Most groups agree, as does Obama, that the United States must cut carbon dioxide emissions by at least 25 percent by 2020 and 80 percent by midcentury to avoid some of the direst consequences predicted by computer models. This puts them in conflict with a "discussion draft" of a bill being floated by House Committee on Energy and Commerce Chairman John Dingell of Michigan, a longtime supporter of the Detroit auto industry. Dingell's bill outlines much more lenient cuts in the short term. As it happens, Dingell could lose his chairmanship to Rep. Henry Waxman, who—to many environmentalists' delight—would promote a more aggressive climate change approach.
One disagreement among environmentalists is how the government should spend the money—trillions of dollars over several decades, according to estimates—that an emissions credit auction would generate. Some groups want to see that money invested in conservation or green technology. Others, however, say that it was that type of earmarking that created tension last time around and helped sink the bill. One idea being floated: giving the money back to taxpayers, as a sort of divided payment.