Do you know that there's actually a quite large group of scientists that defends the theory that the only thing preventing an ice age right now is the sheer amount of pollution and heat generated by the human race? There's evidence that the sun is going through a low activity period (neutrino emissions are too low), and evidence linking such low activity "seasons" to previous ice ages. These "studies" that show up every day on newspapers about global warming never take into account a true geological perspective - they compare the global temperature with what it was a few years ago, and don't give a damn if a few million years back, with no "artificial" pollution whatsoever, the temperature was way higher than it is now.
Now, I'm not for pollution, nor against caring for the environment, but all these green hippies are yet to provide concrete proof instead of a collection of very loud screams accompanied by localized "evidence".