claim: When stomata-derived CO2 ( red ) is compared to ice core-derived CO2 ( blue ), the stomata generally show much more variability in the atmospheric CO2 level and often show levels much higher than the ice cores.
evidence: Because of the way air is trapped in ice ( pores in the ice close off slowly to form bubbles deep within the firn ) and the time period represented in each ice sample analyzed, these figures represent averages of atmospheric concentrations of up to a few centuries rather than annual or decadal levels.