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This page gives an overview of the contribution of aviation to climate change and describes some of the solutions which can address this impact.

What is aviation’s contribution to climate change?

Emissions from aviation are a significant contributor to climate change. The cumulative impact of aviation on man-made climate change in 2005 was estimated at 4.9%, which comprises the impact of greenhouse gas emissions including carbon dioxide (CO2) and non-CO2 effects such as nitrogen oxides (NOx), vapour trails and cloud formation triggered by the altitude at which aircraft operate.

Emissions from aviation are growing faster than any other mode of transport. CO2 emissions alone from EU international aviation increased almost 21% since 2013, while other sectors have reduced their emissions. As a result, they’ve grown from 1.5% of total EU emissions in 1990 to 3.4% today. If unmitigated, aviation emissions are expected to double or triple by 2050 and in doing so consume up to one-quarter of the global carbon budget under a 1.5 degree scenario.

Was aviation left out of the Paris agreement?

Unlike the Kyoto protocol, which had specific emission targets only for developed countries, the Paris agreement calls on all states to adopt “economy-wide” emission reduction targets. This “economy-wide” requirement means that despite there being no explicit reference to aviation - nor indeed are any other specific industrial sectors mentioned - the aviation sector remains covered by the agreement just like all other sectors.

To ensure compliance with the agreement, T&E is calling for the inclusion of aviation emissions in countries’ climate pledges under the Paris agreement – known as nationally determined contributions (NDCs). Such an inclusion would encourage states to take action, both at national and international level as appropriate, to address aviation’s climate impact. The same argument holds for shipping. The EU’s 2030 target already includes outbound aviation emissions, and other jurisdictions should follow suit.

Currently, parties are working with the UN’s aviation agency, the International Civil Aviation Organisation (ICAO), to adopt global measures. However there is a limit to the level of ambition that a UN agency with 193 members can agree to. There is therefore a need for more ambitious and effective action at national and regional level.

This is especially the case for domestic aviation emissions, which fall outside the remit of ICAO, and comprise some one-third of global aviation emissions. Domestic EU emission are covered by the EU ETS while China plans to cover its domestic emissions within its own ETS system. Canada has announced carbon pricing for its domestic aviation emissions, which account for 35% of its aviation emissions.

Does aviation receive subsidies to operate in Europe?

Yes, aviation is heavily subsidised. Firstly, aviation receives a direct subsidy of €3 billion a year for operation and infrastructure developments.

Secondly, aviation is exempt from the basic consumer tax, VAT, that is placed on almost every good and service across the EU leading to a shortfall of at least €17 billion per year in EU member state budgets. Finally, aviation fuel is not taxed anywhere in the EU.On average, across the EU consumers pay 48c per litre of fuel tax every time they fill up their cars, but airlines pay no tax when they fill up their 737/A320s, leading to a shortfall of €32 billion a year.

These subsidies artificially boost aviation demand, while at the same time reduce the incentives for more sustainable aviation such as cleaner aircraft and fuels. Emissions will continue to soar while they continue to exist.

Aviation in the EU ETS

Europe included emissions from flights to and from the continent in its Emissions Trading System (EU ETS) from 2012, a cap-and-trade scheme which would see the number of pollution permits, known as allowances, decrease over time. However strong international opposition, stoked by industry both within and outside Europe, forced the EU in late 2012 to exempt from the scheme all flights to and from Europe. This remains the case today, with the exemption now to continue until at least 2024.

All flights within Europe remain covered by this scheme, and after several years of record lows due to oversupply, allowance prices have begun to recover. Crucially, a reform introduced in 2017 means that the number of allowances granted annually to the aviation sector will start to decrease after 2021 and end in 2068, meaning the European aviation sector will eventually have to decarbonise. EU ETS therefore remains one of the few measures in place attempting to address the sector’s soaring emissions.

To read more, see Aviation in the ETS.

