Characterizing the Mayan Terminal Classic Period
Escobar, J., Curtis, J.H., Brenner, M., Hodell, D.A. and Holmes, J.A. 2010. Isotope measurements of single ostracod valves and gastropod shells for climate reconstruction: Evaluation of within-sample variability and determination of optimum sample size. Journal of Paleolimnology 43: 921-938.
With respect to the climate, their results "allow calculation of mean isotope values and thus provide a rough estimate of the low-frequency variability over the entire sediment sequence," and these results indicated that "relatively dry periods were persistently dry [italics added], whereas relatively wet periods were composed of wet and dry times." Their findings also "confirm the interpretations of Hodell et al. (1995, 2007) and Curtis et al. (1996) that there were persistent dry climate episodes associated with the Terminal Classic Maya Period." In fact, they find that "the Terminal Classic Period from ca. AD 910 to 990 was not only the driest period in the last 3,000 years, but also a persistently dry period [italics added]." And in further support of this interpretation, they note that "the core section encompassing the Classic Maya collapse has the lowest sedimentation rate among all layers and the lowest oxygen isotope variability."
In this regard, it can be additionally noted that the AD 910 to 990 time period falls within the time-of-occurrence of the Medieval Warm Period for many locations throughout the entire world, which observation suggests that the climate of the Yucatan Peninsula during that time period likely was also persistently warm. And that "double whammy" of persistent warmth and persistent dryness appears to have been just a bit too much for the Mayans of that trying time to endure.
Curtis, J.H., Hodell, D.A. and Brenner, M. 1996. Climate variability on the Yucatan Peninsula (Mexico) during the past 3,500 years, and implications for Maya cultural evolution. Quaternary Research 46: 37-47.
Hodell, D.A., Brenner, M. and Curtis, J.H. 2007. Climate and cultural history of the Northeastern Yucatan Peninsula, Quintana Roo, Mexico. Climatic Change 83: 215-240.
Hodell, D.A., Curtis, J.H. and Brenner, M. 1995. Possible role of climate in the collapse of classic Maya civilization. Nature 375: 391-394.