(via Tom Nelson) Ken Caldeira resigns as IPCC lead author, saying:

New Directions for the Intergovernmental Climate Panel – NYTimes.com

Clearly, at the outset, the early IPCC reports played an important role showing that there was a high degree of consensus around the reality and basic science of human-induced climate change. It was important to show that, despite a few climate-science deniers, the fundamental science was well-accepted by the mainstream scientific community.

But can anybody point to any important positive outcomes resulting from the IPCC AR4 process? [AR4 is shorthand for the panel’s fourth assessment, which was published in 2007.] Is there reason to expect a greater positive impact from the IPCC AR5 process? [This is the forthcoming fifth assessment of climate science and policies, coming in 2013 and 2014]

I am all for scientific reviews and assessments, and I think the multi-model comparisons reviewed by the IPCC have been especially useful. However, it is not clear how much additional benefit there is to having a huge bureaucratic scientific review effort under UN auspices…

(As an aside, I recently resigned as a lead author of an IPCC AR5 chapter simply because I felt I had more effective ways of using the limited amount of time that I have to engage in scientific activities. My resignation was made possible because I believe that the chapter team that I was part of was on the right track and doing an excellent job without my contribution. Had I had a scientific criticism of my chapter team, you can be assured that I would have stayed involved. So, my resignation was a vote of confidence in my scientific peers, not a critique. It is just not clear to me that, at this point, working on IPCC chapters is the most effective use of my time.