SC21

• Gases from volcanic eruptions formed the early Earth's atmosphere
• The Earth's early atmosphere was thought to contain:

  • little to no oxygen
  • large amounts of carbon dioxide
  • some water vapour
  • small amounts of other gases
• The oceans formed when the water vapour condensed to form liquid water
• Over time, the levels of carbon dioxide decreased dramatically as it was able to dissolve into the formed oceans
• Plants started to appear on Earth and absorb carbon dioxide for photosynthesis which further reduced the amount of carbon dioxide in the atmosphere
• Oxygen was a waste product of plants so the levels of oxygen in the atmosphere increased
• Test for Oxygen - place a glowing splint into the gas and if it relights then oxygen is present
• The greenhouse effect consists mainly of the gases methane, carbon dioxide and water vapour which can absorb energy radiated from the Earth and re-emit it back (maintains habitable temperature)
• There is a correlation between carbon dioxide percentage in the atmosphere and the mean global temperature:

  • linked to use of fossil fuels by humans
  • uncertain of measurement accuracy due to historical errors and the locations tested/recorded
• Current atmosphere mainly consists of nitrogen and oxygen with small amounts of other gases like carbon dioxide, water vapour and argon
• Human activities increase levels of greenhouse gases such as methane and carbon dioxide from farming and burning fossil fuels
• To mitigate environmental impacts, companies must consider the scale, associated risks and any environmental impact of their business
• Greenhouse Gases:

  1. Energy is transferred from the Sun to the Earth
  2. Some energy is absorbed by Earth's surface, warming it up
  3. Some of the Sun's energy is reflected back into space as infrared waves
  4. Same gases in the air absorb energy emitted from Earth
  5. When gases re-emit the energy, some of it goes back to the Earth's surface and warms it up
• Climate Change - the change in the average weather patterns over a long period of time

  Human activity that influences this includes:

  • increased burning fossil fuels released more carbon dioxide
  • cattle have bacteria that release methane (farming)
• Effects of Climate Change:

  • melting ice caps rise sea levels and increase risks of flooding worldwide
  • animals are forced out of natural habitats and may become extinct
  • extreme weather events (warmer oceans mean more typhoons)
  • more acidic carbon dioxide dissolved in oceans will lower the pH and harm organisms