Dear moderators,<\/p>\n
I appreciate that you opened this topic pertaining to the role of water in Earth climate, although with a narrow (and in my opinion somewhat unfortunate) focus on anthropogenic \u201cwater vapour emissions\u201d. <\/p>\n
1) I put this framing in quotes because I think that reduction of anthropogenic interferences with global water cycle and especially with land hydrology to \u201canthropogenic water vapour emissions\u201d is neither possible nor reasonable. <\/p>\n
2) I am afraid that discussing \u201d water emissions\u201d from fuel combustion, irrigation (or, e.g. laundry drying :-)) without considering possible (and in my opinion possibly quite significant) \u201cnegative emissions\u201d may be seriously misleading. There may be, and likely were, many possible sources of a such \u201cnegative emissions\u201d, for example: soil destruction, land deforestation, wetland drying, landscape drainage by agricultural meliorations, by river regulations and by building infrastructure that prevents soaking and speeds up runoff.<\/p>\n
3) In view of the circumstance that these \u201cnegative emissions\u201d were not mentioned in your post, I am somewhat afraid that they were not considered in the attribution of 4% of the \u201cincrease over background\u201d (Do you mean an increase in average global absolute air humidity?) to \u201cdirect anthropogenic sources\u201d. If so, the attribution would have been very questionable already for this single reason.<\/p>\n
4) Moreover, I have a feeling that your post omitted the hint that changes in latent heat flux accompanying \u201cpositive\u201d or \u201cnegative\u201d \u201cwater vapour emissions\u201d could have a significant influence on mean global surface temperature (GMST). As suggest results of a modelling study published by Lague et al<\/p>\n