It's very interesting the spin in this article or in the study. They did not study the green house gases blamed for global warming. They studied water vapor. They admit that with the increase in temperature there would be an increase in vapor. I don't think it's disputed that there has been a slight warming over the past few decades, so naturally you would expect more water vapor, so this study simply confirms this. How the "so called" greenhouse gases and global warming theory is intertwined and supported by this study, I have know idea. Of course the skeptics aren't going to be swayed since this study absolutely proved nothing as to the greenhouse gas and global warming theory. The study simply supports the theory (and pretty much accepted) that the earth has warmed, but does not point to a cause.
Follow the link in post 11. Quick summary: greenhouse gases provide a radiative forcing, causing an increase in the temperature of the atmosphere, and the water vapor content (relative humidity) is a feedback, causing a further increase in the atmospheric temperature. The feedback (positive in this case) augments the effect of the increased radiative forcing. There are other possible negative feedbacks, such as increased cloud cover, which would reflect more solar energy back to space.