The document discusses ozone depletion and its causes and effects. It is caused mainly by CFCs released into the atmosphere. Ozone depletion is a serious problem, with a larger and deeper hole observed over Antarctica compared to the Arctic. This leads to increased UV radiation reaching the Earth's surface, which can harm human health, marine life, and crop production. The Montreal Protocol was implemented in 1987 to reduce CFC substances and has been signed by 189 countries to effectively address the issue at an international level.

1. Unit 20 – Ozone Depletion

2. Watch the video and answer the question 1. How serious is Ozone depletion? 2. What causes Ozone depletion? http:// www.youtube.com/watch?v =YRh3yH7Hnew

3. Text pg 172

4. Destruction of Ozone (oxygen atoms) in the stratosphere (layer in atmosphere) caused mainly by release of CFCs Ozone Depletion Definition Important!

5. Troposphere Stratosphere Ozone Layer Refer to text pg 166

6. Act as a shield , Protection from harmful Ultraviolet rays from the sun

7. Characteristics of Ozone layer contains ozone gas able to REPLACE ITSELF as Ozone gas is continually created in atmosphere (Same as how Oxygen replaces itself) However CFC destroys the Ozone gas faster than its replacement

9. WHOS THE CULPRIT? Look at Text page 167 Write down the 4 CAUSES of Ozone depletion on your worksheet now.

10. Extent – How serious is the problem? 1.Arctic (North pole) – Thinning of the ozone layer + small hole 2.Antarctica (South pole) – Bigger and deeper hole in the ozone layer Which is more serious?

11. Consequences of Ozone depletion Human Health Skin cancer, cataracts, Weakens immune system Marine Food Chain UV kills plankton (marine food) Affects food chain Global Climate Increase global warming due to Increase UV (less plankton = > CO2) Damage materials UV radiation deteriorate materials eg Plastics, PVC Affect Plant Growth & Reduce Crop production (UV stump growth) Important text pg 169

13. Measures (1) International level Montreal protocol signed in 1987 Comprise of 189 countries now To reduce CFC substances

14. Measures (2) National level Singapore banned use of CFC products in 1991D Countries can control the import and manufacture of CFC products

15. Measures (3) Individual level You and me Can use CFC free products Educate and encourage others too

16. Less effective More effective Which is more effective? Why? What is the purpose of it? Kyoto Protocol Montreal Protocol Reduce emission of greenhouse gas (Global Warming) Limit the production and use of CFCs (Ozone depletion) Limiting GHG = controlling burning of fossil fuel (affects industrialization and economic productivity). Limiting CFC products will not affect economy growth