Parts 4,5 Geography AS Unit 1 Global Challenges World at Risk


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4. On-going climate change evidence

Short Term:

  • Weather Records - collected since 1861, show detailed climate changes
  • Polar Ice Melt - current research into behaviour of polar ice - show climatic changes, e.g. increased melting = increased temperatures
  • Ecosystem Changes - show available food/shelter > affects species - species distribution changes show climate changes.(
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4. The causes of climate change may be natural

1. Variations in Earth's orbit that affect the global climate

  • Stretch - orbital path switches from circle/ellipse every 96,000 yrs, alters amount of energy received at different times of year - currently elliptical.
  • Tilt - Earth is always tilted on it's axis, changes between 21.8 - 24.4 over 41,000 yr cycle. Tilt alters amount latitudes receive - affects climate - 
  • Wobble - Axis wobbles on 22,000 yr cycle =seasons will gradually swap over

2. Variations in solar output

  • Sun's output energy isn't constant, sunspots increase solar energy output
  • Thought to increase/decrease on 10 yr cycle, e.g little ice age, activity low

3. Meteor Impacts

  • Impact of meteor or asteroid = crater + material in atmosphere
  • =loss of sunlight(energy) block out for months- years, e.g dinosaur extinct

4. Volcanic Eruptions - material in atmosphere > blocked sunlight

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4. The causes of climate change may be human

1. Enhanced greenhouse gas emissions (CO2, methane, ozone, water vapour)

  • Greenhouse gas effect: they absorb outgoing energy=less lost to space
  • C02 released when fossil fuels burnt > since industrial revolution (mid 19th) atmospheric C02 increased > 280ppm - 380ppm -was stable 10,000 yrs

2. Destruction of natural CO2 sinks

  • CO2 sinks store CO2=kept out of atmosphere = not contributing to g h effect
  • Biggest sinks in oceans- CO2 dissolves in sea water, also plants - take in CO2 & convert to organic matter (photosynthesis), & in soil as dead O M.
  • Sinks can't keep pace with increasing emissions =CO2 direct to atmosphere
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4. Climate change is unprecedented

-       Increases in global average air temperatures (approx ^  0.74 C 1900-2000)

-       Increases in global average sea temperatures

-       Melting of snow and ice

-       Rising global average sea level

-       Changes in rainfall patterns

-       Changes in wind regimes

-       Changes in the nature of extreme weather events

-       Changes in the biophysical world.

-     PH of oceans decreased since 1750 due to increased CO2 levels

-     11/12 hottest years on record occurred between 1995-2006

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5. The impacts of climate change on Africa (North)

  • Africa is the world's poorest continent - 2/3 countries are in world's 50 poorest
  • 34% population aged 15-24 illiterate
  • Many countries owe millions in debt - G8 canceled them for 18 in 2005 - some are so heavily indebted that repayments sometimes exceed their entire GNP.
  • The continent as a whole it is 0.5 C warmer than in 1900
  • Temperatures have increased more further inland -coastal areas are cooled by the sea. Some inland areas have experienced double the global increase. e.g Kenya increased by 3.5 C since 1985
  • Droughts become more common
  • Rainy seasons are now more unreliable & decreasing overall - 40%expected.
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5. The impacts of climate change on Africa (North)

Economic impacts:

  • Changing rainfall patterns = shorter growing season (dependent on agriculture) - predicted up to 50% reduction by 2020
  • Coastalisation - migrant fell drought to coastal cities - strain economies + water supplies, e.g. Cotonou (+ shanty towns)

Social Impacts:

  • UN environmental programme reported 2007, 14 countries in Africa were suffering water shortages & 11 more will join them by 2032.
  • Competition for water is likely to arise between countries such as the Nile (Egypt, Sudan and Ethiopia) = conflict
  • As scarcity increases so does dependence on poor quality sources >> increase in water-born diseases, e.g.cholera (particularly young and old) = pressure on health care systems - government budgets.
  • Increased humidity = mosquitos spread ove
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5. The impacts of climate change on The Arctic

**These case studies demonstrate the concept of an unfair world, whereby the poor areas suffer most despite having contributed very little to greenhouse emissions.**

  • Encompasses the North Pole, includes: North America, Asia, & Europe = disputes over possessions of resources, conflicts of how should be mngd
  • Greenhouse gases
  • The arctic is vulnerable mainly environmentally and ecologically


  • Annual av temp increasing 2 x faster than rest of world
  • Snow cover declined 10% in last 30 years
  • Permafrost melting = released CO2&methane(permafrost is a naturalsink)
  • Sea ice cover declined 15-20% over last 30 years = *ALBEDOreduction
  • Melting ice sheets, e.g. Greenland ice sheet = fresh water injection to Arctic Ocean --> changes in water density, salinity reduced
  • Polewards migration of non-native species + disease = conflict
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5. The impacts of climate change on The Arctic


  • Loss of Inuit culture - traditional living & hunting compramised
  • Declining food security
  • Increased shipping through pole > exploitation material & habitat, e.g. fishing


  • Access to raw materials - thought to be undiscovered oil & gas reserves - unfrozen ground = easier to find & extract
  • New shipping routes in summer
  • Warmer soils = opportunity for agriculture// thawing permafrost  infrastructure :(

Consequences will affect the rest of the World **Melting ice sheets = sea level rise**   **Salinity & depth affect ocean currents, e.g. thermohaline circulation**

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5.Potential impacts of global sea level rise -disp

Sea level rise is a worldwide process, however it's affects in different places will vary.

Vulnerable areas

  • large river delta's - Nile, Mississippi
  • low lying areas already experiencing floods, e.g. Bangladesh, Netherlands
  • small low lying islands in the Pacific & Indian Oceans - small physical size- knowhere to escape to, dense & growing populations, remoteness

World's most impoverished countries will have to cope with greatest effects, yet they have the smallest impact on global warming....

Emissions per person, per year (tonnes of carbon) = USA 5.6, UK 2.7, Kiribati 0.07

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5.Disproportionate effects of climate change cases

Located in the South Pacific, made up of 33 atolls, straddles the equator

  • Highest land = 1.5m - one of the most low lying lands in the world
  • Home to 95,000 people
  • Has seen nest to no rain in past 3 years > coconut trees dying
  • Weak economy - heavily reliant on coconuts alone
  • Can't afrd protection- sea wall 1 atoll=$100M(2x country produces annually)!


  • Asia pacific region expected sea level rise of 1/2 metre by 2070
  • Flooding & storms = erosion


  • Families forced to rebuild homes further inland
  • Water supplies contaminated by encroaching salt water (Brackish)
  • 'Flood refugees' 2003- 4,000 applied for NZ residence, 2006 - 10,000
  • Australia's government refused to commit to taking refugees
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5.Salinity changes: shutting down the Atlantic the

  • Oceans and winds help distribute heat between its warmest/coldest parts.
  • The current of warm water in the atlantic = gulf stream. This makes the UK's climate warmer than it would otherwise be for its latitude and as it flows the ocean releases heat into the atmosphere.
  • As the ocean cools it becomes denser and sinks to the ocean floor.
  • This forms an ocean circulation called thermohaline circulation.
  • This is a flow of warm and cold water that circulates around the world's oceans.


  • The TC is driven by cold dense arctic water and dense salty/saline water
  • With global warming arctic sea water warms and becomes less dense. Melt water in rivers dilute the salinity of the arctic ocean making it less dense.
  • The consequences of this is the gulf stream switching off or reversing causing the UK to freeze.
  • There's a 50% chance it will shut down within 200 years.
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