Bill McKibben gets Bjorn Lomberg exactly right here:
Doubtless scientists and economists will spend many hours working their way through Cool It, flagging the distortions and half-truths as they did with Lomborg's earlier book. In fact, though, its real political intent soon becomes clear, which is to try to paint those who wish to control carbon emissions as well-meaning fools who will inadvertently block improvements in the life of the poor. Just ask yourself this question: Why has Lomborg decided to compare the efficacy of (largely theoretical) funding to stop global warming with his other priorities, like fighting malaria or ensuring clean water? If fighting malaria was his real goal, he could as easily have asked the question: Why don't we divert to it some of the (large and nontheoretical) sums spent on, say, the military? The answer he gave when I asked this question at our dialogue was that he thought military spending was bad and that therefore it made more sense to compare global warming dollars with other "good" spending. But of course this makes less sense. If he thought that money spent for the military was doing damage, then he could kill two birds with one stone by diverting some of it to his other projects. Proposing that, though, would lose him much of the right-wing support that made his earlier book a best seller -- he'd no longer be able to count on even The Wall Street Journal editorial page.
The "why do X when we could use that money to do Z" argument is very, very useful to readers. By evaluating what X and Z are, you can generally tell what the author is trying to do. For instance: "Why pay trillions to continue a failed war in Iraq rather than use some of that money to enact universal health care?" here, your author thinks the Iraq War is a stupid idea and universal health care a good idea, and would like to see priorities shift. That's one form of the argument -- call it reprioritization.
There's another, though, which is sneakier. "Why do [largescale policy that will actually fix the problem at hand] when we could [enact minor, industry-friendly legislation that is totally insufficient to the task]?" This is used on all sorts of issues: Why comprehensively reform the health care system when we could give everybody a tax exemption? Why reform education when we could demonize teacher's unions? Or, in Lomberg's case, why cap carbon emissions when we could hand out malaria nets? These arguments do not argue for reprioritization -- in fact, they accept the stated priorities of the reformers. What they try and do, rather, is disrupt actual reform by offering weak, insufficient solutions that powerful interests prefer. It's the status quo in reformist clothing, and all the more dangerous for it.