Video from 2015.
"'The role of climate change in the collapse of Classic Maya civilisation is somewhat controversial, partly because previous records are limited to qualitative reconstructions, for example whether conditions were wetter or drier,' said Nick Evans, a PhD student in Cambridge's Department of Earth Sciences and the paper's first author. 'Our study represents a substantial advance as it provides statistically robust estimates of rainfall and humidity levels during the Maya downfall.'" Source: Archaeology News Network.
Note: Researchers found that "annual precipitation decreased between 41% and 54% during the period of the Maya civilisation's collapse, with periods of up to 70% rainfall reduction during peak drought conditions, and that relative humidity declined by 2% to 7% compared to today."
No one really knows what happened to the Classic Mayan civilization. A number of theories have been proposed, but the drought theory is one of the more plausible. According to Wikipedia, "[c]limatic factors were first implicated in the collapse as early as 1931 by Mayanists Thomas Gann and J. E. S. Thompson. In The Great Maya Droughts, Richardson Gill gathers and analyzes an array of climatic, historical, hydrologic, tree ring, volcanic, geologic, lake bed, and archeological research, and demonstrates that a prolonged series of droughts probably caused the Classic Maya collapse. The drought theory provides a comprehensive explanation, because non-environmental and cultural factors (excessive warfare, foreign invasion, peasant revolt, less trade, etc.) can all be explained by the effects of prolonged drought on Classic Maya civilization."