Though I disagree with McArdle on the magnitude of potential warming, I think her assessment of Waxman-Markey is dead on:
But the real question, I think, is whether the low cost is a feature or a bug. The only way a bill is going to have an impact is if it causes real financial pain to American households--enough to get them to change their behavior. Waxman-Markey obviously is not going to do that. And indeed, the projections of its effect on global warming are entirely negligible.
So the reason to get this mad about Waxman-Markey is either that you think it provides a framework for future action, or that you think it will persuade China and India to get on board. The latter is, I think, entirely wishful thinking on the part of American environmentalists. China is not going to let its citizens languish in subsistence farming because 30 years from now, some computer models say there will be some not-well-specified bad effects from high temperatures. Nor is India. Global warming isn't even high on the list of environmental concerns they'll want to attack as they get rich; local air pollution is far more pressing. Thinking that we're somehow going to lead them by example is like thinking that poor rural teens are going to buy electric cars because Ed Begley jr. has one.
No, I think the argument has to rest on the notion that Waxman-Markey gives us a framework to advance. And it might. But then again, Europe's much-vaunted system has had multiple spectacular failures, and the only reductions it has actually achieved seem to come largely from controversial offsets with large auditing problems.