[JimMorrison]

The average temperature of the world is gradually, and consistently increasing.

Greenhouse effect (Co2) can perhaps not be 100% conclusively linked to this phenomenon, however observations of nearby planets and their atmospheres, plus empirical laboratory testing shows that this -could- contribute to atmospheric warming.

Ultimately, the real point is not whether or not humanity is directly causing the climactic trend. The point is that it is happening, and that if it continues to happen, things are going to get a lot harder for everyone.

So you have to ask yourself, are we helping to solve the problem? Just not causing something through deliberate personal action, doesn't absolve you from the repercussions of the situation.

Living with your head in the sand isn't going to do anyone any good. And just remember, there is a significant chance that sand will be underwater within the decade, and we wouldn't want anyone to drown out of total ignorance, would we?