Speaker: Robyn Eckersley, School of Social and Political Sciences, University of Melbourne (appearing via videoconference). Discussant: Robert Socolow, Mechanical and Aerospace Engineering

Speaker: David Schlosberg, Department of Politics and International Affairs, Northern Arizona University and Barron Visiting Professor in the Environment and Humanities, Princeton University. Discussant: Stephen Pacala, D. Petrie Professor in Ecology and Evolutionary Biology and Director, Princeton Environmental Institute

Zarine Kharas, founder and CEO of online fundraising website Justgiving.com.

John Gray is emeritus professor of European thought at the LSE and author of Gray's Anatomy.

Peter Singer is the Ira W DeCamp Professor of Bioethics at the University Center for Human Values at Princeton University.