Scientists also find proxy climate data beneath the oceans. Corals are small marine organisms that as adults form a colony on the ocean floor. Reefs and small islands consisting of coral are common in tropical seas and oceans. Corals build their skeletons from aragonite, a crystal form of calcium carbonate, which is extracted from the oceans in which they live. By knowing the concentration of certain forms or isotopes of oxygen present in the aragonite, the temperature of the ocean can be determined. These temperatures can then be used to determine what the oceanic climate was like during the period of time in which the coral lived.
Corals are very valuable sources of proxy data to climate scientists because they continuously record information about the temperature of the sea throughout their lifetimes. Scientists have found coral data to be very accurate records of sea surface temperatures from the past.
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