Effects of Greenhouse Gases (Cambridge International IGCSE Science)

Spec point — Describe how the greenhouse gases carbon dioxide and methane cause global warming, limited to: the absorption, reflection and emission of thermal energy reducing thermal energy loss to space

Effects of greenhouse gases

Extended Tier Only

• The Sun emits energy in the form of radiation that enters the Earth’s atmosphere

• Some of this energy is reflected from the Earth's surface

• The Earth’s surface absorbs energy and then re-emits it as thermal energy (infrared radiation)

• Some energy passes through the atmosphere and is emitted into space

• Greenhouse gases, such as carbon dioxide and methane, absorb some of the thermal energy

• These greenhouse gases then re-emit thermal energy in all directions

• This reduces the thermal energy lost to space and traps more thermal energy in the Earth’s atmosphere, keeping the Earth warm

  • This process is known as the greenhouse effect

Diagram showing how the greenhouse effect occurs

• As the concentration of greenhouse gases in the atmosphere increases due to human activity, more thermal energy is trapped

• This causes the Earth’s average temperature to rise, which is called global warming

  • This process is called the enhanced greenhouse effect

Consequences of global warming

• Climate change due to the increase in Earth’s temperature
• Water levels will rise as glaciers melt because of high temperatures, causing flooding in low-lying countries
• Extinction of species due to the destruction of natural habitats
• Migration of species as they will move to areas that are more habitable (no droughts)
• Spread of diseases caused by warmer climate
• Loss of habitat due to climate change (animals that live on glaciers or in low-lying countries)