Internal hydroclimate variability and the decline of the Classic Maya Civilisation

The decline of the Classic Maya civilisation ( ∼ 8th–10th centuries CE) occurred in part from drought stress induced by natural climate variability. Using the EC-Earth3 8K simulation, driven by time-varying orbital and greenhouse gas forcing, we show that the convergence of internal hydroclimatic rhythms alone, generated severe, prolonged droughts comparable to, or even greater than, observed extreme events. We identify the interaction of multi-centennial oscillations ( ∼ 600 years) and centennial ( ∼ 160 years) cycles, superimposed with robust sub-centennial oscillations ( ∼ 60–90 years) and persistent multi-decadal and inter-annual variability, created a shifting wet/dry regime over the Yucatán Peninsula. Severe droughts arose when different frequency modulations aligned in their dry phases. Our results provide the first model-based demonstration of how internal climate variability alone can trigger extreme events capable of reshaping societies, revealing key climatic drivers of societal vulnerability, with direct implications for how internal variability may interact with anthropogenic forcing to amplify future climate risks.