Several fundamental first-order questions regarding the evolution of Earth’s climate remain open. How have global mean surface temperature and atmospheric carbon dioxide varied across the Phanerozoic and what are the dominant mechanisms controlling large-scale climate change? How are near-surface oceanic and atmospheric circulation affected by changing paleogeographies and what impact do these changes have on global climate? How does climate sensitivity vary under different climate states and across different time scales? Recent advances in proxy system development, computational efficiency of earth system models, and statistical techniques have opened the door to test previous hypotheses, reconcile perceived proxy-model discrepancies, and explore these questions from new angles. This session seeks to showcase new and innovative approaches that have improved our understanding of ancient climates and have broad applicability across a variety of time scales, with a focus on temperature, atmospheric carbon dioxide, and climate sensitivity.