The level of carbon dioxide millions of years ago should be lower as compared to today. This is due to the increase of global warming which release carbon dioxide and other gases into the air, hence, the level of carbon dioxide in today’s world has increased.

That’s all I know. 🙂

I just read a book about a research of measuring CO2 level in Mauna Loa, Hawaii from 1958 – today. The result showed that CO2 level is increasing in LINEAR way along with the year OMG! 😯 I cannot imagine what will happen in the future 🙁

You would have to be more specific. If we are going back to the time of the dinosaurs, then CO2 would have been much less abundant than it is today.

Go back a few hundered million years further and the planet is a mass of volcanic activity and CO2 would have been much higher. Oxygen did not become a significant component of our atmosphere until plants colonised the land between 4 and 5 hundred million years ago.

Plants didn’t need to be on land to affect atmospheric oxygen – long before land colonization, there is evidence in the fossil record of a great rise in oxygen in the oceans, and since water doesn’t hold oxygen very well, the atmosphere would have taken much of it.

There are some other indirect measures of atmospheric proportions from the distant past, but they are controversial.

Interesting. How does the fossil record record oceanic oxygen levels?

Anyhoo i doubt the question required him to go back further than land colonisation. 🙂

Indirectly, I suppose the size of things in the oceans was limited by the 02 levels :S