Shifting to more fuel-efficient transportation can sharply reduce carbon emissions. Projections based on recent trends would have these emissions nearly doubling by 2010. However, if a combination of improved mass transit, greater use of bicycles for short trips, and a carbon tax kept the world fleet to 500 million cars in the year 2010, and if these vehicles averaged 50 miles to the gallon rather than the current 20, automobile carbon emissions would fall to 273 million tons, half of what they are today. Carbon emissions can also be lowered by improving the efficiency of electricity-using devices. This accounts for 28 percent of the 1.5 billion tons of global carbon emissions coming from fossil fuels.
Electricity is used in many different ways, all of which can become far more efficient .
More efficient lighting systems have a particularly large potential. Worldwide, lighting accounts for about 17 percent of electricity use or 250 million tons of annual carbon emissions. These emissions continue to grow rapidly as electric lighting is used more widely in developing countries. If the world were to double the efficiency of these systems by the year 2010, it could cut a projected 450 million tons of carbon emissions from lighting in half, to 225 million tons. For common household use, compact fluorescent bulbs using 18 watts of electricity can already provide the same illumination as incandescent bulbs that use 75 watts.