A little knowledge is a dangerous thing.  A very little knowledge is a very dangerous thing.  In my opinion as knowledge decreases danger increases.......so real ignorance is really dangerous.  Again, IMO, to deny global climate change, global warming and man's role in causing these phenomena is a demonstration of extreme ignornace.  BTW: I use the term "ignorance" in its classical sense...absence of knowledge.  I consider stupidity to be the persistent refusal to acquire knowledge and, instead, maintain views and opinions based on ignornace. 

IMO: Definitive evidence of climate change (global warming) and humankind's role in it is readily available.  To ignore that evidence and maintain a "denier" status goes beyone ignorance into the realm of stupidity....and stupidity is far mor dangerous than ignorance.