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Climate change

Climate change: the basics

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 is already increasing the risk of extreme weather events such as forest fires

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.


The climate impact of flying

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 of 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.


The missing policies on aviation emissions

Currently, only domestic aviation (which accounts for just 4% of the UK’s total aviation emissions) is included in the UK’s climate law. This law, the 2008 Climate Change Act, requires the Government to set five-year emissions reductions targets, known as ‘carbon budgets’. The UK’s share of international aviation emissions has historically been left out of these budgets.

Aviation has consistently fallen through the nets of most global climate policy initiatives.

In April 2021, however, the Government announced that international aviation and shipping (IAS) emissions would be included in the UK’s climate law, requiring these sectors to be part of the UK’s 2050 net zero emission target. This is a big step forward in holding the industry to account for its emissions, and something we have long campaigned for, though a policy plan in order to ensure the sector reaches these targets remains to be seen.

Aviation has consistently fallen through the nets of most global 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. 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. Since 2012, intra-EU flights have been included in the EU Emissions Trading System (ETS), which has a more stringent emissions cap than CORSIA. Following Brexit, the UK created the UK ETS, linked to its European counterpart, to maintain a carbon price on UK domestic flights and flights departing the UK for EEA destinations. How the UK ETS (and EU ETS) will operate in parallel to CORSIA is currently subject to review.

No policies exist anywhere in the world to directly tackle aviation’s non-CO2 impacts.


Solutions and smokescreens

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.


The future? What we want to see

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:

  • Less flying (see our What can I do? page for more on this); all credible net zero emissions models that include aviation involve some degree of demand limits, whether through lifestyle change, pricing, or airport capacity limits.
  • Quicker take-up of new technologies improving aircraft efficiency; as an aircraft can be in passenger service for several decades, new measures are needed to drive faster improvements in the fleet.
  • Investment – now – in the radical, but expensive and potentially difficult-to-deliver technologies that will be needed either to generate zero carbon synthetic fuel for aviation, or to capture and permanently store CO2.
  • Measures to eliminate aviation’s non-CO2 impacts.