Art Bell welcomes back Peter Ward, professor of biology and earth sciences at the University of Washington and NASA Astrobiology Institute investigator, to discuss his book Under a Green Sky and the science of mass extinctions. Ward explains that while the dinosaur extinction 65 million years ago was caused by an asteroid impact, the other 15 mass extinctions over 500 million years show no such evidence.

Ward presents his theory that most mass extinctions were driven by greenhouse gas-induced ocean chemistry changes. He describes how rising CO2 levels acidify oceans until marine organisms cannot form shells, and how saturated oceans can suddenly release massive amounts of carbon dioxide in catastrophic overturning events. He draws a parallel to the 1986 Lake Nyos disaster in Africa, where volcanic CO2 burst from a lake and killed nearly 2,000 people.

The conversation grows urgent as Ward reveals the Southern Ocean around Antarctica is already saturated with CO2 decades ahead of predictions. He warns that current warming trends mirror conditions that preceded the Permian extinction, the worst in Earth's history, which eliminated roughly 90 percent of all species. The first hour covers the Chad UFO photo controversy and open lines.