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.