Improvements in energy efficiency alone are probably insufficient to stabilize carbon dioxide concentrations and mitigate their global warming potential. In this lecture, Dr. Martin Hoffert, Professor Emeritus at New York University, demonstrates that a global transition to sustainable carbon-free energy systems must be initiated to avoid a "stabilization crunch" and to meet Rio Treaty implementation demands.

Concentrations of stratospheric ozone have decreased significantly over the last two decades, resulting in detrimental impacts on humanity and the biosphere. In this presentation, Dr. Donald Wuebbles, professor at the University of Illinois, discusses the expectations for future levels of ozone, the attempts to prevent further effects on ozone, and the concerns that remain for ozone recovery.