Climate change is one of the biggest and most complex global challenges of our time. It is caused by the release of greenhouse gases such as carbon dioxide trapping more of the sun’s heat in the earth’s atmosphere leading to temperature rises. Climate change is already increasing the risks of extreme weather such as heatwaves and flooding, food insecurity, sea level rises, loss of biodiversity, and forest fires. These impacts are set to worsen in future as CO2 concentrations in our atmosphere increase. CO2 has a lifespan measured in centuries so today’s emissions will combine with those that have accumulated since the start of the industrial revolution.
Climate change will impact all countries, but it is the world’s poorest nations, who – having contributed least to the climate problem – will nevertheless bear the brunt as they have the fewest resources to protect themselves and their food production from extreme weather.
Aviation is almost completely dependent on fossil fuel kerosene, and the large amount of energy needed for planes to get, and stay, airborne makes air travel the most carbon-intensive form of travel in most cases (see graph). Taking one return long haul flight can generate more emissions than any other activity in a whole year.
Around 4.5 billion passengers flew in 2018. Yet the large majority of the world’s population (estimates vary between 80 and 95%) have never set foot on an aircraft; both globally and within the UK most flying is done by a minority people on higher than average incomes. In the UK, where the number of people who fly in any given year is much higher (around 50%), and where emissions in many other sectors are falling, aviation represents around 10% of total CO2 (compared to 2% of global emissions).
Taking one return long haul flight can generate more emissions than any other lifestyle activity in a whole year.
Aircraft also release NOx, soot, and water vapour in the upper atmosphere, and create contrails, that combine to create a net warming effect which roughly doubles the total global warming impact of aviation compared to CO2 alone.
Aviation has consistently fallen through the nets of most global and UK climate policy initiatives. The Kyoto Protocol, adopted in 1997, left international aviation and shipping (IAS) out of the commitments made by industrialised countries to cut emissions, instead requesting states to work with the relevant UN agencies responsible for these sectors.
Aviation has consistently fallen through the nets of most global and UK climate policy initiatives.
So far, the only climate goal adopted by the UN aviation agency, ICAO, is to keep net emissions from international aviation at or below 2020 levels, primarily using offsets under its Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA). ICAO is currently assessing the feasibility of a long-term 2050 goal, although the earliest date it could be agreed is at its next Assembly in 2022. Intra-EU flights are currently included in the EU Emissions Trading System (ETS), which has a more stringent emissions cap than CORSIA. Following Brexit, the UK will leave this scheme on 31 December 2020, although it currently plans on maintaining a carbon price by creating a UK ETS linked to its European counterpart. How the EU ETS, or the proposed UK ETS, will continue to operate in parallel to CORSIA are currently subject to review.
The UK’s climate law, the 2008 Climate Change Act (updated in 2019 to require net zero emissions by 2050), meanwhile left international aviation and shipping emissions in a kind of limbo. While the Act’s target implicitly applies to all sectors, international aviation and shipping emissions have been left out of the 5-yearly carbon budgets that the Act requires, given questions about how to account for them. Carbon budgets for other sectors have nevertheless always been set with a view to including aviation and shipping at some time in the future, allowing ‘headroom’ for these emissions, though getting the Government to act as though this represents any kind of meaningful limit on aviation emissions has always been a challenge. The Committee on Climate Change has advised Government that it should be planning for net zero emissions in the aviation sector by 2050.
No policies exist anywhere in the world to directly tackle aviation’s non-CO2 impacts.
While technologies now exist for many sectors to shift to renewable energy, there are no radical technology options currently available to decarbonise aviation. New aircraft are typically more efficient than the ones they replace and – with the right incentives – this trend should continue, but annual efficiency improvements in aviation average around one percentage point per year. Commercial electric aircraft are unlikely to be available for anything other than very short journeys until after 2050, and while zero carbon kerosene is technically possible to make using captured CO2 and hydrogen (produced with renewable electricity), it is not currently being produced at a commercial scale. Biofuels require careful evaluation. Those made from agricultural and food waste can have lower lifecycle emissions than using kerosene, but are unlikely to be available in sufficient quantities to make a significant contribution. Others can be associated with unsustainable production (growing crops for fuels can contribute directly and indirectly to deforestation for example, and can compete with growing food).
Offsetting in aviation involves either paying for an emissions reduction in some other economic sector to compensate for the emissions from a flight, or paying for enough trees to be planted to absorb an equivalent amount of CO2. But neither of these approaches provide a long term solution for aviation given the need to get to net zero emissions in the coming decades. With all countries and all sectors needing to achieve net zero, there won’t be spare emissions reductions available to buy as offsets, and while reforestation is needed in order to help capture the CO2 that has built up in the atmosphere since the industrial revolution, it won’t be possible to keep planting (and protecting) enough trees annually to absorb continually accumulating CO2 from fossil fuel use.
It won’t be possible to keep planting (and protecting) enough trees annually to absorb continually accumulating CO2 from fossil fuel use.
Some academics have argued that the only way to achieve net zero emissions by 2050 – the target the UK has now committed to – is to gradually close our airports and stop flying. After that time, they say, technology options such as CCS and electric aircraft may be available, allowing us to take to the skies again without generating additional CO2, but in the meantime we should accept that zero emissions will require zero flying. Others anticipate carbon removal technologies being available more quickly, but nevertheless argue for the urgency of overcoming the challenges to rolling these out.
For aviation to have any place in a net zero future, we think there will be a need for: