The true cost of flying
The carbon emissions associated with flying are an increasingly hot issue.
In today’s Sydney Morning Herald blog there is a post Our flying footprint
With the environmental impact of flying such a hot issue we can expect the cost of flying to keep rising as the planet gets warmer. We already pay a litany of taxes, handling charges and hidden levies each time we fly. We now find we have to stump up more and more cash to use our frequent flyer points. How long can it be before carbon offsets are also factored into each and every airfare?
The post goes on to link to a number of Australian and UK based online calculators you can use to calculate your emissions. Carbon Planet has such a calculator in the pipe-line too and is doing the basic research properly, and transparently, so people can actually trust the calculations.
Carbon Planet explains its decision to use a more relaxed approach to offset amounts.
If you look around the web, you’ll find a variety of web pages that allow you to calculate your CO2 emissions from air travel. Confusingly, they all seem to give different results! In particular, you may find that some calculators differ from each other by a factor of three. This is because scientists have determined that the global warming impact of aircraft is actually equivalent to about three times their actual CO2 emissions. The reasons are complex, but relate to the fact that aircraft inject their CO2 emissions high in the atmosphere, and the fact that aircraft emit relatively more Nitrous Oxide (which has 310 times more global warming impact than CO2). Some flight emissions calculators take this into account and some don’t, resulting in a huge disparity. The simple form above takes this Radiative Forcing Index into account to produce our best rough estimate. Carbon Planet is investigating this area further and will eventually adopt a comprehensive flight emissions model and calculator supported by detailed scientific references. In the meantime, the values above represent a good estimate of the impact of various kinds of flight emissions.
The accuracy of these calculations is in flux. For example, only last week the science weekly, New Scientist ran an article Night flights give bigger boost to global warming.
Nicola Stuber of the University of Reading, UK, and her colleagues used computer models to study the warming effect of contrails created by aircraft entering the North Atlantic flight corridor over south-east England. This showed, as expected, that winter flights make a disproportionate contribution to warming because winter weather favours the formation of contrails.
More striking was the difference between night and day. While night flights accounted for only 25 per cent of air traffic at the monitored site, their contrails contributed up to 80 per cent of the warming in cloud-free conditions. That’s because daytime contrails partly offset the overall warming effect by blocking incoming sunlight (Nature, vol 441, p 864).
The team also showed that the 36 per cent of flights over the US east coast that occur during the night account for 53 per cent of the warming. The 48 per cent of all flights in the North Atlantic corridor that are at night account for 58 per cent of the warming. The simplest way to minimise the warming effect of contrails would be to reschedule flights for the daytime, Stuber says.
So now any flight emissions calculator needs to take into account radial distance at altitude along actual flight-paths, radiative forcing index, flight time, weather during the flight, number of passengers and the type of craft. It needs to account for the CO2 costs at the gate, for the food, for the time of the staff, the carts that load and unload baggage. For now its simpler to use a rough calculation and round up a bit to make whole tonnes of CO2.
You can offset your flights through Carbon Planet. — DS
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