Ahead of the 2009 Climate Change conference in Copenhagen, Geoff Watts chairs a special Frontiers debate on one of global warming's most contentious issues - population growth. Delegates in Copenhagen will address how to reduce greenhouse gases, blamed for warming the planet. But in focusing on energy production, is there a factor that is being ignored because it is too controversial - the sheer numbers of us on the planet? Geoff and guests grapple with the complex issues surrounding population and climate change. If there is a relationship, what can be done about it? Joining Geoff on the panel are: John Guillebaud, Emeritus Professor of Family Planning and Reproductive Health at University College London David Satterthwaite, Senior Fellow in Human Settlements at the International Institute for Environment and Development Karen Newman, Co-ordinator at the Population and Sustainability Network.