The Greenhouse Effect (Cambridge (CIE) AS Environmental Management)

The Natural Greenhouse Effect

• The Sun emits energy in the form of solar radiation (including visible light and ultraviolet rays) that enters the Earth’s atmosphere

  • This is known as insolation

• Some thermal energy is reflected from the Earth's surface

  • Most thermal energy is absorbed and re-emitted back from the Earth’s surface in the form of longwave radiation (infrared radiation)

• This energy passes through the atmosphere where some thermal energy passes straight through and is emitted into space

• But some thermal energy is absorbed by greenhouse gases and is re-emitted in all directions

  • Greenhouse gases include water vapour (H₂O), carbon dioxide (CO₂), methane (CH₄), nitrous oxides (NOₓ), ozone (O₃), and some artificial gaseous compounds such as chlorofluorocarbons (CFCs)

  • These gases act like a blanket, allowing sunlight to pass through but preventing a significant amount of the infrared radiation from escaping back into space

• This reduces the thermal energy lost into space and traps it within the Earth’s atmosphere, keeping the Earth warm

• This process is known as the greenhouse effect

  • The greenhouse effect is a naturally occurring phenomenon

  • The greenhouse effect is important to ensure that Earth is warm enough for life

  • If it were not for the insulating effect of greenhouse gases, Earth would experience dramatic temperature fluctuations, similar to its neighbouring planets

  • Without the greenhouse effect, the average temperature would be much colder, making the planet uninhabitable for living organisms