Aviation Emissions

During the 1970s studies began to be carried out on the environmental impacts of aviation with particular focus on the effects of supersonic aircraft (Lee & Raper, 2003).  With the continued rise in air traffic (Lee et al, 2009), research has continued with the focus shifted to subsonic aircraft and emissions with an impact on the climate, such as nitrogen oxides (NO_x) (Lee & Raper, 2003).  There have been technological and operational improvements that have reduced the climate impact of flights but the continued growth of air traffic has outweighed these potential emissions reductions (Kahn-Ribeiro et al, 2007), (Owen et al, 2010).

The Intergovernmental Panel on Climate Change (IPCC) report, Aviation and the Global Atmosphere, which will be referred to as the IPCC Aviation Report (Penner et al, 1999), was the first climate assessment of a single industry sector (Lee & Raper, 2003). Subsequent research has refined the measurement and modelling of emissions and updated these initial findings, for example Sausen et al (2005), Lee et al (2009). Aircraft require specific treatment as they are a unique form of transport, operating up to several kilometres above the Earth.  The impacts of non carbon dioxide (non-CO₂) emissions in the atmosphere can be very different to those emissions occurring at ground level (Ellis et al, 1999).

The IPCC Aviation Report (Prather et al, 1999) broadly classified aviation emissions into three categories;

• Radiatively active substances e.g. carbon dioxide (CO₂)
• Emissions of chemical species that produce or destroy radiatively active substances e.g. NO_x
• Emission of substances that trigger additional clouds, and contrails e.g. water vapour, soot.

 

CO₂, has a long atmospheric residence time, leading to the gas being well mixed in the atmosphere.  CO₂ emissions from aircraft are directly related to fuel burn. Aviation CO₂ emissions can be included in general climate change studies (Ellis et al, 1999), (Lee & Raper, 2003).

There is a need to research more aircraft specific emissions such as NO_x and contrails (Ponater et al, 1996).  These emissions have shorter lifetimes, compared to CO₂, and can be more localised (Ellis et al, 1999). Analysis of emissions inventories show that aviation emissions are concentrated at altitudes between 10 – 12km (Lee & Raper, 2003).

The Future Civil Aviation Scenario Tool (FAST) is a computer model used in CATE to model emissions from civil aviation (Owen et al, 2010).  FAST uses inventories of aircraft movements and PIANO fuel flow profiles (Lissys Ltd, 2010) to model the current aircraft fleet and future scenarios. Global totals and 3D gridded data are produced using FAST for distance, fuel, NO_x, CO₂, soot and particle emissions.

Link to the climate models section of the CATE website