IN-DEPTH: Capping international aviation emissions. A ticking clock

The international aviation sector represents one of the major emissions sources of carbon dioxide and other GHG gases within the transportation sector, which amounts to one fifth of global greenhouse gas (GHG) emissions in total. Unlike the domestic aviation, it is one of the remaining sectors of the world economy which has not been subjected to any emissions reduction regulation yet.
According to the first IPCC report on aviation of 1999, the scale of air pollution caused by air transport accounted around 2% of total anthropogenic carbon dioxide emissions in 1992. Since then, the aviation sector has experienced an accelerated growth worldwide, expanding both in terms of air traffic and number of carriers, which has led to an 89%increase in carbon emissions between 1990 and 2013. The international aviation sector is considered the main driving force behind the emissions as it accounted for 65% of global aviation fuel consumption in 2010.
The amount of carbon emissions from the international flights has increased from 185 to 488 Mt in the 1990-2013 period. Given the growing role of aviation in the global economy, the carbon dioxide emissions are projected to grow up to 755 Mt in 2020 and exceed 2500 Mt by 2050 following a business-as-usual scenario (see the graph).

The global step to regulate the sector is expected in early October, at the end of the 39th ICAO Assembly. The on-going discussions date back to the first UNFCCC Conference of the Parties in 1995 in Berlin (COP 1) where the initial difficulties emerged regarding the characteristics of the emissions allocation system. The usual “national-territorial” approach adopted by the UNFCC to regulate emissions in other sectors could not be applied in the case of international aviation due to the share of emissions occurring above international waters. Subsequently with the Kyoto Protocol in 1997, countries agreed to delegate the responsibility of regulating international aviation emissions to a UN agency, the International Civil Aviation Organization (ICAO).

Co2 emission trends from international aviation, 2005 to 2050 (Source: ICAO, Environmental Report 2013)


Over the past decade, there has been little progress on reaching international consensus on the type of measure aimed at aviation emissions reduction. The long-established tax exemption for fuels used in international air transport, set by the 1944 Chicago Convention on International Civil Aviation, has furthered hindered the emissions reduction efforts.

The single to-date instance of non-domestic flights emissions regulation is the EU Emissions Trading Scheme (ETS), established by the EU Directive 2008/101/EC. The initial scope of the EU ETS policy covered all flights to and from European Economic area beginning from 2012. However, due to the complaints of the non-EU flight carriers, the request to comply for international flights was suspended at the end of 2012. Even though the cost-effectiveness of the emission trading system was recognized at the 33th ICAO Assembly in 2001, several governments, along with the ICAO, have strongly opposed the inclusion within the EU ETS, arguing it is against the principle of state sovereignty established by the Chicago Convention. The so-called “stop-the-clock” legislation (EU Regulation 20/2014) ensued with extending the exemption of international aviation emissions from the ETS until the end of 2016 (see the timeline).

ICAO Policy Timeline, own elaboration


The aim of the temporary EU ETS suspension was to put pressure on ICAO to come up with a common measure to regulate aviation emissions within the given three-year period. The ICAO Member States set the global aspirational goals for the international aviation at their 37th Assembly in 2013. The two main targets established include improving fuel efficiency by 2% per year and reaching “carbon neutral” growth from 2020 onward. In order to accomplish their goals, the ICAO Member States have considered a basket of measures, ranging from developing sustainable alternative fuels, increasing fuel efficiency through introducing new technological standards to operational improvements. However, the main instrument aimed at achieving the “carbon neutrality” target is the so-called “global market-based measure” (GMBM). The GMBM is still in the process of development and the two main elements to be defined are setting the limit on future CO2 emissions and the criteria for offsetting emissions of individual air carriers, for those who are unable or prefer not to reduce them.

The work to establish the GMBM is due to be finalized at the 39th ICAO Assembly, taking place between 27th September and 7th October this year. The three-year suspension of the EU ETS is soon coming to an end and the upcoming ICAO meeting might constitute a vital step towards reaching global consensus on addressing emissions from international aviation. In the light of the commitments agreed with under the Paris Agreement last year, the decision to cap international aviation emissions would significantly contribute to achieving the goal of limiting the global temperature increase below 2°C, particularly considering the projected growth of the aviation sector in the years ahead.



(Image: Boeing 757-300, 2011. Photo credit: Bill Abbott/Flickr)