Last spring Tennessee Republican Rep. Marsha Blackburn asked Al Gore during a House hearing if his investments in green energy meant he would benefit personally from cap and trade. "If you believe that the reason I have been working on this issue for 30 years is because of greed, you don't know me," Mr. Gore responded (and, yes, according to two reporters present, he sighed). Mr. Gore is quite right that his arguments should be judged on their merits, not on his investments. He's wrong to think his investments are irrelevant, and, even more, that sincerity is dispositive of anything. Sincerity is no substitute for disinterestedness. Here are a couple questions: When so much of his position and prestige are invested in a predicted climate crisis, is Mr. Gore likely to be open to contrary evidence? Is he likely to be particularly fastidious about whether proposed steps will actually have an effect on global warming if they also happen to benefit his investments? Ms. Blackburn's challenge was in a sense late. Mr. Gore long ago jumped over to the side where salesmanship, by whatever means, was the trumping priority. As far back as 1989, he insisted there was "no dispute worthy of recognition" about the danger of manmade climate change. By now, he titularly heads a vast establishment with a stake in one side of the argument.