Emissions are expected to increase further.

The main aircraft engine emission pollutants are Figure 1.8: carbon dioxide (CO2), nitrogen oxides (NOX), sulphur oxides (SOX), unburned hydrocarbons (HC), carbon monoxide (CO), particulate matter (PM) and soot. They are considered here in terms of either full‑flight (gate‑to‑gate), or a landing‑take‑off cycle below 3,000 feet for local air quality purposes.

Aircraft CO2 emissions increased from 88 to 156 million tonnes (+77%) between 1990 and 2005 according to the data reported by EU28 and EFTA Members States to the United Nations Framework Convention on Climate Change (UNFCCC) Figure 1.9. According to data from the IMPACT emissions model, CO2 emissions increased by 5% between 2005 and 2014. The increase in emissions is however less than the increase in passenger kilometres flown over the same period (2005 to 2014). This was due to an improvement in fuel efficiency driven by the introduction of new aircraft, removal of older aircraft, and improvements in operational practice. The average fuel burn per passenger kilometre flown for passenger aircraft, excluding business aviation, went down by 19% over this same period. However, projections indicate that future technology improvements are unlikely to balance the effect of future traffic growth. Under the base traffic forecast and advanced technology improvement rate, CO2 emissions increases by 44% from 144 Mt in 2005 to 207 Mt in 2035.

NOX emissions have also increased significantly Figure 1.10: +85% (316 to 585 thousand tonnes) between 1990 and 2005 according to the Convention on Long‑Range Transboundary Air Pollution (CLRTAP) data from the UN Economic Commission for Europe, and +13% between 2005 and 2014 according to IMPACT data. Under the base air traffic forecast and assuming an advanced NOX technology improvement rate, emissions would reach around 920 thousand tonnes in 2035 (+42% compared to 2005).

Emissions of HC, CO and non‑volatile PM have decreased between 2005 and 2014, while full-flight emissions of volatile PM have increased by 7%. However, the total emissions of each of these pollutants are forecast to increase over the next twenty years Figure 1.13, Table 1.3.

Aviation emissions in context

In 2012, aviation represented 13% of all EU transport CO2 emissions, and 3% of the total EU CO2 emissions. It was also estimated that European aviation represented 22% of global aviation’s CO2 emissions. Similarly, aviation now comprises 14% of all EU transport NOX emissions, and 7% of the total EU NOX emissions. In absolute terms, NOX emissions from aviation have doubled since 1990, and their relative share has quadrupled, as other economic sectors have achieved significant reductions [25].