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the environment and the effects of man-made pollution on
‘Climate Change’ has seeped into the public consciousness,
brought about to some degree by the increase in the
frequency and severity of natural disasters.
Whilst the ‘experts’ argue over the causes of the ferocity
of 2005’s hurricane Katrina or the increase in the number
and intensity of forest fires that take place each year, the
public has begun to make the connection between them
and global warming.
I Another change has also occurred. Aviation has been added
to the list of suspects who are assumed to be responsible for
raising the earth’s temperature. Only a few years ago, the
main causes for global warming were thought to be factories,
power stations, households and cars. Now, aviation has joined
that group.
Impact of aircraft on the environment
According to a UK Royal Commission Special Report The
Environmental Effects of Civil Aircraft in Flight, published in
November 2002, aviation impacts on the environment in four
main ways; through climate change, stratospheric ozone
reduction, regional pollution downwind of airports and local
pollution caused by airport activity and infrastructure.
109
be a consequence of the change in the absorption of solar
radiation and the absorption and emission of thermal radiation
and may determine levels of localised rainfall and the
frequency and intensity of heat waves.
In short, aircraft emit a number of different harmful
pollutants into the atmosphere, which have varying affects on
the atmosphere itself according to where exactly they are
released. The cruise altitude of sub-sonic aircraft puts them in
contact with both the troposphere and the stratosphere,
which, in turn, can alter the damage the emissions can create.
Challenges to revenue streams
Air travel was not omitted from the 1997 UN Kyoto Protocol, as
many people believe. CO2 emissions from domestic flights are
subject to emission targets outlined in the Kyoto Protocol.
International air travel has only been excluded from these
targets while the International Civil Aviation Organization
(ICAO) is looking for a solution that would facilitate their
introduction into the protocol. However, additional pressure is
being applied by governments, which are looking for ways to
impose measures on the air transport industry beyond the
terms of the Kyoto agreement, rather than allowing the
During flight, aircraft engines emit carbon dioxide (CO2),
oxides of nitrogen including (NOx), oxides of sulphur, water
vapour and particles consisting mainly of sulphate from the
sulphur oxides and soot. Since the cruise altitude of most
subsonic jets is generally between 9 and 13 km above the
earth’s surface, these emissions are predominantly released
in the transition area between the troposphere and
the stratosphere.
The impact of these emissions varies depending on whether
they are released in the upper troposphere or the lower
stratosphere. The troposphere contains more water vapour, is
more turbulent than the stratosphere and influences weather
patterns to a greater degree. The stratosphere, on the other
hand, has a higher concentration of ozone. Since the altitude
of the stratosphere and troposphere also varies according to
location, weather and time of year, aircraft often move from
one layer to the other during their flight. This is significant, as
aircraft emissions of oxides of nitrogen in the troposphere will
increase ozone levels and therefore decrease surface UV levels,
whereas the same emissions in the stratosphere act in the
opposite way. Although it is still open for debate, it is
suggested that climate change resulting from emissions may
Air travel was not
omitted from
the 1997 UN
Kyoto Protocol,
as many
people believe
Tax exemption was
originally put in place to
promote a level playing
field for competition
THE ENVIRONMENT
110
industry to continue with its own strategy for reducing the
harmful effects of aircraft.
Taxation, a particular favourite of governments, has been
proposed in various forms, including the lifting of the taxfree
status awarded to aviation fuel under article 24 of the
1944 UN Chicago convention. This rather ignores the reason
why the tax exemption was granted in the first place, as it
was originally put in place to act as an instrument to stop
distortions in the market and promote a level playing field
for competition.
Additional forms of taxation present myriad complications
and complexities, which would most likely introduce
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