AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Levels of carbon dioxide and methane in the atmosphere are increasing, and…
Full specification wording
Global warming: Levels of carbon dioxide and methane in the atmosphere are increasing, and contribute to ‘global warming’.
Carbon dioxide and methane are greenhouse gases.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 2 of 2
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Carbon dioxide and methane are greenhouse gases. Their atmospheric concentrations are rising because human activities add them faster than natural processes remove them. Carbon dioxide increases mainly from burning fossil fuels such as coal, oil and natural gas, and from deforestation, which reduces photosynthesis that removes carbon dioxide. Methane increases from agriculture, including livestock digestion and rice paddy fields, and from landfill sites and fossil fuel extraction. These gases absorb outgoing infrared radiation from the Earth's surface and re-emit it, so less heat escapes to space. This strengthens the greenhouse effect and contributes to global warming. Use the correct terms: greenhouse gas, infrared radiation, greenhouse effect.
What earns the marks
- Carbon dioxide is a greenhouse gas and its atmospheric concentration is increasing.
- Methane is a greenhouse gas and its atmospheric concentration is increasing.
- Burning fossil fuels such as coal, oil and natural gas releases carbon dioxide.
- Deforestation reduces the removal of carbon dioxide by photosynthesis, contributing to its increase.
- Agriculture, including livestock and rice paddy fields, and landfill sites release methane.
- Greenhouse gases absorb outgoing infrared radiation and re-emit it, so less heat escapes to space, contributing to global warming.
Common mistakes and how to put them right
Saying carbon dioxide or methane 'destroys' the ozone layer.
Put it right: These gases contribute to global warming by absorbing infrared radiation; ozone depletion is caused mainly by CFCs.
Confusing the greenhouse effect with global warming.
Put it right: The greenhouse effect is a natural process that keeps Earth warm; global warming is the recent increase in average temperature due to extra greenhouse gases.
Thinking methane is unimportant because it is present in smaller amounts than carbon dioxide.
Put it right: Methane is a more potent greenhouse gas per molecule, so even smaller increases contribute to warming.
Exam tips
- Name the human activities that increase each gas: fossil fuel combustion and deforestation for carbon dioxide; livestock, rice paddies and landfill for methane.
- Use the phrase 'absorb infrared radiation' rather than 'absorb heat' to show precise scientific understanding.
- Link the increase in greenhouse gases to the enhanced greenhouse effect and global warming in one clear chain of reasoning.
Try the lesson
The start of the Global warming: Levels of carbon dioxide and methane in the atmosphere are increasing, and contribute to ‘global warming’. lesson, made from checked teaching notes for this specification point.
Have a go first
Which two gases are named as increasing in the atmosphere and contributing to global warming?
Listen
Carbon dioxide and methane are greenhouse gases. Their atmospheric concentrations are rising because human activities add them faster than natural processes remove them. Carbon dioxide increases mainly from burning fossil fuels such as coal, oil and natural gas, and from deforestation, which reduces photosynthesis that removes carbon dioxide. Methane increases from agriculture, including livestock digestion and rice paddy fields, and from landfill sites and fossil fuel extraction. These gases absorb outgoing infrared radiation from the Earth's surface and re-emit it, so less heat escapes to space. This strengthens the greenhouse effect and contributes to global warming. Use the correct terms: greenhouse gas, infrared radiation, greenhouse effect. A strong answer earns marks for these points. Carbon dioxide is a greenhouse gas and its atmospheric concentration is increasing. Methane is a greenhouse gas and its atmospheric concentration is increasing. Burning fossil fuels such as coal, oil and natural gas releases carbon dioxide. Deforestation reduces the removal of carbon dioxide by photosynthesis, contributing to its increase. A common slip: Saying carbon dioxide or methane 'destroys' the ozone layer. Instead, these gases contribute to global warming by absorbing infrared radiation; ozone depletion is caused mainly by CFCs. Exam tip: Name the human activities that increase each gas: fossil fuel combustion and deforestation for carbon dioxide; livestock, rice paddies and landfill for methane.
See it
Key words
Say what each word means before you turn the card.
Greenhouse gas
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Greenhouse effect
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Global warming
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Infrared radiation
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See every definition
- Greenhouse gas
- Carbon dioxide and methane are examples, and their atmospheric concentrations are rising because human activities add them faster than natural processes remove them.
- Greenhouse effect
- A natural process that keeps Earth warm, strengthened when greenhouse gases absorb outgoing infrared radiation and re-emit it so less heat escapes to space.
- Global warming
- The recent increase in average temperature due to extra greenhouse gases, to which increasing carbon dioxide and methane levels contribute.
- Infrared radiation
- Outgoing radiation from the Earth's surface that greenhouse gases absorb and re-emit, so less heat escapes to space.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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