C13 - The Earth's Atmosphere

• How was the Earth's early atmosphere formed?

  By volcanic activity
• What was the main component of the Earth's early atmosphere?

  Carbon dioxide
• What other gases were likely present in the early atmosphere?

  Nitrogen, water vapour, methane, ammonia
• How did the spread of plants affect atmospheric oxygen levels?

  It increased the levels of oxygen
• What process decreased carbon dioxide levels in the early atmosphere?

  Photosynthesis by algae and plants
• What geological processes removed carbon dioxide from the atmosphere?

  Formation of sedimentary rocks and fossil fuels
• How were ammonia and methane removed from the atmosphere?

  By reactions with oxygen
• What percentage of today's atmosphere is nitrogen?

  About 80%
• What percentage of today's atmosphere is oxygen?

  About 20%
• What other gases are present in small proportions in the atmosphere?

  Carbon dioxide, water vapour, noble gases
• What has caused the increase in carbon dioxide levels recently?

  Burning of fossil fuels
• Why is it difficult to predict the effects of rising greenhouse gases on climate?

  Due to uncertainties in climate models
• What is the consensus among peer-reviewed evidence regarding greenhouse gases?

  They will increase average global temperatures
• What is necessary to reduce greenhouse gases in the atmosphere?

  Reduce fossil fuel use and conserve energy
• Why will changes to reduce fossil fuel use cost money?

  Economies are based on fossil fuel energy
• What are potential risks of global climate changes?

  Rising sea levels, threats to ecosystems
• What do hydrocarbon fuels produce when burnt in plenty of air?

  Carbon dioxide and water
• What is the main greenhouse gas produced from burning fuels?

  Carbon dioxide
• What can sulphur impurities in fuels cause?

  Sulphur dioxide and acid rain
• How can sulphur be managed in fuels?

  Remove it before burning or from flue gas
• What happens when hydrocarbon fuels are burnt with insufficient oxygen?

  Poisonous carbon monoxide is formed
• What can be produced from burning diesel fuel?

  Particulates of carbon and unburnt hydrocarbons
• What is the effect of particulates of carbon in the atmosphere?

  They can cause global dimming
• What do high temperatures in engines produce from nitrogen in the air?

  Oxides of nitrogen
• What health issues can oxides of nitrogen cause?

  Breathing problems
• What environmental issue can oxides of nitrogen contribute to?

  Acid rain