Parts 5,6 Geography AS Unit 1 Global Challenges World at Risk


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5.Thermohaline Circulation


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5.How the Thermohaline Circulation works

  • The water is both cold and very saline whih makes it denser heavier and causes it to sink.
  • By sinking it draws warmer water in from the ocean surface above. This in turn draws water across the ocean surface from the tropics.
  • Eventually this movement from the tropics draws cold water up from the ocean bottom ready to be warmed again.
  • This pattern is being disturbed and more freshwater is entering the arctic ocean as a result of global warming which melts the ice and increases rainfall.
  • Melt water lowers the salinity which decreases the density of the ocean and slows down the rate at which the ocean sinks.
  • Global warming could turn off the North Atlantic Drift which supplies Europe  with warm water and air.
  • It this is stopped January temperatures in Western Europe would drop by at least 5 degrees creating bitter winters.
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5.Combined effects of sea level rise may =TIPPING

  • "The point in which temp increase will cause catastrophic & irreversibleeffects"
  • Positive feedback (climate change sped up by past events) loops may cause this - melting arctic sea ice = deeper sea water = darker = lower albedo = more radiation absorbed = warmer water = more ice melts :S
  • Effects: Increased volume of water = eustatic, + increased temps = thermal expansion,
  • If all remaining ice sheets melted=global sea level rise 60-80 metres

How to prevent this:

  • Need to consume less
  • Reduce greenhouse gases
  • Reduce air travel
  • Use renewable energy
  • Use public transport
  • Diversify from fossil fuels to renewable
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5.Why are climate changes difficult to predict?

  • Scientific organisations such as the IPCC are trying to address this
  • Simulation models only range from low, medium, and high greenhouse gas emissions - producing very different outcomes
  • Have to project growth by estimates - many current developing countries > difficult to predict the level and nature of this, e.g. China, India
  • Don't know what level of international action will be taken to reduce
  • Don't fully know the impact of positive feedback, e.g. permafrost thawing
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6.Mitigation and adaption key terms

Mitigation - mitigation strategies aim to reduce how much climate change occurs e.g switching to renewable energy sources, such as wind power - occur at levels from local to international - governments can decide how to implement strategies e.g the UK government target is to recycle 30 % of domestic waste by 2010

Adaptation - adaptation strategies aim to change lifestyles to better cope with a new environment e.g developing drought resistant crops  - most will be local in scale - need to be tailored to local impact

Adaptive capacity - the extent to which a system can cope with climate change, in human terms dependant on human, physical and financial resources

Climate vulnerability - the degree to which a natural or human system lacks the ability to cope with climate change, vulnerability is a result of the magnitude the change, its onset speed, the sensitivity of the the system

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6.Mitigation Strategies

Carbon tax - taxing companies or people who produce CO2, increasing tax discourges overconsumption of energy

Changing energy mix - using other energy sources as well as fossil fuels e.g nuclear power

Modified agricultural practices - cut methane generation from farm animals e.g developing new types of feed

Tree planting - planting new trees can create carbon sinks which will store more CO2 as organic matter

Waste strategies - increasing the amount of recycled waste should directly cut methane emissions from landfills

Carbon-neutral development - companies balance out emissions by paying for strategies that take up an equal amount of carbon e.g tree planting

Carbon capture development - storing carbon using methods such as deep sea or geogical burial

Side effects - e.g changing energy mix would reduce emissions, but nuclear power would lead to nuclear waste, expensive and dangerous to dispose of

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6.Adaptation Strategies

Land use planning - preventing development on floodplains and vulnerable coasts, removal of urban scrubland to prevent the spread of fire

Agricultural technology - drought resistant farming, the use of urban waste water on fields

Flood adaptations - building physical defences such as flood barriers to reduce the impacts of flododing, and having better flood warning systems

Lifestyle adaption - people adapting to suit new conditions e.g planting crops that will flourish in new climatic conditions 

Water resource management - using freshwater resources more efficiently to cope with drought conditions e.g installing water metres in home to discourage people from using a lot of water

Community awareness - educating local communities on potential impacts of climate change, adaptions can be tailored to specific communities

Limitations - e.g building physical defences such as the Thames barrier will always have a limited capacity as sea level continues to rise

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6.Tuvalu - adapting to climate change

Tuvalu is a small island state in the Pacific Ocean, between Australia and Hawaii. Its population of 10,500 is spread over 9 small islands, none of which are more than 5m above sea level. It is too remote for significant tourism and its economy relies on semi substinence farming and fishing as well as foreign aid. Tuvalu lacks adaptive capacity, it is a developing nation with a stin GDP of $12 million. 

How can Tuvalu adapt to the threat?

Relocate - In 2001, New Zealand agreed to accept 75 Tuvauans per year as environmental refugees possibly until 2050

Change behaviour - In 2000, Tuvalu joined the United nations with the aim of bringing its climate issues to the worlds attention, it was hoped that other counries would take action to mitigate

Modify the threat - beach mining is being regulated to reduce erosion risk

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