Like virtually every area of human activity, air transport has an impact on the environment.
This impact takes several forms, including the disturbance caused by aircraft noise and aircraft engine emissions. A major concern for the industry is greenhouse gas emissions from aviation and their implication for climate change.
Aviation produces around 2% of the world’s manmade emissions of carbon dioxide (CO2), according to the United Nations Intergovernmental Panel on Climate Change (IPCC). Despite growth in passenger numbers at an average of 5% each year, aviation has managed to decouple its emissions growth to around 3%. This is through massive investment in new technology and coordinated action to implement new operating procedures.
As aviation grows to meet increasing demand, particularly in fast-growing emerging markets, the IPCC forecasts that its share of global manmade CO2 emissions will increase to around 3% in 2050.
However, a growing carbon footprint is unacceptable for any industry which is why the aviation industry, from manufacturers to airports to airlines to air traffic management, are all working hard to limit greenhouse gas emissions.
On this website, we provide information on how aviation contributes to climate change, and discuss the industry’s work to address this.
Aviation is responsible for 2% of manmade CO2 emissions worldwide
The October 2006 report by Sir Nicholas Stern states that the largest contributor to human-induced CO2 is power generation (24%), mostly produced in coal and gas fired stations. Next is land use change at 18%, then agriculture, industry and transport at 14% each (aviation is part of transport). Buildings (8%), other energy related activities (5%) and waste (3%) make up the rest.
CO2 is not the only greenhouse gas emitted by aircraft, however. The exhaust from aircraft engines is made up of: 7% to 8% CO2 and water vapour; around 0.03% nitrogen oxides, unburned hydrocarbons, carbon monoxide and sulphur oxides; traces of hydroxyl family and nitrogen compounds and small amounts of soot particles (although the industry has managed to more or less eliminate soot emissions over the past few decades). Between 91.5% and 92.5% of aircraft engine exhaust is normal atmospheric oxygen and nitrogen.
The water vapour trails (contrails) created by aircraft also have an impact, but research is inconclusive about whether these have a net warming or cooling effect on the earth. Under some meteorological conditions they can remain in the atmosphere and form ‘cirrus’ clouds, which may have an effect on climate change. For example, some research suggests these clouds may have different cooling and warming effects, depending on whether flights are during the day or night. This type of research can identify if there are any potential benefits in altering operational behaviour. More work is being done in this area and the aviation industry is assisting with research into the effects of contrails on climate change, including putting high-altitude atmospheric testing equipment on some passenger aircraft.
There are many references to aviation having a greater effect than other industries because of the height at which the emissions are released. The most significant greenhouse gas, CO2, does not have any additional impact due to difference in altitude, the impact is the same. However, other emissions such as NOx and water vapour can have more of an effect at higher altitudes. This greater effect is expressed by scientists as a multiplier.
Recent research suggests that aviation CO2 emissions should be multiplied by 1.9 times to take account of the added impact of these other gasses at altitude. However, it is important to realise that most other emitters also release non-CO2 gasses and require a multiplier to determine their overall climate change impact (also known as radiative forcing). The background rate for road transport, for example, is 1.5 times its CO2 emissions.
When these non-CO2 emissions and the multiplier are taken into account, the IPCC estimates aviation accounts for about 3% of total manmade climate impact. However, using a radiative forcing multiplier whilst calculating the emissions of individual flights is considered inappropriate by a number of experts as it is a tool used to describe longer-term impacts. On top of this, other sectors generally do not have non-CO2 impacts added when using carbon calculators.
Looking to the future, the industry is taking many measures to mitigate its climate change impact and the IPCC estimates that aviation’s total contribution, including CO2 and other effects, would likely rise to 5% (with a worst-case scenario of 15% of human emissions) by 2050. However, it is important to note that the proportional impact of aviation will also depend on the success of other sectors to regulate their emissions.
The aviation industry is doing a great deal to limit its environmental impact
Read more about how we are addressing the issue of climate change through our climate plan; the technology being deployed to reduce emissions; the search for sustainable sources of energy; improvements to operations that are helping to reduce emissions, delays and noise; infrastructure innovation and the important role economic measures will play in allowing aviation to undertake its climate plan.