Stratospheric water vapour decreasing?

A recent study located at a href="http://www.sciencemag.org/cgi/content/abstract/science.1182488" rel="nofollow"http://www.sciencemag.org/cgi/content/ab…/a has stated that stratospheric water vapour has decreased by 10% since 2000. As the stratosphere cools I would expect it's ability to retain water vapour to be lost because concentration is dependent on temperature. After looking at the following a href="http://hal.archives-ouvertes.fr/docs/00/29/65/66/PDF/acp-8-2885-2008.pdf" rel="nofollow"http://hal.archives-ouvertes.fr/docs/00/…/a I see that stratospheric water vapour loses substantial concentration below an altitude of 13km. This area of the atmosphere has a temperature of roughly 205K as given by my previous link. What is the dew point of an air parcel at this temperature and would it not allow as much water vapour into the upper stratosphere? And what would be the overall effects of less stratospheric water vapour?