The book uniquely synthesizes geological and biological archives to provide insights into past climate transitions, informing predictions about future changes. It examines how massive ice sheets sculpted landscapes and altered drainage systems, and how life has adapted to extreme cold and seasonal changes. The book progresses from fundamental principles of glacial geology and climate science to exploring geological evidence and unique ecosystems. It then synthesizes these findings to examine the role of the Arctic and Antarctic in the global climate system, discussing the implications of melting glaciers and permafrost for future climate scenarios.