This is why I'm a skeptic, change my mind: Let's say we have 150 years of accurate temperature data, and it shows an increase of a few degrees. What is the standard deviation in global temperature for 150 year periods for the last 100K or 1M years? How do we know what is significant change? Any data gathered from models (ice core, tree rings, ...) just doesn't have the resolution to answer these questions.
I believe the cause for concern among the proponents of awareness and regulation is that a notable change is happening, and we desperately want the status quo. Whether or not this change falls within normal variations is irrelevant to this argument.