The scientific consensus has been that greenhouse gas (GHG) emissions reductions on the order of 80 percent from 1990 levels are necessary to avoid dangerous temperature increases. Now, however, scientists are indicating that even more drastic emissions reductions may be necessary because of delays in getting on the 80-percent reductions trajectory. At the December 2011 climate talks in Durban, South Africa, delegates from 194 countries agreed to begin talks that will lead to emissions reduction commitments from major GHG emitters, including the United States, China, and India. This agreement, which includes major emitters from developed and developing nations, is an important step forward.

Achieving even the global emissions reduction goal of 80 percent below 1990 levels is an enormous challenge. The electric sector will play a major role in achieving emissions reduction goals due to the volume of its emissions and the ability to substitute electricity for more polluting forms of energy use. It is the sector emitting the most GHGs, responsible for 41 percent of world CO2 emissions. The task of decarbonizing the electric sector is a daunting one; the electric sector is not only the largest source of global GHG emissions, but trends indicate that electricity consumption will grow, despite energy efficiency policies. Fortunately there is already good progress in development of strategies to decarbonize the electric sector. End-use energy efficiency is the most economical decarbonization mechanism and will be an essential component in the transition to a low carbon electric sector. The focus of this paper is on the other components, which have to do with electric power supply.