Global greenhouse gas emissions grew by 25 per cent between 1990 and 2010, from approximately 40 to almost 50 billion tonnes of CO₂ equivalents. In the same time period, emissions from international aviation and shipping increased by 70 per cent, nearly three times faster.
As a result, international transport increased its share of global CO₂ emissions from 2.2 per cent in 1990 to 3.1 per cent in 2010. Not included in these numbers is the fact that that emissions from aviation also impact cloud formation, ozone generation and methane reduction, and these effects increase the impact of aviation on climate change by a factor of at least two.
A recent study prepared for the European Parliament provides an overview of potential CO₂ mitigation targets for international aviation and shipping, and analyses which targets would be compatible with a global long-term goal of keeping temperature increase below 2°C compared to pre-industrial levels.
According to the study, initiatives and actions by the International Civil Aviation Organization (ICAO) and the International Maritime Organization (IMO) to address greenhouse gas (GHG) emissions, started late and are clearly insufficient. In the long run, measures proposed by IMO and ICAO will mitigate the growth in CO₂ emissions from the two sectors, but not lead to absolute emission reductions.
If efforts in aviation and shipping continue to lag behind those in other sectors, their shares of total global CO₂ emissions are expected to rise substantially. In the baseline scenario they would reach 22 per cent for aviation and 17 per cent for shipping by 2050. Together these two sectors would then be responsible for almost 40 per cent of global CO₂ emissions. If all technological and operational improvements deliver the expected results, the sectors would still be responsible for 25 per cent of the global permissible CO₂ emissions of a 2°C path.
The study investigated several possible mitigation targets, ranging from a somewhat lowered increase in future emissions, over stabilisation at 2020 levels, to full decarbonisation by 2050. While achieving full decarbonisation within 30 years may seem unrealistic, stabilising emissions at 2020 levels (i.e. carbon neutral growth as from 2020) is clearly not enough.
It was calculated that to stay below a 2°C temperature increase, aviation emissions in 2030 should not exceed 39 per cent of 2005 emission levels, and by 2050 they should be 41 per cent lower than in 2005. Shipping emissions should be 13 and 63 per cent lower in 2030 and 2050, respectively, compared to 2005 levels. If non-CO₂ impacts are also included, these targets would need to be even more stringent.
According to the study, these reduction targets are unlikely to be achieved by purely technological and operational improvements within the sectors. Additional measures will be needed, such as encouraging behavioural change that leads to reduced demand for international transport services and enabling offsetting of transport emissions by financing emission reductions in other sectors. Moreover, it is pointed out that the non-CO₂ climate impacts of aviation in particular will not be reduced if fossil fuels are replaced by
hydrocarbons extracted from renewable sources. Only electric propulsion, demand reduction or offsetting remaining emissions will enable full decarbonisation of the aviation sector.
The International Council on Clean Transportation (ICCT) has shown that bigger reductions in shipping emissions are possible by more widespread application of existing best technologies and practices. If all ships were to achieve the energy efficiency of the top five per cent of the current fleet by 2035, global emissions from international shipping would decline despite the increased growth in demand. The most important measure for achieving such improved efficiency is designing for and operating at lower speeds.
Since the Paris agreement of the Framework Convention on Climate Change did not include provisions on limiting emissions from international aviation and shipping, the initiative still rests primarily with ICAO and IMO.
Christer Ågren
The report “Emission Reduction Targets for International Aviation and Shipping” (November 2015) was prepared by Ökoinstitut for the European Parliament’s Environment Committee, and is available at: http://www.europarl.europa.eu/studies.
