Adding 9% to aviation GHG emissions for flight delays and indirect routings?

An issue of some significance when considering aviation’s global contribution to greenhouse gas (GHG) emissions is to what extent there is scope to reduce this through better air traffic management, shorter air routes, airport design, etc. Considerable progress has been made in this area in recent years, particularly in Australasia.

A number of the carbon calculators in use a few month ago when I looked worked on the basis of adding 9% to the great circle distance between two airports to allow for non-direct routes and delays/circling. The one from Back Aviation Solutions, which uses the OAG data base of global airline schedules, was among those that used this approach.

The UK Department for Environment, Food and Rural Affairs (DEFRA) is commonly cited as providing official backing for using 9% (see page 34, paragraph 4 of the DEFRA methodology paper [the link is now to an UPDATED paper]).

In the absence of anything better, the New Zealand Ministry for the Environment has used this +9% factor in an official New Zealand Government calculator (see http://www.mfe.govt.nz/publications/climate/guidance-greenhouse-gas-reporting-apr08/html/page3.html Section 3.3.4).

Intuitively this 9% number seemed too high, at least in the New Zealand context. For example, Airways New Zealand has been making progress in reducing domestic delay, and the introduction of flexi-tracking by both Australia and New Zealand has had a significant impact on reducing fuel consumption by allowing long-haul flights in our region to take advantage of favourable jet stream winds. Of course, accurate fuel consumption should be calculated on a time rather than a distance basis.

I have followed the references through to find the origin of the +9% factor.

DEFRA cites IPCC (1999) Aviation and the Global Atmosphere, J. E. Penner, D. H. Lister, D. J. Griggs, D. J. Dokken and M. McFarland (Eds). Special Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge (see section 8.2.2.3 at http://www.grida.no/Climate/ipcc/aviation/121.htm#8223 ). This makes it clear that the +9% only relates to aircraft operations within Europe and is based on an old 1992 report from Eurocontrol “Penalties to Air Traffic Associated with the ATS Route Network in the Continental ECAC States Area” Document no. 921016.

As I understand it, in 1992 Europe was just beginning to emerge out of the cold war and major blocks of air space were reserved for military use. One would have expected more up-to-date data to be available and sure enough Eurocontrol does seem to collect and publish it. Eurocontrol has a Performance Review Commission that produces an Annual Report, the most recent being for 2006. This includes reporting on “flight efficiency” which, for example, points to the additional distance for long-haul flights to and from Europe being significantly less than for intra-European flights (see http://www.eurocontrol.int/prc/gallery/content/public/Docs/PRR_2006.pdf and in particular Figure 62 on page 52).

Given the importance to New Zealand (and indeed the rest of the SW Pacific) of long-haul flights, this issue is of significant interest.

One wonders why this more recent information was not being used in carbon calculators and why a figure based on European experience is being applied globally. Work clearly needs to done to provide a more accurate figure for such calculations.

Intuitively I would have expected that the factor for flights across the Pacific and Indian Oceans to be much lower (possibly even negative?).

On 1 April 2008 Flight International reported that ICAO has been looking at standards for carbon calculators (see previous post). The answer that ICAO came up with is to take the great circle distance then add 50km for flights of less than 550km, add 100km for flights between 550km and 5500km, and add 125km for flights above 5500km.