Human activities which contribute to an increase in greenhouse gases in the atmosphere: Some human activities increase the amounts of greenhouse gases in the atmosphere. These include:

The idea

Human activities add greenhouse gases such as carbon dioxide, methane and water vapour to the atmosphere. Burning fossil fuels in power stations, factories and vehicles releases carbon dioxide that was locked in coal, oil and gas. Deforestation removes trees that absorb carbon dioxide during photosynthesis and releases stored carbon when timber is burned or decays. Agriculture contributes methane from livestock digestion and from rice paddy fields, while fertiliser use releases nitrous oxide. Landfill sites and livestock also produce methane as organic waste decomposes without oxygen. Cement production releases carbon dioxide from heating limestone. These activities raise atmospheric concentrations above natural levels, strengthening the greenhouse effect.

What earns the marks

• Burning fossil fuels such as coal, oil and natural gas in power stations, industry and transport releases carbon dioxide.
• Deforestation reduces carbon dioxide absorption by photosynthesis and can release stored carbon when trees are burned or decompose.
• Agriculture increases methane through livestock digestion and rice paddy fields, and can release nitrous oxide from fertilisers.
• Decay of organic waste in landfill sites produces methane.
• Industrial processes such as cement production release carbon dioxide from the breakdown of limestone.

Common mistakes and how to put them right

• Listing only carbon dioxide and ignoring methane and other greenhouse gases.

  Put it right by naming at least two gases and linking each to a specific activity.

• Confusing deforestation with destruction of the ozone layer.

  Put it right by explaining that deforestation affects carbon dioxide levels through reduced photosynthesis and carbon release.

• Treating all human activities as equally significant without linking each to a named gas.

  Put it right by pairing each activity with the gas it increases.

Exam tips

• Match each activity to a named greenhouse gas, for example fossil fuel combustion to carbon dioxide and livestock to methane.
• Use the command word 'include' to justify giving several distinct activities rather than one detailed example.
• Keep the focus on increases in atmospheric amounts, not on unrelated pollution effects.