9.2 Carbon dioxide and methane as greenhouse gases

• What do greenhouse gases maintain on Earth?


  Temperatures high enough to support life
• Which gases are considered greenhouse gases?


  Water vapour, carbon dioxide, and methane
• What is the greenhouse gas effect?


  • Electromagnetic radiation from the sun passes through the atmosphere
  • Earth absorbs some radiation and warms up
  • Some heat is radiated as infrared radiation
  • Greenhouse gases absorb some infrared radiation
  • Atmosphere warms up, leading to the greenhouse effect and global warming
• What human activities increase greenhouse gases?


  Driving, consuming electricity, raising livestock
• What gases are increased by driving and consuming electricity?


  Carbon dioxide and methane
• How does raising livestock contribute to greenhouse gases?


  It produces methane emissions
• What is a source of methane emissions from landfills?


  Decay of organic waste
• What do many scientists believe about human activities and Earth's temperature?


  They will cause an increase in temperature
• Why is it difficult to model global climate change?


  Because it involves complex systems
• What can result from simplified models of climate change?


  Speculation and biased opinions in media
• What is a major cause of climate change?


  An increase in average global temperature
• What are potential effects of global climate change?


  • Extinction of species
  • Raising sea levels from melting ice caps
  • Migration due to drought/flooding
  • Decrease in crop yield for major crops
• What is the carbon footprint?


  Total amount of carbon dioxide and greenhouse gases emitted
• How can the carbon footprint be reduced?


  By reducing emissions of carbon dioxide and methane
• What is one way to reduce electricity consumption?


  Use less electricity or alternative sources
• What is a challenge in reducing carbon footprint through tree planting?


  It takes away land for crops
• Why might action to reduce carbon footprint be limited?


  It can be more difficult and expensive