A decade ago, many people saw carbon offsetting as an excuse for carrying on bad behaviour. Need to fly? I can still fly ... look at me - I'm not so bad after all. And the critics lined up to shoot it down. So what has changed, asks Tom Heap, and is it something we should all be doing? With contributions from Juliet Davenport of Good Energy, Charlotte Ashton in Zimbabwe, Tim Brown of Tradewater, Mike Childs from Friends of the Earth and Professor Julia Jones who tells us about her experience of conservation projects in Madagascar. The producer in Bristol is Miles Warde