Air samples are more important than datum
It’s not enough for studies on atmosphere components to only rely on clearly recording and studying datum. Earth atmosphere components are really complex, including solidities, fluids, and gas, with complicated physicochemical properties. There are limited datum from detecting existing air samples. And there is possibility that some unknown substances make much difference during climate changing process but could not be detected for now. Therefore, air samples are the most comprehensive data resources. Today’s scientific researches often need early air samples. Nowadays these samples usually come from polar deposits. Although these samples are precious few and hard to define a particular year, they still help scientists study greenhouse gas concentration changes for the past 200 years. Modern advanced techniques also helped discover atmosphere component like hydro fluorocarbon, which were not paid attention to before.