Study: Renewables played crucial role in U.S. CO2 reductions

Summary

After a nearly 20-year upward trend, U.S. CO2 emissions from energy took a sharp and unexpected turn downwards in 2007. By 2013, the country’s annual CO2 emissions had decreased by 11% – a decline not witnessed since the 1979 oil crisis.
Experts have generally attributed this decrease to the economic recession, and to a huge surge in cheap natural gas displacing coal in the U.S. energy mix. But those same experts mostly overlooked another key factor: the parallel rise in renewable energy production from sources like wind and solar, which expanded substantially over the same 2007-2013 timeframe.
Between 2007 and 2013, wind generated electricity grew almost five-fold to 168 TWh and utility-scale solar from 0.6 TWh to 8.7 TWh. During the same period, bioenergy production grew 39 percent to 4,800 trillion BTUs.
Given these increases, how much did renewables contribute to the emissions reductions in the United States? In a paper published this month in the journal Energy Policy, we use a method called decomposition analysis to answer just that.