5 Global warming

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Objectives

• Students should learn:• that increasing levels of carbon dioxide and

methane contribute to global warming• that an increase in the Earth’s temperature

may cause changes in the climate• that an increase in temperature may also

reduce biodiversity and cause changes in the distribution of species.

Outcomes

• Most students should be able to:• explain what is meant by ‘the greenhouse effect’• describe how increasing levels of carbon dioxide

and methane contribute to global warming• describe some of the consequences of global

warming.• Some students should also be able to:• evaluate the impact of the greenhouse effect on

conditions on the Earth.

Specification

• Levels of carbon dioxide and methane in the atmosphere are increasing and contribute to ‘global warming’. An increase in the Earth’s temperature of only a few degrees Celsius:

• – may cause big changes in the Earth’s climate• – may cause a rise in sea level• – may reduce biodiversity• – may cause changes in migration patterns, e.g. in birds• – may result in changes in the distribution of species.• Carbon dioxide can be sequestered in oceans, lakes and

ponds and this is an important factor in removing carbon dioxide from the atmosphere.

Biology B3 4.5 Global warning

Answers to in-text questions

a Deforestation so less removed, burning fossil fuels producescarbon dioxide. b Any two of: carbon dioxide, methane, water vapour.Summary answers

1 carbon dioxide/methane, methane/carbon dioxide, atmosphere, global warming, temperature, climate, biodiversity

 

2 a Look for an accurately drawn bar chart from the figures given, correctly labelled axes, neat columns etc.

b Levels of carbon dioxide have risen steadily since 1970 as a result of deforestation, burning fossil fuels, etc.

c The Sun’s energy heats the Earth. Much of this is reflected back into space but some is absorbed by greenhouse gases which re-radiate it back. Therefore the Earth’s surface is kept warm enough for life. Increased levels of greenhouse gases leads to excess warming. This could result in climate change such as more extreme weather events. Melting of polar ice capsmay also increase sea levels and flood low-lying land.

 

3 Look for accurate information and good examples.

Compulsory slides you must complete and use;

http://geology.com/sea-level-rise/netherlands.shtml

increasing levels of carbon dioxide and methane contribute to global warming

The greenhouse effect

‘fun’ activity

• Give out the show me board and pens• Ask the form to close their books and draw

and label as accurately as they can the diagram to show how global warming occurs

• Now show the slide with the picture on and see who is best

Global warming and greenhouse gasesOne of the greatest threats caused by air pollution is global warming. Global warming is caused by a build-up of greenhouses gases, which leads to an increase in the Earth’s temperature.

A greenhouse gas is an atmospheric gas that absorbs infrared light.

Key greenhouses gases include:

carbon dioxide (CO2)

methane (CH4)

water vapour (H2O)

nitrous oxide (N2O)

Atmospheric carbon dioxide

Carbon dioxide levels

Burning fossil fuels, deforestation and flooding land for the construction of hydroelectric dams have all contributed to rising levels of carbon dioxide.

Carbon dioxide is one of the most important greenhouse gases because atmospheric concentrations have risen dramatically over the past century. Why do you think this is?

How many examples of burning fossil fuels can you think of? Are there any alternatives?

Global warming

Photodisc 4(NT)

Rising levels of carbon dioxide

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Global warming

• Carbon dioxide is released when fuels like gas, coal, oil, petrol and wood are burned.

• Greenhouse gases cause the temperature of the Earth to rise slowly.

• This causes climate change.• Methane released from

cattle and rice fields is also a greenhouse gas.

Most fuels contain carbon

Carbon dioxidereleased when fuelburned

Extra carbon dioxide in the air slows downheat loss from Earth

Climate change

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Preventing global warming

• Energy efficiency means less fuel burned to make electricity.

• Fuel cell buses.• Renewable energy sources like water

power, solar, wind farms, bio fuels.• Nuclear power.• The Kyoto agreement to reduce CO2

emissions.

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The greenhouse effect