chemistry of the atmosphere

• What are the main gases in the atmosphere today?

  ~80% nitrogen and ~20% oxygen
• What does ∼ mean in the context of gas proportions?

  It means around or approximately
• How long have the proportions of gases in the atmosphere remained stable?

  For 200 million years
• Why is evidence about the Earth's early atmosphere limited?

  Due to the time scale of 4.6 billion years
• What was one theory about the Earth's early atmosphere?

  Intense volcanic activity released gases
• What gases did volcanoes produce that built up in the atmosphere?

  Nitrogen (N2)
• What happened to water vapor in the early atmosphere?

  It condensed to form the oceans
• How did CO2 levels decrease in the early atmosphere?

  CO2 dissolved in water and formed sediments
• What gases may have been present in the early atmosphere?

  Mainly CO2 with little or no O2
• What is the only theory of the early atmosphere that needs to be known?

  The theory of volcanic activity releasing gases
• How did algae and plants contribute to oxygen levels in the atmosphere?

  They produced O2 through photosynthesis
• When did algae first produce oxygen?

  About 2.7 billion years ago
• What happened to oxygen levels over the next billion years?

  Oxygen levels gradually increased
• How did algae and plants decrease CO2 levels in the atmosphere?

  By photosynthesis
• What geological processes contributed to the decrease of CO2?

  Formation of sedimentary rocks and fossil fuels
• What types of sedimentary rocks contain carbon?

  Limestone and coal
• How are fossil fuels produced?

  From the remains of decayed plants and animals
• How do the processes of photosynthesis and sedimentary rock formation affect atmospheric CO2 levels?

  Photosynthesis decreases CO2, rocks store carbon
• What do greenhouse gases maintain on Earth?

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

  Water vapour, CO2, and CH4
• 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 gases are increased by driving and consuming electricity?

  CO2
• What human activities increase greenhouse gases?

  Driving, consuming electricity, raising livestock
• What greenhouse gas is released from decaying organic waste?

  CH4
• What greenhouse gas is produced by raising livestock?

  CH4
• 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 simplified models of climate change lead to?

  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 a carbon footprint?

  Total amount of CO2 and greenhouse gases emitted
• How can the carbon footprint be reduced?

  By reducing emissions of CO2 and CH4
• What is a major source of atmospheric pollutants?

  Combustion of fuels
• What are some ways to reduce carbon emissions?

  Use less electricity and travel less
• 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
• What elements do most fuels contain?

  Carbon and/or hydrogen, and some sulfur
• What gases are released when a fuel burns?

  Carbon dioxide, water, carbon monoxide, nitrogen oxides
• What forms particulates in the atmosphere during combustion?

  Solid particles and unburned hydrocarbons
• What happens during incomplete combustion?

  Some fuel doesn't burn, releasing soot and carbon monoxide