# Methane and carbon dioxide are both greenhouse gases. Explain how an increase in the concentration of greenhouse gases in the atmosphere leads to climate change.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 3.3 Climate change · Explain · 5 marks

> Scientists have recorded a steady rise in atmospheric methane levels over the past century, largely due to livestock farming, landfill sites and the extraction of fossil fuels. Methane is considered to be a more potent greenhouse gas than carbon dioxide.

## Mark scheme (5 marks)

1. Greenhouse gases allow short-wave solar radiation / sunlight to pass through the atmosphere and reach Earth's surface
2. Earth's surface absorbs this radiation and re-emits it as long-wave infrared / heat radiation
3. Greenhouse gases absorb this outgoing infrared / heat radiation (rather than allowing it to escape into space)
4. The absorbed energy is re-emitted in all directions, including back towards Earth, warming the surface / atmosphere
5. Higher concentrations of greenhouse gases mean more infrared radiation is absorbed / retained, so global temperatures rise further, causing climate change

## Key terms

- [greenhouse gases](https://www.gradenine.co.uk/glossary/greenhouse-gases)
- [climate change](https://www.gradenine.co.uk/glossary/climate-change)
- [concentration](https://www.gradenine.co.uk/glossary/concentration)

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/methane-and-carbon-dioxide-are-both-7972c51e) · Published by Druglandscape Ltd.