The geologic record is a fascinating source for surprising information on past warm climates. The climate of the Cretaceous and Eocene (146-34 Million years ago) was exceptionally warm. Crocodiles and Palm trees, which cannot survive a few nights of sub freezing temperatures, could be found in the waters of Greenland and in the middle of present day Northern North America, where current winter temperatures can drop to -30C. The Pliocene (2-5 Myr ago) was only slightly warmer than present-day climate, but recent evidence shows that it was characterized by a permanent El Nino in the equatorial Pacific, where today El Nino occurs only every 4 years. We'll discuss possible physical mechanism for both of these past warm climates and the possible implied lessons.