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CHAPTER 10 Global Warming and Ozone Depletion.

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Presentation on theme: "CHAPTER 10 Global Warming and Ozone Depletion."— Presentation transcript:

1 CHAPTER 10 Global Warming and Ozone Depletion

2 Learning Outcomes You Will Learn: to describe what is global warming
to describe the causes and consequences of global warming

3 Relay Summary

4 Activity 1 ( relay summary)
Each row will be asked to come forward in front of the classroom. You are to write down on the whiteboard what comes to your mind when you first think of global warming. The “LAST” person is to do a summary based on the responses seen on the board.

5 The Inconvenient Truth

6 Changes in the Earth’s Climate
In the last 150 years, global temperatures have been rising and the amount of carbon dioxide in the atmosphere has reached phenomenal levels. 1979 2005 Ice cover in the Arctic sea has decreased dramatically due to rising global temperatures. Source: NASA

7 What do you need to know about global warming?
Greenhouse effect Global warming

8 The atmosphere

9 The Greenhouse Effect Earth is surrounded by a layer of gases= atmosphere Provides the Earth with greenhouse gases Examples of gases in the atmosphere: Carbon dioxide, methane, nitrous oxide, chlorofuorocarbons(CFCs) = GREENHOUSE GASES Greenhouse gases trap the heat from the sun’s rays

10 Greenhouse effect-A natural process?
Warming process = greenhouse effect Maintains the Earth’s average temperature at 15 degrees celsius. Makes our Earth a warm and comfortable place to live in


12 So, what is actually global warming?

13 Global warming Average increase in the air temperature of the atmosphere near the Earth’s surface which can contribute to changes in global climate patterns

14 Identify the activities .

15 Global Warming The amount of greenhouse gases in the atmosphere has increased dramatically over the last two centuries because of industrialisation and other human activities. Due to the rapid increase in the amount of greenhouse gases, more heat is trapped in the atmosphere, causing the phenomenon known as the enhanced greenhouse effect. As a result, average global temperatures around the world have increased. This is known as global warming.

16 Causes of global warming
Sources of carbon dioxide: Burning fossil fuels in cars, factories and power plants Sources of nitrous oxides: Vehicle exhaust pipes, fertilisers, livestock wastes Increase in greenhouse gas emissions due to human activities Sources of CFCs: Aerosol cans, air-conditioners, refrigerators, plastic forms Sources of methane: Landfills, rice paddies, guts of cattle


18 Extent of global warming
Not all places on the Earth experience the same temperature increase due to global warming. The Poles experience higher temperature increases than the Equator. The reflectivity of ice plays a crucial role in reflecting sunlight back into space. Ice reflects about 80-90% of sunlight back into space. As the ice in the Polar regions melts due to global warming, the darker-coloured ocean bodies absorb more sunlight. Thus, global warming is more pronounced in the Polar regions.

19 Consequences of global warming
Changes in weather conditions Prolonged droughts in dry regions Frequent heat waves Severe flooding in wet regions Severe flooding Severe drought

20 Consequences of global warming
Impact on plants Change in rainfall and temperature patterns affect vegetation growth around the world Impact on animals Reduction in ice cover affects the natural habitats of polar bears and Adelie penguins and force them to migrate or face extinction. A polar bear threads what was once solid ice. Polar bears are drowning as warmer waters have widened the distance between ice floes.

21 Consequences of global warming
Impact on people Rising temperatures in the Tropics allow mosquitoes to thrive, causing the spread of diseases like dengue fever, malaria and yellow fever Heat waves cause people to die of dehydration or heat stroke. A nurse tends to a heat wave victim in Pakistan as temperatures soar to as high as 45 degrees Celsius.

22 Consequences of global warming
Rising sea levels As the seas expand and ice in the Polar regions melts due to rising temperatures, sea levels around the world will increase. Low-lying coastal wetlands and islands, coral reefs and parts of the world’s coastal cities will be subjected to flooding.

23 Consequences of global warming
Rising sea levels Agricultural lowlands and deltas in parts of Bangladesh, India, and China, where most of the world’s rice is grown, will be flooded. Low-lying islands in the Pacific Ocean (e.g. Marshall Islands) and the Indian Ocean (e.g. Maldives) will be submerged under the rising sea levels. Natural habitats and ecosystems along coastal areas will be at risk (e.g. French Polynesia).

24 Exit card Watch a short trailer from the movie, “the inconvenient truth”. Your question: State the impacts of global warming that you can see from the video.


26 Ozone Depletion The ozone layer contains ozone gas and lies about 15 to 50 km above the Earth’s surface. It protects life on Earth by preventing about 95 per cent of the Sun’s harmful ultraviolet (UV) rays from reaching the Earth’s surface. In 1985, scientists discovered that the ozone layer was so severely depleted to the extent that a gapping ‘hole’ had appeared in the ozone layer over the Antarctica. This gradual destruction of the ozone layer is known as ozone depletion. Ozone hole over the Antarctic in 22 Sep 2004

27 Cause of ozone depletion
CFCs have been identified as the main cause of damage to the ozone layer. CFCs are mainly found in aerosol cans, refrigerators, air-conditioners and plastic foams. Once CFCs are released into the air, the chlorine in them reacts and destroys the ozone particles in the ozone layer. Each CFC molecule can last up to years in the atmosphere! In this time span, it can continuously destroy ozone particles.

