PJ Media

The initial airburst might be able to get some debris up to the stratosphere, however it is impossible for fires alone to get smoke higher than a couple of thousand feet. Most of the soot will fall out of the atmosphere on it’s own within a few hundred feet of the initiating fire.
As I pointed out to you earlier, we already have one example of the conflaguration you are talking about. And the disaster scenario you propose didn’t happen.