The Younger Dryas cold period began about 12,900 years ago and lasted approximately 1,000 years.
Notes on verification
Start date (~12,900 years ago) is well corroborated across multiple sources. Duration is slightly underestimated (commonly cited as 1,200-1,300 years rather than 1,000), but within reasonable approximation range. [cascade flags: aggregator_dropped_primary_exists,wikipedia_dropped_other_sources_exist | tier=silver indep_score=0.77 clusters=2 claim_tier=notable]
Sources
- Fungi, Feces Show Comet Didn't Kill Ice Age Mammals? (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)