David Roberts, an environmental writer for Grist.com, has written a great critique of the coal industry's "clean coal" campaign, pointing out that "it's an obvious scam -- easily exposed, easily debunked. Just because it's obvious, though, doesn't mean the media won't fall for it. Indeed, the entire 'clean coal' propaganda push is premised on the media's gullibility." Roberts notes, as have others, including a recent report by the Center for American Progress (CAP), that "the companies funding 'clean coal' PR aren't spending much on carbon capture and sequestration (CCS) research." They have therefore made no progress in reducing the greenhouse gas emissions that make coal a potent cause of global warming. The concept of "clean coal" was invented to answer concerns about global warming, and its advocates play a rhetorical game of bait-and-switch on precisely this topic. When pressed about how coal can be clean, Roberts observes, "they revert to the other definition of 'clean' -- the notion that coal plants have reduced their emissions of traditional air pollutants like particulates and mercury (as opposed to greenhouse gases)."