Let me say immediately that I don't doubt that Planet Earth is on its way out. I couldn't be more gloomy about its future. I'm also not much of a fan of Clive James, in fact I was involved in an angry lunchtime argument with him on the subject of Iraq and what he called 'the triumph of Democracy' the last time I saw him, some years ago. I am, on the other hand, constantly interested in how I can know whether what I read and hear is reliable. I couldn't for example put my hand on my heart and say that my belief that climate change is irreversible is based on anything very much more substantial than a tendency to trust in the green and the left, and the fact that I know from history and experience that human beings are inclined to do what they want to do until they use up the ability to do it.