You are correct that water vapor is the primary greenhouse gas. Despite that, water vapor emissions are not generally considered to impact warming. I think that is because the water content of the atmosphere is already in balance due to the massive amount of evaporation and condensation (e.g. rain) that is constantly going on. If we dump some extra water vapor into the atmosphere, that will balance out as a bit of extra rain and/or a bit less evaporation somewhere else; atmospheric water vapor levels won't change.
I don't know whether a large scale, ongoing intervention, such as permanently flooding a large area, could nudge this balance sufficiently to result in a sustained (if small) increase in atmospheric water vapor content, and thus an increase in warming. An interesting question!
I don't know whether a large scale, ongoing intervention, such as permanently flooding a large area, could nudge this balance sufficiently to result in a sustained (if small) increase in atmospheric water vapor content, and thus an increase in warming. An interesting question!
I wrote about the role of water vapor in global temperatures a while back at https://climateer.substack.com/i/60052576/you-thought-the-ma.... My primary source was an IPCC report, specifically the sidebar on pages 8 and 9 of this PDF: https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapt....