GCSE Chemistry · AQA 8462 · Topic 4.9.2
Carbon dioxide and methane as greenhouse gases
Key points
- Greenhouse gases such as carbon dioxide, methane and water vapour let short-wavelength radiation from the Sun pass through but absorb longer-wavelength (infrared) radiation given off by the Earth, keeping the planet warm enough for life.
- Human activities increase them: burning fossil fuels and deforestation add carbon dioxide; cattle farming, rice fields and landfill add methane.
- Most scientists agree, based on peer-reviewed evidence, that increased greenhouse gases will cause the average global temperature to rise, leading to climate change. Simplified models and media coverage can make this seem uncertain.
- Effects include rising sea levels, more extreme weather, changes in rainfall and food production, and changes to the distribution of species.
- The carbon footprint is the total amount of and other greenhouse gases emitted over the full life cycle of a product, service or event.
- It can be reduced by using renewable energy, energy conservation, carbon capture and storage, carbon taxes and offsetting (e.g. planting trees), though there are economic and political problems.
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Without greenhouse gases the Earth would be too cold for life, but adding more of them is warming the planet. You need to explain the greenhouse effect, link human activities to particular gases, describe likely effects and know how carbon…
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