What is the natural greenhouse effect and how have humans impacted the atmosphere?

Investigate the natural greenhouse effect and the impacts that humans have on the atmosphere, including the enhanced greenhouse effect.

The natural greenhouse effect
The greenhouse effect is a good thing – it regulates the Earth’s air temperature.  This is how it works:

  • Heat (short wave radiation) from the sun reaches the Earth’s outer atmosphere.
  • The greenhouse gasses (the main ones are: carbon dioxide, methane and nitrous oxide) allow some of the radiation to pass through, some is absorbed by the atmosphere and some is reflected back into space.
  • The radiation that reaches the Earth warms the surface.
  • The Earth then releases (radiates) this warmth as long wave radiation.
  • This long wave radiation reaches the greenhouse gases, which allow some of the heat to escape and keep some of the heat in the atmosphere.


So the greenhouse effect keeps the temperature just right – not too cold and not too hot.  This enables life on Earth to flourish.  It is important that the correct amount of greenhouse gases is in the atmosphere in order for the balance to be maintained.

The enhanced greenhouse effect
Many scientists believe that the human activities are increasing the amount of greenhouse gases in the atmosphere and are therefore upsetting the balance.  As more greenhouse gasses are added the same amount if incoming short-wave radiation gets through the atmosphere, but less of the longwave radiated heat from the Earth can escape, so this heat warms the atmosphere.

Image result for greenhouse effect

Greenhouse gases
The main sources of human introduced greenhouse gases are shown in the diagram below.  It also shows what percentage each greenhouse gas contributes.