Humankind dug up a huuuuuge percentage of the oil that our dead dinosaurs had turned into, and within a century, have used up most of it. To tell me that this ISN'T going to affect the planet is firstly ludicrous and secondly irrelevant -- at best we have rough guesses, but the ONLY safe course of action to protect ourselves is to make sure we do as little environmental change to this planet as we can.
Not worrying about climate change is like the crew of a space station randomly making changes to their life support systems. "Oh well, it probably won't matter, the chances are small", they say. But what of the risks? The risks are huge. 6 billion lives are at stake. In this case caution is the only sane policy.