You are researching ice cores.  The bottom of your core has…

You are researching ice cores.  The bottom of your core has been dated at 500 CE (common era).  The ice at this depth and age contains a higher ratio of O18 (Oxygen Isotope 18) than O16 (Oxygen Isotope 16).  What can you conclude about the temperatures and the amount of ice on Earth at this time?

Oceanographers or geographers that study climate change can…

Oceanographers or geographers that study climate change can use foraminifera to see what type of oxygen was around at a certain year before present because their shells are composed of calcium carbonate.  Calcium carbonate contains __________ that are used to calculate past climates.