The Politico is reporting that carbon dioxide emissions are at a 20-year low: "In a surprising turnaround, the amount of carbon dioxide being released into the atmosphere in the U.S. has fallen dramatically to its lowest level in 20 years, and government officials say the biggest reason is that cheap and plentiful natural gas has led many power plant operators to switch from dirtier-burning coal."
For related information from the Energy Information Administration (EIA), see here.