Millions of years later, parts of G have been turned into a fossil fuel, powering a boat as gas. Fossil Fuel is fuel made of the remains of a once living organism (coal or gas). This is the last of G being released into the atmosphere. By burning the fossil fuel, we let more carbon into the atmosphere.
And that's it! After this process of him being let back into the atmosphere, he will repeat the process. G is just a small example of carbon in the Carbon Cycle. The Carbon Cycle is never ending, or at least till the Earth ends!