I searched on the words "vapor" and "vapour" and found nothing. I also search on the word "water" and found nothing relevant to my question.
I'd try looking at "Physical Science Basis" and "Impacts, Adaptation and Vulnerability" reports; try the Summaries for Policymakers first, and the full reports if those don't have what you need (though go straight to the full reports if you have time -- they can be fascinating!).
I hope that helps.
I guess the "for the Physical Science Basis" report is something different that I haven't found yet.
With JavaScript on, apparantly the UX concept is 'Easter eggs': There are 4 images arranged horizontally at the top. If you click image, one the section beneath it changes. The second image is "Physical Science Basis".
All that work making the reports accessible, hamstrung by web design.