Because of the enormous credibility of the Intergovernmental Panel on Climate Change's reports, and because they suggest that human-induced climate change is a very real risk, opponents of action on climate change must attack the IPCC or completely cede the scientific high ground in the debate.
With the release of the latest IPCC report, a whole new crop of specious skeptical arguments has arisen. Here's a good example, which appeared in this week's Weekly Standard:
One possible reason for the timing is that there appear to be some significant retreats from the 2001 IPCC report. The IPCC has actually lowered its estimate of the magnitude of human influence on warming, though we shall have to wait for the full report in May to understand how and why. Only readers with detailed knowledge of the 2001 report would notice these changes, which is why most news accounts failed to report them.
As with most skeptical arguments, there is a grain of truth here, sitting under a mountain of deception.