ah yes, Al Gore. now I'm afraid I have to agree with you completely.
But I'm sure the IPCC was no more persuaded one way or the other by Mr. Powerpoint than you or I.
When you say common sense SASless, perhaps you mean intuition or pattern recognition: such as spotting a phoney like Al Gore. But let's not forget that common sense also had it that the world was flat and the sun went around the earth: it was obvious and everyone knew it.
And science is not about proof, it is about confirmation or disconfirmation. You can prove something in law, but never in science. Good science tests theory by experiment to a degree of certainty, or it builds theory from observation; in turn putting it to the test. Laws of science are not real or permanent, they are the merely the best current explanation.
So in a world of competing information, who do you believe? The majority of climate scientists or the dissenting minority, some of whom conduct research sponsored by the coal and petroleum industries? That doesn't, necessarily mean it's biased research, or a biased interpretation of the results. But it makes you wonder if they are trying as hard as they should to disconfirm.