28 Cause of ozone depletion
Although the ozone layer can replace itself over time as ozone is continually produced in the atmosphere, the rate of ozone depletion far exceeds that of its replacement. With the depletion of the ozone layer, huge amounts of UV rays can reach the Earth’s surface. This has severe consequences on animals, plants, and people. UV rays reaching the Earth’s surface due to ozone depletion

29 Extent of ozone depletion
Since the 1980s, the ozone layer has been thinning throughout the world, with the exception of the Tropics. Ozone depletion is most severe over the Arctic and Antarctic regions. Generally, ozone depletion is greater at higher latitudes. Ozone depletion over the Antarctic and Arctic regions

30 Consequences of ozone depletion
Impact on animals and plants The increase in UV radiation damages plant tissues and may destroy crops, causing a decline in food supply. Excessive UV radiation kills plankton, which is the food for many marine animals. As a result, the survival of the marine animals dependent on plankton will be threatened. Fish supply could decrease and some marine species may face extinction. Some species of whales feed on plankton to survive. Without plentiful plankton in the oceans, they may be pushed to the brink of extinction.

31 Consequences of ozone depletion
Impact on people People may develop more severe sunburns, eye cataracts (clouding of the eye’s lens which reduces vision and if left untreated, may cause blindness), and skin cancers. Excessive exposure to UV rays weakens the immune system, making people more vulnerable to illnesses and diseases.

32 Measures to Reduce the Impact of Ozone Depletion: International efforts
Montreal Protocol (1987) Signed by many countries around the world to reduce the emissions of CFCs The ozone layer is estimated to recover to 1980s levels by 2050 and 1950 levels by 2100 if the world takes consistent preventive measures to ban the production and use of CFCs. However, due to the persistent nature and huge amounts of CFCs in the atmosphere, ozone recovery will take a long time.

33 Measures to Reduce the Impact of Global Warming: International efforts
Kyoto Protocol (1997) Aims to reduce emissions of carbon dioxide, methane and nitrous oxide to about 5.2% below 1990 levels by 2012 However, some developed countries did not sign the treaty because they argue it will adversely affect the profits of their industries and cause many people to lose their jobs. Singapore signed the Kyoto Protocol in 2006.

34 Measures to Reduce the Impact of Global Warming: National efforts
Using alternative sources of energy Promoting the usage of vehicles that run on alternative fuel (e.g. hybrid cars) which consume less fuel and emit less pollutants For example, Singapore introduced the Green Vehicle Rebate in 2001 to promote the use of ‘green’ cars. From 01January 2006, buyers of hybrid cars are also entitled to tax incentives and rebates.

35 Measures to Reduce the Impact of Global Warming: National efforts
Enforcing laws and regulations Introduce and enforce laws that regulate the emission of greenhouse gases by vehicles, industries and power stations Encourage industries to develop energy efficient technologies Look out for this green label on electrical appliances. Products with this label require less energy to produce which means less fossil fuels are burned during its production. Thus, less greenhouse gases are released into the atmosphere.

36 Measures to Reduce the Impact of Ozone Depletion: National efforts
Reducing use of CFCs Use of CFCs are banned in accordance to the Montreal Protocol Ozone friendly substitutes are developed to replace CFCs in refrigerators, aerosol cans and air-conditioners. CFC- free For instance, since 1995, Singapore law requires all new cars to be fitted with CFC-free air-conditioning systems.

37 Measures to Reduce the Impact of Global Warming: Individual efforts
Helping to reduce emissions of greenhouse gases Taking public transport, choosing to cycle or walk to destinations whenever possible Car pooling Using energy efficient appliances Reducing electricity usage in your home, school and workplace

38 Measures to Reduce the Impact of Ozone Depletion: Individual efforts
Helping to reduce ozone depletion Avoid buying products which contain CFCs Ensure proper disposal of products with CFCs, such as old air-conditioners, through a waste management company

39 Global Warming and Ozone Depletion: The Challenges Ahead
We have to take action now to reduce the catastrophic impacts of global warming and ozone depletion. If every one puts in a little effort to change our lifestyles, it will go a long way to ensure that the Earth will be a pleasant place for our future generations.

40 Skills Builder: Suggested Answers
Yes, ideally all countries should sign the Kyoto Protocol. They should progressively work towards reducing the emissions of greenhouse gases. We should act now to reduce the impact of global warming. Otherwise, if the levels of greenhouse gases in the atmosphere are allowed to rise further, the Earth will be subjected to disastrous environmental, economic and social consequences, which far outweigh the disadvantages of unemployment and costs brought about by signing the treaty. Moreover, even if the threat of global warming does not materialise, measures which reduce greenhouse gas emissions can lead to other environmental, health and economic benefits (e.g. improving energy efficiency is environmentally friendly and can help reduce fossil fuel usage and result in lower fuel costs). Can you think of more of such benefits?

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