Yes, you can register to be a reviewer. No “climate science” degree required. That certainly qualifies Dr. Michael Mann.
The Expert Review of the First Order Draft Draft of the Working Group I Contribution to the IPCC Sixth Assessment Report will run from 29 Apr 2019 to 23 Jun 2019. Registration will be open until 2019-06-15 23:59 (CST).
This is interesting:
Self Declaration of Expertise
I declare that I have scientific, technical or socioeconomic expertise in one or more areas relevant to the report and am therefore qualified to serve as an Expert Reviewer on the chapter(s) indicated.
My advice, go for it, follow the link: