Future fate of methane, interaction with SRM, general request for expertise...

[Andrew Lockley]

I've been doing some research on the fate of methane recently.  It appears the chemistry is made substantially more complex by the interaction of pollution and possible geoengineering.

I'm writing to ask if anyone has insights into this, or opinions on the matter.  

Particularly, if SRM with sulfur is used, it appears that the sulfur precursors compete with methane for reagents. Has this effect been factored into the calculations on the efficacy of SRM?  No use dumping sulfur up into the stratophere if there's nothing left for it to react with, or if the effect on the lifetime of methane outweighs the SRM effect.  ( useful link http://www.sciencemag.org/cgi/content/abstract/326/5953/716 )

Furthermore, there is an added complexity in that the source of the radicals needed to oxidise methane is ultimately ozone.  I understand that there is still significant depletion of stratospheric ozone, and thus it may be the case that the life of methane in the atmosphere is longer than was historically the case.  As ozone is itself a GHG, does anyone have opinions on using O3 production and addition to the atmosphere as a geoengineering measure, with the aim of restoring the ozone layer and also encouraging the degradation of methane?  Would the GWP of O3 outweigh that of the methane it ultimately destroys?

Finally, I'm interested to know if anyone has particular opinions or insights into the chemistry of radicals and reactive oxygen species in the atmosphere.  I'm interested in the possibility of creating and using such chemicals to degrade methane.  NOx may also offer options.  Can such chemicals be easily and safely created on a large scale?  Can they be added to the atmosphere safely, and left to diffuse?  I feel a little bit of a dunce asking these questions, but my knowledge of atmospheric photochemistry simply isn't good enough to avoid making basic mistakes in this regard.

I'd really appreciate any comments, ideas and assistance people are able to offer.

Thanks!

A