# Are oxygen levels declining?

1. Apr 30, 2008

### boomerang

This was prompted by another thread which got me thinking.

If CO2 levels are increasing then surely O2 levels must be decreasing?

I mean I am just going by basic chemistry, we have hydrocarbons (fossil fuels) where
are being burnt and I believe the basic formula is:-

Hydrogen and Carbon (from fossil fuels) + O2 (from atmosphere)= CO2 + H20.

So it would seem to a 'layman' like me that if CO2 is increasing then O2 must be decreasing?

The only source of O2 that I am aware of is plants, but I believe they have to take CO2
out of the atmosphere to make O2, so if CO2 is increasing then O2 (oxygen) must be decreasing?

I did a bit of chemistry so I think that is right.

2. Apr 30, 2008

### vanesch

Staff Emeritus
I remember having read such an observation somewhere in the 4th assesment report of the IPCC (physical basis blah blah). One sees indeed a small decrease in O2 levels qualitatively in correlation with the CO2 rise, although it is at the limit of what is measurable.

3. Apr 30, 2008

### Staff: Mentor

Ie, remember that CO2 concentration is measured in parts per million while O2 is measured in percent.

4. Apr 30, 2008

### vanesch

Staff Emeritus
Yes, that's why this observation was so difficult...

5. Apr 30, 2008

### jim mcnamara

$$CO_2$$ concetrations vary from winter to summer in a given year - peaking in winter; lower in summer due to increased photosynthesis during spring and summer.

Due in part to the northern hemisphere has more vegetated land mass than does the southern hemisphere.

FWIW.