How do greenhouse gases cause climate change, and what is the carbon footprint?
Greenhouse gases and the greenhouse effect; human activities that increase carbon dioxide and methane; global climate change and its effects; and the carbon footprint.
A focused answer to AQA GCSE Chemistry 4.9.2, covering the greenhouse effect, the main greenhouse gases, human activities that increase them, the effects of global climate change, and the idea of a carbon footprint.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this dot point is asking
AQA wants you to name the main greenhouse gases, explain the greenhouse effect, describe human activities that increase greenhouse gases, explain the effects of global climate change, and define and discuss the carbon footprint. The spec also expects you to recognise that climate predictions involve complex models, incomplete data and sometimes biased reporting.
The greenhouse effect
Sunlight (short-wavelength radiation) passes through the atmosphere and warms the surface; the surface then radiates longer-wavelength infrared, which the greenhouse gases absorb. Without this natural greenhouse effect the Earth would be too cold for life, but increasing the amount of these gases enhances the effect and warms the planet further.
Human activities
Global climate change
The extra greenhouse gases cause global climate change. Likely effects include:
- Rising sea levels from melting polar ice and the thermal expansion of seawater, causing flooding of low-lying land.
- More frequent and severe extreme weather, such as storms, floods and droughts.
- Changes to rainfall patterns, temperatures and habitats, affecting wildlife distribution and farming.
Because the climate is a complex system with many interacting factors, predictions are difficult, and there can be conflicting evidence and bias in how findings are reported in the media.
The carbon footprint
Try this
Q1. Name two greenhouse gases. [2 marks]
- Cue. Carbon dioxide and methane (or water vapour).
Q2. Describe one effect of global climate change. [1 mark]
- Cue. Rising sea levels (or more extreme weather, or changing habitats).
Q3. State one way to reduce the carbon footprint of a product. [1 mark]
- Cue. Use renewable energy (or use less energy, recycle materials, or capture carbon dioxide).
Exam-style practice questions
Practice questions written in the style of AQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AQA 20194 marksExplain how greenhouse gases keep the Earth warm (the greenhouse effect), name two greenhouse gases, and describe two human activities that increase the amount of greenhouse gases in the atmosphere.Show worked answer →
A 4-mark Paper 2 question on the greenhouse effect and human causes.
Greenhouse effect (2 marks): greenhouse gases absorb the heat (infrared) radiation given off by the Earth's surface and re-emit some of it back towards the Earth, keeping the planet warm. Two greenhouse gases (1 mark): any two of carbon dioxide, methane, water vapour. Human activities (1 mark): burning fossil fuels and deforestation increase carbon dioxide; cattle farming and waste rotting in landfill increase methane (any two activities).
Markers reward the absorb-and-re-emit mechanism, two named gases and two human activities.
AQA 20213 marksDefine the term carbon footprint. Describe two ways the carbon footprint of a product could be reduced, and explain one reason why predictions about the scale of future climate change are difficult to make.Show worked answer →
A 3-mark question on carbon footprint and the limits of prediction.
Definition (1 mark): the carbon footprint is the total amount of greenhouse gases (carbon dioxide and others) given off over the whole life cycle of a product, service or event. Ways to reduce (1 mark): use less energy or more renewable energy; use fewer or recycled materials; capture and store carbon dioxide (any two). Why predictions are hard (1 mark): the climate system is very complex with many interacting factors, so models give a range of outcomes; there can also be incomplete data, bias and conflicting evidence in how it is reported.
Markers reward the whole-life-cycle definition, two reduction methods and a valid reason that prediction is difficult.
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Sources & how we know this
- AQA GCSE Chemistry (8462) specification — AQA (2016)