What exactly is a published climatologist? I am trying to get Gallup to do a scientific poll of published climatologists to greatly strengthen the credibility of the 97% consensus. 

This must start with very excellent formal definitions of these two key terms: "published" and "climatologist". 

The end result of this process is intended to be an exhaustively comprehensive list of: "published climatologists". 

What is the best process for deriving the definition of these two key terms to maximize the plausibility of their specification? 

I am shooting to actually directly ask all of the world's published climatologists using a very high quality (comparable to Gallup polls) survey that has only true/false or multiple choice answers. 

The current best guess of the definition of a published climatologist (based on all the feedback) requires three factors:

(1) They must have at least one published paper directly pertaining to climate change. 

(2) This must have been in a peer reviewed academic journal directly related to climatology or meteorology. 

(3) They must have a PhD degree in climatology or meteorology. 

This will screen out many very well qualified individuals because we cannot afford to have any unqualified individuals in this set.
Not answering the question asked, but the underlying motivation:

The level of consensus hasn't been verified by a poll. The way the 97% figure has been arrived at, AIUI, is by going through every single peer-reviewed and published paper on the topic of anthropogenic climate change and looking at whether says that it does or does not exist, and then assigning these views to the authors of the papers. Why bother with a sampled poll when you already have studies using the entire literature? 

If you want more detail on the methods used, the various studies that came up with the 97% and similar figures are themselves peer-reviewed and published. This is a review paper looking at them.