evidence for causes of climate change

• atmospheric co2

  • analysed gas composiyion of bubbles formed in ancient ice cores
  • data shows correlation between co2 and temp but no causation
• average global temperatures

  • trend of increasing global temp
  • corresponds with time in which humans burnt fossil fuels
• pollen grains preserved in peat bogs

  • peat= compact, partially decomposed organic matter
  • peat cores taken from bog and layers analysed to assess pollen grains trapped
  • pollen grains unique to that plant so plant species growing around bog at diff times identified
  • diff plant species grow under diff climactic conditions, so plants present at different times can be used as a measure of climate at that time
• dendrochronology

  • tree trunks grow in diameter each growing season as they produce vascular tissue in rings
  • light coloured rings= fast growth in summer/spring
  • dark coloured rings= slow growth in autumn
  • produces a measure of the climate each year of growth and can identify how this is changing