Dr. Henrik Svensen (Physics of Geological Processes, UiO): Global warming and mass extinctions: What do we know from the geological record?

From the geological record it is known that the Earth has experienced more than six episodes of rapid global warming and associated mass extinctions the past 250 million years. The interest in these episodes has increased the last 15 years, and they may ultimately give important lessons for the future. The cause of these environmental catastrophes is however very much debated. Was it death from above, or something that originated from Earth itself? And why were some mass extinctions severe, whereas others only affected a few ecological niches?