Co2 problem, how about Oxygen?

[Simple Mind]

If, like we are being told, tere is to much Co2 in the Atmosphere, how is it about the Oxygen? As much as i know tere is oxygen destroyed every time a substance is being burned?! We are burning an awful lot of stuff, how come tere is still enough oxygen left despite of us cutting down all the Forests and polluting all the Oceans?

[Public Animal No. 9]

There's about 21% oxygen in the atmosphere, but only about 380 parts per million of CO2. 21% = 210,000 parts per million, so there is plenty of O2. The issue with the increase in carbon is that it's coming from fossil fuels, which have not been a significant part of the carbon cycle prior to the industrial age. The carbon cycle is how carbon moves from oceans, soils, and (decaying) plants and animals to the atmosphere and then back into plants, animals, oceans, and soils. Fossil carbon stayed out of that cycle for the most part until the last couple of hundred years (mostly the last 50), which has added the extra CO2. The amount of O2 captured by the burning of fossil fuels is miniscule compared to the total amount available, so there's no serious concern about running out.

[Fear Itself]

Originally Posted by Simple Mind

As much as i know tere is oxygen destroyed every time a substance is being burned?!

Oxygen is not destroyed by burning, it is combined with other elements to form CO2, water and other ash by-products of combustion. But it is still oxygen, even when in combination in another molecule.

We are burning an awful lot of stuff, how come tere is still enough oxygen left despite of us cutting down all the Forests and polluting all the Oceans?

The oxygen is constantly liberated from these by-products through natural processes, such as photosynthesis.

[Chronos]

Every molecule of CO₂ which is formed corresponds to the destruction of one molecule of O₂, and to get that O₂ back, you have to destroy the CO₂. The reason it's not an issue is that, as Public Animal No. 9 says, there's a lot more oxygen than carbon.

[Squink]

Originally Posted by Chronos

as Public Animal No. 9 says, there's a lot more oxygen than carbon.

IIRC, the tonnage of C and H locked up in methane clathrates is enough to make a sizeable dent in world oxygen levels.
Wikipedia's article on the Clathrate Gun Hypothesis states that a large release of such methane could "greatly affect available oxygen content of the atmosphere", but gives no detailed figures.