO2 levels
More carbon dioxide in the environment leads to an increase in global warming due to the “green house effect”
In a greenhouse, sunlight goes through the glass but does not come out as easily. The greenhouse heats up.

13. The Greenhouse Effect
However, gases in the atmosphere absorb some of this radiation and trap the heat. This makes the earth warm enough for life to exist.
In recent years the levels of these greenhouse gases has increased meaning more heat is trapped than usual.
Long wave infra red radiation from the sun should be reflected back into space
Atmosphere

14. The greenhouse effect Look at Fig 514 in your text book.
Heat and energy in the atmosphere comes from solar radiation absorbed by the earth and from greenhouse gas absorption. How much is it in total?
What percentage of this goes into the Earth’s land and ocean surface?
What would happen if the greenhouse gas absorption was to increase?
= 519
(324/519) x 100 = 62%
More heat would go into the earth.

15. Analysing Greenhouse gases
Read the hand out on the Greenhouse effect and answer all the questions.
Name the Greenhouse gases. What are the sources of these gases?
Which gas do you think presents the biggest danger? Why?
The “Greenhouse Effect” is a natural phenomenon. The “Enhanced Greenhouse Effect” has been caused by the increase of “Greenhouse gases”. Explain the difference.

16. Analysing Greenhouse gases
So. Are greenhouse gases really increasing?

17. Changing Carbon Dioxide levels
Mauna Loa is in Hawaii and has the longest running record of CO2 levels.
Levels go up and down due to leaves falling off the trees (this is measuring Northern Hemisphere).
Trend shows general increase

18. Analysing Greenhouse gases
Does an increase in greenhouse gases REALLY equate to higher temperatures?

19. Changing temperature levels
Present day
The most recent ice age
Changes in CO2 (bottom line) over thousands of years can be determined from CO2 trapped in the Antarctic Ice.
The temperature can be determined from the same gas sample as the ratio of oxygen isotopes O16and O18 .
Conclusion:
There is a clear correlation between atmospheric CO2 and temperatures.
Correlation of course does not mean causation.
Note that the CO2 levels today are higher than ever in the past.
The dashed blue line is an extrapolation of the curve.

20. What are the effects of the greenhouse effect?
How would a global temperature rise affect arctic ecosystems?
Do some research in preparation to make a persuasive poster, leaflet or PowerPoint next week.

21. The Precautionary Principle
Someone wishing to take a certain kind of action should prove that the action does not cause serious or irreversible harm to the public if there is no scientific consensus about the outcome of the action. Or
If you do not know what the result of a change in your behaviour will be, you must prove that it is not harmful.

22. The Precautionary Principle
Read page 81 – 83 in your text book including the TOK section.
There are arguments for and against using the Precautionary Principle as a basis for environmental politics
Research the precautionary principle from both sides of this argument. Next lesson you will be allocated a position (for or against) and put into pairs to debate the issue.

23. Websites http://click4biology.info/c4b/5/eco5.2.htm#one