Dinosaur forecast: cloudy, and other lessons from past warm climates

Dr. Eli. Tziperman
Harvard University

The geologic record is a fascinating source for surprising information about 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 even a few nights of sub freezing temperatures, could be found in the waters of Greenland and in present day Wyoming, 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 Niño in the equatorial Pacific, where today El Niño occurs only every 4 years.

State-of-the-art climate models cannot reproduce nor explain these past warm climates even at high atmospheric CO2 concentrations. One wonders whether these models are missing some significant feedbacks that may also affect their global warming predictions. We'll discuss possible physical mechanism for both of these past warm climates and the possible implied lessons.