While this discussion is arguably (cough) pointless, it could be argued that just about any human being on this planet actively contributes to global warming.

Heck, even if you live in the jungles of Papua New Guinea, you're probably torching some wood/shrubs every now and then.

So - if we all contribute, it comes down to how much one can contribute before your actions become indefensible.

Chances are the bulk of the world's population will suggest that limit is below your contribution.