May I add to that? Thank you.
I wouldn't want the impression to be left that there is any political interference in the actual writing of the IPCC documents. In the three assessment reports, which I've been part of, the actual writing was left up to the authors. What must be discussed was not dictated; what was done was a review of the various aspects of the climate system under broad chapter headings. Everything from the beginning to the end of a chapter was up to the authors of the chapter, who are practising scientists in the field.
IPCC does not do research. It assesses existing research, and that's very important to get across. IPCC is not conducting studies; it's not going out and running models. IPCC is like a massive attempt at writing a review article that assesses our current understanding of the science of climate change, which is then passed to policy-makers.
The people doing it are not the policy-makers; they pass the best science available to the policy-makers, so they can make the best policy decisions that they deem should be made.