I still have not found an answer to the original question but i have been thinking about this.
Even though water is a bigger green house gas its not as clear cut as that when it comes to global 'warming'. Some of you may be aware of something called global dimming. The effect was first really noticed in the US after 911 when all the flights were grounded.
There is a good documentary on it i watched a few years ago, i recommend
anyone thats interested in global warming watch it
If you go by some of that theory more water vapor that enters the air could produce more clouds to reflect light back into space it could just even things out if other pollutants are reduced its really impossible to hypothesize. It shows that its not as clear cut one might think.