There is much debate over the appropriate co2 content of the atmosphere.
No one that I know of has ever questioned the impact of both human and
natural activities on the world's OXYGEN supply. After all 6 billion or
so can
live in a primordial swamp with oodles of co2 but we haven't any
personal
oxygen generators handy if the Oxygen begins to drop off.
I have occaisionally looked for comparisons of modern and ancient oxygen
measurements but have come up empty.
Anybody have an idea about where or who has good documentation of this?