SAQs
Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering these questions.
Rewrite the paragraph below using terms from the list provided to fill the gaps.
droughts, floods, global warming, greenhouse gases, rainfall, sea levels.
The rise in the mean global surface temperature referred to as ……………… is partly due to an increase in the concentration of ……………… in the atmosphere. This change in the global climate is expected to melt Arctic sea ice, leading to rising ……………… and to alter the pattern of ………………, so that there are more severe ……………… in wetter regions, and more severe ………………in drier regions.
The rise in the mean global surface temperature referred to as global warming is partly due to an increase in the concentration of greenhouse gases in the atmosphere. This change in the global climate is expected to melt Arctic sea ice, leading to rising sea levels and to alter the pattern of rainfall, so that there are more severe floods in wetter regions, and more severe droughts in drier regions.
Which of the following statements are false? In each case explain why it is incorrect.
- The global climate is affected by fluctuations in the amount of energy reaching the Earth from the sun.
- Volcanic eruptions into the atmosphere increase the temperature of the air and contribute to global warming.
- Greenhouse gases are only produced by human activity.
- Methane released by decomposing solid waste and livestock farming contributes to the greenhouse effect.
2 is false. Dust, ash and gases released during volcanic eruptions create a shield around the Earth that reflects sunlight energy back into space, so that the Earth’s atmosphere is cooled – not warmed. The statement would have been correct if it said that volcanic eruptions contribute to climate change.
3 is also false. Greenhouse gases occur naturally in the atmosphere and keep the global mean surface temperature of the Earth at around 15 ºC. Without these natural greenhouse gases, the global mean surface temperature would be around –18 ºC.
Rearrange the following statements into the correct order to produce a coherent explanation of how the rising emission of greenhouse gases generated by human activity is contributing to global warming.
- Heat energy is infra-red radiation, which has a long wavelength and low energy, and is absorbed by greenhouse gases in the atmosphere.
- Visible sunlight has a short wavelength and high energy, which enables it to pass through greenhouse gases in the Earth’s atmosphere.
- Heat is radiated from the surface of the Earth back towards the atmosphere.
- Sunlight energy reaches the Earth and heats the Earth’s surface.
- Human activity since the start of the 20th century has increased the emission of greenhouse gases and accelerated the rate of global warming.
- Heat energy trapped in the atmosphere by the greenhouse gases causes the atmosphere to become warmer.
The correct sequence of statements explaining how the rising emission of greenhouse gases in the Earth’s atmosphere is leading to global warming is as follows:
- Visible sunlight has a short wavelength and high energy, which enables it to pass through greenhouse gases in the Earth’s atmosphere.
- Sunlight energy reaches the Earth and heats the Earth’s surface.
- Heat is radiated from the surface of the Earth back towards the atmosphere.
- Heat energy is infra-red radiation, which has a long wavelength and low energy, and is absorbed by greenhouse gases in the atmosphere.
- Heat energy trapped in the atmosphere by the greenhouse gases causes the atmosphere to become warmer.
- Human activity since the start of the 20th century has increased the emission of greenhouse gases and accelerated the rate of global warming.
Complete the following statements of evidence that climate change is occurring in Ethiopia by writing the missing numbers in the spaces provided:
- Since 1950 the average minimum temperature in Ethiopia has been rising by about …… ºC per decade.
- Before 1990 there were 10 floods in Ethiopia, but between 1990 and 2014 there were …… reported flood events.
- Before 1990 there were 6 droughts in Ethiopia, but between 1990 and 2014 more than …… drought events were reported.
- In 1965, about 1.5 million people were affected by droughts, but in 2003 about …… million people in Ethiopia were drought-affected.
The completed statements of evidence for climate change in Ethiopia are:
- Since 1950 the average minimum temperature in Ethiopia has been rising by about 0.37 ºC per decade.
- Before 1990 there were 10 floods in Ethiopia, but between 1990 and 2014 there were 46 reported flood events.
- Before 1990 there were 6 droughts in Ethiopia, but between 1990 and 2014 9 drought events were reported.
- In 1965, about 1.5 million people were affected by droughts, but in 2003 about 13 million people in Ethiopia were drought-affected.