CC17 Atmospheric Science

• Gases produced by the eruption of VOLCANOES formed the Earth’s early atmosphere.
• Evidence for carbon dioxide and water vapour in the early atmosphere:

  • The mixture of gases released by volcanoes today (carbon dioxide, water vapour, nitrogen etc.)
  • The atmospheres of other planets in our solar system today (Venus and Mars – mainly carbon dioxide released by volcanoes), which have not been changed by living organisms. 
• Evidence for little or no oxygen in the early atmosphere:

  • Oxygen isn’t produced by volcanoes.
  • Iron pyrite that is broken down by oxygen is often found in very ancient rock.
• Later during the early atmospheric stages rocks contained bands of iron oxide suggesting oxygen levels started to increase.
• atmosphere now =

  • MORE oxygen 
  • LESS carbon dioxide
  • LESS water vapour

  MORE nitrogen
• atmosphere then =

  • Little or no oxygen 
  • Large amount of carbon dioxide
  • Water vapour
  • Small amount of other gases (e.g. nitrogen, methane, ammonia)
• • Earth cooled. The water vapour in atmosphere condensed and formed the oceans, decreasing the amount of water vapour in the atmosphere. 
• Carbon dioxide dissolved in oceans, reducing  the amount of carbon dioxide in the atmosphere. Sea creatures used this to make  calcium carbonate for shells. When they died it became part of sedimentary rock.
• Forms of life evolved in the oceans and photosynthesis began, which uses up carbon dioxide and releases oxygen – plants evolved and released oxygen so levels of oxygen INCREASED in the oceans, then increased in the atmosphere.
• Test for oxygen = Relights a glowing splint
• Greenhouse gases in the atmosphere (including carbon dioxide, water vapour and methane), absorb heat radiated from the Earth. They then release energy in all directions, reducing the amount of heat radiated into space, keeping the Earth warm. This is the greenhouse effect.
• Sources of greenhouse gases = Increased burning of fossil fuels, Methane is released when oil and natural gas are extracted from the ground and processed, Respiration by living organisms – increased human population, more carbon dioxide.
• • As carbon dioxide levels have risen, so has the average temperature of the Earth’s surface.

  There is a strong correlation between carbon dioxide levels and surface temperature
• • Since about 1850, there’s been a steady increase in the burning of fossil fuels for industry.
  • During this time, carbon dioxide levels have increased.

  Combustion releases carbon dioxide so this is good evidence that increased use of fossil fuels has caused this rise.
• • Oldest temperature records are only from one place so can’t be used to assess global temperature changes.
  • Early temperature measurements aren’t very accurate. Modern thermometers are less prone to error and have a greater resolution
  • Today we can analyse large amounts of data from around the world and from different sensors and satellites.
• Evidence for historical CO2 levels comes from measuring concentrations of CO2 gas trapped in ice cores.
• Effects of climate change = Changing weather patterns will cause some areas to become drier and others wetter, More of the acidic CO2 gas released will dissolve in seawater lowering its pH, harming organisms in the seas and oceans, Rising average global temp will cause ice at the poles and glaciers to melt
• Using renewable energy resources – can reduce greenhouse gas emissions.
• Global engineering solutions – reflecting sunlight back into space or capturing CO2 from the air and bury it underground. However, some countries may not help to reduce emissions or pay for large-scale engineering, and delicate ecosystems may be disrupted.
• Helping local people to adapt to new conditions – building flood defences, dams, irrigation systems. But, they may destroy important habitats or they may not work.