I've just calculated roughly how many tonnes of carbon I'm releasing into the atmosphere each year. It's about the same as the New Zealand national average. And a whole lot better than the world average shown on this chart.
I learnt a lot doing this exercise, too. I calculated how efficient my car was, and also discovered that my electricity supplier creates electricity from 100% renewable sources, which pleased me greatly. I could work on my car travel. (Hmm, I wonder how long it would take to cycle to Miranda?)
Look for this image (above) on this site, and start by entering your country.