This is fascinating: over the past decade, the rise of Natural Gas and the fall of Coal has helped drive electricity production as a source of CO2 emissions down from the top spot to #2 after transportation:
For the first time in 40 years, power plants are no longer the biggest source of U.S. greenhouse gas pollution. That dubious distinction now belongs to the transport sector: cars, trucks, planes, trains and boats.
The big reversal didn’t happen because transportation emissions have been increasing. In fact, since 2000 the U.S. has experienced the flattest stretch of transportation-related pollution in modern record keeping, according to data compiled by the U.S. Energy Information Administration. The big change has come from the cleanup of America’s electric grid.
Note the post GFC fall off in transportation emissions as miles traveled plummeted; that has completely recovered, but vehicles are more efficient today.