Quartz: US carbon emissions from energy production last year hit the lowest levels since 1994, according to a report today from the federal Energy Information Administration: Carbon emissions have now declined every year since 2007 save for 2010. The start of that period coincides, of course, with the great recession. The economic slowdown reduced energy needs as well as prompting more energy efficiency; but you can also thank the natural-gas boom that began around the same time, and which has shifted electricity...