Here is Aiguo Dai's (National Center for Atomospheric Research) 2010 drought research updated in 2012, showing drought projections through the end of the century.  It is the near-term maps up to mid-century that are dreadfully worrisome, given the amount of time one can assume it would take to transition an entire global economy from it's fossil-fuel foundation to a renewable economy.  James Hanson expresses concern that large-scale multi-country multi-year droughts would create many millions of climate refuges and could make the globe "ungovernable."
http://www2.ucar.edu/atmosnews/news/2904/climate-change-drought-may-threaten-much-globe-within-decades