CLIMATE CHANGE EVIDENCE

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  • Climate Change- Evidence
    • Climate Change is any long term change in weather
      • any significant change in the weather of a region over a period of at least several decades
      • Climate is constantly changing, it always has and it always will
      • Last 2.5million years, global temperatures has shifted between cold glacial periods that last around 100,000years and warmer interglacial periods that last 10,000 years
        • we are now in an interglacial period
      • 20,000years ago Earth was cold. 15,000 years ago tarted to warm up
        • over last 10,000 years climate has been warm with minor fluctuations
          • over last 1000 years climate has been fairly constant with small fluctuations in annual temp.
            • over last century global temp. as increased rapidly.-Called global warming. Sharp rise in average temp (0.7oC 1900 and 2000)
              • Global temps rose steadily from early 2othC until 1940's (13.5oC to 14oC)then dropped.Scientists thought another glacial period but risen even more
                • changes in climate over last century are result of human acitivities
    • EVIDENCE FOR CLIMATE CHANGE
      • OBSERVATIONS
        • HISTORICAL RECORDS
          • can indirectly show different conditions in the past.
            • e.g. agricultural reports showing changing conditions throughout human history
        • WEATHER RECORDS
          • details of weather conditions consistently collected since 1861. Used to show detailed cimate changes
      • PHYSICAL EVIDENCE
        • POLLEN ANALYSIS
          • pollen is often preserved in sediment
            • this pollen can be identified to the plant it came from
        • COLEPTERA
          • these are beetles whose remains are preseved in sediment
            • different species live in different climatic conditions
        • TREE RINGS (DENDROCHRONOLOGY)
          • as trees grown new tree ring is produced
            • rings are thicker in warm, wet conditions
              • trees can reliably show date and climate conditions upto 10,000 year ago
      • BIOLOGICAL EVIDENCE
        • ICE CORES
          • scientist drill deep into ice sheets to extract the cores
            • ice sheets made up of layers of ice- one layer is formed every year
              • analyse gases trapped
                • can tell what temperature was  like and how it has changed over time
                  • high CO2 indicate warm climate at that time
                  • Oxygen has two main isotopes 0-18 and 0-16
                    • O-16 is lighter than O-18
                      • Cold periods less energy for evaporation so water molecules with O-16 evaporate easier and falls as snow
                        • High levels of O-16 to O-18 = cold climate
        • SEA FLOOR SEDIMENTS
          • sediments deposited on sea floor record chemical composition of seawater when deposited
            • like oxygen contain Oxygen isotopes
              • during periods of cold climate water molecules O-16 more easily evaporated so ocean becomes rich in O-18
                • high levels of O-18= cold period
        • SEA LEVEL CHANGES
          • as climate warms ice caps melt and sea levels rise.
          • E.G. POOLE HARBOUR, DORSET
            • Shows sea level is higher than it used to be
        • RETREATING GLACIERS
          • look at historical pics and at deposited rocks
            • distance of rocks from current galicer indicates climate change
              • If front of glacier miles away from rocks shows temp. increased

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