The IPCC was created in 1988 to establish a consensus within climate science wrt climate change.
The Science of Climate Change. Science 18 May 2001
The work of the Intergovernmental Panel on Climate Change (IPCC) represents the consensus of the international scientific community on climate change science. We recognize the IPCC as the world's most reliable source of information on climate change and its causes, and we endorse its method of achieving this consensus. Despite increasing consensus on the science underpinning predictions of global climate change, doubts have been expressed recently about the need to mitigate the risks posed by global climate change. We do not consider such doubts justified.
The balance of the scientific evidence demands effective steps now to avert damaging changes to Earth's climate.
In effect, whilst dissenting voices were recognised apparently they were not allowed to influence the consensus.
Unfortunately, the Climategate scandal has raised some questions with respect to the methods by which that consensus was reached and is being defended. Whilst suspicion isn’t proof of guilt this inevitably casts some doubt over the consensus itself.
A number of investigations into Climategate are planned or ongoing. http://ct2765.blogspot.com/2010/03/climategate-cru-e-mails.html
In addition the UN is reported to be planning its own investigation into the working of the IPCC.
UN to commission independent scientific inquiry into IPCC. Guardian 26 February 2010
UN climate body to appoint scientists to review climate change panel as UK climate change secretary writes to Rajendra Pachauri to express concern over 'damaging mistakes'
The experts will look at the way the Intergovernmental Panel on Climate Change (IPCC) operates and will recommend where they think changes are needed.
There appears to be sufficient doubt to warrant the investigations as cited above. We need to wait until those investigations have reached a conclusion. Only then will the reliability of the IPCC processes and findings be fully understood.