How and why has climate changed in the past?

  • Created by: shonaf15
  • Created on: 14-10-18 10:49
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  • How and why has climate changed in the past?
    • Key definitions
      • Climate change
        • the large-scale, long term shift in the planet's weather patterns or average temperature.
      • Global warming
        • a gradual increase in the overall temperature of the eart's atmosphere generally attriibuted to the greenhouse effect caused by increased level of carbon dioxide, CFC's and other pollutants.
      • Quaternary period
        • the current geological period dating from 2.6 million years ago to the present day. we live in the holocene epoch of the Quaternary period, which covers the last 12,000 years.
    • Earth has had tropical climates and ice ages many times in i'ts 4.5 billion years
    • Natural causes of climate change
      • Eruption theory
        • Large volcanic eruptions give out large quantities of dust and gases such as sulphur dioxide.
          • the dust and gases create a 'blanket' around the earth, reducing the sunlight exposure, therefore cooling the earth
          • Large asteroid collisions act in the same way, throwing dust and ash into the atmosphere.
        • Example: Mt. pinatubo (1991)
      • orbital theory
        • changes in how the earth moves changes the amount of sunlight we receive.
        • According to Milankovitch, every 100,000 years the earth's orbit changes from circular to eliliptical.
          • he also said that about every 40,000 years, the earth's axis moves and wobbles which affects the amount of sunlight we receive.
      • sunspot theory
        • Sunspots are darker areas on the sun surface that come and go in cycles or roughly 11 years.
        • temperatures are greater when there are plenty of sunspots becuase the other parts of the sun have to work harder than ever!
          • Example: between 1645-1715, few sunspots were observed and this coincides with the Little Ice Age.

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