The Center for Climate Strategies just published this new report which deconstructs data from US-DOE. Projected greenhouse gas emissions for 2020 are down by 23 % compared to 2007 projections. The main drivers in the decline are a range of regulatory policies, accounting for almost 3/4 of the decline in emissions. The economic slump accounted for 18 % of the drop, while shifting from coal to natural gas for electric generation accounts for just 6 % of the drop. CAFE standards, and state energy efficiency standards each account for more than twice as much in greenhouse gas reductions than the switch to gas. In fact, energy efficiency standards are projected to reduce emissions more than twice as much as renewable portfolio standards.