Cosmic-Ray-Driven Reaction and Greenhouse Effect of Halogenated Molecules: Culprits for Atmospheric Ozone Depletion and Global Climate Change (arXiv, PDF)written by Qing-Bin Lu, a physicist (mostly biophysicist) at the University in Waterloo, in October 2012. The first detail that seems bizarre to me is the amount of hype surrounding a preprint that's been out for more than half a year. If there were real, active experts who follow what's going on in climatology and if the paper were right and important, they would have known it for half a year and not just now when the paper happened to appear in a journal.
WUWT, Google News
It doesn't seem to be the case so at least one of the assumptions has to be invalid.