Global Warming and the Hidden Costs of Aviation

A recent study
reveals that aviation might pump 20% more carbon dioxide into the atmosphere by
2025 as previously estimated. Vexing is not the possibly underestimated figure;
but the fact that this study was only recently uncovered: As covered by The Independent
or Spiegel
Online, the British environmental association Aviation Environmental Federation now
presents the study on their webpage although it was already presented last
summer at an international conference in Barcelona. Jeff Gazzard, a spokesman
for the Aviation Environmental Federation, is convinced that this omission to
make the report publicly available was deliberate. The study contains alarming
piece of evidence that challenges the rather liberal approach to aviation of the
Kyoto Protocol: Only domestic aviation emissions are accounted for in a countries’
emissions totals, while emissions from international aviation are omitted (see Kyoto
Protocol, Decision 2/CP3).

Aviation is known to seriously impact the climate in
two ways: Firstly, aeroplanes emit greenhouse gases. This is particularly
serious as these emissions are in a height in which due to low temperatures the
molecules are only decomposed slowly and remain there for a long time. Secondly
the emitted water vapour builds up con trails and alters the cloud coverage –
yielding more reflection of radiation back to Earth and thus enhanced global
warming.

Quantifying the impact of the various substances an
airplane emits is a formidably difficult endeavour: For example, the nitric
oxide emitted from aeroplanes builds up atmospheric ozone – a particularly
strong greenhouse gas. At the same time, the nitric oxide decomposes methane,
another strong greenhouse gas. However, according to current knowledge, the former
effect outweighs the latter.

The four models used to produce the result presented
in the now published study predict that the emissions reach between 1.2 billion
and 1.5 billion tonnes annually by 2025. This is higher than the most
pessimistic estimates we have so far, meaning that the highest emissions
considered by the IPCC will be met or exceeded. Certainly, these figures might
be too high as future technological advances are difficult to incorporate. Such
uncertainties will always, willy-nilly, have to be incorporated in our
reasoning about climate change.

What this episode of a lost report illustrates
most lucidly is how difficult it is to find your way in a jungle of information
within a field where science and politics intersect. The scientific value of the
discussed report can be seen as assured by being presented at an international
conference, just like other reports on this very issue are published in
peer-reviewed journals. It seems that being omitted by the scientific
community, and later being exhumed by an environmental organization enhances
the coverage these findings get in the media. Whether this is good or bad is
hard to decide – in the end climate change is an area where all traditional quality
guarantors of scientific research are undermined by political interests anyway.
Think of the not-only scientific allocation of the IPPC or the fact that due to
non-scientific reasons it was not allowed to discuss some emission scenarios in
the IPCC work. For the general public and for the decision maker alike the
problem remains: How to distinguish reliable form unreliable information, and,
in the first place, how to gain access to the relevant information on our
impact on the future climate.