Climate Change

Climate Change

Evidence
1. Long-term
  1. Past 400,000 years - more detailed fluctuation
    1. Cold glacial periods - 100,000 years
    2. Warmer inter-glacial periods - 10,000 years
    3. Currently interglacial
  2. Ice cores
    1. Layer of ice formed every year
    2. Drill deep into ice to retrieve a core
    3. Analyse trapped gasses to determine temp. each year
  3. Pollen analysis
    1. Pollen often preserved in sediment
    2. Pollen can be identified and dated
    3. Pollen from similar plants indicates similar conditions
  4. Sea level change
    1. Affected by volume of water stored as ice
    2. Sea level shown by raised beaches
      1. Can be dated, indicating less ice so warmer periods
2. Medium-term
  1. Last glacial period 18,000 years ago
  2. 5,000 years ago, temperatures were 1-2Oc higher than today
  3. Historical records
    1. Agricultural reports
    2. Indirect indicator
  4. Tree rings
    1. Ring formed each year
    2. Good conditions lead to thick ring
    3. Take cores and count rings to find age
      1. Analyse each ring to determine climate every year
    4. Reliably show and date conditions up to 10,000 years
  5. Retreating glaciers
    1. Size and extension determined by deposited rocks
      1. Rocks can be dated to show when deposited
    2. Distance from rocks determines climate change
      1. Rocks miles away - increased temperatures
3. Short-term
  1. Sharp rise over past 1,000 years
  2. General increase shown - pattern not constant
  3. Weather records
    1. Collected since 1861
    2. Show climate change per short period of time
  4. Polar ice melt
    1. Reduction of ice at both poles
    2. Increased melting = increased temperatures
  5. Ecosystem changes
    1. Temperature affects food and shelter
    2. Affects species in different areas
    3. Analyse species to indicate climate changes
Causes
1. Natural
  1. Milankovitch Cycle
    1. Orbit
      1. Circle - ellipse every 96,000 years
    2. Tilt
      1. Varies between 21.8 - 14.4 over 41,000 years
    3. Wobble
      1. Wobbles like a spinning top every 22,000 years
  2. Solar Output
    1. Sunspots show increased solar output
    2. Thought to increase and decrease over 11 year cycle
  3. Eruptions
    1. Place large quantities of ash into atmosphere
    2. Block out solar radiation
    3. Cool Earth
2. Human
  1. Enhanced greenhouse gas emissions
    1. Too much greenhouse gas in atmosphere, warming Earth
    2. Fossil fuels
      1. Coal power stations
      2. Transport
  2. Destruction of Co2 sinks
    1. Oceans and plants
    2. Deforestation
    3. Increased emissions mean sinks can't keep up
Impacts
1. Melting Ice
  1. Water stored as ice returns to oceans
    1. Rising sea level
      1. Eustatic sea level rise
2. Oceans get warmer
  1. Expand - thermal expansion
3. Thawing permafrost
  1. Ground frozen for 2+ years
  2. Permafrost are natural sinks
  3. Releases Co2
  4. Collapse of buildings and pipelines built on it
4. Increase in frequency of extreme weather events
5. Changes in distributions of climatic regions
6. Difficult to predict climate change as too much uncertainty
7. Possible Tipping Point
  1. Catastrophic and irreversible changes
    1. e.g. ice melt + destruction of natural Co2 sinks

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