Not even a worldwide depression that permanently lowers global economic output and emissions to, say, 1970 levels, would stop CO2 concentrations from rising over the remainder of the century.

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Right now the U.S. economy is "decarbonizing, " that is, lowering the amount of carbon emissions per dollar of economic output, at a rate of about 1.5% per year.

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Furthermore, there is a positive environmental impact as natural gas from shale, for example, produces roughly 50% of the carbon dioxide emissions compared to coal for the same energy output.

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Nuclear power was repackaged as clean energy, becoming the centerpiece of the DPJ's plan to cut carbon emissions by 25%, in relation to Japan's 1990 output levels, by 2020.

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Such a program would cap greenhouse gas emissions at certain levels, and allow more efficient energy producers to sell emissions permits to other, less efficient companies, thereby creating market-wide incentives to reduce carbon output.

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By changing operating procedures and burning a higher grade of coal, Midwest boosted output from the 40-year-old plants 12% last year--while reducing emissions.

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When anticipated supply is sufficiently high, gas undercuts coal as the fuel of choice for electrical generation, which results in reduced carbon dioxide emissions, as natural gas produces only about 50% to 70% of the carbon dioxide per unit output (depending upon your metric) that coal does.

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