Well not in the strict sense, I mean what's the raw material for industrial uses?
Given that these things are not filtered out of the atmosphere, there's gotta be a raw material that I'm guessing is likely to be fossil sourced. Which means their production and use is actively contributing to climate change.
I just blogged a musing on it, with Grufty Jim's knowledge on carbon dioxide, but as for nitrous we're totally in the dark.
http://bristlingbadger.blogspot.com/2008/07/stop-burping-stop-climate-change.html
Any ideas or info (with references) gratefully received.