> What is the Mauna Loa data?

It's *the* data set in the context of carbon dioxide changes in the atmosphere (the station is located on a volcano on Hawaii, in a relatively clean and homogeneous environment in the Pacific).

Actually, simply googling "mauna loa data wikipedia" points you to a wiki page about the Mauna Loa Observatory.

> Since 1956 Mauna Loa Observatory (MLO) has been monitoring and collecting data relating to atmospheric change, and is known especially for the continuous monitoring of atmospheric carbon dioxide