The Younger Dryas cold period began about 12,900 years ago, when glacial temperatures returned within decades and persisted for approximately 1,500 years before ending abruptly.
Notes on verification
Core claim (onset ~12,900 years ago, rapid cooling within decades, abrupt end) is well corroborated by Britannica, ScienceDirect, and PNAS. The stated duration of ~1,500 years is a slight overstatement; most sources indicate ~1,200-1,300 years. [cascade flags: aggregator_dropped_primary_exists | tier=silver indep_score=0.77 clusters=2 claim_tier=notable]
Sources
- Did a Comet Really Kill the Mammoths 12,900 Years Ago? (seed:history_and_archaeology)
- https://www.pnas.org/doi/10.1073/pnas.2007869117 (corroboration)
- https://www.sciencedirect.com/topics/earth-and-planetary-sciences/younger-dryas (corroboration)