the climate during the last 11.000 years has changed only a little. Even the recorded and well documented climate changes of the past, like the Medieval Long Summer (950-1250 AD) & Little Ice Age (1350-1850 AD), have little effect on the overall climate status. What changes have have been recorded was to the global temperature and to the extreme weather phenomena.
For example during LIA there global temperature (at least in the northern hemisphere) was an approx. 1oC below normal, more rain and snow. Even river Thames was Frozen during winters with frost fairs held over it.
During sumerian times around 3300 -3000 BC there was generally a hotter era, but the fertile crescent might be a little greener than our days.
So, I would suggest arid type bases with scattered greens.