I was looking for a carbon-dioxide-emissions-from-air-travel calculator. Well, one thing led to another, and pretty soon I had compiled the following table and histogram:
| Calculator | Answer | In kg |
|---|---|---|
| atmosfair | Climate impact 10,020 kg CO2 | 10,020 |
| brighterplanet | 11418.75 kg CO2e | 11,419 |
| carbonfootprint | 5.10 metric tons of CO2e | 5,100 |
| carbonfund | 16,700 lbs CO2 | 7,575 |
| carbonneutral | CO2 Emissions (t) 5.28 | 5,280 |
| chooseclimate | 12,038 kg CO2 Equivalent | 12,038 |
| clevel | 6.00 Tonnes CO2 | 6,000 |
| climatecare | 5.51 tonnes of CO2 | 5,510 |
| climatecare air new zealand | 2,694 kg of CO2 | 2,694 |
| climatepartner | 8,422 kg CO2 | 8,422 |
| co2nsensus | 5,559.00 kg CO2e | 5,559 |
| flygrn | 5.56 tonnes of CO2 | 5,560 |
| greentripper | 8.12 t CO2 | 8,120 |
| icao | 1761.1 CO2 (KG) | 1,761 |
| myclimate | CO2 amount: 6.0 t | 6,000 |
| myclimate lufthansa/swiss | CO2 amount: 2.5 t | 2,500 |
| offsetters | 5.99 tonnes CO2e | 5,990 |
| omnicalculator flight-emissions | CO2 Emission 10800 kg | 10,800 |
| southpole | 6.653 Tons* | 6,653 |
| terrapass | 14,780 lbs CO2e | 6,704 |
Calculators accessed 2020-01-25. *By email, southpole clarified that their Ton is 1,000 kg.
That’s the results of entering the same trip into twenty different carbon-dioxide-emissions-from-air-travel calculators. I was shocked, and intrigued. Converting everything to kg (and wondering what are tons anyhow...) and setting aside questionable comparisons (what does “CO2e”, “impact”, “equivalent” mean?), there’s a factor six difference between some of those estimates! How the heck does that happen? More astonishingly, I have nineteen different estimates... are there really (at least) nineteen different ways to do this calculation? I started digging into the details, and this project was born.