Actual data- measured directly
Proxies- data which has been inferred from other sources (frozen isotopes, dendrochronology- tree rings, coral records)
Frozen isotopes; proportion of O18 to O16 tells us the air temperature
-Atmospheric carbon dioxide level can be measured
-They show us INTERGLACIALS - periods of global warming (ICE CORES)
Coral; proportions of different isotopes taken up by coral as the sea temperature changes
Dendrochronology; dating of trees using rings. Looking at this we can see what the environment was like at different times. Thicker the ring, the warmer the climate.
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