I like this post from Al Fin

He debunks the man-made global warming claims.  I would take a simpler tack, because I am not quite so well prepared to go toe to toe with people on this level.  My level is one of a common sense type argument.  For instance, why treat what the climate scientists say as unassailable?  They have a vested interest in the outcome, as the outcome of any investigation that is biased from the start is only going to give a biased result.  To put it another way, who is trying to disprove global warming?  All of the effort is to confirm what they already believe.  Is there any wonder that the results are going to point in that direction?