With respect, “Statistician”, your post is wrong-on-the-facts …
“We imposed an a priori criterion that a researcher must have authored a minimum of 20 climate publications to be considered a climate researcher, thus reducing the database to 908 researchers. Varying this minimum publication cutoff did not materially alter results (see Materials and Methods).”
The PNAS article is free, and the methods of the study are described in comprehensive detail … so folks can check for themselves how accurately the level of consensus was gauged. The short summary is, they queried a pretty fair sample of every serious climate researcher in the world.
Expert credibility in climate change