As conservatives go, I’m a squish on global warming. So I’m inclined to be a bit more sympathetic to McCain on the subject than most conservatives. But the more I listen to him on the subject, the less sense I can make of his position.

A few times over the weekend, he said that we should avoid a carbon tax because it would function as gas-tax increase. Instead we should go with his plan for “cap and trade”: The government would set a cap on emissions and create an artificial market in carbon-emission permits. There is a debate between proponents of each approach, but for the most part people who want the federal government to discourage emissions see them as interchangeable, and so do people who oppose any such federal intervention.

And it’s hard to see what difference it would make from McCain’s perspective. If you apply a cap to the oil industry, it’ll take a hit that will be partly passed on to consumers, right? So gas prices will go up by government fiat. It would be just like a tax, although the government won’t get the money.

McCain says that gas prices will go down, because cap and trade will stimulate the development of new green energy sources. I don’t see how this works at all. If the prices go down, won’t consumption just go right back up, defeating the whole point of the exercise? And if this fanciful model worked, carbon taxes would have the exact same effect, right?

I ran into former senator Phil Gramm, a co-chairman of McCain’s campaign, and asked him if he’s a cap-and-trade man. “No, I’m not,” he said. He added that if he did favor using governmental action to reduce carbon emissions, he would prefer cap-and-trade and the promotion of nuclear power. “One makes the government richer, one [just] makes the environment cleaner.”