A comprehensive, classroom-ready lesson exploring how and why Earth’s climate has changed over geological time. Students develop a secure understanding of the difference between weather, climate and climate change, before examining the transition from warmer greenhouse conditions to cooler icehouse conditions over the last 100 million years. The lesson covers the Mid-Cretaceous, PETM, Antarctic glaciation, Quaternary glacial–interglacial cycles, the Devensian glacial maximum and the Holocene, with clear explanations of the roles of CO₂, continental drift and ocean circulation. Activities include classification and retrieval tasks, a climate chronology, interpretation of a 60-million-year global temperature graph, evidence-based questioning, challenge questions and a final synoptic plenary considering whether past natural climate change proves that current climate change is natural. Designed to build both subject knowledge and geographical/data interpretation skills, with learning intentions, success criteria, key terminology and teacher answers included, making it suitable for a structured lesson or revision resource.