Explain how human activities have increased the concentration of carbon dioxide in the Earth's atmosphere and why this is a cause for concern.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Burning fossil fuels in power stations, vehicles and industry releases large amounts of CO₂ into the atmosphere.
Deforestation removes trees that normally absorb CO₂ during photosynthesis, so less gas is removed.
CO₂ is a greenhouse gas; it absorbs infrared radiation emitted by the Earth’s surface and traps heat.
The extra heat causes global warming and climate change, leading to rising sea levels, extreme weather and ecosystem disruption, which is why it is a concern.
Deforestation removes trees that normally absorb CO₂ during photosynthesis, so less gas is removed.
CO₂ is a greenhouse gas; it absorbs infrared radiation emitted by the Earth’s surface and traps heat.
The extra heat causes global warming and climate change, leading to rising sea levels, extreme weather and ecosystem disruption, which is why it is a concern.
Examiner tips
- Use the exact phrases: ‘burning fossil fuels’, ‘deforestation’, ‘greenhouse gas’, ‘global warming/climate change’.
- Show the causal chain: source → increase → greenhouse effect → climate impact.
- Keep each point brief and directly linked to the marks.
Common mistakes
- Confusing CO₂ with other gases (e.g. methane).
- Omitting the link between CO₂ and the greenhouse effect.
- Using vague terms like ‘more pollution’ instead of specific causes.
Mark scheme (4 marks)
- Burning fossil fuels (in power stations / vehicles / industry) releases carbon dioxide
- Deforestation reduces the amount of carbon dioxide removed from the atmosphere by photosynthesis
- Carbon dioxide is a greenhouse gas that absorbs (infrared) radiation from the Earth's surface
- This leads to enhanced global warming / climate change, causing concern such as rising sea levels / extreme weather events / disruption to ecosystems
Related
- All Eduqas GCSE Chemistry revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
More Chemistry of the atmosphere questions
- Explain how the greenhouse effect keeps the Earth warm enough to support life.
- Explain why scientists are concerned about increasing levels of methane in the E…
- Explain why the concentration of oxygen in the Earth's atmosphere increased sign…
- Describe how the Earth's early atmosphere changed over billions of years to prod…