Real Death Star

Yahoo had an article about a possible "real death star": http://news.yahoo.com/s/space/20080310/sc_space/realdeathstarcouldstrikeearth
Pretty wild how much stuff out there in our universe could destroy us in the blink of an eye (even if the impending star explosion would happen 100,000s of years from now). Also made me think of global warming while reading it. It mentioned that the gamma rays could produce an ozone depletion of up to 25% (CFCs only got us down to a 3-4% depletion). And also that there would be a bit of a smog effect because of the way it would react with the upper atmosphere. This would lead to some global cooling. And that's where I thought of global warming tie-ins; I wonder if our ozone hole was letting out greenhouse gasses. Maybe that is a short term solution to global warming? Anybody know more about the ozone layer and what it allows to pass in and out of the Earth's atmosphere? 'Cap.