What is ICAO’s global market-based measure?

In October 2016 ICAO agreed the outlines of a global market-based measure to address CO2 emissions from international aviation, starting as a voluntary measure from 2021. The Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) aims to stabilise CO2 emissions at 2020 levels. The measure will be voluntary until 2027 and mandatory on nearly all states thereafter until 2035.

However its target will be achieved through the purchase of offsets or alternative fuels. Offsets involve paying other sectors to reduce their emissions, rather than reducing your own. It has failed to work in the past, with the vast majority of offset credits purchased by entities subject to the EU ETS failing to deliver emission reductions. And it won’t work in the future as the Paris Agreement requires all-sectors to cut their emissions. This leaves no room for one sector to shirk its responsibilities by paying another sector to cut its emissions instead. Alternative fuels are discussed below, but it is highly unlikely that ICAO will put in place the sort of safeguards needed to ensure only those fuels which deliver real emission reductions are used.

CORSIA risks being used as an exercise in greenwashing, with states citing the need to respect a global consensus as an excuse not to adopt more effective policies.

Will alternative fuels and technology bring aviation emissions down?

As present, there are no credible forecasts suggesting that sustainable biofuels can make any noticeable dent in aviation’s fossil fuel demands for the foreseeable future. Arable land is a limited resource. Land-based biofuels are therefore not truly ‘renewable’ since the land used is lost for other purposes, including food production, carbon sequestration, nature, and to ensure the livelihoods of communities. Sustainable feedstocks available for production of non-land-based biofuels, made of waste and residues, are limited and there are other sectors competing for access to them.

Electrofuels such as power-to-liquid are a potential source of zero or lower carbon alternative fuels. Such fuels are not a silver bullet: they require enormous amounts of renewable energy and their environmental effectiveness depends on the source of the CO2 required to produce the fuels. However they do provide the potential to significantly reduce emissions from the sector. Currently these fuels are expensive and are unlikely to become available without clear policy support, either in the form of blending mandates or carbon pricing.

Both biofuels and electrofuels still produce water vapour and as a result may have a similar potential for contrail and cirrus cloud formation as jet fuel. Any incentives provided should therefore take into account both CO2 and non-CO2 climate impacts to maximize the environmental benefit of limited feedstocks on energy required for production.

Futuristic aviation technologies, whether electric or hydrogen-powered aircraft, are many decades away and may never materialise. In addition, technological improvements of future aircraft in the 2030-2040 time frame have already been largely factored into the ICAO CO2 standard work and reveal no silver bullets – rather an ever diminishing annual improvement in new aircraft efficiency of about 1% or less is evident.

What is being done to address aviation’s non-CO2 climate impacts?

Despite their considerable impact, no measures are in place at regional or global level to address aviation’s non-CO2 climate impacts. This report examines the latest research on aviation’s non-CO2 climate impacts, and identifies ways to mitigate them. The major impacts come from contrail and induced cirrus cloud formation which is a result of water vapour emitted as well as NOx emitted during flight cruise.

In the 2017 revision to the EU ETS Directive, the European Commission was tasked with presenting by early 2020 an updated analysis of the non-CO2 effects of aviation, accompanied by a proposal on how best to address those effects Read our briefing about the non-CO2 effects of aviation here.

Should we fly less?

As it is currently difficult to reduce emissions from this sector, it is right to ask whether we should all fly less as a means of reducing the sector’s soaring emissions. Flying less could mean taking a more sustainable mode of transport, such as train, or changing your destination to one which can be reached by less climate-intensive means.. It could also mean teleconferencing instead of attending business meetings, or going on longer individual holidays, rather than several short, carbon intensive, trips.

Whatever the means of achieving it, demand reduction should not be a taboo subject. The sector’s emissions are soaring at a rate too high to ignore and policy-makers should at the very least not recklessly champion endless aviation growth while at the same time knowing how difficult it is to decarbonise the sector.