The IPCC is supposed to provide a detailed and comprehensive review of the literature. However, as we have seen on many other occasions, it does not do so, providing instead a highly biased and selective review. A good example is on the issue of the surface temperature record, discussed in AR4 chapter 3.  Many papers have been published raising questions about the reliability of these measurements, on such issues as:

•  The extent of the "urban heat island" effect.
•  The validity of the numerous "adjustments" applied to the temperature measurements. 
•  The poor siting of many temperature recording stations.

These papers are simply ignored by the IPCC.  For a long list of such papers, see the discussion by Roger Pielke Sr.

(Pielke also notes another example of IPCC bias here,  regarding lack of discussion and references on research into the effects of changing land use, despite the recommendations on a National Research Council report in 2005.)