Why are oxygen levels not dropping if carbon dioxide levels are increasing?

Answer 1

The oxygen levels are dropping but because the total carbon dioxide level changes are in the 100 ppm range and the oxygen levels are in the 21 percent range the impact is not noticeable to the casual observer on a yearly basis.

Carbon dioxide levels have risen some 35 per cent, from the historic range of 260-280 parts per million (ppm) to the present level of 400 ppm, since the beginning of the Industrial Age. While this is significant for global warming, it must be remembered that the measurements are still only in parts per million of the total gases in the atmosphere. The oxygen levels have also fallen a corresponding by several parts per million.

For the math, consider oxygen at 21% of the atmosphere (210,000 ppm), if the entire CO2 addition of 100 ppm or so were to directly result in a reduction the oxygen levels O2 levels would have gone down from 210,000 ppm to 209,900 ppm as 1 ppm of CO2 is created by the combination of carbon 1 ppm of O2 . This is a reduction of less than 0.05% over a period of decades. It should be noted that due to the changing growth of trees and crops in winter and summer there is a seasonal rise and fall of atmospheric oxygen in the hemispheres which hides this trend to some extent. Even at this low level of decrease the reduction can be tracked by scientists. The American National Center for Atmospheric Research in Boulder, Colorado has published a paper on its tracking the low levels of oxygen depletion. The data gives yet another confirmation of the impact of increased CO2 emissions and the reduction of CO2 take up by trees and forests due to deforestation.