David Victor: "The IPCC process is dominated by insiders":

Climate change: Embed the social sciences in climate policy : Nature News & Comment

...the IPCC must become a more attractive place for social-science and humanities scholars who are not usually involved in the climate field and might find IPCC involvement daunting. The IPCC process is dominated by insiders who move from assessment to assessment and are tolerant of the crushing rounds of review and layers of oversight that consume hundreds of hours and require travel to the corners of the globe. Practically nothing else in science service has such a high ratio of input to output. The IPCC must use volunteers' time more efficiently.