Chemistry of the atmosphere

• What has been the composition of the Earth's atmosphere for the last 200 million years?

  About 80% nitrogen and 20% oxygen, with small proportions of other gases.
• Why is evidence for the Earth's early atmosphere limited?


  Because of the time scale of 4.6 billion years.
• What does one theory suggest about the Earth's early atmosphere?


  It suggests that volcanic activity released gases that formed the early atmosphere.
• What gases may have been present in the Earth's early atmosphere?

  Mainly carbon dioxide, with little or no oxygen, and small proportions of methane and ammonia.
• How did the formation of oceans affect carbon dioxide levels in the atmosphere?


  Carbon dioxide dissolved in water, leading to the precipitation of carbonates and reducing atmospheric carbon dioxide.
• What are the main changes in the atmosphere over time and their causes?

  • Increase in oxygen due to photosynthesis by algae and plants.
  • Decrease in carbon dioxide due to photosynthesis and formation of sedimentary rocks and fossil fuels.
• When did algae first produce oxygen?


  About 2.7 billion years ago.
• What role do algae and plants play in the atmosphere?

  They produce oxygen and decrease carbon dioxide through photosynthesis.
• What is the greenhouse effect?


  • Interaction of short and long wavelength radiation with matter.
  • Maintains temperatures on Earth high enough to support life.
• What are the main greenhouse gases in the atmosphere?


  Water vapour, carbon dioxide, and methane.
• What human activities contribute to an increase in greenhouse gases?


  Activities that increase carbon dioxide and methane levels.
• What do many scientists believe about human activities and global climate change?


  They believe human activities will cause the Earth's surface temperature to increase, resulting in climate change.
• Why is it difficult to model global climate change?


  Because it involves complex systems that lead to simplified models and speculation.
• What are the potential effects of global climate change?


  • Rising sea levels
  • Increased frequency of extreme weather events
  • Changes in ecosystems
  • Impact on agriculture
• What is the carbon footprint?


  The total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service, or event.
• How can the carbon footprint be reduced?


  By reducing emissions of carbon dioxide and methane.
• What are the main atmospheric pollutants from fuels?

  • Carbon dioxide
  • Water vapour
  • Carbon monoxide
  • Sulfur dioxide
  • Oxides of nitrogen
  • Particulates
• What are the effects of carbon monoxide as an atmospheric pollutant?


  It is a toxic gas that is colorless and odorless, making it hard to detect.
• What health problems are caused by sulfur dioxide and oxides of nitrogen?


  They cause respiratory problems in humans and contribute to acid rain.
• What problems do particulates cause in the atmosphere?


  They cause global dimming and health problems for humans.
• What are the sources of atmospheric pollutants from fuels?


  • Combustion of fuels
  • Fuels containing carbon, hydrogen, and sulfur