MemeWatch: "The science isn't settled"

On Bill Maher the other night, conservative talk radio host Amy Holmes trotted out the familiar right-wing talking point on global warming: "the science isn't settled." This then leads to a familiar, well-worn argument over various minutiae of the debate (what about the errors regarding the claim that Himalayan glaciers are melting? etc.). It would be nice to see someone like Maher respond by asking what it would mean for the science to be "settled." Would this mean that everyone who claims some kind of scientific credential would have to agree. If that were the case, the science still wouldn't be settled on whether the earth is round or flat. It would be a slightly less inane media world if every time someone tried this line they were forced to outline some kind of meaningful definition of what "settled" science is. I suppose the resulting danger would be some kind of vernacular postmodernism in which Republicans claimed that all scientific consensus is merely an arbitrary closure, an attempt to pin down the endless sliding of signifiers. Soon Frank Luntz will be talking like that -- when he isn't criticizing the lefty academy for preaching some combination of cultural relativism and Marxism.