So after running into varied and conflicting carbon calculators, all with different info on how much carbon the average American puts into the atmosphere yearly, I consulted carbon expert Jamais of Open the Future. Does he know what the accurate number is?

His short answer: “Nope.”

His long answer: “Most of the carbon footprint estimation tools are craptastic.”

Carbon calculators avaliable on the web usually don’t consider a whole number of complicated stuff, such as air travel emissions, says Jamais. In addition, these calculators tend to obfuscate what exactly they’re calculating. Carbon emissions per person or per household? The total amount of carbon or the total amount of carbon dioxide (CO2 includes the weight of the oxygen atoms, not just the carbon atoms)? Metric tons or standard tons (Tonne= “metric ton” = 1000 kg= 2200 pounds = 1.1 standard tons)?

“The upshot is that I have yet to find a carbon footprint calculator that gives what I’d consider an *accurate* result.”

His conclusion: Try about 20 tonnes per person, or 22 standard tons per person in the US. This figure comes from the overall CO2 output figures generated by the Department of Energy‘s Carbon Dioxide Information Analysis Center for the UN.

Thus, 20 tonnes / 22 tons per person it is for my future nerdy personal carbon calculations!

Considering that, then it seems that The Nature Conservancy’s calculator with its 27 ton estimate for the average American — based on the US EPA Inventory of Greenhouse Gas Emissions and Sinks — comes closest. This calculator’s also the most detailed calculator of the ones I’ve tried — and scored 12 tons. It’s the damned long flights that did it.

I’ll get more specific ’bout this later, but for now, go try the calculator yourself –

Update, 7/5/07: Here’s part III, with a review of make me sustainable.

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