The one year resolution data from a speleothem at the Tzabnah cave in Tecoh, Northwestern Yucatan, is interesting in many ways, particularly with regard to what is not discussed in this study. The study emphasizes droughts during the Terminal Classic. Spectral analysis has shown that positive 18O anomalies indicate dry conditions and these occurred 501-518 (17 years), 527-539 (11 years), 658-668 (10 years), and 804-938 (130 years). During these periods precipitation decreased between 52 and 36% of the present annual precipitation. The later Terminal Classic period is subdivided into eight different drought episodes. If we set these to the side, it is interesting to note that the three other droughts (501-668) were much more severe than any of the single droughts during the Terminal Classic (as seen in figure 6 of the article).
Why did not these more severe “hiatus” droughts collapse the polities of the Maya area (the first drought event actually occurred before the so-called “hiatus”)? The population density was lower than during the Late Classic but it was large enough to cause stress on a local level. Following the logics of the “drought-hypotheses” there would have been drastic population reductions. There is no indication that population dropped by 40-50% during these droughts (like what is argued to have happened in Colonial Yucatan, an area and period that had even less population density). If the “hiatus” population actually dropped by that much we must explain why and how the Late Classic population dramatically increased from an even lower level than previous estimates.
Sure enough, the Terminal Classic droughts were many and people and polities may not have had enough time to recover before the next drought hit but I believe the answer is something else. The major polities remained during the stressful “hiatus” period largely because the political economy that these inland sites depended on also remained. That seems not to be the case during the Terminal Classic when coastal trade began to emerge which became the foundation for the Postclassic political economy. I believe the answer to the final abandonment of the central lowlands had to with changes in the political economy (but the droughts were, of course, not unimportant in this development).
Medina-Elizalde, Martín, et al. (2010). High resolution stalagmite climate record from the Yucatán peninsula spanning the Maya Terminal Classic period. Earth and Planetary Science Letters, 298:255-262.