Climate change

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  • Created on: 13-02-15 18:58
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  • Global Climate Change over the past 20,000
    • Evidence of the past climate shows that change has occurred naturally over throughout history
      • The earth has swung between relatively cooler periods creating ice ages and warmer periods when the ice retreated
      • Some scientists argue that climate change isn't a natural process anymore and there is evidence that suggests the earth is warming faster than in the past as a result of human action
    • Evidence of climatic change
      • Inferred/indirect evidence
        • Pollen Analysis
          • Temperature and precipitation are primary controls on the distribution of many plant species
          • Each species has a distinctively shaped pollen grain, pollen tends to resist decay
          • Normally found in oxygen free environments such as peat bogs, the further you go down the older the pollen.
            • Species compete against each other, so the species that lasts the longest is in the top layer, the other species will be lower because other species grown taller and restrict growing conditions of that species such as temperature and precipitation
          • This evidence can then be carbon dated to show the age, this is when the ratio of two different carbon atoms, C14 and C12 determines the age
          • Pollen analysis isn't always entirely accurate, for example, wind can often transport the pollen meaning when It is recovered the actual location of the pollen isn't accurate, also different species produce different amounts of pollen
          • Advantages of Pollen Analysis
            • Because each species has a distinctive pollen grain so It is possible to tell what types of trees, scrubs and flowers where around at that time. Therefore a representation of the climate.
            • One flower from a plant can produce 10,000 - 100,000 pollen grains, so only small samples of sediment are needed for analysis
            • Allows the postglacial period to be divided into periods according to patterns of plant life,
            • Because pollen is deposited in layers, if undisturbed, a core sample can be carbon dated to provide a sequence
          • Disadvantages of pollen analysis
            • Different plants produce different amounts of pollen skewing results
            • Exotic pollen can confuse the samples in from distant sites
            • Do not provide a direct interpretation of climate
            • Can be incorrectly identified
              • Some look very similar under a microscope
            • Taller plants result in a wider disperal
      • Dendrochronlogy
        • Analysis of tree rings of core samples
        • Each year the growth of the tree is shown in the trunk of a tree by a single ring.
        • The width of a ring depends on the growing conditions that year, for example the better the conditions the larger the width, better growing conditions include things such as temperature and precipitation
        • Limitations include the fact that it doesn't give you the exact temperature or climate
        • Cell damage can show natural disasters such as the santorini earthquake shown in medusa
        • Core samples from living and dead samples can be used to find prehistoric records
      • Oxygen Isotope Analysis
        • An isotope is an element with a different atomic numbers, oxygen has two useful isotopes, 016 and 018.
        • 016 evaporates more easily than 018, so the ratio between the two shows how sea temperature changes
        • During the warmer periods, 016 evaporates and then returns to the sea as precipitation, so the ratio is equal, however during the colder periods the 016 will fall as snow and become trapped in the glaciers mass, so the ratio will favour 018,
        • Oxygen is trapped within the sediments at the bottom of the sea and s there fore locked up as a record of temperature change
      • Ice core samples
        • Drilled from areas like the Greenland ice cap, are trapped inside can be analysed for carbon dioxide content, the greater the amount of carbon dioxide, the warmer the climate


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