Greenhouse Gases and Global Warming

Greenhouse Gases and Global Warming

Greenhouse gases in our atmosphere help keep Earth warm, but rising levels caused by human activity are leading to global warming and climate change.

 

What are greenhouse gases?

  • Greenhouse gases trap heat energy in Earth’s atmosphere
  • They allow short-wave radiation from the Sun in but absorb and re-radiate long-wave infrared radiation
 

Main greenhouse gases:

  • Carbon dioxide (CO₂)
  • Methane (CH₄)
  • Water vapour (H₂O)
 

💡 These gases form a natural insulating layer, which is vital for life – but too much can cause problems.

 

Sources of greenhouse gases

Gas

Main Human Sources

Carbon dioxide

Burning fossil fuels, deforestation

Methane

Cattle farming, landfills, rice fields

Water vapour

Naturally occurring (increases with warming)

The greenhouse effect (natural process)

  1. Sun’s energy reaches Earth
  2. Earth absorbs and re-radiates it as infrared
  3. Greenhouse gases absorb and re-radiate the infrared back to Earth
  4. This keeps Earth’s temperature stable
 

Global warming (human-enhanced effect)

  • Human activities increase levels of greenhouse gases
  • This strengthens the greenhouse effect → more heat trapped
  • Leads to global warming – a gradual increase in Earth’s average temperature
 

Consequences of global warming

  • Rising sea levels (melting ice caps and glaciers)
  • More extreme weather (storms, droughts, heatwaves)
  • Changes in rainfall patterns
  • Habitat loss and species extinction
  • Food insecurity and changes in crop yields
 

Reducing greenhouse gas emissions

  • Use renewable energy sources
  • Improve energy efficiency
  • Reduce deforestation
  • Encourage dietary changes (less beef and dairy)
  • Carbon capture and storage (CCS) technology

Questions 

  1. Name the three main greenhouse gases.
  2. What human activity adds the most carbon dioxide?
  3. What does methane mostly come from?
  4. What is the greenhouse effect?
  5. Give two consequences of global warming.

Summary 

  • Greenhouse gases trap heat and keep Earth warm
  • CO₂, CH₄ and H₂O are the key greenhouse gases
  • Human activity increases their levels, causing global warming
  • Global warming leads to climate change, including rising sea levels and extreme weather
  • We can reduce emissions through renewable energy, efficiency, and lifestyle changes