Kevin Trenberth has his own response to Spencer and Braswell in Remote Sensing. It's billed as a commentary rather than a proper paper.
The first thing you notice is this:
Received: 8 September 2011 / Accepted: 8 September 2011 / Published: 16 September 2011
so presumably it's fair to say that this is not a peer-reviewed contribution to the literature.
I've not had time to read it yet, but my eye alighted upon this sentence.
There are obvious differences among models. As noted by Dessler , it is important to sample all model results and not just select a few that may have certain specific deficiencies, as was done by SB11 .
Which is a surprising thing to say given that Spencer has already pointed out that he has picked models that span the range of sensitivities. I note that Spencer's blog post is dated 7 September. Presumably then Trenberth is guilty of being in such a hurry to get his rebuttal out that he managed to preempt Spencer's explanation.
However, given that the blog-post explanation merely reiterated the one in the Spencer's original paper, we might conclude that Trenberth was also in too much of a hurry to actually read that either.
Steve M has some rather more considered thoughts, which really make Trenberth look rather grubby. Then there's this:
Clouds were the major source of uncertainty in climate models in Charney 1979 and remained so in IPCC AR4 (2007). If Dessler 2011 did in fact show that "cloud effects are small", this would be an epochal achievement in climate science. Given that a preprint of Dessler 2011 only became available on Sept 2, 2011, there has been little opportunity to analyse its results so far. Whether Dessler 2011 really proves that "cloud effects are small" remains to be seen. If, like Dessler 2010, it makes such assertions based on r2 of ~0.01, I think people could reasonably disagree on whether such far reaching claims had been firmly established.
One has to appreciate the achievement of Trenberth in giving us so much to laugh about.