In the Inkstain comments, James criticizes Steve for supporting the idea that an intelligent lay person could think the high (dangerous) end is more likely:
Depends what you mean by high end versus low end, but if you assume that the presentation is intended to be an unbiased one according to the approximate consensus of a large number of experts then your “intelligent lay person” is simply claiming that these experts are all wrong, with no apparent justification for such an assertion.James is criticizing Steve's overweighting the high end outcome against the consensus while implicitly supporting his own underweighting of the high end position.
If someone puts up some argument as to why the science is wrong, that’s another matter entirely. Most likely such a person would be a scientist with some demonstrated understanding of the area, although in principle anyone could do it.
So what am I, an allegedly intelligent layperson, supposed to think of this? My starting point is Fred Hutchison, the intellectual pioneer I once wrote about who believes he's disproven relativity, evolution, and global warming. First thing is, don't be Fred.
Second, if you're going to predict something that goes beyond the consensus, you better have darn good reasons, and here I think both James and Steve are distinguishable from Fred. James makes a scientific claim, and his referees didn't contradict him. Steve points out "known unknowns" expressed in more depth by Eli Rabett could make the high end more likely. The consensus doesn't speak about the unknowns since they're unknown, but if you don't count on luck, then it seems there's a decent chance that at least some of them will be increase the high end odds. The consensus position has also seemingly ignored James' argument. In both cases, and distinguished from Lindzen, Pielke Sr., and Fred Hutchison, these arguments seem reasonable and don't directly contradict the scientific consensus.
They do contradict each other though, and I have no basis myself to say which is right. I will argue this, though: there's nothing wrong with saying where your gut tells you the likely scientific conclusion will be, so long as you don't pretend that prediction is scientific. For example, I'm predicting that whenever the Fifth Assessment Report comes out (not the one due next month), it will say that it's more likely than not that AGW has already caused intensification of tropical storms. This goes beyond the consensus position that only discusses future warming.
Am I to be condemned for saying this? Someone can do better than condemn me for such foolishness, and bet me over it instead.
*I think Fleck overstates his criticism, btw, by implying that Roberts' position supports using your informed gut to contradict the consensus. Roberts would disagree with that, based on his full post.