The greenhouse effect

Without greenhouse gases in its atmosphere, the Earth would be about 18 °C colder on average than it is now. That would make it too cold to support life as we know it.

Greenhouse gases present in the atmosphere include:

These greenhouse gases:

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

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

How the greenhouse effect worksHow the greenhouse effect works
Question

Name three greenhouse gases.

Carbon dioxide, methane and water vapour.

Comparison of gases - Higher

Different substances in the atmosphere may absorb, transmit or reflect electromagnetic waves in different ways, depending on the wavelengths of the radiation.

GasShort wavelength radiation (eg ultra violet)Long wavelength radiation (eg infra red)
NitrogenTransmitTransmit
OxygenTransmitTransmit
Carbon dioxideTransmitAbsorb
MethaneTransmitAbsorb

The information in the table shows that carbon dioxide and methane are greenhouse gases because they absorb the long wavelength radiation from the Earth.