In reply to Jed Rothwell's message of Fri, 25 Apr 2008 13:22:59 -0400: Hi, [snip] >If volcanoes added far more CO2 to >the mix then we do, than plants would have a negligible effect and >the atmosphere and there would be practically no free oxygen. (By the >way, decreasing levels of free oxygen have not been examined, and >recent evidence shows this, too, is a threat.) [snip] At 400 quad / year energy use, and assuming that all the energy is derived from carbon combustion (e.g. anthracite), and further assuming that all the energy is used in the form of heat (or that electricity production from heat is 100% efficient), and that the biosphere wasn't recycling CO2 (IOW CO2 just accumulated) it would take 34000 years to use all the Oxygen in the atmosphere.
Also consider that people live quite well at considerable elevations, where the Oxygen levels are considerably reduced. In short, I suspect we could go on like this for at least 1000 years, without even noticing any effect on our breathing from Oxygen depletion. In fact we are more likely to run out of fossil fuels before we run out of Oxygen to burn them. So, IMO Oxygen depletion is not a problem - certainly not on the scale of global warming. Regards, Robin van Spaandonk The shrub is a plant.
