She mentioned to me a year ago that I should read Geoengineeringwatch to become informed. Other than that, the most glaring error is that she says methane destroys ozone. The EPA says no way:
http://www.epa.gov/ozone/defns.html
I can't completely blame her for not knowing that the Wigington claims of high UVB are so wrong. She may not even understand what you very succinctly and accurately explained showing that the levels he claims do not even exist out in space. If she relies solely on geoengineeringwatch for her information, she will see no response to the conundrum between the Wigington claims and the UVB constant in space. Wigington and Foote have no response because there is no way to explain away their error.
However, it appears to me that either the EPA site you link to is in error or too much is being read into it in this case. I'm not positive but it appears that in the case of the EPA glossary, it is speaking to the
ozone depletion potential of a
substance which is regulated for certain uses such as refrigerants and not strictly speaking about methane as a gas which could deplete ozone.
After some digging, I have come to understand that there is indeed a mechanism by which methane can act as a sink for ozone in the stratosphere.
Methane is not alone in this action, other completely naturally produced substances such as water vapor and nitrogen oxides in the upper stratosphere and sulfuric acid(from volcanoes) in the lower stratosphere tend to reduce ozone.
The specific action of methane which reduces ozone is when it is oxidized to H2O, OH, and HO2, unstable hydroxides referred to HOx.
These radical and unstable compounds can also react with ozone (O3) thus acting as a 'sink' decreasing the steady-state level of ozone in the stratosphere. You can read a detailed explanation
here.
However, methane is a common, natural gas produced by the gut of animals and insects, anaerobic decomposition in wetlands and even plants. There is a global methane cycle and the relative levels are interesting.
What is so far unclear to me is whether or not the relatively modest increase in methane we have seen has any significant effect on ozone levels. When compared to ordinary water vapor and nitrogen oxides which play exactly the same role as natural 'sinks' for the steady-state concentration of ozone, does methane play an increasing role?
Obviously, if the catastrophic methane releases claimed to be in progress by Wigington were actually happening, the situation would be clearly awful, but that notion has been debunked much to Wigington's consternation by men as qualified as Gavin Schmidt. Yes, Wigington's response was that Schmidt is just a "shill".
So, if you want to debunk the claims of Wigington being repeated by Coulter, you need to understand that his claims about methane depleting ozone might be technically true, but his actual claims are that the following are already underway:
a) an ongoing catastrophic methane release is responsible for
b) catastrophic ozone loss that this is responsible for
c) his claimed UVB levels.
Wigington has failed to provide any credible evidence for any of his chain of claims a,b, or c.