The greenhouse effect

Without greenhouse gases in its atmosphere, the Earth would be about 32°C colder on average than it is now. Greenhouse gases:

  • absorb heat radiated from the Earth
  • then release energy in all directions, which keeps the Earth warm

Water vapour and carbon dioxide are naturally present in the atmosphere and greenhouse gases. Another common greenhouse gas is methane.

Infrared radiation from the Sun is only partly absorbed by the Earth. The rest is radiated into the atmosphere. Although some of the infrared radiation escapes, some is absorbed by greenhouse gases. This keeps the energy in the atmosphere, warming it up. This gradual warming of the atmosphere over many years is referred to as global warming.

The diagram gives more details about this process, called the greenhouse effect.

Image and text to explain how the greenhouse effects works.How the greenhouse effect works
Question

Name three greenhouse gases.

  • carbon dioxide
  • methane
  • water vapour