Carbon Offsetting Flights - the true cost

In general, I'm cynical about carbon offsetting but I do offset flights. I try to avoid flying if possible, but when there's no alternative I use the airline's own offsetting service. It's a token gesture, I know, but it still feels better than nothing. However, I'm astonished by the variation in the offsetting fees for similar flights from different airlines.


Booking a return flight to Amsterdam with KLM recently, I was struck by the low cost of offsetting - just 97 Euro cents. To offset the same flight with BA costs £1.80. Both airlines claim to be supporting certified carbon offsetting projects. However, KLM states categorically that only the actual cost of offsetting is claimed from the customer and KLM receives none of the revenue. I couldn't find a similar claim on BA's site.

Taking this further, I used the flight offset calculators on the carbon offset sites certified by Defra and got figures ranging from £1.22 to £2.51. The variation in price was less worrying than the variation in carbon emissions. Carbon Passport considered the emissions would be 0.08 tonnes of CO2 costing £1.22. Pure reckoned the distance was 458 miles, emitting 0.15 tonnes of CO2 costing £2.51 (without Gift Aid - Pure is a charity) and Carbon Retirement makes it 0.13 tonnes costing £2.18.

As for how much CO2 my presence on the flight actually contributes, I looked for clarifiation from Defra. The latest conversion factor is 98.3g per passenger kilometre. That works out to 0.73 tonnes, to which BA adds 9% to account for indirect routing and delays - so Carbon Passport is closest at 0.8 tonnes. So what does all this prove? Well, it certainly doesn't make me feel any more positive about carbon offsetting, that's for sure.