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CognitoGreenhouse gases and climate change
Key facts & methods
The greenhouse effect
- Short-wave radiation (visible light and UV) from Sun passes through atmosphere and heats Earth's surface.
- Earth re-emits longer-wave infrared (IR) radiation.
- Greenhouse gases absorb IR radiation and re-emit it in all directions — including back to Earth.
- This warms the planet — the greenhouse effect is NATURAL and essential for life (without it Earth would be ~-18°C).
- The ENHANCED greenhouse effect = increased concentrations of greenhouse gases due to human activity.
Greenhouse gases
- Carbon dioxide (CO2): from combustion of fossil fuels, deforestation.
- Methane (CH4): from livestock, rice paddies, decomposition in landfill, natural gas leaks.
- Water vapour (H2O): naturally the most abundant greenhouse gas — increased by warming.
- Nitrous oxide (N2O): from fertilisers, agriculture.
- CO2 and CH4 levels have increased significantly since industrialisation.
Consequences of climate change
- Rising global temperatures.
- Melting ice caps and glaciers → sea levels rise → coastal flooding.
- More extreme weather events: storms, droughts, heatwaves, floods.
- Ecosystem disruption: species migration, coral bleaching, habitat loss.
- Food and water security threats.
- Ocean acidification (CO2 dissolves in seawater forming carbonic acid).
Reducing greenhouse gas emissions
- Renewable energy (wind, solar, hydro) instead of fossil fuels.
- Improved energy efficiency in buildings and transport.
- Electric vehicles. Carbon capture and storage (CCS).
- Reducing deforestation and planting trees (carbon sinks).
- Reducing methane from livestock and landfill.
- International agreements (e.g. Paris Agreement: limit warming to 1.5-2°C above pre-industrial).
Exam questions — 4 questions · 10 marks · AQA 8462 style
⚡ Show all working — the AI marks against the AQA mark scheme. Method marks awarded for correct working even if the final answer is wrong.
1 markGreenhouse mechanismAQA 8462 style
How do greenhouse gases contribute to warming the Earth's surface?
A They block all radiation from the Sun reaching Earth
B They absorb outgoing infrared radiation from Earth and re-emit some back toward Earth
C They produce heat through chemical reactions in the atmosphere
D They increase the amount of solar radiation reaching Earth's surface
3 marksHuman contributionsAQA 8462 style
Give two human activities that have increased CO2 levels in the atmosphere, and one that has increased methane levels. (3 marks)
Hint: CO2 sources: burning fuels, deforestation. CH4 sources: livestock, landfill, rice paddies. Name the activity and the connection to gas.
+30 XP
1 markMost significant human-generated greenhouse gasAQA 8462 style
Which greenhouse gas has increased most significantly due to human industrial activity since 1750?
A Water vapour
B Carbon dioxide
C Argon
D Nitrogen
3 marksEvaluate a reduction strategyAQA 8462 style
Evaluate the use of wind turbines as a strategy to reduce CO2 emissions. Consider both advantages and disadvantages. (3 marks)
Hint: At least two advantages and two disadvantages. Be specific — not just generic pros/cons.
+30 XP
Module complete! 🎉
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