Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
The three inventories show that more than 60% of the fuel burned and NO x emissions occur
above 8 km, whereas a major fraction of CO and HC are emitted near the ground.
Although the three inventories show comparably low variations for total global monthly figures
over the year, the seasonal dependency can be quite large for some regions (Figure 9-14).
Operations in the North Atlantic and North Pacific show a clear yearly cycle, with a maximum in
the northern summer and a minimum during winter. In contrast, Southern Hemisphere
operations show little seasonal variation overall, with small peaks in February and November.
DLR has also examined longer trends in fuel burned and emissions for air traffic (Schmitt and
Brunner, 1997). 3-D gridded inventories of fuel burned and emissions were calculated for 1982
through 1992 using ICAO statistics on annual values for international scheduled air traffic and
ABC time table data of all scheduled air traffic for the same week of September in 1986, 1989,
and 1992. Emissions inventories were produced for each of these data sets using the same
methods as in the 1992 DLR inventory described above. These inventories concentrate on
scheduled services because reasonably accurate calculations are possible for this segment of
aviation. Because these data do not include nonscheduled flights, military traffic, general
aviation, or former Soviet Union/China traffic, they are of limited use in global modeling studies.
However, they do provide a consistent set of data to track the growth of the international and
domestic scheduled sector. Table 9-6 gives the totals for the yearly inventories.
9.3.5. Error Analysis and Assessment of Inventories
Simplifying assumptions used in creating all of the 3-D emissions inventories have introduced
systematic errors in the calculations. An analysis of the effects of the simplifying assumptions on
fuel burned used in the 1992 NASA inventory has been performed by Baughcum et al. (1996b).
All of the assumptions have the effect of biasing the calculation toward an underestimate of fuel
burned and emissions produced, as detailed in Table 9-7. The effects of the assumptions on the
ANCAT and DLR inventories may be expected to be similar, because most of the simplifying
assumptions used in those inventory calculations were similar to those in the NASA inventory.
The assumption of great-circle flight paths results in an underestimate of distance flown,
although the practice of routing to take advantage of winds may result in lower fuel consumption
than a great-circle path for a given flight. A study of international and domestic flights from
German airports showed an average increase in flight distance of 10% for medium- and longhaul
flights above 700 km, with larger deviations from great-circle routes for shorter flights
(Schmitt and Brunner, 1997). Ground delays and in-flight holding at relatively low altitudes
caused by congestion in the air traffic control system also adds to fuel consumption. Aircraft in
service are subject to factors that may increase fuel consumption by up to 3% (e.g., engine
deterioration, added weight from added systems, and increased surface roughness). Factors
that cause underestimates of fuel burned do not necessarily operate at the same time, so they
are not additive. Sutkus et al. (1999) compared fuel burned for certain carriers and certain
http://www.ipcc.ch/ipccreports/sres/aviation/137.htm (3 von 6)08.05.2008 02:44:22
Figure 9-10: Geographical distribution of fuel burned
by civil aviation (May 1992).
Figure 9-11: Differences in geographical distribution
of fuel burned.