protective stratospheric ozone layer by about 3 to 8% overall since the 1970s. In the upper stratosphere, ozone depletion has been from 15 to 20%. Again, the model is better able to reproduce these values when increased water vapor is included. This is especially true in the upper stratosphere, where ozone is most sensitive to water. The model indicates that increased water vapor accounts for about 40% of the ozone loss in the upper stratosphere, and about 20% of the overall loss to date. There are two driving forces behind the change in stratospheric moisture. Increasing emissions of methane are transformed into water in the stratosphere by chemical reactions. This can account for about a third of the observed increase in moisture there. http://www.giss.nasa.gov/research/briefs/shindell_05/ Why did you change topics to ozone? We were discussing O2 depletion in the entire atmosphere, and I presume (because we are on the topic of this post) as an indicator of an anthropogenic cause of CO2 increase. Any casual reader of your comment is going to interpret it in that fashion, and your comment suggests oxygen depletion is not an indicator of an anthropogenic source of CO2 increase. As such, you need to support the claim. Your shift to ozone depletion has no bearing whatsoever on the matter, and dodges the point. Your explanation of the chemistry is similarly irrelevant. I well understand the reaction, and anyone who doesn't can google it quickly enough. But you still haven't provided the necessary foundation for your argument,