To limit and control the amount of carbon dioxide (CO₂) added to the atmosphere, special taxes, called carbon taxes, have been proposed and in some cases adopted, on fuels containing carbon. Fuels such as coal, gasoline, heating oil, and natural gas, release energy by combining the carbon they contain with oxygen in the air, to produce carbon dioxide. Increased use of carbon-containing fossil fuels in modern times has greatly increased the rate at which carbon dioxide is entering the atmosphere. Measurable increases in atmospheric levels of the gas have been detected. Since carbon dioxide is the principle component of so-called greenhouse gases, changes in its concentration in the earth's atmosphere are a concern. Increases in the level of carbon dioxide, and other greenhouse gases such as methane, nitrous oxide, ozone, and man-made chlorofluorocarbons can be expected to result in warmer temperatures on the surface of the...