Ronald Bailey on cutting GHGs in his piece over at Reason:
First, let’s consider just how big a technological challenge it will be to cut greenhouse gases by 70 percent. Former General Electric executive Don Dears provides some sense of the size of the challenge when he points out that an 80 percent cut means reducing U.S. carbon dioxide emissions from about 6 gigatons (1 gigaton = 1 billion tons) today to 1 gigaton by 2050. One gigaton is the amount the U.S. emitted around 1920, when there were just 100 million Americans.
Now let’s widen the focus to include cuts that the whole world will need to make in order to stabilize concentrations of greenhouse gases in the atmosphere. Currently, the world emits about 26 gigatons of carbon dioxide. In 2007, the International Energy Agency (IEA) projected that by 2030 carbon dioxide emissions will rise by 57 percent to 42 gigatons per year. Climate researchers estimate that in order to stabilize atmospheric concentrations of carbon dioxide at 450 parts per million (ppm) (where there’s a good chance that average temperatures would increase by less than 2 degrees Celsius) emissions must be cut by 80 percent from current levels by 2050. This means that the world will have to produce considerably more energy while emitting only 5 gigatons of carbon dioxide annually. If IEA estimates of future energy demand are accurate, this implies that the world would have to find the equivalent of 37 gigatons of carbon-free energy by 2030.
So just how big is a gigaton? Cutting a gigaton of carbon dioxide is equivalent to replacing 1,000 conventional 500-megawatt coal-fired electric generation plants with zero-emission plants. Zero-emission might mean coal-fired plants using carbon capture and sequestration (CCS) technologies, perhaps costing as much as $80 per ton. By some estimates, CCS would increase the cost of producing electricity by 25 to 40 percent. Cutting another gigaton would be equal to building 500 one-gigawatt nuclear power plants. The world currently has 439 nuclear plants in operation. One gigaton more would require increasing the number of windmills operating in the U.S. by 150-fold, or increasing solar photovoltaics by 10,000-fold. It would take farming an area 15-times the size of Iowa to produce the biomass to replace 1 gigaton of carbon dioxide emissions.