As I talked about it before, CNN has a page devoted to Going Green and they have added a Carbon Calculator. You can find out the amount of carbon your flight emits. For example, I found out a flight from New York to Istanbul, Turkey  is 16118 KM and produces 1.942 tonnes of CO2 per person. It also tells you the amount of rainforests needed to absorb the carbon and in our example, it is 38.8 km !!