'U.S. has been steadily increasing its energy efficiency (or reducing its energy intensity) at least since WWII due to technical innovation – all that's required is for govt to stay the hell out of the way' -- 'Since 2007...carbon emissions have fallen 6% over past 5 years. Some of that has been due to recession...But not all. The drop has also come as cheap natural gas has shuttered coal plants. & some of decline can be attributed to various conservation measures'