Chapter 8 of the IPCC AR4 report is about "Climate Models and Their Evaluation".
One of the weaknesses of these models is in how they deal with clouds, and in particular, feedback to the climate from cloud formation. This is acknowledged by the IPCC, for example on page 593, "The relatively poor simulation of these clouds in the present climate is a reason for some concern."
The main section on cloud feedbacks is pages 635-638, section 126.96.36.199. Clouds exert a negative feedback on global warming, since warming leads to more evaporation of water, which leads to more cloud formation, which reflects sunlight. In the jargon of climate science, the global mean cloud radiative feedback (CRF) is negative.
This section illustrates the usual biased commentary by the IPCC on the literature of the field. For example, a paper by skeptic Richard Lindzen and colleagues is referred to with the remark "Lindzen et al (2001) speculated that ...". A paper by Somerville (Cloud optical thickness feedbacks in the CO2 climate problem, Advances in Space Research, 5, 209-212, 1985) that explains clearly the negative feedback mechanism, is not cited.
Steve McIntyre notes that substantial parts of this section are very similar to a review article by Bony et al, 2006, but that key parts of the text have been changed in a way to downplay the negative feedback. The review article has 14 authors, and all of them are involved with writing the chapter, one as coordinating lead author (David Randall) and three others as lead authors.
Here are some comparisons between the two versions:
In the first example, the "strongly negative CRF" is deleted from the IPCC version.
In the second, the argument for higher albedo is not mentioned at all.
In the third, the word "strong" has been removed, and questioning language such as "suggestion" and "might" have been inserted.
The two versions were written by the same 14 authors, at more or less the same time (2006), but the science has been distorted in the IPCC version, to try to weaken the argument for negative feedback (and thus strengthen the argument for dangerous global warming).