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Article 1: Climate Proxies Notes

  • Defined as preserved physical characteristics of the past that can be utilized to indicate past climate conditions
  • Examples: ice cores, tree rings, corals, sub-fossil pollen etc.
  • Proxies are cross-verified to improve accuracy
  • Not all proxies are uniform, more in the Northern hemisphere
  • Ice cores - cylindrical samples from within ice sheets
    • Isotopes of ice cores indicate temperature
    • Can reveal the climate records for the past 650,000 years
  • Tree rings
    • Reveals climate for past thousands of years
  • Fossil leaves
    • CO2 content of past atmospheres for leaves
  • Boreholes
    • Do not require calibration
    • Record the surface temperature
    • Potential risk of contamination by groundwater
  • Corals
    • Ocean coral skeletal rings
    • Cooler temps, corals used heavier isotopes
    • Warmer temps, coral used more normal oxygen isotopes
  • Pollen grains
    • Found in sediments
    • Measure layers of varve
  • Water isotopes and temp reconstruction
    • Imply glacial-interglacial temp changes were twice as large than previously believed
    • Hydrogen and oxygen isotopes
      • Isotope fractionation - the vapour pressure of heavier isotopes is lower, so the vapour contains more of the lighter isotopes and when precipitation occurs heavier isotopes are present
  • Pseudoproxies - the skill of combing proxy data
    • Proxy records are compared with the known temperature of the model