Why has atmospheric O2 stayed constant and not elevated or decreased in conjunction with CO2 increases? Does weathering show a net gain? We%26#039;ve had ~21% levels since the biological era. That was marked by the simultaneous decrease in atmospheric CO2 and the increase in O2 due to life processes. Shouldn%26#039;t there be less O2?

Best Answer

This question makes me nervous, and I have a feeling there is no known answer. Weathering played a large role in O2 formation at the onset in the form of the atomic O2 molecule. My best guess would be that photosynthesis is a reversible process. Where respiration and decay, in organic matter take up O2 to form CO2. But like I said this is a scary question and really beyond me.

Asker's Rating:

I don%26#039;t know why your were hesitant? You did keep the subject matter in perspective. I wasn%26#039;t talking about selective gases absorbers. Typical O2 fluctuations far out weigh the 0.03 decline as noted by CSIRO studies. The terrestrial filtering system is doing just fine.

Other Answers (2)

• Because the amount of the CO2 increase is tiny. About 0.01%.
  
  One reason some people don%26#039;t understand global warming is a lack of understanding how such a tiny increase can have such a big effect.
  
  But it%26#039;s just a relatively simple physics calculation. That much increase in CO2 holds in a small part of the Sun%26#039;s heat that%26#039;s not natural, causing temperatures to rise, as we%26#039;ve seen.
  
  Simple for a scientist to understand, not so simple for someone who doesn%26#039;t understand science.
• Oxygen levels have, in fact, declined as CO2 has risen. But the rise in CO2 has been about 100 parts per million (or about 0.01%), and Oxygen levels have fallen by the same amount. So it doesn%26#039;t make much practical difference.