Proponents of carbon trading schemes in the US have often felt like a bride jilted at the altar. In 2009, they were flush with optimism after the House of Representatives passed the Waxman-Markey Bill, which would have established a federal cap-and-trade programme to reduce carbon emissions, but their hopes were crushed when the bill failed to pass the Senate. Their hearts broken by the federal government, carbon traders have instead sought solace in the arms of the 10 states that have state or