This is the question asked by Phil Plait in his The Very, Very Thin Wedge of Denial from Slate.
To me, one of the most fascinating aspects of climate change denial is how deniers essentially never publish in legitimate journals, but instead rely on talk shows, grossly error-laden op-eds, and hugely out-of-date claims (that were never right to start with)…Despite a lot of sound and fury from the denial machine, deniers have not really been able to come up with a coherent argument against a consensus.
And take a look at this chart for visual context:
