science 1

• Global systems, including the carbon cycle, rely on interactions involving the biosphere, lithosphere, hydrosphere and atmosphere
• Investigating how human activity affects global systems


  1. Modelling a cycle, such as the water, carbon, nitrogen or phosphorus cycle within the biosphere

  2. Explaining the causes and effects of the greenhouse effect

  3. Investigating the effect of climate change on sea levels and biodiversity

  4. Considering the long-term effects of loss of biodiversity

  5. Investigating currently occurring changes to permafrost and sea ice and the impacts of these changes

  6. Examining the factors that drive the deep ocean currents, their role in regulating global climate, and their effects on marine life

  7. Investigating how Aboriginal and Torres Strait Islander Peoples are reducing Australia's greenhouse gas emissions through the reinstatement of traditional fire management regimes
• Sustainability


  The ability to maintain desirable conditions and access to desirable resources over a long period of time
• The human race has just one planet to call home for the foreseeable future
• We must have sustainability as a core goal for continued human life
• It is important to understand how the Earth system works, so we can critically think about the sustainability of our current practices
• Earth subsystems


  • Lithosphere: the land (e.g., soil and rock)
  • Hydrosphere: The water (e.g., oceans, lakes, rivers, glaciers)
  • Biosphere: The living things (e.g., plants, animals, fungi)
  • Atmosphere: The air
• The four subsystems remain interconnected
• Carbon cycle


  • Carbon is the 4th most abundant element in the universe and a core component of all known life
  • Carbon is a fundamental component of substances such as fats, proteins and carbohydrates
  • Carbon naturally flows between different reservoirs across the four subsystems
• Sinks or reservoirs


  Hold carbon for extended periods of time
• Fluxes or Processes


  Shown with arrows and move carbon from one sink to another
• Photosynthesis


  Plants take in carbon from the air or water to build sugar molecules storing energy from sunlight
• Respiration


  Plants and animals release carbon to the air or water as they burn sugars to access the stored energy
• Decomposition


  Dead matter releases carbon to the atmosphere as it is broken down by decomposers such as bacteria and fungi to recycle the nutrients
• Gas exchange


  Carbon is exchanged between the atmosphere and the water
• Shell building


  Aquatic organisms take in carbon from the water to build their shells
• Weathering


  Limestone releases carbon to the atmosphere as it is broken down by chemical weathering
• Fossilisation


  Dead matter is slowly converted to fossil fuels at high temperatures and pressures underground
• Combustion


  Carbon is released to the atmosphere by humans burning fossil fuels
• Without human influence the carbon cycle is relatively stable, with the quantity of carbon in each sink remaining roughly constant over time
• Human mining and combustion of fossil fuels has been moving carbon from the lithosphere to the atmosphere much faster than natural processes store away carbon in the lithosphere
• Human deforestation has also reduced the rate that plants remove carbon dioxide from the atmosphere
• The result is an anthropogenic (human-caused) increase in the concentration of carbon dioxide in the atmosphere
• As the concentration of carbon dioxide in the atmosphere increases this increases the concentration of carbon dioxide in the oceans

  1. In water, carbon dioxide can form carbonic acid: CO2 + H2O ⇌ H2CO3

  2. Increasing atmospheric carbon dioxide increases the concentration of carbonic acid in the oceans, increasing their acidity
• This is harmful to aquatic organisms, especially those who build shells out of calcium carbonate such as molluscs, corals, echinoderms and some algae
• A mollusc shell dissolves under acidic conditions. The shell almost completely dissolves after 45 days when placed in seawater with pH and carbonate levels projected by models for the year 2100.
• Greenhouse effect


  • Almost all energy available at the surface of the Earth comes from the Sun
  • Some of the energy from the sun is reflected back into space, some is trapped by gases in the Earth's atmosphere, warming the Earth
  • This is caused by greenhouse gases such as CO2, CH4, and N2O
  • Human activity has increased the concentration of greenhouse gases in the atmosphere, enhancing the greenhouse effect
• Greenhouse effect scenarios


  • No greenhouse effect: Most radiation reflected into space, average temperature -18 °C
  • Natural greenhouse effect: Some radiation trapped by atmosphere, average temperature 14 °C
  • Anthropogenic enhanced greenhouse effect: More radiation trapped by atmosphere, average temperature rising
• Weather


  • Day-to-day conditions of the atmosphere in terms of temperature, wind, precipitation, etc.
  • Influenced by the lithosphere, Biosphere and hydrosphere
• Climate


  Long-term (e.g. 30-year) average of weather conditions, including extreme events
• The anthropogenic enhanced greenhouse effect is causing a rapid increase in average temperature on earth
• Rising temperatures are causing melting of the polar ice and permafrost
• Polar ice is white in colour and so reflects more radiation back into space than the water or earth underneath – the more ice melts, the more the Earth absorbs radiation
• Polar ice and permafrost contain trapped greenhouse gases such as carbon dioxide and methane – the more ice melts, the more greenhouse gases are added to the atmosphere
• Humans build on solid permafrost – as it thaws our structures can be destroyed
• Rising temperatures cause thermal expansion of water, coupled with influx of meltwater, sea levels are rising
• Average temperatures could be as much as 5 °C higher by 2100 – would lead to roughly 20 m sea level rise (worst case scenario)
• Melting polar ice adds large quantities of cold fresh water to the oceans – potential to disrupt currents, destabilising ecosystems and changing climates
• As water temperatures rise the corals become stressed and expel the algae

  The corals lose most of their colour and their main food source becoming much more vulnerable to disease and likely to die
• As temperatures rise, the solubility of oxygen in water decreases, reducing the amount of oxygen available to aquatic organisms