AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Human activities which contribute to an increase in greenhouse gases in the atmosphere: methane.
Methane is a greenhouse gas released by human activities including farming cattle and other livestock, growing rice in flooded paddy fields, and decomposing organic waste in landfill sites.
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Methane is a greenhouse gas released by human activities including farming cattle and other livestock, growing rice in flooded paddy fields, and decomposing organic waste in landfill sites. It absorbs outgoing infrared radiation and re-emits it, contributing to the greenhouse effect and global warming.
For example: Cattle digestion and anaerobic decay of rubbish in landfill produce methane; when this reaches the atmosphere it absorbs infrared radiation emitted by the Earth's surface and re-emits it, so more energy is retained and average global temperature rises.
What earns the marks
- State that methane is a greenhouse gas that absorbs infrared radiation emitted by the Earth's surface.
- Identify human sources of methane such as livestock farming, rice paddy fields and landfill sites.
- Explain that methane absorbs and re-emits infrared radiation, contributing to warming of the Earth's surface.
- Compare methane with carbon dioxide, noting that methane is a more potent greenhouse gas per molecule over a shorter timescale.
- Link increased methane concentration to climate change consequences such as rising global temperatures.
Common mistakes and how to put them right
Saying methane comes mainly from burning fossil fuels.
Put it right by naming livestock, rice paddies and landfill as the main human sources.
Stating that methane destroys the ozone layer.
Put it right by describing methane as a greenhouse gas that absorbs and re-emits infrared radiation.
Writing that methane traps heat from the Sun.
Put it right by explaining that it absorbs outgoing infrared radiation from the Earth's surface.
Exam tips
- Give one named source, such as cattle or landfill, then explain the greenhouse mechanism for full credit.
- Use comparative language such as 'more potent per molecule than carbon dioxide' when asked to compare greenhouse gases.
- Keep the mechanism precise: absorbed infrared is re-emitted, so more energy remains in the atmosphere.
Try the lesson
The start of the Human activities which contribute to an increase in greenhouse gases in the atmosphere: methane. lesson, made from checked teaching notes for this specification point.
Have a go first
Which human activity releases the greenhouse gas methane into the atmosphere?
Listen
Methane is a greenhouse gas released by human activities including farming cattle and other livestock, growing rice in flooded paddy fields, and decomposing organic waste in landfill sites. It absorbs outgoing infrared radiation and re-emits it, contributing to the greenhouse effect and global warming. For example, cattle digestion and anaerobic decay of rubbish in landfill produce methane; when this reaches the atmosphere it absorbs infrared radiation emitted by the Earth's surface and re-emits it, so more energy is retained and average global temperature rises. A strong answer earns marks for these points. State that methane is a greenhouse gas that absorbs infrared radiation emitted by the Earth's surface. Identify human sources of methane such as livestock farming, rice paddy fields and landfill sites. Explain that methane absorbs and re-emits infrared radiation, contributing to warming of the Earth's surface. Compare methane with carbon dioxide, noting that methane is a more potent greenhouse gas per molecule over a shorter timescale. A common slip: Saying methane comes mainly from burning fossil fuels. Instead, naming livestock, rice paddies and landfill as the main human sources. Exam tip: Give one named source, such as cattle or landfill, then explain the greenhouse mechanism for full credit.
Key words
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Greenhouse gases
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Agriculture and waste as methane sources
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Infrared absorption and re-emission
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Global warming
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See every definition
- Greenhouse gases
- Gases such as methane that absorb outgoing infrared radiation and re-emit it, contributing to the greenhouse effect and global warming.
- Agriculture and waste as methane sources
- Human activities including farming cattle and other livestock, growing rice in flooded paddy fields, and decomposing organic waste in landfill sites.
- Infrared absorption and re-emission
- Methane absorbs infrared radiation emitted by the Earth's surface and re-emits it, so more energy is retained and average global temperature rises.
- Global warming
- Warming of the Earth's surface caused by methane absorbing and re-emitting infrared radiation, with rising global temperatures linked to increased methane concentration.
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