The Greenhouse Effect (OCR Gateway GCSE Chemistry: Combined Science)

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The Greenhouse Effect

  • When shortwave radiation from the sun strikes the Earth’s surface it is absorbed and re-emitted from the surface of the Earth as infrared radiation
  • Much of the radiation, however, is trapped inside the Earth’s atmosphere by greenhouse gases which can absorb and store the energy
  • Carbon dioxide, methane and water vapour are gases that have this effect
  • Increasing levels of carbon dioxide and methane, although present in only small amounts, are causing significant upset to the Earth’s natural conditions by trapping extra heat energy
  • This process is called the enhanced greenhouse effect

The Greenhouse effect, IGCSE & GCSE Biology revision notes

Greenhouse gases trap some of the Sun's radiation causing the Earth to warm up

Carbon dioxide

  • Sources: Combustion of wood and fossil fuels, respiration of plants and animals, thermal decomposition of carbonate rocks and the effect of acids on carbonates

Methane

  • Sources: Digestive processes of animals, decomposition of vegetation, bacterial action in swamps and in rice paddy fields

Examiner Tip

It is important to understand the difference between the greenhouse effect and the enhanced greenhouse effect. The greenhouse effect ensures the mean global temperature is around 15oC and without greenhouse gases the surface of the Earth would swing between extreme heat and extreme cold. The enhanced greenhouse effect, due an increase in greenhouse gas concentrations, most scientists believe, is leading to global warming.

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Stewart

Author: Stewart

Expertise: Chemistry Lead

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Exam Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.