Quote Originally Posted by benagain
Yea, I know they can take soil samples and whotnot and get a pretty good idea of what probably happened a million years ago .
Actually they drill ice cores from the artic. This ice is formed by compacting snow. Because itâ??s formed in this way small bubbles of air are trapped. These samples of air are samples of the atmosphere. They are not guesses or pretty close, they are exact!

As well they can take samples of the dissolved Oxygen in the water. And measure the ratioâ??s of the different isotopes. Isotopes are atoms with the same number of protons but different numbers of neutrons. The ratio of the oxygen isotopes can be used to very accurately estimate the salinity of the ocean and itâ??s temperature. Since the temperature, salinity and oxygen isotopes have a causal relationship there is a very small margin of error.