I feel as it's real and not a myth. Al Gore's movie seemed quite believable to me.

And even if it's not "real" humans are definitely harming the environment. Pollution is no doubt harmful. Just the other day I was gazing at the sky and was amazed at how dark it was because of some factory that was nearby. I was on the highway and saw the black smoke piling up and it was disgusting. That is definitely not a good thing for the environment. And of course that factory was the result of humans..

There have been attempts to attribute it to other natural cycles. I think the natural period of sunspots was one of the common misconceptions early - and although this does influence global temperatures it would be stretching he bounds of acceptability to use it as an explanation for current environmental changes (as some educated twits have done some news programmes, much to their later chagrin and embarrassment.)