evidence for natural climate change

• tree rings - trees produce one ring within the trunks every year
• tree rings


  the thickness of the ring depends on the climate

  • when its warmer the rings are thicker
  • when its cooler the rings are thinner
• ice cores - one layer of ice is formed each year
• scientist drill into the ice sheets to get long cores of ice

  by analysing the gases trapped in the layers of ice they can tell what the temperature was each year
• historical records


  recorded data from thermometers are a reliable short time record