20 January 2011
Updated assessment of aviation’s impact on the atmosphere
In an update of the 1999 assessment of aviation impacts on climate change and ozone
depletion by the Intergovernmental Panel on Climate Change (IPCC), a new study has detailed
recent research on aviation emissions and investigated the potential for using alternative
aviation fuels.
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Aviation levels have increased substantially since the 1960s and are projected to rise in the future. Emissions from
aircraft engines change the chemistry of the atmosphere and can modify the global climate and deplete the ozone
layer.
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Undertaken as part of the EU ATTICA project, the research confirms the major effects on climate change resulting
from air traffic emissions, including: the warming impact of CO2, soot particles, water vapour, contrails (condensation
trails from engines) and increased cirrus cloud formation; and the cooling impact from sulphate particles. These results
are for subsonic aircraft that fly at altitudes ranging from 8-12 km.
In addition, aviation nitrogen oxide emissions have both a warming effect through the formation of ozone, a
greenhouse gas (GHG), in the lower atmosphere, and a cooling effect, through the destruction of methane, also a
GHG. The overall impact on the climate from nitrogen oxide emissions is probably warming. However, nitrogen oxide
emissions from subsonic aircraft do not appear to deplete ozone in the upper atmosphere.
Estimates suggest aviation contributed about 3.5 per cent (excluding the effects on increased cloudiness) to the total
climate warming from human activities in 2005, and this figure is expected to rise to 4 to 4.7 per cent by 2050. In 2005,
2.5 per cent of man-made CO2 emissions came from aviation. Projections suggest CO 2 from aviation in 2050 will
increase 2.7 to 3.9 times, compared with 2000 levels.
Further work is needed to understand and quantify the effects of aviation on clouds, including contrails, increased
cirrus cloud development from spreading contrails and altered properties of clouds from soot emissions. Nevertheless,
the effect of contrails and probable additional cloud formation is likely to have an overall warming impact on the
climate.
Technological advances have the potential to mitigate some of aviation’s impacts on climate change and the ozone
layer but could take some time to reach the market: aircraft are generally in use for around 20-25 years and although
feasible, technology that significantly reduces emissions of CO 2, nitrogen oxide, water and aerosols typically takes
time to develop. In addition, technological advances would probably require trade-offs between reducing nitrogen
oxide emissions and contrail development (at a cost of higher fuel consumption) and reducing CO2 emissions through
lowering fuel consumption. Operational changes, such as adjusting flight altitudes and times of flights, could potentially
cut down contrail formation and reduce the impact on the climate.
Conventional kerosene jet fuels could be replaced with alternative fuels, such as liquid hydrogen or biofuels. Liquid
hydrogen produces water and nitrogen oxide, but not carbon emissions. Overall climate impacts depend on the energy
sources used to produce the liquid hydrogen. Substantial changes to the aircraft design, general infrastructure and fuel
production would be necessary and would probably only occur as part of a wider hydrogen-fuelled economy.
1. ATTICA (European Assessment of Transport Impacts on Climate Change and Ozone Depletion was supported by the European Commission
under the Sixth Framework Programme. www.pa.op.dlr.de/attica
Source: Lee, D.S., Pitari, G., Grewe V. et al. (2010) Transport impacts on atmosphere and climate: Aviation. Atmospheric Environment. 44: 4678–
4734.
Contact: [email protected]
Theme(s): Air pollution, Climate change and energy
Opinions expressed in this News Alert do not necessarily reflect those of the European Commission
To cite this article/service: "Science for Environment Policy": European Commission DG Environment News Alert Service, edited by
SCU, The University of the West of England, Bristol.
European Commission DG ENV
News Alert Issue 225
January 2011
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