Now let’s suppose a most improbable, rhapsodic lobbying success for Mr. Gore, Mr. Khosla and folks on their side of the table–say, a government mandate to replace half the gasoline consumed in the U.S. with a carbon-neutral alternative. This would represent a monumental, $400 billion-a-year business opportunity for the green energy lobby. The impact on global carbon emissions? Four percent–less than China’s predicted emissions growth over the next three or four years.

Don’t doubt that this is precisely the chasm that keeps Mr. Gore from running for president. He could neither win the office nor govern on the basis of imposing the kinds of costs supposedly necessary to deal with an impending “climate crisis.” Yet his credibility would become laughable if he failed to insist on such costs. How much more practical, then, to cash in on the crowd-pleasing role of angry prophet, without having to take responsibility for policies that the public will eventually discover to be fraudulent.