There are droughts and droughts. Some suspect a 150 years drought led to the collapse of Maya civilization.
> Our results show rather modest rainfall reductions between times when the Classic Maya Civilization flourished and its collapse -- between AD 800-950. These reductions amount to only 25 to 40 per cent in annual rainfall. But they were large enough for evaporation to become dominant over rainfall, and open water availability was rapidly reduced. The data suggest that the main cause was a decrease in summer storm activity
> Studies of] Yucatecan lake sediment cores ... provide unambiguous evidence for a severe 200-year drought from AD 800 to 1000 ... the most severe in the last 7,000 years ... precisely at the time of the Maya Collapse.
> Our results show rather modest rainfall reductions between times when the Classic Maya Civilization flourished and its collapse -- between AD 800-950. These reductions amount to only 25 to 40 per cent in annual rainfall. But they were large enough for evaporation to become dominant over rainfall, and open water availability was rapidly reduced. The data suggest that the main cause was a decrease in summer storm activity
http://www.sciencedaily.com/releases/2012/02/120223142455.ht...
> Studies of] Yucatecan lake sediment cores ... provide unambiguous evidence for a severe 200-year drought from AD 800 to 1000 ... the most severe in the last 7,000 years ... precisely at the time of the Maya Collapse.
http://en.wikipedia.org/wiki/Classic_Maya_collapse#Drought_t...