earth - atmosphere

• Proportions of gases


  • carbon dioxide, CO2
  • oxygen, O2
  • nitrogen, N2
  • water vapour, H2O
  • other gases (ammonia, NH3, and methane, CH4)
• Carbon dioxide, CO2, released by volcanoes. Biggest component of the atmosphere.
• Very little oxygen, O2, present.
• Nitrogen, N2, released by volcanoes.
• Water vapour, H2O, released by volcanoes. Existed as vapour as Earth was too hot for it to condense.
• Ammonia, NH3, and methane, CH4, may also have been present.
• Because it was billions of years ago there is very little evidence to draw upon.
• Amount of carbon dioxide, CO2, in atmosphere begins to reduce because: water condenses to form the oceans, in which CO2 then dissolves; algae (and later plants) start to photosynthesise; CO2 precipitates in the oceans as solid carbonates (sediments) that form rocks; CO2 taken in by plants and animals, with carbon locked up as fossil fuels
• Oxygen, O2, starts to increase as a product of photosynthesis.
• Nitrogen, N2, continues to increase. Nitrogen is a very stable molecule so any process that produces it causes the overall amount to build up over time.
• Water vapour, H2O, starts to decrease. As the Earth cools, the vapour condenses and forms the oceans.
• Still limited evidence as billions of years ago, but can look at processes that happen today (like photosynthesis) and make theories about the past.
• Proportions of gases


  • carbon dioxide, CO2 - about 0.04%
  • oxygen, O2 - about 20%
  • nitrogen, N2 - about 80%
  • water vapour, H2O - Very little overall. Collects in large clouds as part of the water cycle.
  • other gases - Small proportions of other gases such as the noble gases.
• Ice core evidence for millions of years ago and lots of global measurements taken recently.
• Greenhouse gases


  Gases, such as carbon dioxide, methane, and water vapour, that absorb radiation and maintain temperatures on the Earth to support life
• In the last 150 years, more greenhouse gases have been released due to human activities.
• Sources of increased greenhouse gases

  • carbon dioxide - combustion of fossil fuels, deforestation
  • methane - planting rice fields, cattle farming
• Pollutants released in combustion of fuels


  • carbon monoxide - colourless and odourless toxic gas
  • particulates (soot and unburnt hydrocarbons) - global dimming, respiratory problems, potential to cause cancer
  • sulfur dioxide - acid rain and respiratory problems
  • oxides of nitrogen - acid rain and respiratory problems
• Scientists have gathered peer-reviewed evidence to demonstrate that increasing the amount of greenhouse gases in the atmosphere will increase the overall average temperature of the Earth. This is called global warming.
• It is difficult to make predictions about the atmosphere as it is so big and complex. This leads some people to doubt what scientists say.
• Global climate change


  The change in long-term weather patterns across the planet
• Effects of climate change

  • sea levels rising
  • extreme weather events
  • changes in the amount and time of rainfall
  • changes to ecosystems and habitats
  • polar ice caps melting
• Increasing the amount of greenhouse gases in the atmosphere

  Increases the global average temperature of the Earth, which results in global climate change
• Carbon footprint


  The amount of carbon dioxide and methane that is released into the atmosphere by a product, person, or process