Atmospheric CO effect on stable carbon isotope composition of terrestrial fossil archives.

The C/C ratio of C plant matter is thought to be controlled by the isotopic composition of atmospheric CO and stomatal response to environmental conditions, particularly mean annual precipitation (MAP). The effect of CO concentration on C/C ratios is currently debated, yet crucial to reconstructing ancient environments and quantifying the carbon cycle. Here we compare high-resolution ice core measurements of atmospheric CO with fossil plant and faunal isotope records.