Short answer: It's impossible to have a definite "yes" or "no" answer to the question "Is global warming really happening?"
Long answer: In truth, it's pretty much impossible to find unbiased scientific studies for either side of the argument. On one hand, yes, polution is terrible for the environment. On the other, even recorded winters have been very up and down, and before people started keeping track of this it is absolutely impossible to accurately know what the weather was like.
My personal opinion: There may be some sort of greenhouse effect going on, but I don't think that is the immediate cause of the mild winters we have seen in the past decade or so. I'm only 19 years old, but I remember the winters of the mid-90's being whoppers compared to what we've seen from 1997 and on. As I see it, it's impossible to think that global warming could have such a sudden and drastic effect on our winters. We're just not getting as much snow right now - that's that. That being said, I think it's stupid for us to continue consuming the earth's natural resources at the rate at which we are and that we should all be more concsious of what is going on around us. If that qualifies me as an environmentalist, hippy, tree-hugger, etc., then so be it. If you can't realize that we all need clean air, clean water, and furtile soil to live, then you are a fool.