Over the course of its 22-year history, the IPCC has become "too cumbersome, too bureaucratic, too big, too slow, and too much aligned with government interests and not the people's interests," writes climate scientist Michael Hulme in an e-mail.
Dr. Hulme, a researcher at the University of East Anglia in England, is one of the scientists contributing to the recommendations. He also has served as a lead author and a contributing author to IPCC reports.
One result, he says, is a group that has gained too much authority, lending its pronouncements a scientifically and politically unhealthy air of infallibility.
Beyond what he and others see as an increasingly ossified organization, the IPCC faces a broader challenge:
Countering the growing impression, which critics say it hasn't discouraged, "that we march from ignorance and uncertainty toward enlightenment and certainty" in climate science, says Roger Pielke Jr., a professor at the University of Colorado at Boulder who specializes in science policy. "The reality is that over time, uncertainties can also increase." Read more.