The average global temperature is already certain to increase by 2 degrees  Fahrenheit. It will increase by far more, with other major attendant changes in  climate, unless we reduce global emissions of greenhouse gases (ghgs) by at least  50% by 2050. The effects of failure to accomplish that daunting task will be  catastrophic. They include the deaths of millions and the displacement of scores of  millions. The worst effects will be experienced in places like central India and  central Africa, which will suffer extreme desertification, and in many island states,  coastal Indonesia and large portions of Bangladesh, which will be underwater. The  US will suffer some significant adverse effects, however, including desertification of  much of the southwest, submersion of significant parts of Florida and Louisiana,  increases in the incidence and severity of storms of various types, and a 13 degree  increase in the average summer temperature in Washington, DC.

The main impediments to effective climate change mitigation are economic and  political. Hydrocarbons are much less expensive than carbon-free alternative sources of energy. I will focus primarily on the electricity sector, which accounts for  nearly half of CO2 emissions,16 but the economic and political impediments are  similar in the transportation and industrial sectors.