The Greenhouse Effect (AQA GCSE Combined Science: Synergy: Life & Environmental Sciences): Revision Note

The Greenhouse Effect

• Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life

• This is known as the greenhouse effect 

• The main greenhouse gases are:

  • Carbon dioxide

  • Methane

  • Water vapour 

What is the greenhouse effect?

• Short wavelength radiation (ultraviolet radiation) is emitted from the sun

• It passes through the atmosphere and is absorbed by the Earth's surface

• When it strikes the Earth's surface:

  • Some of it is absorbed

  • Some is re-emitted from the surface of the Earth as long wavelength radiation (infrared radiation)

• Greenhouse gases absorb this outgoing long-wavelength radiation

  • This reduces the amount of radiation that escapes to space

  • This causes the temperature at the Earth's surface to increase

• Although only present in small amounts, increasing levels of carbon dioxide and methane are significantly upsetting Earth’s natural conditions by trapping extra heat energy

The greenhouse effect 

Absorption, transmission and reflection

Higher Tier Only

• Different substances may absorb, transmit or reflect electromagnetic radiation in ways that vary with wavelength

• This is why the atmosphere transmits short-wavelength radiation from the Sun, while greenhouse gases absorb the longer-wavelength radiation re-emitted by Earth's surface