Describe how carbon dioxide emissions from human activity contribute to climate change, and explain one consequence of this for the Earth's environment.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Carbon dioxide levels in the atmosphere have risen significantly since the Industrial Revolution, largely due to the burning of fossil fuels. Scientists monitor these changes to understand their effects on global climate patterns.
Model answer (4 marks)
Burning fossil fuels releases carbon dioxide into the atmosphere, increasing its concentration.
The extra CO₂ acts as a greenhouse gas, trapping more infrared radiation and raising global temperatures.
Higher temperatures cause polar ice caps to melt.
The melt adds water to the oceans, raising sea levels and threatening coastal areas.
The extra CO₂ acts as a greenhouse gas, trapping more infrared radiation and raising global temperatures.
Higher temperatures cause polar ice caps to melt.
The melt adds water to the oceans, raising sea levels and threatening coastal areas.
Examiner tips
- Use the exact wording from the mark scheme (e.g. ‘trapping more heat’),
- Show the causal chain: emission → concentration ↑ → heat trapping ↑ → temperature ↑ → consequence.
- Mention a specific consequence and explain the mechanism behind it.
Common mistakes
- Using vague terms like ‘more CO₂’ without linking to heat trapping
- Failing to state a clear environmental consequence
- Not explaining why the consequence occurs
Mark scheme (4 marks)
- Burning fossil fuels releases carbon dioxide into the atmosphere, increasing its concentration
- Increased carbon dioxide traps more heat / infrared radiation in the atmosphere, causing global temperatures to rise
- States a valid environmental consequence, e.g. melting of polar ice caps / rising sea levels / more extreme weather events / changes in precipitation patterns
- Explains why that consequence occurs, e.g. higher temperatures cause ice to melt, adding water to the oceans and so sea levels rise; or warmer oceans increase evaporation leading to more intense storms
Key terms in this question
climate change · carbon dioxide
Related
- All OCR GCSE Chemistry A: Gateway Science (J248) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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