A couple of years ago I did a comparison of carbon footprint calculators, and found that my carbon footprint was somewhere between 1.54 and 9.31 tonnes. Given the wildly different results, I’ve been hoping somebody would do a more scientific study at some point, and work out why it’s so hard to get accurate figures. Luckily, someone has.
Jack Carrinton, an intern at the Agency for the Conservation of Energy, recently created a fictional average family and worked out their carbon footprints on a series of popular online calculators. You can read the results here (pdf). “The results show a huge variation in the scope and quality of calculators available” he concludes. “The size of yourcarbon footprint depends on who you ask.”
As I discovered, many calculators do not factor in consumption, and there are big differences in how aviation is calculated. Overall, he suggests Resurgence’s calculator is probably the most accurate.
We ran a carbon footprinting workshop a couple of weeks ago, as part of Transition Luton. I used George Marshall’s book Carbon Detox, and I was quite pleased with how that worked in a group context. We worked out seven subtotals and plotted the numbers on A5 cards shown above. Once we’d got the overall total, we drew our footprint on the graph. The numbers on the right show tonnes of CO2, so you know how tall to make your footprint.
Once you’ve drawn it, you can compare your footprint to the UK average – the light blue one. You can also see what our footprint would be if everyone on the planet emitted the same amount – that’s the dark blue one – and see how far you’ve got to go over the next fifty years.
I thought the workshop went well, and it’s so much better doing it together and being able to discuss what you find. Drop me a line if you’d like more information about how to do it, and if you’d like to use the graph, just right click this for a downloadable print-res version.
The Earthbound Report 
