The AGW lobby claims that its position is endorsed by scientific consensus. This argument is flawed for a number of reasons
Firstly, there is no consensus; there is a majority belief. Leaving aside the objection that belief is a facet of religion, not of science, let us examine the nature of this "majority". Its magnitude is systematically overstated, as demonstrated by, for example, Peiser's damning critique of the Oreskes paper. Peiser's critique may be flawed, but not to the extent that it falsifies Peiser's basic claim, i.e. that Oreskes overstated the magnitude of the majority.
Secondly, when it comes to the "green" wing of the AGW lobby, it is interesting that many of them choose to ignore scientific consensus on other matters (e.g. the safety of genetically modified foods). A possible conclusion is that it is not consensus that determines their espousal of AGW, but merely that it conforms to an already-existing belief system.
Thirdly, and most importantly, consensus has no part to play in science. Consensus, democratic voting, etc. are tools of politicians, not of scientsts. The equivalent tool of science is replicable evidence. In fact, very many important scientific breakthroughs occurred as a direct consequence of researchers ignoring or actively contesting the consensus. Charlatans invoke the "consensus" claim when the scientific argument for their case is weak or absent. You do not hear real scientists claiming, "The consensus is that a satellite in a circular orbit with an altitude of 35,786 km will be geosynchronous." Not only does consensus have no place in real science, it is antithetical to it.
Quite simply, if it is consensus then, by definition, it is not science.